TY  - CONF
AU  - Lukić, Ivana
AU  - Stamenić, Marko
AU  - Tadić, Vanja
AU  - Skala, Dejan
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6984
AB  - The high potential of industrial hemp (Cannabis sativa), mainly due to the high-quality fibers and bioactive compounds, coupled with the decriminalization and/or legalization in some regions of the world, led to the steady growth of scientific research over the past couple of decades [1, 2]. From an industrial point of view, cannabinoids, primarily non-psychotropic cannabidiol (CBD), are considered the most valuable compounds, as they possess a broad range of therapeutic properties, such as anxiolytic, neuroprotective, antibiotic, antiinflammatory activity, and anti-oxidant. The hemp industry has already adopted supercritical carbon dioxide scCO2 extraction as a well-established process since it is a promising ‘green’ alternative to conventional extraction methods, selective, with short processing time, and low impact on the environment.
In the present study, the preliminary analysis was performed to determine the influence of different
scCO2 densities based on the different combinations of process pressure and temperature on the kinetics of supercritical extraction of Cannabis sativa, extract yield and the chemical composition of obtained extracts. Experiments were performed at temperatures ranging from 40 to 60 °C and pressures ranging from 10 to 30 MPa. Prior to extraction, the plant material was grounded and submitted to decarboxylation process at 120 °C for 1 h, in order to transform cannabidiolic acid, which is the precursor present in the plant material, to CBD.
Experimental design for optimization plays an important role both in science and industry, because it allows evaluation of the effects of multiple factors and their interactions on one or more response variables. The present work was focused on the further optimization of scCO2 extraction with the aim to maximize the yield of extracts with high recoveries of CBD, by means of response surface methodology (RSM), based on a central composite design (CCD) using Design of Experiment software (Stat-Ease, Design Expert). For this purpose, independent variables were temperature (40-60 °C), pressure (10-30 MPa), and scCO2 consumption (20-60 gCO2/gplant).
The results showed that supercritical CO2 extraction enabled the achievement of up to 5% of total extract yield and 266–435 mg/g of CBD depending on the conditions. The high pressure and temperature, 30 MPa 60 °C, respectively, conditions that correspond to the highest density of the scCO2, generated the highest extract yield. On the contrary, lower pressure, corresponding to the lower density of CO2 was favourable for achieving a high CBD content. In addition, a higher scCO2 consumption, which is related to longer processing time, was the most dominant factor affecting the extraction process exerting a significant effect, on both examined responses, yield and CBD content. A linear model equation was proposed to express both the yield and the CBD content as a function of independent variables.
PB  - Budapest : University of Technology and Economics
C3  - Book of Abstract / 19th European Meeting on Supercritical Fluids, Budapest, Hungary, 21-24 May 2023
T1  - Optimization of Cannabis sativa supercritical CO2 extraction using Design of experiments approach
SP  - 135
UR  - https://hdl.handle.net/21.15107/rcub_technorep_6984
ER  - 

@conference{
author = "Lukić, Ivana and Stamenić, Marko and Tadić, Vanja and Skala, Dejan",
year = "2023",
abstract = "The high potential of industrial hemp (Cannabis sativa), mainly due to the high-quality fibers and bioactive compounds, coupled with the decriminalization and/or legalization in some regions of the world, led to the steady growth of scientific research over the past couple of decades [1, 2]. From an industrial point of view, cannabinoids, primarily non-psychotropic cannabidiol (CBD), are considered the most valuable compounds, as they possess a broad range of therapeutic properties, such as anxiolytic, neuroprotective, antibiotic, antiinflammatory activity, and anti-oxidant. The hemp industry has already adopted supercritical carbon dioxide scCO2 extraction as a well-established process since it is a promising ‘green’ alternative to conventional extraction methods, selective, with short processing time, and low impact on the environment.
In the present study, the preliminary analysis was performed to determine the influence of different
scCO2 densities based on the different combinations of process pressure and temperature on the kinetics of supercritical extraction of Cannabis sativa, extract yield and the chemical composition of obtained extracts. Experiments were performed at temperatures ranging from 40 to 60 °C and pressures ranging from 10 to 30 MPa. Prior to extraction, the plant material was grounded and submitted to decarboxylation process at 120 °C for 1 h, in order to transform cannabidiolic acid, which is the precursor present in the plant material, to CBD.
Experimental design for optimization plays an important role both in science and industry, because it allows evaluation of the effects of multiple factors and their interactions on one or more response variables. The present work was focused on the further optimization of scCO2 extraction with the aim to maximize the yield of extracts with high recoveries of CBD, by means of response surface methodology (RSM), based on a central composite design (CCD) using Design of Experiment software (Stat-Ease, Design Expert). For this purpose, independent variables were temperature (40-60 °C), pressure (10-30 MPa), and scCO2 consumption (20-60 gCO2/gplant).
The results showed that supercritical CO2 extraction enabled the achievement of up to 5% of total extract yield and 266–435 mg/g of CBD depending on the conditions. The high pressure and temperature, 30 MPa 60 °C, respectively, conditions that correspond to the highest density of the scCO2, generated the highest extract yield. On the contrary, lower pressure, corresponding to the lower density of CO2 was favourable for achieving a high CBD content. In addition, a higher scCO2 consumption, which is related to longer processing time, was the most dominant factor affecting the extraction process exerting a significant effect, on both examined responses, yield and CBD content. A linear model equation was proposed to express both the yield and the CBD content as a function of independent variables.",
publisher = "Budapest : University of Technology and Economics",
journal = "Book of Abstract / 19th European Meeting on Supercritical Fluids, Budapest, Hungary, 21-24 May 2023",
title = "Optimization of Cannabis sativa supercritical CO2 extraction using Design of experiments approach",
pages = "135",
url = "https://hdl.handle.net/21.15107/rcub_technorep_6984"
}

Lukić, I., Stamenić, M., Tadić, V.,& Skala, D.. (2023). Optimization of Cannabis sativa supercritical CO2 extraction using Design of experiments approach. in Book of Abstract / 19th European Meeting on Supercritical Fluids, Budapest, Hungary, 21-24 May 2023
Budapest : University of Technology and Economics., 135.
https://hdl.handle.net/21.15107/rcub_technorep_6984

Lukić I, Stamenić M, Tadić V, Skala D. Optimization of Cannabis sativa supercritical CO2 extraction using Design of experiments approach. in Book of Abstract / 19th European Meeting on Supercritical Fluids, Budapest, Hungary, 21-24 May 2023. 2023;:135.
https://hdl.handle.net/21.15107/rcub_technorep_6984 .

Lukić, Ivana, Stamenić, Marko, Tadić, Vanja, Skala, Dejan, "Optimization of Cannabis sativa supercritical CO2 extraction using Design of experiments approach" in Book of Abstract / 19th European Meeting on Supercritical Fluids, Budapest, Hungary, 21-24 May 2023 (2023):135,
https://hdl.handle.net/21.15107/rcub_technorep_6984 .

TY  - CONF
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6934
AB  - Biodiesel, a mixture of fatty acid methyl esters (FAME), is an excellent non-toxic, and biodegradable substitute for mineral diesel fuels produced from crude oil. It is made from renewable sources by transesterification of triglycerides with methanol, or by a reaction usually defined as methanolysis. Usage of low-quality feedstock, such as waste cooking oil (WCO), is challenging due to the undesirable side reactions as a result of the presence of free fatty acids (FFA), and water, thus a pretreatment stage before subjecting it to the transesterification process is usually required. In the present study, a two-step approach based on an adsorptive pretreatment with quicklime in order to remove FFA from WCO, followed by methanolysis using CaO∙ZnO as a heterogeneous catalyst was proposed. The first step was analyzed with the goal to define the optimal temperature of adsorption, the adsorbent particle size, calcination procedure, as well as the necessary amount of quicklime used. The analysis of adsorption kinetics was performed using pseudo-first and pseudo-second order kinetic models, and the efficiency of quicklime in the FFA removal from the WCO was also determined. The results showed that FFA from WCO could be successfully removed using quicklime as adsorbent at 30 °C for 1 h, with a removal efficiency of 72% and an adsorption capacity of 910 mg/g. The amount of Ca2+ ion present in the oil after the pretreatment was determined to be 12.64 mg/kg, showing that a very small amount of calcium from CaO was dissolved in treated WCO. The FTIR analysis of quicklime after the adsorption of FFA confirmed the interaction of the carboxyl group in FFA with the active site of the adsorbent. Adsorptive pretreatment had a positive effect on the rate of transesterification reaction with CaO∙ZnO as a catalyst, enabling the achievement of over 96% of FAME yield in only 15 min at 60 °C. The present study showed that quicklime, being cheap, available, and efficient, has considerable potential for the removal of FFA from the WCO. Besides, both the adsorption and the heterogeneously catalyzed methanolysis are environmentally and economically acceptable processes.
PB  - Valladolid : The lnstitute of Bioeconomy of University of Valladolid
C3  - Book of abstracts / 2nd Greenering International Conference, 21–23th March 2023, Valladolid, Spain
T1  - Adsorptive pretreatment of waste cooking oil using quicklime for two-step biodiesel production
UR  - https://hdl.handle.net/21.15107/rcub_technorep_6934
ER  - 

@conference{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2023",
abstract = "Biodiesel, a mixture of fatty acid methyl esters (FAME), is an excellent non-toxic, and biodegradable substitute for mineral diesel fuels produced from crude oil. It is made from renewable sources by transesterification of triglycerides with methanol, or by a reaction usually defined as methanolysis. Usage of low-quality feedstock, such as waste cooking oil (WCO), is challenging due to the undesirable side reactions as a result of the presence of free fatty acids (FFA), and water, thus a pretreatment stage before subjecting it to the transesterification process is usually required. In the present study, a two-step approach based on an adsorptive pretreatment with quicklime in order to remove FFA from WCO, followed by methanolysis using CaO∙ZnO as a heterogeneous catalyst was proposed. The first step was analyzed with the goal to define the optimal temperature of adsorption, the adsorbent particle size, calcination procedure, as well as the necessary amount of quicklime used. The analysis of adsorption kinetics was performed using pseudo-first and pseudo-second order kinetic models, and the efficiency of quicklime in the FFA removal from the WCO was also determined. The results showed that FFA from WCO could be successfully removed using quicklime as adsorbent at 30 °C for 1 h, with a removal efficiency of 72% and an adsorption capacity of 910 mg/g. The amount of Ca2+ ion present in the oil after the pretreatment was determined to be 12.64 mg/kg, showing that a very small amount of calcium from CaO was dissolved in treated WCO. The FTIR analysis of quicklime after the adsorption of FFA confirmed the interaction of the carboxyl group in FFA with the active site of the adsorbent. Adsorptive pretreatment had a positive effect on the rate of transesterification reaction with CaO∙ZnO as a catalyst, enabling the achievement of over 96% of FAME yield in only 15 min at 60 °C. The present study showed that quicklime, being cheap, available, and efficient, has considerable potential for the removal of FFA from the WCO. Besides, both the adsorption and the heterogeneously catalyzed methanolysis are environmentally and economically acceptable processes.",
publisher = "Valladolid : The lnstitute of Bioeconomy of University of Valladolid",
journal = "Book of abstracts / 2nd Greenering International Conference, 21–23th March 2023, Valladolid, Spain",
title = "Adsorptive pretreatment of waste cooking oil using quicklime for two-step biodiesel production",
url = "https://hdl.handle.net/21.15107/rcub_technorep_6934"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2023). Adsorptive pretreatment of waste cooking oil using quicklime for two-step biodiesel production. in Book of abstracts / 2nd Greenering International Conference, 21–23th March 2023, Valladolid, Spain
Valladolid : The lnstitute of Bioeconomy of University of Valladolid..
https://hdl.handle.net/21.15107/rcub_technorep_6934

Lukić I, Kesić Ž, Zdujić M, Skala D. Adsorptive pretreatment of waste cooking oil using quicklime for two-step biodiesel production. in Book of abstracts / 2nd Greenering International Conference, 21–23th March 2023, Valladolid, Spain. 2023;.
https://hdl.handle.net/21.15107/rcub_technorep_6934 .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Adsorptive pretreatment of waste cooking oil using quicklime for two-step biodiesel production" in Book of abstracts / 2nd Greenering International Conference, 21–23th March 2023, Valladolid, Spain (2023),
https://hdl.handle.net/21.15107/rcub_technorep_6934 .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2023
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6569
AB  - Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. The presence of FFA in WCO usually requires a pretreatment stage before subjecting it to methanolysis. In the present work, heterogeneously catalyzed methanolysis of WCO with and without pretreatment was investigated. Removal of FFA from WCO was conducted by using only quicklime or with the addition of a small amount of methanol (FFA to methanol = 1:3 molar ratio). The obtained results showed that pretreatment of WCO with quicklime at 30 °C after 1 h reduces the FFA content by 72 %, while the adsorption capacity was determined to be 910 mg g-1. The adsorptive pretreatment, as a simple operation, using low-cost quicklime under mild conditions, had a positive effect on the transesterification rate with CaO∙ZnO as a catalyst, enabling the achievement of over 96 % of biodiesel yield in only 15 min, compared to 1 h without the pretreatment. Furthermore, pretreated WCO allows an increase in repeated catalyst use and overall savings in the necessary amount of catalyst. The present study showed that quicklime is an economic, environmental-friendly, and sustainable material for FFA removal from WCO.
PB  - Association of the Chemical Engineers of Serbia
T2  - Hemijska industrija
T1  - Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis
EP  - 84
IS  - 1
SP  - 69
VL  - 77
DO  - 10.2298/HEMIND220628005L
ER  - 

@article{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2023",
abstract = "Synthesis of biodiesel from various plant oils is realized by the transesterification of triglycerides with methanol or by a reaction usually defined as methanolysis. The usage of low-quality oils, such as waste cooking oil (WCO), is followed by undesirable side reactions as a result of the increased content of free fatty acids (FFA), and water. The presence of FFA in WCO usually requires a pretreatment stage before subjecting it to methanolysis. In the present work, heterogeneously catalyzed methanolysis of WCO with and without pretreatment was investigated. Removal of FFA from WCO was conducted by using only quicklime or with the addition of a small amount of methanol (FFA to methanol = 1:3 molar ratio). The obtained results showed that pretreatment of WCO with quicklime at 30 °C after 1 h reduces the FFA content by 72 %, while the adsorption capacity was determined to be 910 mg g-1. The adsorptive pretreatment, as a simple operation, using low-cost quicklime under mild conditions, had a positive effect on the transesterification rate with CaO∙ZnO as a catalyst, enabling the achievement of over 96 % of biodiesel yield in only 15 min, compared to 1 h without the pretreatment. Furthermore, pretreated WCO allows an increase in repeated catalyst use and overall savings in the necessary amount of catalyst. The present study showed that quicklime is an economic, environmental-friendly, and sustainable material for FFA removal from WCO.",
publisher = "Association of the Chemical Engineers of Serbia",
journal = "Hemijska industrija",
title = "Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis",
pages = "84-69",
number = "1",
volume = "77",
doi = "10.2298/HEMIND220628005L"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2023). Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis. in Hemijska industrija
Association of the Chemical Engineers of Serbia., 77(1), 69-84.
https://doi.org/10.2298/HEMIND220628005L

Lukić I, Kesić Ž, Zdujić M, Skala D. Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis. in Hemijska industrija. 2023;77(1):69-84.
doi:10.2298/HEMIND220628005L .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Adsorptive pretreatment of waste cooking oil using quicklime for fatty acid methyl esters synthesis" in Hemijska industrija, 77, no. 1 (2023):69-84,
https://doi.org/10.2298/HEMIND220628005L . .

TY  - CONF
AU  - Lukić, Ivana
AU  - Milovanović, Stoja
AU  - Stamenić, Marko
AU  - Tadić, Vanja
AU  - Skala, Dejan
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/6985
AB  - Cannabis sativa is one of the oldest plant cultures, which has been used for centuries as a source of textile fibres, for paper production, as well as a source of bioactive compounds used in medicine. Although being restrained for a long time, its high potential, coupled with the progress in legislation and/or legalization in some regions of the world, led to the significant increase of scientific research towards isolation of cannabinoids, primarily a non-psychotropic cannabidiol (CBD), over the past couple decades. 
Beside cannabinoids, found only in cannabis plants, Cannabis sativa is characterized by very complex chemical composition with almost 500 constituents, including terpenes, flavonoids, phenolic compounds and fatty acids [2]. The co-presence of these numerous molecules in preparations obtained from Cannabis sativa may lead to a greater biological activity due to  the “entourage” or synergistic effect [3]. CBD has attracted considerable interest due to its numerous therapeutic properties and pharmacological activities [1]. However, cannabinoids are characterized by a low solubility in aqueous media and, as a consequence, a relatively poor bioavailability. Therefore, improvement of their stability, shelf-life and bioavailability, by incorporation into biocompatible carriers is still a challenge. 
As an answer to this issue, integrated process of supercritical fluid extraction (SFE) from Cannabis sativa and supercritical solvent impregnation (SSI) of obtained extract into starch aerogel was tested. Starch gels were prepared starting from hydrogel formed from an aqueous solution of cornstarch (1:10 w/v). During replacement of water with acetone, by successive increase of its concentration until 100%, acetogel was formed and further subjected to drying using supercritical CO2 (scCO2) at 45 °C and 8-10 MPa to obtain aerogel. For comparison, a part of acetogel was dried in the oven at 60 °C to obtain xerogel. Textural properties and morphology of prepared materials were determined by N2 adsorption–desorption isotherms and scanning electron microscopy (SEM) analysis. Aerogel with highest specific surface area of 208.6 m2/g, obtained at 45 °C and 10 MPa, was further used for extract impregnation. Integrated SFE-SSI process was performed at 40 °C and 10 MPa, conditions determined as optimal in the process of SFE of Cannabis sativa taking into account the yield of the obtained extract based on the composition, primarily regarding the CBD content. The amounts of impregnated extracts were 2.6 and 15.3% for xerogel and aerogel, respectively. The presence of the extract on the surface of impregnated samples was confirmed by FTIR analysis. Release study showed controlled release of extracts in PBS solution.
C3  - 2nd International Conference on Aerogels for Biomedical and Environmental Applications (AERoGELS2022), 29 June–1 July 2022, Athens, Greece, 2022
T1  - Starch aerogels loaded with Cannabis sativa extract using integrated process of supercritical CO2 extraction and impregnation
SP  - P-28
UR  - https://hdl.handle.net/21.15107/rcub_technorep_6985
ER  - 

@conference{
author = "Lukić, Ivana and Milovanović, Stoja and Stamenić, Marko and Tadić, Vanja and Skala, Dejan",
year = "2022",
abstract = "Cannabis sativa is one of the oldest plant cultures, which has been used for centuries as a source of textile fibres, for paper production, as well as a source of bioactive compounds used in medicine. Although being restrained for a long time, its high potential, coupled with the progress in legislation and/or legalization in some regions of the world, led to the significant increase of scientific research towards isolation of cannabinoids, primarily a non-psychotropic cannabidiol (CBD), over the past couple decades. 
Beside cannabinoids, found only in cannabis plants, Cannabis sativa is characterized by very complex chemical composition with almost 500 constituents, including terpenes, flavonoids, phenolic compounds and fatty acids [2]. The co-presence of these numerous molecules in preparations obtained from Cannabis sativa may lead to a greater biological activity due to  the “entourage” or synergistic effect [3]. CBD has attracted considerable interest due to its numerous therapeutic properties and pharmacological activities [1]. However, cannabinoids are characterized by a low solubility in aqueous media and, as a consequence, a relatively poor bioavailability. Therefore, improvement of their stability, shelf-life and bioavailability, by incorporation into biocompatible carriers is still a challenge. 
As an answer to this issue, integrated process of supercritical fluid extraction (SFE) from Cannabis sativa and supercritical solvent impregnation (SSI) of obtained extract into starch aerogel was tested. Starch gels were prepared starting from hydrogel formed from an aqueous solution of cornstarch (1:10 w/v). During replacement of water with acetone, by successive increase of its concentration until 100%, acetogel was formed and further subjected to drying using supercritical CO2 (scCO2) at 45 °C and 8-10 MPa to obtain aerogel. For comparison, a part of acetogel was dried in the oven at 60 °C to obtain xerogel. Textural properties and morphology of prepared materials were determined by N2 adsorption–desorption isotherms and scanning electron microscopy (SEM) analysis. Aerogel with highest specific surface area of 208.6 m2/g, obtained at 45 °C and 10 MPa, was further used for extract impregnation. Integrated SFE-SSI process was performed at 40 °C and 10 MPa, conditions determined as optimal in the process of SFE of Cannabis sativa taking into account the yield of the obtained extract based on the composition, primarily regarding the CBD content. The amounts of impregnated extracts were 2.6 and 15.3% for xerogel and aerogel, respectively. The presence of the extract on the surface of impregnated samples was confirmed by FTIR analysis. Release study showed controlled release of extracts in PBS solution.",
journal = "2nd International Conference on Aerogels for Biomedical and Environmental Applications (AERoGELS2022), 29 June–1 July 2022, Athens, Greece, 2022",
title = "Starch aerogels loaded with Cannabis sativa extract using integrated process of supercritical CO2 extraction and impregnation",
pages = "P-28",
url = "https://hdl.handle.net/21.15107/rcub_technorep_6985"
}

Lukić, I., Milovanović, S., Stamenić, M., Tadić, V.,& Skala, D.. (2022). Starch aerogels loaded with Cannabis sativa extract using integrated process of supercritical CO2 extraction and impregnation. in 2nd International Conference on Aerogels for Biomedical and Environmental Applications (AERoGELS2022), 29 June–1 July 2022, Athens, Greece, 2022, P-28.
https://hdl.handle.net/21.15107/rcub_technorep_6985

Lukić I, Milovanović S, Stamenić M, Tadić V, Skala D. Starch aerogels loaded with Cannabis sativa extract using integrated process of supercritical CO2 extraction and impregnation. in 2nd International Conference on Aerogels for Biomedical and Environmental Applications (AERoGELS2022), 29 June–1 July 2022, Athens, Greece, 2022. 2022;:P-28.
https://hdl.handle.net/21.15107/rcub_technorep_6985 .

Lukić, Ivana, Milovanović, Stoja, Stamenić, Marko, Tadić, Vanja, Skala, Dejan, "Starch aerogels loaded with Cannabis sativa extract using integrated process of supercritical CO2 extraction and impregnation" in 2nd International Conference on Aerogels for Biomedical and Environmental Applications (AERoGELS2022), 29 June–1 July 2022, Athens, Greece, 2022 (2022):P-28,
https://hdl.handle.net/21.15107/rcub_technorep_6985 .

TY  - JOUR
AU  - Bogdanović, Aleksandra
AU  - Tadić, Vanja
AU  - Petrović, Slobodan
AU  - Skala, Dejan
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4543
AB  - Supercritical CO2 extraction was applied on fenugreek (Trigonella foenum-graecum L., Fabaceae) seeds with the aim to define optimal process conditions to obtain the maximal extract yields content of steroidal sapogenins. Central composite rotatable design (CCRD) combined with response surface methodology (RSM) was applied to determine optimal process conditions defined by the influence and interaction of pressure, temperature and time of extraction through consumption of SC CO2. Optimization experiments revealed that the pressure of 24.73 MPa, the temperature of 38.2 degrees C and the consumption of SC CO2 of 19.24 g/g(DM) were the best process conditions enabling the maximal yield of extract and gain of the highest content of sapogenins. The optimal values of pressure and temperature defined SC CO2 density of 885.47 kg/m(3), which provided the maximal yield of the extract with the highest content of steroidal sapogenins. The achieved yield of extract at these conditions was 0.073g/g(DM), with 0.774 mg/g(DM) diosgenin, 0.477 mg/g(DM) protodioscin, 0.713 mg/g(DM) sarsapogenin and 0.205 mg/g(DM) oleanolic and ursolic acid with a significant quantity of 2.475 mg/g(DM) in the obtained extract.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - Supercritical CO2 extraction of steroidal sapogenins from fenugreek (tngonella foenum-graecum l.) Seed
EP  - 182
IS  - 2
SP  - 171
VL  - 26
DO  - 10.2298/CICEQ191001036B
ER  - 

@article{
author = "Bogdanović, Aleksandra and Tadić, Vanja and Petrović, Slobodan and Skala, Dejan",
year = "2020",
abstract = "Supercritical CO2 extraction was applied on fenugreek (Trigonella foenum-graecum L., Fabaceae) seeds with the aim to define optimal process conditions to obtain the maximal extract yields content of steroidal sapogenins. Central composite rotatable design (CCRD) combined with response surface methodology (RSM) was applied to determine optimal process conditions defined by the influence and interaction of pressure, temperature and time of extraction through consumption of SC CO2. Optimization experiments revealed that the pressure of 24.73 MPa, the temperature of 38.2 degrees C and the consumption of SC CO2 of 19.24 g/g(DM) were the best process conditions enabling the maximal yield of extract and gain of the highest content of sapogenins. The optimal values of pressure and temperature defined SC CO2 density of 885.47 kg/m(3), which provided the maximal yield of the extract with the highest content of steroidal sapogenins. The achieved yield of extract at these conditions was 0.073g/g(DM), with 0.774 mg/g(DM) diosgenin, 0.477 mg/g(DM) protodioscin, 0.713 mg/g(DM) sarsapogenin and 0.205 mg/g(DM) oleanolic and ursolic acid with a significant quantity of 2.475 mg/g(DM) in the obtained extract.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "Supercritical CO2 extraction of steroidal sapogenins from fenugreek (tngonella foenum-graecum l.) Seed",
pages = "182-171",
number = "2",
volume = "26",
doi = "10.2298/CICEQ191001036B"
}

Bogdanović, A., Tadić, V., Petrović, S.,& Skala, D.. (2020). Supercritical CO2 extraction of steroidal sapogenins from fenugreek (tngonella foenum-graecum l.) Seed. in Chemical Industry & Chemical Engineering Quarterly
Savez hemijskih inženjera, Beograd., 26(2), 171-182.
https://doi.org/10.2298/CICEQ191001036B

Bogdanović A, Tadić V, Petrović S, Skala D. Supercritical CO2 extraction of steroidal sapogenins from fenugreek (tngonella foenum-graecum l.) Seed. in Chemical Industry & Chemical Engineering Quarterly. 2020;26(2):171-182.
doi:10.2298/CICEQ191001036B .

Bogdanović, Aleksandra, Tadić, Vanja, Petrović, Slobodan, Skala, Dejan, "Supercritical CO2 extraction of steroidal sapogenins from fenugreek (tngonella foenum-graecum l.) Seed" in Chemical Industry & Chemical Engineering Quarterly, 26, no. 2 (2020):171-182,
https://doi.org/10.2298/CICEQ191001036B . .

TY  - JOUR
AU  - Zdujić, Miodrag
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Janković-Častvan, Ivona
AU  - Marković, Smilja
AU  - Jovalekić, Čedomir
AU  - Skala, Dejan
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4261
AB  - The powder mixtures of calcium oxide (CaO) and silica gel (SiO2) in molar ratios of 1:1, 1.5:1, 2:1 and 3:1 were mechanochemically treated with the addition of water, and were subsequently calcined with a goal of synthesizing CaSiO3, Ca3Si2O7, Ca2SiO4 compounds and CaO/Ca2SiO4 two-phase mixture. The prepared materials were characterized by XRD, FTIR, SEM/EDS, particle size laser diffraction (PSLD), UV-vis diffuse reflectance spectroscopy (DRS), N-2 adsorption/desorption isotherms, Hammett indicator for basic strength and volumetric analysis for free CaO content. The catalytic activity of calcium silicates with different Ca/Si ratios was tested in the transesterification of triacylglycerols (sunflower oil) with methanol. Samples obtained with initial composition 2CaO center dot SiO2 and 3CaO center dot SiO2 calcined at 700 degrees C, and 3CaO center dot SiO2 calcined at 900 degrees C had high catalytic activity, resulting with triacylglycerols conversion and fatty acids methyl ester formation (FAME or biodiesel) above 96%. The activity of these samples can be attributed to the existence of free CaO defined by CaO/Ca2SiO4 complex mixture. The effect of different amount of catalyst used for transesterification (0.2-2 wt%) was analyzed using the most active catalyst i.e. 3CaO center dot SiO2 calcined at 700 degrees C as well as possibility of its reuse for biodiesel synthesis. It was also found that CaSiO3, Ca3Si2O7 and Ca2SiO4, phases did not possess catalytic activity.
PB  - Elsevier Science Bv, Amsterdam
T2  - Advanced Powder Technology
T1  - Synthesis of CaO-SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil
EP  - 1150
IS  - 6
SP  - 1141
VL  - 30
DO  - 10.1016/j.apt.2019.03.009
ER  - 

@article{
author = "Zdujić, Miodrag and Lukić, Ivana and Kesić, Željka and Janković-Častvan, Ivona and Marković, Smilja and Jovalekić, Čedomir and Skala, Dejan",
year = "2019",
abstract = "The powder mixtures of calcium oxide (CaO) and silica gel (SiO2) in molar ratios of 1:1, 1.5:1, 2:1 and 3:1 were mechanochemically treated with the addition of water, and were subsequently calcined with a goal of synthesizing CaSiO3, Ca3Si2O7, Ca2SiO4 compounds and CaO/Ca2SiO4 two-phase mixture. The prepared materials were characterized by XRD, FTIR, SEM/EDS, particle size laser diffraction (PSLD), UV-vis diffuse reflectance spectroscopy (DRS), N-2 adsorption/desorption isotherms, Hammett indicator for basic strength and volumetric analysis for free CaO content. The catalytic activity of calcium silicates with different Ca/Si ratios was tested in the transesterification of triacylglycerols (sunflower oil) with methanol. Samples obtained with initial composition 2CaO center dot SiO2 and 3CaO center dot SiO2 calcined at 700 degrees C, and 3CaO center dot SiO2 calcined at 900 degrees C had high catalytic activity, resulting with triacylglycerols conversion and fatty acids methyl ester formation (FAME or biodiesel) above 96%. The activity of these samples can be attributed to the existence of free CaO defined by CaO/Ca2SiO4 complex mixture. The effect of different amount of catalyst used for transesterification (0.2-2 wt%) was analyzed using the most active catalyst i.e. 3CaO center dot SiO2 calcined at 700 degrees C as well as possibility of its reuse for biodiesel synthesis. It was also found that CaSiO3, Ca3Si2O7 and Ca2SiO4, phases did not possess catalytic activity.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Advanced Powder Technology",
title = "Synthesis of CaO-SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil",
pages = "1150-1141",
number = "6",
volume = "30",
doi = "10.1016/j.apt.2019.03.009"
}

Zdujić, M., Lukić, I., Kesić, Ž., Janković-Častvan, I., Marković, S., Jovalekić, Č.,& Skala, D.. (2019). Synthesis of CaO-SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil. in Advanced Powder Technology
Elsevier Science Bv, Amsterdam., 30(6), 1141-1150.
https://doi.org/10.1016/j.apt.2019.03.009

Zdujić M, Lukić I, Kesić Ž, Janković-Častvan I, Marković S, Jovalekić Č, Skala D. Synthesis of CaO-SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil. in Advanced Powder Technology. 2019;30(6):1141-1150.
doi:10.1016/j.apt.2019.03.009 .

Zdujić, Miodrag, Lukić, Ivana, Kesić, Željka, Janković-Častvan, Ivona, Marković, Smilja, Jovalekić, Čedomir, Skala, Dejan, "Synthesis of CaO-SiO2 compounds and their testing as heterogeneous catalysts for transesterification of sunflower oil" in Advanced Powder Technology, 30, no. 6 (2019):1141-1150,
https://doi.org/10.1016/j.apt.2019.03.009 . .

TY  - JOUR
AU  - Liu, Hui
AU  - Lukić, Ivana
AU  - Miladinović, Marija R.
AU  - Veljković, Vlada B.
AU  - Zdujić, Miodrag
AU  - Zhu, Xiaosun
AU  - Zhang, Yanan
AU  - Skala, Dejan
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4016
AB  - The continuous biodiesel production from soybean oil was carried out under the subcritical condition of methanol with MnCO3/Na-silicate as a heterogeneous catalyst. The transesterification rate was first investigated in a set of experiments performed in a batch autoclave at 448 K using methanol-to-oil molar ratio of 18:1 and various catalyst loadings (5, 10 and 20 wt% based on the oil mass). The results from these experiments, as well as the experimental data and the appropriate kinetic model recently reported in the literature were used for designing a packed bed tubular reactor (PBTR), a main unit of the pilot plant with the capacity of 100 L of biodiesel per day. The pilot plant was constructed and tested under various operating conditions. The first 11 h of the pilot-plant operation was realized in the tubular reactor packed with inert glass beads (i.e. without the catalyst) in order to analyze the effect of the non-catalyzed subcritical biodiesel (fatty acid methyl esters, FAME) production. Then, glass beads were replaced with a mix of MnCO3/Na-silicate catalyst particles and glass beads, and the catalytic biodiesel production was continuously run under the subcritical methanol condition for 85 h. Two mass balance tests during the continuous pilot plant operation were performed.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Energy Conversion and Management
T1  - Continuous biodiesel production under subcritical condition of methanol - Design of pilot plant and packed bed reactor with MnCO3/Na-silicate catalyst
EP  - 504
SP  - 494
VL  - 168
DO  - 10.1016/j.enconman.2018.05.028
ER  - 

@article{
author = "Liu, Hui and Lukić, Ivana and Miladinović, Marija R. and Veljković, Vlada B. and Zdujić, Miodrag and Zhu, Xiaosun and Zhang, Yanan and Skala, Dejan",
year = "2018",
abstract = "The continuous biodiesel production from soybean oil was carried out under the subcritical condition of methanol with MnCO3/Na-silicate as a heterogeneous catalyst. The transesterification rate was first investigated in a set of experiments performed in a batch autoclave at 448 K using methanol-to-oil molar ratio of 18:1 and various catalyst loadings (5, 10 and 20 wt% based on the oil mass). The results from these experiments, as well as the experimental data and the appropriate kinetic model recently reported in the literature were used for designing a packed bed tubular reactor (PBTR), a main unit of the pilot plant with the capacity of 100 L of biodiesel per day. The pilot plant was constructed and tested under various operating conditions. The first 11 h of the pilot-plant operation was realized in the tubular reactor packed with inert glass beads (i.e. without the catalyst) in order to analyze the effect of the non-catalyzed subcritical biodiesel (fatty acid methyl esters, FAME) production. Then, glass beads were replaced with a mix of MnCO3/Na-silicate catalyst particles and glass beads, and the catalytic biodiesel production was continuously run under the subcritical methanol condition for 85 h. Two mass balance tests during the continuous pilot plant operation were performed.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Energy Conversion and Management",
title = "Continuous biodiesel production under subcritical condition of methanol - Design of pilot plant and packed bed reactor with MnCO3/Na-silicate catalyst",
pages = "504-494",
volume = "168",
doi = "10.1016/j.enconman.2018.05.028"
}

Liu, H., Lukić, I., Miladinović, M. R., Veljković, V. B., Zdujić, M., Zhu, X., Zhang, Y.,& Skala, D.. (2018). Continuous biodiesel production under subcritical condition of methanol - Design of pilot plant and packed bed reactor with MnCO3/Na-silicate catalyst. in Energy Conversion and Management
Pergamon-Elsevier Science Ltd, Oxford., 168, 494-504.
https://doi.org/10.1016/j.enconman.2018.05.028

Liu H, Lukić I, Miladinović MR, Veljković VB, Zdujić M, Zhu X, Zhang Y, Skala D. Continuous biodiesel production under subcritical condition of methanol - Design of pilot plant and packed bed reactor with MnCO3/Na-silicate catalyst. in Energy Conversion and Management. 2018;168:494-504.
doi:10.1016/j.enconman.2018.05.028 .

Liu, Hui, Lukić, Ivana, Miladinović, Marija R., Veljković, Vlada B., Zdujić, Miodrag, Zhu, Xiaosun, Zhang, Yanan, Skala, Dejan, "Continuous biodiesel production under subcritical condition of methanol - Design of pilot plant and packed bed reactor with MnCO3/Na-silicate catalyst" in Energy Conversion and Management, 168 (2018):494-504,
https://doi.org/10.1016/j.enconman.2018.05.028 . .

TY  - JOUR
AU  - Zhang, Yanan
AU  - Liu, Hui
AU  - Zhu, Xiaochan
AU  - Lukić, Ivana
AU  - Zdujić, Miodrag
AU  - Shen, Xiang
AU  - Skala, Dejan
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4023
AB  - The MnCO3/Na silicate (Mn/Na/Si mole ratio of 4.65:1:1.65) catalyst in the form of solid particles with diameter of 0.99-1.99 mm was used as a catalyst for transesterification of soybean oil in batch autoclave at different conditions: 388-468 K, methanol-to-oil mole ratio 12:1-30:1, catalyst amount based on the mass of oil 0-12.5 %. The complete triacylglycerols (TAG) conversion and high yield of fatty acid methyl ester (FAME) was obtained after 1 h at 458 K, methanol-to-oil mole ratio 30:1 and 10 % of catalyst. Kinetics of transesterification process was analyzed by three models: the simple first order irreversible reaction rate, as well as two more complex models recently reported in literature. The catalyst reuse in transesterification process was tested and the average values of 99.0 % of TAG conversion and 97.5 % of FAME yield were obtained after 8 consecutive runs. Different techniques were used to characterize fresh and used MnCO3/Na silicate catalyst. The determined amounts of leached Na ( lt 500 ppm) and Mn ( lt 20 ppm) in biodiesel phase implied that the homogeneous-heterogeneous process influences the catalyst selectivity, whereby leached Na enables the complete transformation of TAG to FAME.
PB  - Srpsko hemijsko društvo, Beograd
T2  - Journal of the Serbian Chemical Society
T1  - Biodiesel synthesis and kinetic analysis based on MnCO3/Na silicate as heterogeneous catalyst
EP  - 365
IS  - 3
SP  - 345
VL  - 83
DO  - 10.2298/JSC170612005Z
ER  - 

@article{
author = "Zhang, Yanan and Liu, Hui and Zhu, Xiaochan and Lukić, Ivana and Zdujić, Miodrag and Shen, Xiang and Skala, Dejan",
year = "2018",
abstract = "The MnCO3/Na silicate (Mn/Na/Si mole ratio of 4.65:1:1.65) catalyst in the form of solid particles with diameter of 0.99-1.99 mm was used as a catalyst for transesterification of soybean oil in batch autoclave at different conditions: 388-468 K, methanol-to-oil mole ratio 12:1-30:1, catalyst amount based on the mass of oil 0-12.5 %. The complete triacylglycerols (TAG) conversion and high yield of fatty acid methyl ester (FAME) was obtained after 1 h at 458 K, methanol-to-oil mole ratio 30:1 and 10 % of catalyst. Kinetics of transesterification process was analyzed by three models: the simple first order irreversible reaction rate, as well as two more complex models recently reported in literature. The catalyst reuse in transesterification process was tested and the average values of 99.0 % of TAG conversion and 97.5 % of FAME yield were obtained after 8 consecutive runs. Different techniques were used to characterize fresh and used MnCO3/Na silicate catalyst. The determined amounts of leached Na ( lt 500 ppm) and Mn ( lt 20 ppm) in biodiesel phase implied that the homogeneous-heterogeneous process influences the catalyst selectivity, whereby leached Na enables the complete transformation of TAG to FAME.",
publisher = "Srpsko hemijsko društvo, Beograd",
journal = "Journal of the Serbian Chemical Society",
title = "Biodiesel synthesis and kinetic analysis based on MnCO3/Na silicate as heterogeneous catalyst",
pages = "365-345",
number = "3",
volume = "83",
doi = "10.2298/JSC170612005Z"
}

Zhang, Y., Liu, H., Zhu, X., Lukić, I., Zdujić, M., Shen, X.,& Skala, D.. (2018). Biodiesel synthesis and kinetic analysis based on MnCO3/Na silicate as heterogeneous catalyst. in Journal of the Serbian Chemical Society
Srpsko hemijsko društvo, Beograd., 83(3), 345-365.
https://doi.org/10.2298/JSC170612005Z

Zhang Y, Liu H, Zhu X, Lukić I, Zdujić M, Shen X, Skala D. Biodiesel synthesis and kinetic analysis based on MnCO3/Na silicate as heterogeneous catalyst. in Journal of the Serbian Chemical Society. 2018;83(3):345-365.
doi:10.2298/JSC170612005Z .

Zhang, Yanan, Liu, Hui, Zhu, Xiaochan, Lukić, Ivana, Zdujić, Miodrag, Shen, Xiang, Skala, Dejan, "Biodiesel synthesis and kinetic analysis based on MnCO3/Na silicate as heterogeneous catalyst" in Journal of the Serbian Chemical Society, 83, no. 3 (2018):345-365,
https://doi.org/10.2298/JSC170612005Z . .

TY  - JOUR
AU  - Wan, Liang
AU  - Liu, Hui
AU  - Nasreen, Sadia
AU  - Lukić, Ivana
AU  - Skala, Dejan
PY  - 2018
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4036
AB  - The manganese carbonate catalyst, prepared by precipitation method, was used in transesterification of soybean oil under subcritical condition of methanol. Catalyst samples were characterized by X-ray diffraction (XRD), Fourier trans-form infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The triacylglycerol (TAG) conversion and fatty acid methyl esters (FAME) yield were determined using high performance liquid chromatography (HPLC). The transesterification was realized for 1 h using various working conditions: 0-3 wt.% of catalyst (based on the mass of oil), the mole ratio of methanol to oil from 13:1 to 27:1 and temperature ranging from 393 to 473 K. A maximum TAG conversion of 98.1% could be obtained at the optimal reaction conditions: 2 wt.% of catalyst, methanol/oil mole ratio of 21:1, for 1 h in a batch reactor at 453 K. Kinetic analysis showed that the model based on mass transfer and chemical reaction at the catalyst surface confirmed the experimental data. Using that kinetic expression, the effect of continuous transesterification was proposed and verified by a 360-h long realized experiment in a laboratory packed-bed reactor (PBR). Slow deactivation of the catalyst was caused by leaching of Mn in both biodiesel and glycerol phases and by blocking the active sites of the catalyst with organic compounds.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst
EP  - 22
IS  - 1
SP  - 9
VL  - 24
DO  - 10.2298/CICEQ170221013W
ER  - 

@article{
author = "Wan, Liang and Liu, Hui and Nasreen, Sadia and Lukić, Ivana and Skala, Dejan",
year = "2018",
abstract = "The manganese carbonate catalyst, prepared by precipitation method, was used in transesterification of soybean oil under subcritical condition of methanol. Catalyst samples were characterized by X-ray diffraction (XRD), Fourier trans-form infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The triacylglycerol (TAG) conversion and fatty acid methyl esters (FAME) yield were determined using high performance liquid chromatography (HPLC). The transesterification was realized for 1 h using various working conditions: 0-3 wt.% of catalyst (based on the mass of oil), the mole ratio of methanol to oil from 13:1 to 27:1 and temperature ranging from 393 to 473 K. A maximum TAG conversion of 98.1% could be obtained at the optimal reaction conditions: 2 wt.% of catalyst, methanol/oil mole ratio of 21:1, for 1 h in a batch reactor at 453 K. Kinetic analysis showed that the model based on mass transfer and chemical reaction at the catalyst surface confirmed the experimental data. Using that kinetic expression, the effect of continuous transesterification was proposed and verified by a 360-h long realized experiment in a laboratory packed-bed reactor (PBR). Slow deactivation of the catalyst was caused by leaching of Mn in both biodiesel and glycerol phases and by blocking the active sites of the catalyst with organic compounds.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst",
pages = "22-9",
number = "1",
volume = "24",
doi = "10.2298/CICEQ170221013W"
}

Wan, L., Liu, H., Nasreen, S., Lukić, I.,& Skala, D.. (2018). High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst. in Chemical Industry & Chemical Engineering Quarterly
Savez hemijskih inženjera, Beograd., 24(1), 9-22.
https://doi.org/10.2298/CICEQ170221013W

Wan L, Liu H, Nasreen S, Lukić I, Skala D. High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst. in Chemical Industry & Chemical Engineering Quarterly. 2018;24(1):9-22.
doi:10.2298/CICEQ170221013W .

Wan, Liang, Liu, Hui, Nasreen, Sadia, Lukić, Ivana, Skala, Dejan, "High temperature transesterification of soybean oil with methanol using manganese carbonate as catalyst" in Chemical Industry & Chemical Engineering Quarterly, 24, no. 1 (2018):9-22,
https://doi.org/10.2298/CICEQ170221013W . .

TY  - JOUR
AU  - Maksimović, Svetolik
AU  - Tadić, Vanja
AU  - Skala, Dejan
AU  - Žižović, Irena
PY  - 2017
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3757
AB  - Helichrysum italicum presents a valuable source of natural bioactive compounds. In this work, a literature review of terpenes, phenolic compounds, and other less common phytochemicals from H. italicum with regard to application of different separation methods is presented. Data including extraction/separation methods and experimental conditions applied, obtained yields, number of identified compounds, content of different compound groups, and analytical techniques applied are shown as corresponding tables. Numerous biological activities of both isolates and individual compounds are emphasized. In addition, the data reported are discussed, and the directions for further investigations are proposed.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Phytochemistry
T1  - Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts
EP  - 28
SP  - 9
VL  - 138
DO  - 10.1016/j.phytochem.2017.01.001
ER  - 

@article{
author = "Maksimović, Svetolik and Tadić, Vanja and Skala, Dejan and Žižović, Irena",
year = "2017",
abstract = "Helichrysum italicum presents a valuable source of natural bioactive compounds. In this work, a literature review of terpenes, phenolic compounds, and other less common phytochemicals from H. italicum with regard to application of different separation methods is presented. Data including extraction/separation methods and experimental conditions applied, obtained yields, number of identified compounds, content of different compound groups, and analytical techniques applied are shown as corresponding tables. Numerous biological activities of both isolates and individual compounds are emphasized. In addition, the data reported are discussed, and the directions for further investigations are proposed.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Phytochemistry",
title = "Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts",
pages = "28-9",
volume = "138",
doi = "10.1016/j.phytochem.2017.01.001"
}

Maksimović, S., Tadić, V., Skala, D.,& Žižović, I.. (2017). Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts. in Phytochemistry
Pergamon-Elsevier Science Ltd, Oxford., 138, 9-28.
https://doi.org/10.1016/j.phytochem.2017.01.001

Maksimović S, Tadić V, Skala D, Žižović I. Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts. in Phytochemistry. 2017;138:9-28.
doi:10.1016/j.phytochem.2017.01.001 .

Maksimović, Svetolik, Tadić, Vanja, Skala, Dejan, Žižović, Irena, "Separation of phytochemicals from Helichrysum italicum: An analysis of different isolation techniques and biological activity of prepared extracts" in Phytochemistry, 138 (2017):9-28,
https://doi.org/10.1016/j.phytochem.2017.01.001 . .

TY  - CHAP
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3160
AB  - Increased environmental concern and awareness of limited reserves of fossil fuels gave a great importance to alternative and renewable energy sources over the past couple decades. An excellent substitute for mineral diesel fuels is biodiesel, a mixture of fatty acid methyl esters (FAME), made by alcoholysis of different triacylglycerols (TAG) from various renewable sources (vegetable oils or animal fats) in the presence of a homogeneous or heterogeneous catalyst. Drawbacks of homogeneously catalyzed alcoholysis, to-day the most commonly used commercial biodiesel production process, have shifted the research focus on technologies based on utilization of solid catalyst. Heterogeneously catalyzed alcoholysis is more environmentally friendly, offers simplified production and improved process efficiency, allowing the possibility of catalyst’s regeneration, too. This technology of biodiesel synthesis is also the base for the continuous process development. Although great attention has been paid to the development of a catalyst that will have good activity and stability, followed by cheap method of synthesis, this task is still a challenge and needs further intensive research. Solid base catalysts have been characterized by high activity under mild reaction conditions and short reaction times, however, due to their sensitivity to the presence of impurities in the oil, primary the presence of free fatty acids (FFA) and water, they were not suitable, according to results of many investigations, for transesterification of lower-cost feedstock, such as non-edible plant oils and the waste cooking oils. For these feedstocks heterogeneous biodiesel synthesis should be performed applying solid acid catalyst. Despite the generally lower activity compared to solid base catalysts and higher reaction temperatures required for transesterification of oils into biodiesel, the main advantage of solid acids is their ability to simultaneously carry out esterification of FFA and transesterification of TAG. It is the main reason why application of solid acids for biodiesel production became a growing field of research during the last few years. In the present chapter, a comprehensive review of different solid acids used for biodiesel synthesis is presented. The method of catalyst preparation, type of precursor and employed calcination temperature greatly affect the acid catalyst activity and its final properties. The concentration of catalytic sites along with other characteristics, like surface area and catalyst porosity, are of great importance for catalytic activity of solid acids. The solid acids synthesis procedures and main catalyst’s characteristics are also analyzed in details, as well as the activity of solid acid catalysts in transesterification of different feedstock, with the emphasis on the lower-quality materials with high FFA content. One of the problems associated with heterogeneous catalysts is their deactivation with time due to poisoning, sintering or leaching of the active components, thus the attention in this review is also devoted to this issue. Furthermore, the transesterification process kinetics, being fundamental to reactor design and optimization of operational conditions in order to achieve maximum yield and lower cost of the process, is discussed.
T2  - Heterogeneous Catalysts: Design, Applications and Research Insights
T1  - Solid acids as catalysts for biodiesel synthesis
EP  - 136
SP  - 21
UR  - https://hdl.handle.net/21.15107/rcub_technorep_3160
ER  - 

@inbook{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2016",
abstract = "Increased environmental concern and awareness of limited reserves of fossil fuels gave a great importance to alternative and renewable energy sources over the past couple decades. An excellent substitute for mineral diesel fuels is biodiesel, a mixture of fatty acid methyl esters (FAME), made by alcoholysis of different triacylglycerols (TAG) from various renewable sources (vegetable oils or animal fats) in the presence of a homogeneous or heterogeneous catalyst. Drawbacks of homogeneously catalyzed alcoholysis, to-day the most commonly used commercial biodiesel production process, have shifted the research focus on technologies based on utilization of solid catalyst. Heterogeneously catalyzed alcoholysis is more environmentally friendly, offers simplified production and improved process efficiency, allowing the possibility of catalyst’s regeneration, too. This technology of biodiesel synthesis is also the base for the continuous process development. Although great attention has been paid to the development of a catalyst that will have good activity and stability, followed by cheap method of synthesis, this task is still a challenge and needs further intensive research. Solid base catalysts have been characterized by high activity under mild reaction conditions and short reaction times, however, due to their sensitivity to the presence of impurities in the oil, primary the presence of free fatty acids (FFA) and water, they were not suitable, according to results of many investigations, for transesterification of lower-cost feedstock, such as non-edible plant oils and the waste cooking oils. For these feedstocks heterogeneous biodiesel synthesis should be performed applying solid acid catalyst. Despite the generally lower activity compared to solid base catalysts and higher reaction temperatures required for transesterification of oils into biodiesel, the main advantage of solid acids is their ability to simultaneously carry out esterification of FFA and transesterification of TAG. It is the main reason why application of solid acids for biodiesel production became a growing field of research during the last few years. In the present chapter, a comprehensive review of different solid acids used for biodiesel synthesis is presented. The method of catalyst preparation, type of precursor and employed calcination temperature greatly affect the acid catalyst activity and its final properties. The concentration of catalytic sites along with other characteristics, like surface area and catalyst porosity, are of great importance for catalytic activity of solid acids. The solid acids synthesis procedures and main catalyst’s characteristics are also analyzed in details, as well as the activity of solid acid catalysts in transesterification of different feedstock, with the emphasis on the lower-quality materials with high FFA content. One of the problems associated with heterogeneous catalysts is their deactivation with time due to poisoning, sintering or leaching of the active components, thus the attention in this review is also devoted to this issue. Furthermore, the transesterification process kinetics, being fundamental to reactor design and optimization of operational conditions in order to achieve maximum yield and lower cost of the process, is discussed.",
journal = "Heterogeneous Catalysts: Design, Applications and Research Insights",
booktitle = "Solid acids as catalysts for biodiesel synthesis",
pages = "136-21",
url = "https://hdl.handle.net/21.15107/rcub_technorep_3160"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2016). Solid acids as catalysts for biodiesel synthesis. in Heterogeneous Catalysts: Design, Applications and Research Insights, 21-136.
https://hdl.handle.net/21.15107/rcub_technorep_3160

Lukić I, Kesić Ž, Zdujić M, Skala D. Solid acids as catalysts for biodiesel synthesis. in Heterogeneous Catalysts: Design, Applications and Research Insights. 2016;:21-136.
https://hdl.handle.net/21.15107/rcub_technorep_3160 .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Solid acids as catalysts for biodiesel synthesis" in Heterogeneous Catalysts: Design, Applications and Research Insights (2016):21-136,
https://hdl.handle.net/21.15107/rcub_technorep_3160 .

TY  - CHAP
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3173
AB  - Limited reserves of fossil fuels as well as the growing concern for the environment, has led to a worldwide search for renewable energy sources, among which biodiesel, a mixture of fatty acid methyl esters (FAME), is one of the most perspective alternative fuels since it is a non-toxic and can be produced from different renewable sources through simple cost-effective alcoholysis, while being compatible with existing infrastructures. Vegetable oils, as renewable in nature and environmentally friendly, with a possibility to be produced on a large scale, represent a promising feedstock for biodiesel production. In this chapter, a comprehensive review of different vegetable oils as a feedstock for biodiesel synthesis is reported, including edible and non-edible oils, as well as waste vegetable oils. Selection of feedstock for biodiesel production mainly depends on the specific conditions and circumstances in some region (climate, presence of certain crops, the economic development of a country, etc.). Various fatty acid compositions of triacylglycerols directly determine the quality and fulfillment of the standards of biodiesel. One of the crucial points which determine technology route for biodiesel synthesis is content of free fatty acids (FFA) which might be present in vegetable oils, as well as the presence of water and other compounds. Also, many analysis performed in the past have shown that the production cost of biodiesel is mainly determined by the price of used feedstock, which represents 70-80% of total production costs of biodiesel. Currently more than 95% of feedstock comes from edible oils since they are easily accessible, consists mainly of triacylglycerols, whereby the properties of biodiesel produced from these oils are suitable to be used as diesel fuel substitute. Most commonly used edible oils for biodiesel production are rapeseed, soybean, sunflower and palm. However, for economic and social reasons, in recent years research and development of biodiesel production has focused on other sources of triacylglycerols, in order to replace edible oils by lower-cost non-edible plant oils and the waste cooking oils, feedstocks that are unsuitable for human consumption. Properties of different oils and biodiesel obtained from them as well as the technologies suitable for biodiesel synthesis are compared in this chapter. The wellknown fact is that the conventional and to-day widely applied homogeneous method of biodiesel synthesis is sensitive to the presence of impurities in the oil, primarily the presence of FFA and water. Furthermore, biodiesel synthesis is followed by creation of large amount of wastewater produced during neutralization of catalyst and purification of final product. The drawbacks of a homogeneous process can be avoided by applying technologies based on utilization of heterogeneous catalyst or by application of the noncatalytic supercritical process of biodiesel synthesis. These technologies for biodiesel production were also analyzed and compared.
T2  - Vegetable Oil: Properties, Uses and Benefits
T1  - Vegetable oil as a feedstock for biodiesel synthesis
EP  - 128
SP  - 83
UR  - https://hdl.handle.net/21.15107/rcub_technorep_3173
ER  - 

@inbook{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2016",
abstract = "Limited reserves of fossil fuels as well as the growing concern for the environment, has led to a worldwide search for renewable energy sources, among which biodiesel, a mixture of fatty acid methyl esters (FAME), is one of the most perspective alternative fuels since it is a non-toxic and can be produced from different renewable sources through simple cost-effective alcoholysis, while being compatible with existing infrastructures. Vegetable oils, as renewable in nature and environmentally friendly, with a possibility to be produced on a large scale, represent a promising feedstock for biodiesel production. In this chapter, a comprehensive review of different vegetable oils as a feedstock for biodiesel synthesis is reported, including edible and non-edible oils, as well as waste vegetable oils. Selection of feedstock for biodiesel production mainly depends on the specific conditions and circumstances in some region (climate, presence of certain crops, the economic development of a country, etc.). Various fatty acid compositions of triacylglycerols directly determine the quality and fulfillment of the standards of biodiesel. One of the crucial points which determine technology route for biodiesel synthesis is content of free fatty acids (FFA) which might be present in vegetable oils, as well as the presence of water and other compounds. Also, many analysis performed in the past have shown that the production cost of biodiesel is mainly determined by the price of used feedstock, which represents 70-80% of total production costs of biodiesel. Currently more than 95% of feedstock comes from edible oils since they are easily accessible, consists mainly of triacylglycerols, whereby the properties of biodiesel produced from these oils are suitable to be used as diesel fuel substitute. Most commonly used edible oils for biodiesel production are rapeseed, soybean, sunflower and palm. However, for economic and social reasons, in recent years research and development of biodiesel production has focused on other sources of triacylglycerols, in order to replace edible oils by lower-cost non-edible plant oils and the waste cooking oils, feedstocks that are unsuitable for human consumption. Properties of different oils and biodiesel obtained from them as well as the technologies suitable for biodiesel synthesis are compared in this chapter. The wellknown fact is that the conventional and to-day widely applied homogeneous method of biodiesel synthesis is sensitive to the presence of impurities in the oil, primarily the presence of FFA and water. Furthermore, biodiesel synthesis is followed by creation of large amount of wastewater produced during neutralization of catalyst and purification of final product. The drawbacks of a homogeneous process can be avoided by applying technologies based on utilization of heterogeneous catalyst or by application of the noncatalytic supercritical process of biodiesel synthesis. These technologies for biodiesel production were also analyzed and compared.",
journal = "Vegetable Oil: Properties, Uses and Benefits",
booktitle = "Vegetable oil as a feedstock for biodiesel synthesis",
pages = "128-83",
url = "https://hdl.handle.net/21.15107/rcub_technorep_3173"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2016). Vegetable oil as a feedstock for biodiesel synthesis. in Vegetable Oil: Properties, Uses and Benefits, 83-128.
https://hdl.handle.net/21.15107/rcub_technorep_3173

Lukić I, Kesić Ž, Zdujić M, Skala D. Vegetable oil as a feedstock for biodiesel synthesis. in Vegetable Oil: Properties, Uses and Benefits. 2016;:83-128.
https://hdl.handle.net/21.15107/rcub_technorep_3173 .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Vegetable oil as a feedstock for biodiesel synthesis" in Vegetable Oil: Properties, Uses and Benefits (2016):83-128,
https://hdl.handle.net/21.15107/rcub_technorep_3173 .

TY  - JOUR
AU  - Kesić, Željka
AU  - Lukić, Ivana
AU  - Zdujić, Miodrag
AU  - Mojović, Ljiljana
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3380
AB  - Vegetable oils are mainly esters of fatty acids and glycerol, which can be converted to fatty acid methyl esters (FAME), also known as biodiesel, by the transesterification reaction with methanol. In order to attain environmental benignity, much attention has been focused in the last decades on utilizing heterogeneous catalysts for biodiesel production instead the homogenously catalyzed transesterification of vegetable oil. The pure CaO or CaO mixed with some other metal oxide due to its low solubility in methanol, FAME and glycerol, low cost and availability, is one of the most promising among the proposed heterogeneous catalysts. Solid catalysts containing CaO usually fulfill a number of important requirements, such as high activity at mild temperature, marginal leaching of Ca cations, long life activity, reusability in transesterification of vegetable oil and easy recovery from the final products of trancesterification (FAME and glycerol). This review is focused on the recent application of pure CaO or CaO in complex catalyst structure and their use as heterogeneous base catalysts for biodiesel synthesis and suitability for industrial application.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - Calcium oxide based catalysts for biodiesel production: a review
EP  - 408
IS  - 4
SP  - 391
VL  - 22
DO  - 10.2298/CICEQ160203010K
ER  - 

@article{
author = "Kesić, Željka and Lukić, Ivana and Zdujić, Miodrag and Mojović, Ljiljana and Skala, Dejan",
year = "2016",
abstract = "Vegetable oils are mainly esters of fatty acids and glycerol, which can be converted to fatty acid methyl esters (FAME), also known as biodiesel, by the transesterification reaction with methanol. In order to attain environmental benignity, much attention has been focused in the last decades on utilizing heterogeneous catalysts for biodiesel production instead the homogenously catalyzed transesterification of vegetable oil. The pure CaO or CaO mixed with some other metal oxide due to its low solubility in methanol, FAME and glycerol, low cost and availability, is one of the most promising among the proposed heterogeneous catalysts. Solid catalysts containing CaO usually fulfill a number of important requirements, such as high activity at mild temperature, marginal leaching of Ca cations, long life activity, reusability in transesterification of vegetable oil and easy recovery from the final products of trancesterification (FAME and glycerol). This review is focused on the recent application of pure CaO or CaO in complex catalyst structure and their use as heterogeneous base catalysts for biodiesel synthesis and suitability for industrial application.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "Calcium oxide based catalysts for biodiesel production: a review",
pages = "408-391",
number = "4",
volume = "22",
doi = "10.2298/CICEQ160203010K"
}

Kesić, Ž., Lukić, I., Zdujić, M., Mojović, L.,& Skala, D.. (2016). Calcium oxide based catalysts for biodiesel production: a review. in Chemical Industry & Chemical Engineering Quarterly
Savez hemijskih inženjera, Beograd., 22(4), 391-408.
https://doi.org/10.2298/CICEQ160203010K

Kesić Ž, Lukić I, Zdujić M, Mojović L, Skala D. Calcium oxide based catalysts for biodiesel production: a review. in Chemical Industry & Chemical Engineering Quarterly. 2016;22(4):391-408.
doi:10.2298/CICEQ160203010K .

Kesić, Željka, Lukić, Ivana, Zdujić, Miodrag, Mojović, Ljiljana, Skala, Dejan, "Calcium oxide based catalysts for biodiesel production: a review" in Chemical Industry & Chemical Engineering Quarterly, 22, no. 4 (2016):391-408,
https://doi.org/10.2298/CICEQ160203010K . .

TY  - JOUR
AU  - Nasreen, Sadia
AU  - Liu, Hui
AU  - Lukić, Ivana
AU  - Qurashi, Liaqat Ali
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3382
AB  - Currently, the catalytic efficiency and reusability of the solid base catalysts cannot meet the demand of industrial biodiesel production under low temperature. The purpose of this study is to define the kinetics of heterogeneous transesterification process that could be used for the prediction of the biodiesel synthesis at high temperature and pressure. The focus in this study was paid to recently repotted data obtained with different catalysts used for biodiesel synthesis in a batch reactor at high temperatures. It was shown that three kinetic models, including: a) irreversible first order reaction, b) reaction with changeable order and c) resistances of mass transfer and chemical reaction at active sites of the catalyst, could be applied for predicting the effect of high temperature of the transesterification. The apparent reaction rate constant of the irreversible first order reaction was determined, as well as the parameters of the other two, more complicated kinetic. models. The best agreement was obtained with the more complicated models and the mean relative percent deviation between calculated and experimentally determined triacylglycerols conversion for these kinetic models is between 3 and 10%.
PB  - Savez hemijskih inženjera, Beograd
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - Heterogeneous kinetics of vegetable oil transesterification at high temperature
EP  - 429
IS  - 4
SP  - 419
VL  - 22
DO  - 10.2298/CICEQ160107011N
ER  - 

@article{
author = "Nasreen, Sadia and Liu, Hui and Lukić, Ivana and Qurashi, Liaqat Ali and Skala, Dejan",
year = "2016",
abstract = "Currently, the catalytic efficiency and reusability of the solid base catalysts cannot meet the demand of industrial biodiesel production under low temperature. The purpose of this study is to define the kinetics of heterogeneous transesterification process that could be used for the prediction of the biodiesel synthesis at high temperature and pressure. The focus in this study was paid to recently repotted data obtained with different catalysts used for biodiesel synthesis in a batch reactor at high temperatures. It was shown that three kinetic models, including: a) irreversible first order reaction, b) reaction with changeable order and c) resistances of mass transfer and chemical reaction at active sites of the catalyst, could be applied for predicting the effect of high temperature of the transesterification. The apparent reaction rate constant of the irreversible first order reaction was determined, as well as the parameters of the other two, more complicated kinetic. models. The best agreement was obtained with the more complicated models and the mean relative percent deviation between calculated and experimentally determined triacylglycerols conversion for these kinetic models is between 3 and 10%.",
publisher = "Savez hemijskih inženjera, Beograd",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "Heterogeneous kinetics of vegetable oil transesterification at high temperature",
pages = "429-419",
number = "4",
volume = "22",
doi = "10.2298/CICEQ160107011N"
}

Nasreen, S., Liu, H., Lukić, I., Qurashi, L. A.,& Skala, D.. (2016). Heterogeneous kinetics of vegetable oil transesterification at high temperature. in Chemical Industry & Chemical Engineering Quarterly
Savez hemijskih inženjera, Beograd., 22(4), 419-429.
https://doi.org/10.2298/CICEQ160107011N

Nasreen S, Liu H, Lukić I, Qurashi LA, Skala D. Heterogeneous kinetics of vegetable oil transesterification at high temperature. in Chemical Industry & Chemical Engineering Quarterly. 2016;22(4):419-429.
doi:10.2298/CICEQ160107011N .

Nasreen, Sadia, Liu, Hui, Lukić, Ivana, Qurashi, Liaqat Ali, Skala, Dejan, "Heterogeneous kinetics of vegetable oil transesterification at high temperature" in Chemical Industry & Chemical Engineering Quarterly, 22, no. 4 (2016):419-429,
https://doi.org/10.2298/CICEQ160107011N . .

TY  - JOUR
AU  - Kesić, Željka
AU  - Lukić, Ivana
AU  - Zdujić, Miodrag
AU  - Jovalekić, Čedomir
AU  - Veljković, Vlada B.
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3383
AB  - Calcium-containing perovskites CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 were synthesized by calcination of mechanochemically treated stoichiometric mixtures of CaCO3 and either TiO2, MnO2, ZrO2 or Fe2O3 powders. X-ray diffraction analysis revealed a pure single perovskite phase for all four samples after calcination. This study proved that the pure perovskite phase exhibited low or no catalytic activity at 60 degrees C for the methanolysis of sunflower oil. However, at 165 degrees C FAME yield of more than 90% was reached after 2 h using CaTiO3, CaMnO3 and CaZrO3 as catalyst. Contrary to inactive pure perovskites at 60 degrees C, the CaTiO3 and Ca2Fe2O5 samples containing a very small amount of "free" CaO also showed methanolysis activity at 60 degrees C. This fact can be used to explain some contradictory statements reported in literature related to the perovskites as catalyst for biodiesel synthesis at mild temperatures.
PB  - Elsevier Science Bv, Amsterdam
T2  - Fuel Processing Technology
T1  - Assessment of CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 perovskites as heterogeneous base catalysts for biodiesel synthesis
EP  - 168
SP  - 162
VL  - 143
DO  - 10.1016/j.fuproc.2015.11.018
ER  - 

@article{
author = "Kesić, Željka and Lukić, Ivana and Zdujić, Miodrag and Jovalekić, Čedomir and Veljković, Vlada B. and Skala, Dejan",
year = "2016",
abstract = "Calcium-containing perovskites CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 were synthesized by calcination of mechanochemically treated stoichiometric mixtures of CaCO3 and either TiO2, MnO2, ZrO2 or Fe2O3 powders. X-ray diffraction analysis revealed a pure single perovskite phase for all four samples after calcination. This study proved that the pure perovskite phase exhibited low or no catalytic activity at 60 degrees C for the methanolysis of sunflower oil. However, at 165 degrees C FAME yield of more than 90% was reached after 2 h using CaTiO3, CaMnO3 and CaZrO3 as catalyst. Contrary to inactive pure perovskites at 60 degrees C, the CaTiO3 and Ca2Fe2O5 samples containing a very small amount of "free" CaO also showed methanolysis activity at 60 degrees C. This fact can be used to explain some contradictory statements reported in literature related to the perovskites as catalyst for biodiesel synthesis at mild temperatures.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Fuel Processing Technology",
title = "Assessment of CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 perovskites as heterogeneous base catalysts for biodiesel synthesis",
pages = "168-162",
volume = "143",
doi = "10.1016/j.fuproc.2015.11.018"
}

Kesić, Ž., Lukić, I., Zdujić, M., Jovalekić, Č., Veljković, V. B.,& Skala, D.. (2016). Assessment of CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 perovskites as heterogeneous base catalysts for biodiesel synthesis. in Fuel Processing Technology
Elsevier Science Bv, Amsterdam., 143, 162-168.
https://doi.org/10.1016/j.fuproc.2015.11.018

Kesić Ž, Lukić I, Zdujić M, Jovalekić Č, Veljković VB, Skala D. Assessment of CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 perovskites as heterogeneous base catalysts for biodiesel synthesis. in Fuel Processing Technology. 2016;143:162-168.
doi:10.1016/j.fuproc.2015.11.018 .

Kesić, Željka, Lukić, Ivana, Zdujić, Miodrag, Jovalekić, Čedomir, Veljković, Vlada B., Skala, Dejan, "Assessment of CaTiO3, CaMnO3, CaZrO3 and Ca2Fe2O5 perovskites as heterogeneous base catalysts for biodiesel synthesis" in Fuel Processing Technology, 143 (2016):162-168,
https://doi.org/10.1016/j.fuproc.2015.11.018 . .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3400
AB  - In the present work, calcium diglyceroxide (CaDG) was synthesized by mechanochemical treatment of CaO dispersed in glycerol, and characterized by X-ray diffraction (XRD), thermal analysis (TGA/DTA), infrared spectroscopy (FTIR), and Hammett indicator method for base strength determination. The obtained CaDG was tested as a catalyst in the methanolysis of sunflower oil under different working conditions: catalyst amount, agitation speed, temperature and methanol to oil molar ratio. The main advantage of CaDG used as a catalyst in methanolysis is related to the initial rate of methanolysis. According to many previously reported data in literature the mass transfer resistance controls the overall rate of methanolysis, but it is not observed with CaDG used as catalyst. Recently developed kinetic model that describes the complex methanolysis process was successfully applied for this system and model parameters were determined, supporting the explanation of the physical effect of the CaDG catalyst on the reduction of mass transfer resistance and increasing the rate of methanolysis. The absence of mass transfer rate at the beginning of process is a consequence of the nature of the CaDG, which is adsorbed at the droplet interfaces between methanol and oil leading to the formation of fine dispersion of these two immiscible liquids.
PB  - Elsevier Sci Ltd, Oxford
T2  - Fuel
T1  - Calcium diglyceroxide synthesized by mechanochemical treatment, its characterization and application as catalyst for fatty acid methyl esters production
EP  - 165
SP  - 159
VL  - 165
DO  - 10.1016/j.fuel.2015.10.063
ER  - 

@article{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2016",
abstract = "In the present work, calcium diglyceroxide (CaDG) was synthesized by mechanochemical treatment of CaO dispersed in glycerol, and characterized by X-ray diffraction (XRD), thermal analysis (TGA/DTA), infrared spectroscopy (FTIR), and Hammett indicator method for base strength determination. The obtained CaDG was tested as a catalyst in the methanolysis of sunflower oil under different working conditions: catalyst amount, agitation speed, temperature and methanol to oil molar ratio. The main advantage of CaDG used as a catalyst in methanolysis is related to the initial rate of methanolysis. According to many previously reported data in literature the mass transfer resistance controls the overall rate of methanolysis, but it is not observed with CaDG used as catalyst. Recently developed kinetic model that describes the complex methanolysis process was successfully applied for this system and model parameters were determined, supporting the explanation of the physical effect of the CaDG catalyst on the reduction of mass transfer resistance and increasing the rate of methanolysis. The absence of mass transfer rate at the beginning of process is a consequence of the nature of the CaDG, which is adsorbed at the droplet interfaces between methanol and oil leading to the formation of fine dispersion of these two immiscible liquids.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Fuel",
title = "Calcium diglyceroxide synthesized by mechanochemical treatment, its characterization and application as catalyst for fatty acid methyl esters production",
pages = "165-159",
volume = "165",
doi = "10.1016/j.fuel.2015.10.063"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2016). Calcium diglyceroxide synthesized by mechanochemical treatment, its characterization and application as catalyst for fatty acid methyl esters production. in Fuel
Elsevier Sci Ltd, Oxford., 165, 159-165.
https://doi.org/10.1016/j.fuel.2015.10.063

Lukić I, Kesić Ž, Zdujić M, Skala D. Calcium diglyceroxide synthesized by mechanochemical treatment, its characterization and application as catalyst for fatty acid methyl esters production. in Fuel. 2016;165:159-165.
doi:10.1016/j.fuel.2015.10.063 .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Calcium diglyceroxide synthesized by mechanochemical treatment, its characterization and application as catalyst for fatty acid methyl esters production" in Fuel, 165 (2016):159-165,
https://doi.org/10.1016/j.fuel.2015.10.063 . .

TY  - JOUR
AU  - Nasreen, Sadia
AU  - Liu, Hui
AU  - Qureshi, Liaqat Ali
AU  - Sissou, Zakari
AU  - Lukić, Ivana
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3433
AB  - A heterogeneous cerium-manganese oxide catalyst was synthesized by a co-precipitation method, characterized and tested in soybean oil transesterification with methanol under subcritical condition for methanol. Conversion of triglycerides after 40 min of transesterification in a batch process was over 99% with a fatty acid methyl ester (FAME) yield of 91.6% when 3 wt.% of catalyst based on oil, and 18:1 methanol/oil molar ratio were applied. The same amount of catalyst was used in 12 cycles of transesterification with catalyst regeneration performed only after the 7th cycle. The catalyst exhibited good tolerance toward soybean oil containing below 1.5 wt.% of water or 4 wt.% of free fatty acids. The mechanisms of Ce/Mn catalytic activity and its deactivation were discussed according to the characterization of the fresh and used catalyst according to results of different analytical methods: the Hammett titration, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), FTIR, X-ray diffraction (XRD), ICP-MS and TG-DSC. It was assumed that deactivation of catalyst was mainly a consequence of manganese solubility in methanol and glycerol.
PB  - Elsevier Science Bv, Amsterdam
T2  - Fuel Processing Technology
T1  - Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol
EP  - 84
SP  - 76
VL  - 148
DO  - 10.1016/j.fuproc.2016.02.035
ER  - 

@article{
author = "Nasreen, Sadia and Liu, Hui and Qureshi, Liaqat Ali and Sissou, Zakari and Lukić, Ivana and Skala, Dejan",
year = "2016",
abstract = "A heterogeneous cerium-manganese oxide catalyst was synthesized by a co-precipitation method, characterized and tested in soybean oil transesterification with methanol under subcritical condition for methanol. Conversion of triglycerides after 40 min of transesterification in a batch process was over 99% with a fatty acid methyl ester (FAME) yield of 91.6% when 3 wt.% of catalyst based on oil, and 18:1 methanol/oil molar ratio were applied. The same amount of catalyst was used in 12 cycles of transesterification with catalyst regeneration performed only after the 7th cycle. The catalyst exhibited good tolerance toward soybean oil containing below 1.5 wt.% of water or 4 wt.% of free fatty acids. The mechanisms of Ce/Mn catalytic activity and its deactivation were discussed according to the characterization of the fresh and used catalyst according to results of different analytical methods: the Hammett titration, BET surface area, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), FTIR, X-ray diffraction (XRD), ICP-MS and TG-DSC. It was assumed that deactivation of catalyst was mainly a consequence of manganese solubility in methanol and glycerol.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Fuel Processing Technology",
title = "Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol",
pages = "84-76",
volume = "148",
doi = "10.1016/j.fuproc.2016.02.035"
}

Nasreen, S., Liu, H., Qureshi, L. A., Sissou, Z., Lukić, I.,& Skala, D.. (2016). Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol. in Fuel Processing Technology
Elsevier Science Bv, Amsterdam., 148, 76-84.
https://doi.org/10.1016/j.fuproc.2016.02.035

Nasreen S, Liu H, Qureshi LA, Sissou Z, Lukić I, Skala D. Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol. in Fuel Processing Technology. 2016;148:76-84.
doi:10.1016/j.fuproc.2016.02.035 .

Nasreen, Sadia, Liu, Hui, Qureshi, Liaqat Ali, Sissou, Zakari, Lukić, Ivana, Skala, Dejan, "Cerium-manganese oxide as catalyst for transesterification of soybean oil with subcritical methanol" in Fuel Processing Technology, 148 (2016):76-84,
https://doi.org/10.1016/j.fuproc.2016.02.035 . .

TY  - JOUR
AU  - Bogdanović, Aleksandra
AU  - Tadić, Vanja
AU  - Arsić, Ivana A.
AU  - Milovanović, Stoja
AU  - Petrović, Slobodan
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3406
AB  - Analysis of yield and composition profile of Melissa officinalis (Lemon balm) extract obtained by two-step CO2 extraction at high pressure was analyzed. The first or essential oil fraction, collected at 10 MPa and 40 degrees C, contained mostly the high volatile and aromatic compounds. The second fraction was consenquently extracted at 30 MPa using different temperature: 25 degrees C (higher pressure than critical pressure but at temperature below the critical; HPCP-CO2), 40 degrees C or 100 degrees C (supercritical CO2; SC-CO2). Obtained yield of essential oil fraction was 0.45% at 10 MPa, while depending on applied extraction temperature (HPCP-CO2 or SC-CO2), the yields of the second fractions collected at 30 MPa varied from 0.44% to 0.94%. Within the study, the content of active substances in obtained extracts was analyzed, too. For comparison with CO2 extracts (HPCP or SC) the yield and characterization of essential oil obtained by hydrodistillation was accomplished, as well. A significant difference was noted not only between the essential oil isolated by hydrodistillation and SC-CO2 extraction (40 degrees C, 10 MPa) but also between total extracts obtained by HPCP-CO2 and SC-CO2 extraction. The pseudo kinetic model was applied to define SC-CO2 extraction of Lemon balm to describe the relation between the yield of extraction and CO2 consumption. Antioxidant activity of obtained extracts was determined by free radical scavenging capacity (RSC) and significant correlation of antioxidant capacity and composition profile between obtained extracts was observed.
PB  - Elsevier, Amsterdam
T2  - Journal of Supercritical Fluids
T1  - Supercritical and high pressure subcritical fluid extraction from Lemon balm (Melissa officinalis L., Lamiaceae)
EP  - 242
SP  - 234
VL  - 107
DO  - 10.1016/j.supflu.2015.09.008
ER  - 

@article{
author = "Bogdanović, Aleksandra and Tadić, Vanja and Arsić, Ivana A. and Milovanović, Stoja and Petrović, Slobodan and Skala, Dejan",
year = "2016",
abstract = "Analysis of yield and composition profile of Melissa officinalis (Lemon balm) extract obtained by two-step CO2 extraction at high pressure was analyzed. The first or essential oil fraction, collected at 10 MPa and 40 degrees C, contained mostly the high volatile and aromatic compounds. The second fraction was consenquently extracted at 30 MPa using different temperature: 25 degrees C (higher pressure than critical pressure but at temperature below the critical; HPCP-CO2), 40 degrees C or 100 degrees C (supercritical CO2; SC-CO2). Obtained yield of essential oil fraction was 0.45% at 10 MPa, while depending on applied extraction temperature (HPCP-CO2 or SC-CO2), the yields of the second fractions collected at 30 MPa varied from 0.44% to 0.94%. Within the study, the content of active substances in obtained extracts was analyzed, too. For comparison with CO2 extracts (HPCP or SC) the yield and characterization of essential oil obtained by hydrodistillation was accomplished, as well. A significant difference was noted not only between the essential oil isolated by hydrodistillation and SC-CO2 extraction (40 degrees C, 10 MPa) but also between total extracts obtained by HPCP-CO2 and SC-CO2 extraction. The pseudo kinetic model was applied to define SC-CO2 extraction of Lemon balm to describe the relation between the yield of extraction and CO2 consumption. Antioxidant activity of obtained extracts was determined by free radical scavenging capacity (RSC) and significant correlation of antioxidant capacity and composition profile between obtained extracts was observed.",
publisher = "Elsevier, Amsterdam",
journal = "Journal of Supercritical Fluids",
title = "Supercritical and high pressure subcritical fluid extraction from Lemon balm (Melissa officinalis L., Lamiaceae)",
pages = "242-234",
volume = "107",
doi = "10.1016/j.supflu.2015.09.008"
}

Bogdanović, A., Tadić, V., Arsić, I. A., Milovanović, S., Petrović, S.,& Skala, D.. (2016). Supercritical and high pressure subcritical fluid extraction from Lemon balm (Melissa officinalis L., Lamiaceae). in Journal of Supercritical Fluids
Elsevier, Amsterdam., 107, 234-242.
https://doi.org/10.1016/j.supflu.2015.09.008

Bogdanović A, Tadić V, Arsić IA, Milovanović S, Petrović S, Skala D. Supercritical and high pressure subcritical fluid extraction from Lemon balm (Melissa officinalis L., Lamiaceae). in Journal of Supercritical Fluids. 2016;107:234-242.
doi:10.1016/j.supflu.2015.09.008 .

Bogdanović, Aleksandra, Tadić, Vanja, Arsić, Ivana A., Milovanović, Stoja, Petrović, Slobodan, Skala, Dejan, "Supercritical and high pressure subcritical fluid extraction from Lemon balm (Melissa officinalis L., Lamiaceae)" in Journal of Supercritical Fluids, 107 (2016):234-242,
https://doi.org/10.1016/j.supflu.2015.09.008 . .

TY  - JOUR
AU  - Bogdanović, Aleksandra
AU  - Tadić, Vanja
AU  - Stamenić, Marko
AU  - Petrović, Slobodan
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3405
AB  - Pretreatment of fenugreek (Trigonella foenum-graecum L, Fabaceae) seeds was achieved using the step of defatting and acid hydrolysis. The obtained hydro-isolate (HI) was used as initial feed for diosgenin isolation by supercritical CO2 extraction (SC-CO2). Preliminary tests performed at conditions resulting in SC-CO2 density ranging from 800 to 920 kg/m(3) indicated that at some pressure, temperature as well as consumption of supercritical fluids the optimal working conditions for diosgenin isolation could be determined. For this purpose, the following range of working conditions of SC-CO2 were tested by using Central Composite Rotatable Design (CCRD) and Response Surface Methodology (RSM): pressure from 16.6 to 33.4 MPa, temperature from 30 to 50 degrees C and consumption of SC-CO2 from 11.6 to 28.4 g(co2)/g(dm). The result of this investigation indicated that maximum yield of 0.81 mg diosgenin from 1 g of fenugreek seeds on dry basis (about 1.3% of total extract) at 24.6 MPa, 43.5 degrees C, and 20.87 g(co2)/g(dm) could be obtained.
PB  - Elsevier Science Bv, Amsterdam
T2  - Journal of Supercritical Fluids
T1  - Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology
EP  - 50
SP  - 44
VL  - 107
DO  - 10.1016/j.supflu.2015.08.003
ER  - 

@article{
author = "Bogdanović, Aleksandra and Tadić, Vanja and Stamenić, Marko and Petrović, Slobodan and Skala, Dejan",
year = "2016",
abstract = "Pretreatment of fenugreek (Trigonella foenum-graecum L, Fabaceae) seeds was achieved using the step of defatting and acid hydrolysis. The obtained hydro-isolate (HI) was used as initial feed for diosgenin isolation by supercritical CO2 extraction (SC-CO2). Preliminary tests performed at conditions resulting in SC-CO2 density ranging from 800 to 920 kg/m(3) indicated that at some pressure, temperature as well as consumption of supercritical fluids the optimal working conditions for diosgenin isolation could be determined. For this purpose, the following range of working conditions of SC-CO2 were tested by using Central Composite Rotatable Design (CCRD) and Response Surface Methodology (RSM): pressure from 16.6 to 33.4 MPa, temperature from 30 to 50 degrees C and consumption of SC-CO2 from 11.6 to 28.4 g(co2)/g(dm). The result of this investigation indicated that maximum yield of 0.81 mg diosgenin from 1 g of fenugreek seeds on dry basis (about 1.3% of total extract) at 24.6 MPa, 43.5 degrees C, and 20.87 g(co2)/g(dm) could be obtained.",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Journal of Supercritical Fluids",
title = "Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology",
pages = "50-44",
volume = "107",
doi = "10.1016/j.supflu.2015.08.003"
}

Bogdanović, A., Tadić, V., Stamenić, M., Petrović, S.,& Skala, D.. (2016). Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology. in Journal of Supercritical Fluids
Elsevier Science Bv, Amsterdam., 107, 44-50.
https://doi.org/10.1016/j.supflu.2015.08.003

Bogdanović A, Tadić V, Stamenić M, Petrović S, Skala D. Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology. in Journal of Supercritical Fluids. 2016;107:44-50.
doi:10.1016/j.supflu.2015.08.003 .

Bogdanović, Aleksandra, Tadić, Vanja, Stamenić, Marko, Petrović, Slobodan, Skala, Dejan, "Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology" in Journal of Supercritical Fluids, 107 (2016):44-50,
https://doi.org/10.1016/j.supflu.2015.08.003 . .

TY  - JOUR
AU  - Bogdanović, Aleksandra
AU  - Tadić, Vanja
AU  - Ristić, Mihailo S.
AU  - Petrović, Slobodan
AU  - Skala, Dejan
PY  - 2016
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/3344
AB  - Supercritical CO2 (SC-CO2) extraction of fenugreek seeds (Trigonella foenum-graecum L, Fabaceae) was analyzed using different pressure and temperature (16.6-33.4 MPa and, 30-50 degrees C), which corresponded to SC-CO2 density between 779 and 957 kg/m(3). The yield of extract as well as its composition were determined and analyzed for different solvent consumption defined as mass of used CO2 for extraction per mass of dry fenugreek seeds. A central composite design (CCD) combined with response surface methodology (RSM) was used to study the best extraction conditions which determined that 27.0 MPa, 42.6 degrees C, and 24.6 gCO(2)/g(dm), were the optimal conditions for isolation of total extract. The calculated yield of extract at these conditions defined by SC-CO2 density of 890 kg/m3 could be 2.57% based on fenugreek seed. Moreover, the best extraction conditions for obtaining extract which contains the maximal amount of sterols, or maximal amount of vitamin E or vitamin D were also analyzed. These RSM optimizations showed that at slightly lower pressure (22.8-24.8 MPa), temperature (39.9-42.0 degrees C) and consumption of SC-CO2 (19.0-19.7 gCO(2)/g(dm)) is followed by smaller amount of isolated extract but with maximum content of sterols (16.28%), or vitamin E or vitamin D (1.44% and 0.71%, respectively) at these conditions. Calculation of molar solubility of total extract, and apparent solubility of sterols, vitamin E and D in SC-CO2 was performed at different pressure and temperature. They were correlated to density of SC-CO2, temperature at which extractions were performed and Hildebrand solubility parameter of solvent and solubility parameter of compounds which are the main constituents of extract. These calculations also show that the highest molar solubility of total extract and apparent molar solubility of its constituents could be obtained using optimal density of SC-CO2 (830-890 kg/m(3)) defined by corresponding values of temperature and pressure (310-320 K and 20-25 MPa).
PB  - Elsevier Science Bv, Amsterdam
T2  - Journal of Supercritical Fluids
T1  - Optimization of supercritical CO2 extraction of fenugreek seed (Trigonella foenum-graecum L.) and calculating of extracts solubility
EP  - 307
SP  - 297
VL  - 117
DO  - 10.1016/j.supflu.2016.07.010
ER  - 

@article{
author = "Bogdanović, Aleksandra and Tadić, Vanja and Ristić, Mihailo S. and Petrović, Slobodan and Skala, Dejan",
year = "2016",
abstract = "Supercritical CO2 (SC-CO2) extraction of fenugreek seeds (Trigonella foenum-graecum L, Fabaceae) was analyzed using different pressure and temperature (16.6-33.4 MPa and, 30-50 degrees C), which corresponded to SC-CO2 density between 779 and 957 kg/m(3). The yield of extract as well as its composition were determined and analyzed for different solvent consumption defined as mass of used CO2 for extraction per mass of dry fenugreek seeds. A central composite design (CCD) combined with response surface methodology (RSM) was used to study the best extraction conditions which determined that 27.0 MPa, 42.6 degrees C, and 24.6 gCO(2)/g(dm), were the optimal conditions for isolation of total extract. The calculated yield of extract at these conditions defined by SC-CO2 density of 890 kg/m3 could be 2.57% based on fenugreek seed. Moreover, the best extraction conditions for obtaining extract which contains the maximal amount of sterols, or maximal amount of vitamin E or vitamin D were also analyzed. These RSM optimizations showed that at slightly lower pressure (22.8-24.8 MPa), temperature (39.9-42.0 degrees C) and consumption of SC-CO2 (19.0-19.7 gCO(2)/g(dm)) is followed by smaller amount of isolated extract but with maximum content of sterols (16.28%), or vitamin E or vitamin D (1.44% and 0.71%, respectively) at these conditions. Calculation of molar solubility of total extract, and apparent solubility of sterols, vitamin E and D in SC-CO2 was performed at different pressure and temperature. They were correlated to density of SC-CO2, temperature at which extractions were performed and Hildebrand solubility parameter of solvent and solubility parameter of compounds which are the main constituents of extract. These calculations also show that the highest molar solubility of total extract and apparent molar solubility of its constituents could be obtained using optimal density of SC-CO2 (830-890 kg/m(3)) defined by corresponding values of temperature and pressure (310-320 K and 20-25 MPa).",
publisher = "Elsevier Science Bv, Amsterdam",
journal = "Journal of Supercritical Fluids",
title = "Optimization of supercritical CO2 extraction of fenugreek seed (Trigonella foenum-graecum L.) and calculating of extracts solubility",
pages = "307-297",
volume = "117",
doi = "10.1016/j.supflu.2016.07.010"
}

Bogdanović, A., Tadić, V., Ristić, M. S., Petrović, S.,& Skala, D.. (2016). Optimization of supercritical CO2 extraction of fenugreek seed (Trigonella foenum-graecum L.) and calculating of extracts solubility. in Journal of Supercritical Fluids
Elsevier Science Bv, Amsterdam., 117, 297-307.
https://doi.org/10.1016/j.supflu.2016.07.010

Bogdanović A, Tadić V, Ristić MS, Petrović S, Skala D. Optimization of supercritical CO2 extraction of fenugreek seed (Trigonella foenum-graecum L.) and calculating of extracts solubility. in Journal of Supercritical Fluids. 2016;117:297-307.
doi:10.1016/j.supflu.2016.07.010 .

Bogdanović, Aleksandra, Tadić, Vanja, Ristić, Mihailo S., Petrović, Slobodan, Skala, Dejan, "Optimization of supercritical CO2 extraction of fenugreek seed (Trigonella foenum-graecum L.) and calculating of extracts solubility" in Journal of Supercritical Fluids, 117 (2016):297-307,
https://doi.org/10.1016/j.supflu.2016.07.010 . .

TY  - JOUR
AU  - Kesić, Željka
AU  - Lukić, Ivana
AU  - Zdujić, Miodrag
AU  - Jovalekić, Čedomir
AU  - Liu, Hui
AU  - Skala, Dejan
PY  - 2015
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2921
AB  - The goal of this study was to prepare a CaO·ZnO catalyst containing a small amount of K2CO3 and analyze its activity for biodiesel synthesis. The catalyst was prepared using the following procedure: CaO and ZnO (mole ratio of 1:2), water and K2CO3 (in various amounts) were mechanochemically treated and after milling heated at 700°C in air atmosphere for obtaining mixed CaO·ZnO/xK2CO3 oxides (x = 0, 1, 2 and 4 mol of K2CO3 per 10 mol of CaO). All the samples were characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanning electron microscopy/ energy-dispersive spectroscopy (SEM/EDS), particle size laser diffraction (PSLD) distribution, solubility measurement of Ca, Zn and K ions in methanol as well as by determination of their alkalinity (Hammett indicator method). Prepared CaO·ZnO/xK2CO3 composite powders were tested as catalysts for methanolysis of sunflower oil at 70 °C using mole ratio of sunflower oil to methanol of 1:10 and with 2 mass% of catalyst based on oil weight. The presence of K2CO3 in prepared samples was found to increase the activity of catalyst, and that such effect is caused by homogeneous-heterogeneous catalysis of biodiesel synthesis.
AB  - Cilj ovih istraživanja bio je da se pripremi CaO·ZnO katalizator koji sadrži malu količinu K2CO3 i analizira njegova aktivnost u sintezi biodizela. Katalizator je pripremljen prema sledećoj proceduri: CaO i ZnO (molski odnos 1:2), voda i K2CO3 (u različitoj količini) su tretirani mehanohemijski i nakon mlevenja zagrevani na 700 °C u atmosferi vazduha da bi se dobila smeša oksida CaO·ZnO/xK2CO3 (x = 0, 1, 2 i 4 mol K2CO3 na 10 mol CaO). Karakterizacija pripremljenih katalizatora izvršena je metodama rendgenske difrakcije (XRD), indukovane kuplovane plazme (ICP), spektroskopije fotoelektrona dobijenih X-zracima (XPS), termogravimetrijske analize (TGA), infracrvene spektroskopije (FTIR), skenirajuće elektronske mikroskopije i energetske disperzione spektroskopije (SEM/EDS), raspodele veličine čestica (PSLD), merenjem rastvorljivosti katalizatora odnosno Ca, Zn i K jona u metanolu, kao i određivanjem njihove baznosti (metodom Hametovih indikatora). Pripremljeni CaO·ZnO/xK2CO3 kompozitni prahovi testirani su kao katalizatori u reakciji metanolize suncokretovog ulja na 70 °C, pri molarnom odnosu suncokretovog ulja i metanola od 1:10 i sa 2 mas.% katalizatora u odnosu na masu ulja. Pokazano je da prisustvo K2CO3 u pripremljenim uzorcima povećava aktivnost katalizatora i da je takav efekat posledica homogeno-heterogene katalize u sintezi biodizela.
PB  - Association of the Chemical Engineers of Serbia
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - Mechanochemical synthesis of CaO·ZnO.K2CO3 catalyst: Characterization and activity for methanolysis of sunflower oil
T1  - Mehanohemijska sinteza CaO·ZnO.K2CO3, katalizatora - karakterizacija i aktivnost u metanolizi suncokretovog ulja
EP  - 12
IS  - 1-1
SP  - 1
VL  - 21
DO  - 10.2298/CICEQ131026041K
ER  - 

@article{
author = "Kesić, Željka and Lukić, Ivana and Zdujić, Miodrag and Jovalekić, Čedomir and Liu, Hui and Skala, Dejan",
year = "2015",
abstract = "The goal of this study was to prepare a CaO·ZnO catalyst containing a small amount of K2CO3 and analyze its activity for biodiesel synthesis. The catalyst was prepared using the following procedure: CaO and ZnO (mole ratio of 1:2), water and K2CO3 (in various amounts) were mechanochemically treated and after milling heated at 700°C in air atmosphere for obtaining mixed CaO·ZnO/xK2CO3 oxides (x = 0, 1, 2 and 4 mol of K2CO3 per 10 mol of CaO). All the samples were characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), scanning electron microscopy/ energy-dispersive spectroscopy (SEM/EDS), particle size laser diffraction (PSLD) distribution, solubility measurement of Ca, Zn and K ions in methanol as well as by determination of their alkalinity (Hammett indicator method). Prepared CaO·ZnO/xK2CO3 composite powders were tested as catalysts for methanolysis of sunflower oil at 70 °C using mole ratio of sunflower oil to methanol of 1:10 and with 2 mass% of catalyst based on oil weight. The presence of K2CO3 in prepared samples was found to increase the activity of catalyst, and that such effect is caused by homogeneous-heterogeneous catalysis of biodiesel synthesis., Cilj ovih istraživanja bio je da se pripremi CaO·ZnO katalizator koji sadrži malu količinu K2CO3 i analizira njegova aktivnost u sintezi biodizela. Katalizator je pripremljen prema sledećoj proceduri: CaO i ZnO (molski odnos 1:2), voda i K2CO3 (u različitoj količini) su tretirani mehanohemijski i nakon mlevenja zagrevani na 700 °C u atmosferi vazduha da bi se dobila smeša oksida CaO·ZnO/xK2CO3 (x = 0, 1, 2 i 4 mol K2CO3 na 10 mol CaO). Karakterizacija pripremljenih katalizatora izvršena je metodama rendgenske difrakcije (XRD), indukovane kuplovane plazme (ICP), spektroskopije fotoelektrona dobijenih X-zracima (XPS), termogravimetrijske analize (TGA), infracrvene spektroskopije (FTIR), skenirajuće elektronske mikroskopije i energetske disperzione spektroskopije (SEM/EDS), raspodele veličine čestica (PSLD), merenjem rastvorljivosti katalizatora odnosno Ca, Zn i K jona u metanolu, kao i određivanjem njihove baznosti (metodom Hametovih indikatora). Pripremljeni CaO·ZnO/xK2CO3 kompozitni prahovi testirani su kao katalizatori u reakciji metanolize suncokretovog ulja na 70 °C, pri molarnom odnosu suncokretovog ulja i metanola od 1:10 i sa 2 mas.% katalizatora u odnosu na masu ulja. Pokazano je da prisustvo K2CO3 u pripremljenim uzorcima povećava aktivnost katalizatora i da je takav efekat posledica homogeno-heterogene katalize u sintezi biodizela.",
publisher = "Association of the Chemical Engineers of Serbia",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "Mechanochemical synthesis of CaO·ZnO.K2CO3 catalyst: Characterization and activity for methanolysis of sunflower oil, Mehanohemijska sinteza CaO·ZnO.K2CO3, katalizatora - karakterizacija i aktivnost u metanolizi suncokretovog ulja",
pages = "12-1",
number = "1-1",
volume = "21",
doi = "10.2298/CICEQ131026041K"
}

Kesić, Ž., Lukić, I., Zdujić, M., Jovalekić, Č., Liu, H.,& Skala, D.. (2015). Mechanochemical synthesis of CaO·ZnO.K2CO3 catalyst: Characterization and activity for methanolysis of sunflower oil. in Chemical Industry & Chemical Engineering Quarterly
Association of the Chemical Engineers of Serbia., 21(1-1), 1-12.
https://doi.org/10.2298/CICEQ131026041K

Kesić Ž, Lukić I, Zdujić M, Jovalekić Č, Liu H, Skala D. Mechanochemical synthesis of CaO·ZnO.K2CO3 catalyst: Characterization and activity for methanolysis of sunflower oil. in Chemical Industry & Chemical Engineering Quarterly. 2015;21(1-1):1-12.
doi:10.2298/CICEQ131026041K .

Kesić, Željka, Lukić, Ivana, Zdujić, Miodrag, Jovalekić, Čedomir, Liu, Hui, Skala, Dejan, "Mechanochemical synthesis of CaO·ZnO.K2CO3 catalyst: Characterization and activity for methanolysis of sunflower oil" in Chemical Industry & Chemical Engineering Quarterly, 21, no. 1-1 (2015):1-12,
https://doi.org/10.2298/CICEQ131026041K . .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Maksimović, Svetolik
AU  - Zdujić, Miodrag
AU  - Krstić, Jugoslav
AU  - Skala, Dejan
PY  - 2014
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2608
AB  - The kinetics of heterogeneous methanolysis of sunflower oil was studied at 60 °C using mechanochemically synthesized CaO·ZnO as catalyst. The influence of agitation speed, catalyst amount, and methanol-to-oil molar ratio on the rate of reaction was analyzed. The rate of the process depends on the two resistances - mass transfer of triglycerides to the catalyst surface and chemical reaction on the catalyst surface, which are defined as the values of the overall triglyceride volumetric mass transfer coefficient, kmt,TG, and the effective pseudo first-order reaction rate constant, k, respectively. These kinetic parameters actually determine the value of the apparent reaction rate constant, kapp, the time dependence of which is defined by the change of triglyceride (TG) conversion. A kinetic model is proposed and the model parameters are determined.
AB  - Kinetika heterogene metanolize suncokretovog ulja je ispitivana na 60 °C korišćenjem CaO·ZnO katalizatora koji je sintetizovan mehanohemijskim putem. Analiziran je uticaj intenziteta mešanja, mase korišćenog katalizatora u sintezi i različitog molskog odnosa metanola i ulja na brzinu metanolize. Brzina procesa metanolize zavisi od dva otpora - otpora prenosu mase triglicerida do površine katalizatora i otpora brzini hemijske reakcije na površini katalizatora. Oba otpora određuju vrednost ukupnog zapreminskog koeficijenta prenosa mase triglicerida, kmt,TG, odnosno efektivne vrednosti konstante brzine hemijske reakcije pseudo-prvog reda, k. Ovi kinetički parametri određuju vrednost prividne konstante brzine procesa metanolize, kapp, koja se menja sa vremenom u zavisnosti od ostvareneog stepena konverzije triglicerida (TG). Predložen je odgovarajući model kojim je moguće definisati brzinu metanolize i određeni su odgovarajući parametri ovog modela.
PB  - Association of the Chemical Engineers of Serbia
T2  - Chemical Industry & Chemical Engineering Quarterly
T1  - Kinetics of heterogeneous methanolysis of sunflower oil with CaO·ZnO catalyst: Influence of different hydrodynamic conditions
T1  - Kinetika heterogene metanolize suncokretovog ulja sa CaO·ZnO kao katalizatorom - uticaj različitih hidrodinamičkih uslova
EP  - 439
IS  - 3
SP  - 425
VL  - 20
DO  - 10.2298/CICEQ130514025L
ER  - 

@article{
author = "Lukić, Ivana and Kesić, Željka and Maksimović, Svetolik and Zdujić, Miodrag and Krstić, Jugoslav and Skala, Dejan",
year = "2014",
abstract = "The kinetics of heterogeneous methanolysis of sunflower oil was studied at 60 °C using mechanochemically synthesized CaO·ZnO as catalyst. The influence of agitation speed, catalyst amount, and methanol-to-oil molar ratio on the rate of reaction was analyzed. The rate of the process depends on the two resistances - mass transfer of triglycerides to the catalyst surface and chemical reaction on the catalyst surface, which are defined as the values of the overall triglyceride volumetric mass transfer coefficient, kmt,TG, and the effective pseudo first-order reaction rate constant, k, respectively. These kinetic parameters actually determine the value of the apparent reaction rate constant, kapp, the time dependence of which is defined by the change of triglyceride (TG) conversion. A kinetic model is proposed and the model parameters are determined., Kinetika heterogene metanolize suncokretovog ulja je ispitivana na 60 °C korišćenjem CaO·ZnO katalizatora koji je sintetizovan mehanohemijskim putem. Analiziran je uticaj intenziteta mešanja, mase korišćenog katalizatora u sintezi i različitog molskog odnosa metanola i ulja na brzinu metanolize. Brzina procesa metanolize zavisi od dva otpora - otpora prenosu mase triglicerida do površine katalizatora i otpora brzini hemijske reakcije na površini katalizatora. Oba otpora određuju vrednost ukupnog zapreminskog koeficijenta prenosa mase triglicerida, kmt,TG, odnosno efektivne vrednosti konstante brzine hemijske reakcije pseudo-prvog reda, k. Ovi kinetički parametri određuju vrednost prividne konstante brzine procesa metanolize, kapp, koja se menja sa vremenom u zavisnosti od ostvareneog stepena konverzije triglicerida (TG). Predložen je odgovarajući model kojim je moguće definisati brzinu metanolize i određeni su odgovarajući parametri ovog modela.",
publisher = "Association of the Chemical Engineers of Serbia",
journal = "Chemical Industry & Chemical Engineering Quarterly",
title = "Kinetics of heterogeneous methanolysis of sunflower oil with CaO·ZnO catalyst: Influence of different hydrodynamic conditions, Kinetika heterogene metanolize suncokretovog ulja sa CaO·ZnO kao katalizatorom - uticaj različitih hidrodinamičkih uslova",
pages = "439-425",
number = "3",
volume = "20",
doi = "10.2298/CICEQ130514025L"
}

Lukić, I., Kesić, Ž., Maksimović, S., Zdujić, M., Krstić, J.,& Skala, D.. (2014). Kinetics of heterogeneous methanolysis of sunflower oil with CaO·ZnO catalyst: Influence of different hydrodynamic conditions. in Chemical Industry & Chemical Engineering Quarterly
Association of the Chemical Engineers of Serbia., 20(3), 425-439.
https://doi.org/10.2298/CICEQ130514025L

Lukić I, Kesić Ž, Maksimović S, Zdujić M, Krstić J, Skala D. Kinetics of heterogeneous methanolysis of sunflower oil with CaO·ZnO catalyst: Influence of different hydrodynamic conditions. in Chemical Industry & Chemical Engineering Quarterly. 2014;20(3):425-439.
doi:10.2298/CICEQ130514025L .

Lukić, Ivana, Kesić, Željka, Maksimović, Svetolik, Zdujić, Miodrag, Krstić, Jugoslav, Skala, Dejan, "Kinetics of heterogeneous methanolysis of sunflower oil with CaO·ZnO catalyst: Influence of different hydrodynamic conditions" in Chemical Industry & Chemical Engineering Quarterly, 20, no. 3 (2014):425-439,
https://doi.org/10.2298/CICEQ130514025L . .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Skala, Dejan
PY  - 2014
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2747
AB  - A heterogeneous catalyst, ZnO supported on alumina/silica, was synthesized by the sol-gel method. The prepared catalysts were employed for methanolysis of sunflower oil. Effects of various supports as well as calcination temperature were evaluated following the kinetics of the reaction. Simple first-order irreversible and reversible reaction models were applied to determine the reaction rate constant. The results proved that under optimized conditions the catalyst exhibited good activity in the methanolysis of sunflower oil and the kinetics of the methanolysis process could be expressed by the first-order reversible reaction model. For other catalysts with lower activity, the first-order irreversible reaction model could be successfully applied to describe well the process kinetics.
PB  - Wiley-VCH Verlag Gmbh, Weinheim
T2  - Chemical Engineering & Technology
T1  - Kinetics of Heterogeneous Biodiesel Synthesis Using Supported ZnO as Catalyst
EP  - 1884
IS  - 11
SP  - 1879
VL  - 37
DO  - 10.1002/ceat.201300714
ER  - 

@article{
author = "Lukić, Ivana and Kesić, Željka and Skala, Dejan",
year = "2014",
abstract = "A heterogeneous catalyst, ZnO supported on alumina/silica, was synthesized by the sol-gel method. The prepared catalysts were employed for methanolysis of sunflower oil. Effects of various supports as well as calcination temperature were evaluated following the kinetics of the reaction. Simple first-order irreversible and reversible reaction models were applied to determine the reaction rate constant. The results proved that under optimized conditions the catalyst exhibited good activity in the methanolysis of sunflower oil and the kinetics of the methanolysis process could be expressed by the first-order reversible reaction model. For other catalysts with lower activity, the first-order irreversible reaction model could be successfully applied to describe well the process kinetics.",
publisher = "Wiley-VCH Verlag Gmbh, Weinheim",
journal = "Chemical Engineering & Technology",
title = "Kinetics of Heterogeneous Biodiesel Synthesis Using Supported ZnO as Catalyst",
pages = "1884-1879",
number = "11",
volume = "37",
doi = "10.1002/ceat.201300714"
}

Lukić, I., Kesić, Ž.,& Skala, D.. (2014). Kinetics of Heterogeneous Biodiesel Synthesis Using Supported ZnO as Catalyst. in Chemical Engineering & Technology
Wiley-VCH Verlag Gmbh, Weinheim., 37(11), 1879-1884.
https://doi.org/10.1002/ceat.201300714

Lukić I, Kesić Ž, Skala D. Kinetics of Heterogeneous Biodiesel Synthesis Using Supported ZnO as Catalyst. in Chemical Engineering & Technology. 2014;37(11):1879-1884.
doi:10.1002/ceat.201300714 .

Lukić, Ivana, Kesić, Željka, Skala, Dejan, "Kinetics of Heterogeneous Biodiesel Synthesis Using Supported ZnO as Catalyst" in Chemical Engineering & Technology, 37, no. 11 (2014):1879-1884,
https://doi.org/10.1002/ceat.201300714 . .

TY  - CONF
AU  - Kesić, Željka
AU  - Lukić, Ivana
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2014
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2574
PB  - Czech Society of Chemical Engineering
C3  - 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P
T1  - Homogeneous-heterogeneous catalytic effect of CaO · ZnO/K2CO3 during biodiesel synthesis
SP  - 233
VL  - 1
UR  - https://hdl.handle.net/21.15107/rcub_technorep_2574
ER  - 

@conference{
author = "Kesić, Željka and Lukić, Ivana and Zdujić, Miodrag and Skala, Dejan",
year = "2014",
publisher = "Czech Society of Chemical Engineering",
journal = "21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P",
title = "Homogeneous-heterogeneous catalytic effect of CaO · ZnO/K2CO3 during biodiesel synthesis",
pages = "233",
volume = "1",
url = "https://hdl.handle.net/21.15107/rcub_technorep_2574"
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Kesić, Ž., Lukić, I., Zdujić, M.,& Skala, D.. (2014). Homogeneous-heterogeneous catalytic effect of CaO · ZnO/K2CO3 during biodiesel synthesis. in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P
Czech Society of Chemical Engineering., 1, 233.
https://hdl.handle.net/21.15107/rcub_technorep_2574

Kesić Ž, Lukić I, Zdujić M, Skala D. Homogeneous-heterogeneous catalytic effect of CaO · ZnO/K2CO3 during biodiesel synthesis. in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P. 2014;1:233.
https://hdl.handle.net/21.15107/rcub_technorep_2574 .

Kesić, Željka, Lukić, Ivana, Zdujić, Miodrag, Skala, Dejan, "Homogeneous-heterogeneous catalytic effect of CaO · ZnO/K2CO3 during biodiesel synthesis" in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P, 1 (2014):233,
https://hdl.handle.net/21.15107/rcub_technorep_2574 .

TY  - CONF
AU  - Lukić, Ivana
AU  - Kesić, Željka
AU  - Zdujić, Miodrag
AU  - Skala, Dejan
PY  - 2014
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2573
PB  - Czech Society of Chemical Engineering
C3  - 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P
T1  - Pretreatment of used vegetable oil using CaO and CaO-ZnO for biodiesel production
SP  - 347
VL  - 1
UR  - https://hdl.handle.net/21.15107/rcub_technorep_2573
ER  - 

@conference{
author = "Lukić, Ivana and Kesić, Željka and Zdujić, Miodrag and Skala, Dejan",
year = "2014",
publisher = "Czech Society of Chemical Engineering",
journal = "21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P",
title = "Pretreatment of used vegetable oil using CaO and CaO-ZnO for biodiesel production",
pages = "347",
volume = "1",
url = "https://hdl.handle.net/21.15107/rcub_technorep_2573"
}

Lukić, I., Kesić, Ž., Zdujić, M.,& Skala, D.. (2014). Pretreatment of used vegetable oil using CaO and CaO-ZnO for biodiesel production. in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P
Czech Society of Chemical Engineering., 1, 347.
https://hdl.handle.net/21.15107/rcub_technorep_2573

Lukić I, Kesić Ž, Zdujić M, Skala D. Pretreatment of used vegetable oil using CaO and CaO-ZnO for biodiesel production. in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P. 2014;1:347.
https://hdl.handle.net/21.15107/rcub_technorep_2573 .

Lukić, Ivana, Kesić, Željka, Zdujić, Miodrag, Skala, Dejan, "Pretreatment of used vegetable oil using CaO and CaO-ZnO for biodiesel production" in 21st International Congress of Chemical and Process Engineering, CHISA 2014 and 17th Conference on P, 1 (2014):347,
https://hdl.handle.net/21.15107/rcub_technorep_2573 .