TY  - JOUR
AU  - Pantić, Nevena
AU  - Spasojević, Milica
AU  - Stojanović, Željko
AU  - Veljović, Đorđe
AU  - Krstić, Jugoslav
AU  - Balaž, Ana Marija
AU  - Prodanović, Radivoje
AU  - Prodanović, Olivera
PY  - 2022
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/5096
AB  - Novel macroporous copolymers of glycidyl methacrylate and ethylene glycol dimethacrylate with mean pore size diameters ranging from 150 to 310 nm were synthesized by dispersion polymerization and modified with ethylenediamine. The glutaraldehyde and periodate method were employed to immobilize horseradish peroxidase (HRP) onto these carriers. The activity of the immobilized enzyme was greatly affected by the pore size of the carrier. The highest specific activities of 9.65 and 8.94 U/g of dry weight were obtained for HRP immobilized by the periodate-route onto poly(GMA‐co‐EGDMA) carriers with pore size diameters of 234 and 297 nm, respectively. Stability studies showed an improved operational stability of immobilized peroxidase at 65 °C and in an organic solvent. HRP immobilized on a copolymer with a pore size of 234 nm, showing the highest specific activity and good stability, had higher activities at almost all pH values than the native enzyme and the increased Km value for pyrogallol oxidation. Immobilized HRP retained 80% of its original activity after five consecutive cycles of the pyrogallol oxidation and 98% of its initial activity in a storage stability study. Enzyme immobilized onto the macroporous copolymer with the pore size diameter of 234 nm showed a substantial degree of phenol removal achieved by immobilized peroxidase.
PB  - Springer
T2  - Journal of Polymers and the Environment
T1  - Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol
DO  - 10.1007/s10924-021-02364-3
ER  - 

@article{
author = "Pantić, Nevena and Spasojević, Milica and Stojanović, Željko and Veljović, Đorđe and Krstić, Jugoslav and Balaž, Ana Marija and Prodanović, Radivoje and Prodanović, Olivera",
year = "2022",
abstract = "Novel macroporous copolymers of glycidyl methacrylate and ethylene glycol dimethacrylate with mean pore size diameters ranging from 150 to 310 nm were synthesized by dispersion polymerization and modified with ethylenediamine. The glutaraldehyde and periodate method were employed to immobilize horseradish peroxidase (HRP) onto these carriers. The activity of the immobilized enzyme was greatly affected by the pore size of the carrier. The highest specific activities of 9.65 and 8.94 U/g of dry weight were obtained for HRP immobilized by the periodate-route onto poly(GMA‐co‐EGDMA) carriers with pore size diameters of 234 and 297 nm, respectively. Stability studies showed an improved operational stability of immobilized peroxidase at 65 °C and in an organic solvent. HRP immobilized on a copolymer with a pore size of 234 nm, showing the highest specific activity and good stability, had higher activities at almost all pH values than the native enzyme and the increased Km value for pyrogallol oxidation. Immobilized HRP retained 80% of its original activity after five consecutive cycles of the pyrogallol oxidation and 98% of its initial activity in a storage stability study. Enzyme immobilized onto the macroporous copolymer with the pore size diameter of 234 nm showed a substantial degree of phenol removal achieved by immobilized peroxidase.",
publisher = "Springer",
journal = "Journal of Polymers and the Environment",
title = "Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol",
doi = "10.1007/s10924-021-02364-3"
}

Pantić, N., Spasojević, M., Stojanović, Ž., Veljović, Đ., Krstić, J., Balaž, A. M., Prodanović, R.,& Prodanović, O.. (2022). Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol. in Journal of Polymers and the Environment
Springer..
https://doi.org/10.1007/s10924-021-02364-3

Pantić N, Spasojević M, Stojanović Ž, Veljović Đ, Krstić J, Balaž AM, Prodanović R, Prodanović O. Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol. in Journal of Polymers and the Environment. 2022;.
doi:10.1007/s10924-021-02364-3 .

Pantić, Nevena, Spasojević, Milica, Stojanović, Željko, Veljović, Đorđe, Krstić, Jugoslav, Balaž, Ana Marija, Prodanović, Radivoje, Prodanović, Olivera, "Immobilization of Horseradish Peroxidase on Macroporous Glycidyl-Based Copolymers with Different Surface Characteristics for the Removal of Phenol" in Journal of Polymers and the Environment (2022),
https://doi.org/10.1007/s10924-021-02364-3 . .

TY  - JOUR
AU  - Miladinović, Marija R.
AU  - Zdujić, Miodrag
AU  - Veljović, Đorđe
AU  - Krstić, Jugoslav
AU  - Banković-Ilić, Ivana B.
AU  - Veljković, Vlada B.
AU  - Stamenković, Olivera S.
PY  - 2020
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4350
AB  - The catalytic activity of the walnut shell ash was investigated in the biodiesel production by the sunflower oil methanolysis. The catalyst was characterized by the TG-DTA, XRD, Hg porosimetry, Ny physisorption, SEM, and Hammett method. In addition, the effects of the catalyst loading and the methanolto-oil molar ratio on the methyl esters synthesis were tested at the reaction temperature of 60 degrees C. The walnut shell ash provided a very fast reaction and a high FAME content (over 98%). As the reaction occurred in the absence of triacylglycerols mass transfer limitation, the pseudo-first-order model was employed for describing the kinetics of the reaction. The catalyst was successfully reused four times after the regeneration of the catalytic activity by recalcination at 800 degrees C.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Renewable Energy
T1  - Valorization of walnut shell ash as a catalyst for biodiesel production
EP  - 1043
SP  - 1033
VL  - 147
DO  - 10.1016/j.renene.2019.09.056
ER  - 

@article{
author = "Miladinović, Marija R. and Zdujić, Miodrag and Veljović, Đorđe and Krstić, Jugoslav and Banković-Ilić, Ivana B. and Veljković, Vlada B. and Stamenković, Olivera S.",
year = "2020",
abstract = "The catalytic activity of the walnut shell ash was investigated in the biodiesel production by the sunflower oil methanolysis. The catalyst was characterized by the TG-DTA, XRD, Hg porosimetry, Ny physisorption, SEM, and Hammett method. In addition, the effects of the catalyst loading and the methanolto-oil molar ratio on the methyl esters synthesis were tested at the reaction temperature of 60 degrees C. The walnut shell ash provided a very fast reaction and a high FAME content (over 98%). As the reaction occurred in the absence of triacylglycerols mass transfer limitation, the pseudo-first-order model was employed for describing the kinetics of the reaction. The catalyst was successfully reused four times after the regeneration of the catalytic activity by recalcination at 800 degrees C.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Renewable Energy",
title = "Valorization of walnut shell ash as a catalyst for biodiesel production",
pages = "1043-1033",
volume = "147",
doi = "10.1016/j.renene.2019.09.056"
}

Miladinović, M. R., Zdujić, M., Veljović, Đ., Krstić, J., Banković-Ilić, I. B., Veljković, V. B.,& Stamenković, O. S.. (2020). Valorization of walnut shell ash as a catalyst for biodiesel production. in Renewable Energy
Pergamon-Elsevier Science Ltd, Oxford., 147, 1033-1043.
https://doi.org/10.1016/j.renene.2019.09.056

Miladinović MR, Zdujić M, Veljović Đ, Krstić J, Banković-Ilić IB, Veljković VB, Stamenković OS. Valorization of walnut shell ash as a catalyst for biodiesel production. in Renewable Energy. 2020;147:1033-1043.
doi:10.1016/j.renene.2019.09.056 .

Miladinović, Marija R., Zdujić, Miodrag, Veljović, Đorđe, Krstić, Jugoslav, Banković-Ilić, Ivana B., Veljković, Vlada B., Stamenković, Olivera S., "Valorization of walnut shell ash as a catalyst for biodiesel production" in Renewable Energy, 147 (2020):1033-1043,
https://doi.org/10.1016/j.renene.2019.09.056 . .

TY  - JOUR
AU  - Simović, Bojana
AU  - Dapčević, Aleksandra
AU  - Zdravković, J.
AU  - Tasić, Nikola
AU  - Kovač, S.
AU  - Krstić, Jugoslav
AU  - Branković, Goran
PY  - 2019
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/4321
AB  - In this work, nine products were prepared by modifying the experimental conditions (6, 12 and 18 hat 110, 135 and 160 degrees C) of hydrothermal treatment of starting nanoanatase in significantly less concentrated alkaline medium than usual in order to obtain a pure titanate phase. The nanocrystalline samples were characterized by XRPD, FESEM, HRTEM/SAED, EDS, TG, FT-IR, UV-Vis and BET analyses. The results revealed that the structure, texture, morphology and band gap energy of samples strongly depend on conditions of hydrothermal treatment. The intensification of hydrothermal treatment significantly increases the solubility of TiO2 promoting the changes in morphology from nearly spherical titania nanoparticles to elongated titanate nanosheets. The single titanate phase was obtained after energetically the most intensive treatment, i.e. 18 hat 160 degrees C. The step-by-step optimization was thus necessary to finally distinguish the titanates from titania in terms of structural and spectral properties and to finally allow the clarification of long-standing confusion between titania and titanates. The obtained single titanate phase was furtherly used to fabricate a humidity sensor, which showed remarkably rapid response and quick recovery time.
PB  - Elsevier Science Sa, Lausanne
T2  - Journal of Alloys and Compounds
T1  - From titania to titanates: Phase and morphological transition in less alkaline medium under mild conditions
EP  - 819
SP  - 810
VL  - 781
DO  - 10.1016/j.jallcom.2018.12.039
ER  - 

@article{
author = "Simović, Bojana and Dapčević, Aleksandra and Zdravković, J. and Tasić, Nikola and Kovač, S. and Krstić, Jugoslav and Branković, Goran",
year = "2019",
abstract = "In this work, nine products were prepared by modifying the experimental conditions (6, 12 and 18 hat 110, 135 and 160 degrees C) of hydrothermal treatment of starting nanoanatase in significantly less concentrated alkaline medium than usual in order to obtain a pure titanate phase. The nanocrystalline samples were characterized by XRPD, FESEM, HRTEM/SAED, EDS, TG, FT-IR, UV-Vis and BET analyses. The results revealed that the structure, texture, morphology and band gap energy of samples strongly depend on conditions of hydrothermal treatment. The intensification of hydrothermal treatment significantly increases the solubility of TiO2 promoting the changes in morphology from nearly spherical titania nanoparticles to elongated titanate nanosheets. The single titanate phase was obtained after energetically the most intensive treatment, i.e. 18 hat 160 degrees C. The step-by-step optimization was thus necessary to finally distinguish the titanates from titania in terms of structural and spectral properties and to finally allow the clarification of long-standing confusion between titania and titanates. The obtained single titanate phase was furtherly used to fabricate a humidity sensor, which showed remarkably rapid response and quick recovery time.",
publisher = "Elsevier Science Sa, Lausanne",
journal = "Journal of Alloys and Compounds",
title = "From titania to titanates: Phase and morphological transition in less alkaline medium under mild conditions",
pages = "819-810",
volume = "781",
doi = "10.1016/j.jallcom.2018.12.039"
}

Simović, B., Dapčević, A., Zdravković, J., Tasić, N., Kovač, S., Krstić, J.,& Branković, G.. (2019). From titania to titanates: Phase and morphological transition in less alkaline medium under mild conditions. in Journal of Alloys and Compounds
Elsevier Science Sa, Lausanne., 781, 810-819.
https://doi.org/10.1016/j.jallcom.2018.12.039

Simović B, Dapčević A, Zdravković J, Tasić N, Kovač S, Krstić J, Branković G. From titania to titanates: Phase and morphological transition in less alkaline medium under mild conditions. in Journal of Alloys and Compounds. 2019;781:810-819.
doi:10.1016/j.jallcom.2018.12.039 .

Simović, Bojana, Dapčević, Aleksandra, Zdravković, J., Tasić, Nikola, Kovač, S., Krstić, Jugoslav, Branković, Goran, "From titania to titanates: Phase and morphological transition in less alkaline medium under mild conditions" in Journal of Alloys and Compounds, 781 (2019):810-819,
https://doi.org/10.1016/j.jallcom.2018.12.039 . .

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  - Maksimović, Svetolik
AU  - Zdujić, Miodrag
AU  - Liu, Hui
AU  - Krstić, Jugoslav
AU  - Skala, Dejan
PY  - 2013
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/2423
AB  - The kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil were studied at different temperatures, ranging from 60 to 96 degrees C using CaO center dot ZnO as catalyst (2 wt% on the basis of oil) and methanol to oil molar ratio of 10:1. Heterogeneous CaO center dot ZnO catalyst was synthesized by mechanochemical treatment of CaO and ZnO powder mixture with the addition of water necessary for the formation of corresponding mixed hydroxides, and their calcination at 700 degrees C in air. It was shown that kinetics of overall process could be described as pseudo-first order reaction. For the sunflower oil methanolysis at 60 and 70 degrees C, the rate of process at the beginning of biodiesel synthesis was limited by triglycerides mass transfer to the catalyst surface, and after that it is governed by the rate of chemical reaction at catalyst surface. At higher temperatures the influence of mass transfer resistance is almost negligible implying that the rate of chemical reaction determines the overall kinetic of biodiesel synthesis. In the case of used vegetable oil, the influence of mass transfer resistance was not observed either at higher or lower temperature. The kinetic model that describes the whole process well was proposed, and it comprises both the triglycerides mass transfer and chemical reaction controlled regime. The overall volumetric mass transfer coefficient was defined, assuming that it depends on the conversion of triglycerides.
PB  - Elsevier Sci Ltd, Oxford
T2  - Fuel
T1  - Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO
EP  - 378
SP  - 367
VL  - 113
DO  - 10.1016/j.fuel.2013.05.093
ER  - 

@article{
author = "Lukić, Ivana and Kesić, Željka and Maksimović, Svetolik and Zdujić, Miodrag and Liu, Hui and Krstić, Jugoslav and Skala, Dejan",
year = "2013",
abstract = "The kinetics of heterogeneous methanolysis of sunflower oil and used vegetable oil were studied at different temperatures, ranging from 60 to 96 degrees C using CaO center dot ZnO as catalyst (2 wt% on the basis of oil) and methanol to oil molar ratio of 10:1. Heterogeneous CaO center dot ZnO catalyst was synthesized by mechanochemical treatment of CaO and ZnO powder mixture with the addition of water necessary for the formation of corresponding mixed hydroxides, and their calcination at 700 degrees C in air. It was shown that kinetics of overall process could be described as pseudo-first order reaction. For the sunflower oil methanolysis at 60 and 70 degrees C, the rate of process at the beginning of biodiesel synthesis was limited by triglycerides mass transfer to the catalyst surface, and after that it is governed by the rate of chemical reaction at catalyst surface. At higher temperatures the influence of mass transfer resistance is almost negligible implying that the rate of chemical reaction determines the overall kinetic of biodiesel synthesis. In the case of used vegetable oil, the influence of mass transfer resistance was not observed either at higher or lower temperature. The kinetic model that describes the whole process well was proposed, and it comprises both the triglycerides mass transfer and chemical reaction controlled regime. The overall volumetric mass transfer coefficient was defined, assuming that it depends on the conversion of triglycerides.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Fuel",
title = "Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO",
pages = "378-367",
volume = "113",
doi = "10.1016/j.fuel.2013.05.093"
}

Lukić, I., Kesić, Ž., Maksimović, S., Zdujić, M., Liu, H., Krstić, J.,& Skala, D.. (2013). Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO. in Fuel
Elsevier Sci Ltd, Oxford., 113, 367-378.
https://doi.org/10.1016/j.fuel.2013.05.093

Lukić I, Kesić Ž, Maksimović S, Zdujić M, Liu H, Krstić J, Skala D. Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO. in Fuel. 2013;113:367-378.
doi:10.1016/j.fuel.2013.05.093 .

Lukić, Ivana, Kesić, Željka, Maksimović, Svetolik, Zdujić, Miodrag, Liu, Hui, Krstić, Jugoslav, Skala, Dejan, "Kinetics of sunflower and used vegetable oil methanolysis catalyzed by CaO·ZnO" in Fuel, 113 (2013):367-378,
https://doi.org/10.1016/j.fuel.2013.05.093 . .

TY  - JOUR
AU  - Dokic, Marko
AU  - Kesic, Zeljka
AU  - Krstić, Jugoslav
AU  - Jovanović, Dušan M.
AU  - Skala, Dejan
PY  - 2012
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/5672
AB  - A difficulty of biodiesel synthesis based on alkaline catalysts obviously exists if free fatty acids (FFAs) content in vegetable oil is above 0.5 wt.%. In this study, the ferric sulfate supported on silica (Fe-2(SO4)(3)/SiO2) was synthesized, activated (at different temperature: 120-600 degrees C) and tested for heterogeneous esterification of FFA (oleic acid) present in sunflower oil (5 wt.%). The catalyst samples were characterized by BET, TG/DTG, XRD and FTIR analyses. Obtained results showed that catalyst activated at 500 degrees C for 2 h in air atmosphere gave the maximal conversion of oleic acid (similar to 97%). Repeated use of catalyst without additional catalyst treatment or re-activation indicated that catalyst posses desired stability and activity. A pseudo-homogeneous kinetic model was proposed with good agreement between calculated and experimental data.
PB  - Elsevier Sci Ltd, Oxford
T2  - Fuel
T1  - Decrease of free fatty acid content in vegetable oil using silica supported ferric sulfate catalyst
EP  - 602
SP  - 595
VL  - 97
DO  - 10.1016/j.fuel.2012.03.039
ER  - 

@article{
author = "Dokic, Marko and Kesic, Zeljka and Krstić, Jugoslav and Jovanović, Dušan M. and Skala, Dejan",
year = "2012",
abstract = "A difficulty of biodiesel synthesis based on alkaline catalysts obviously exists if free fatty acids (FFAs) content in vegetable oil is above 0.5 wt.%. In this study, the ferric sulfate supported on silica (Fe-2(SO4)(3)/SiO2) was synthesized, activated (at different temperature: 120-600 degrees C) and tested for heterogeneous esterification of FFA (oleic acid) present in sunflower oil (5 wt.%). The catalyst samples were characterized by BET, TG/DTG, XRD and FTIR analyses. Obtained results showed that catalyst activated at 500 degrees C for 2 h in air atmosphere gave the maximal conversion of oleic acid (similar to 97%). Repeated use of catalyst without additional catalyst treatment or re-activation indicated that catalyst posses desired stability and activity. A pseudo-homogeneous kinetic model was proposed with good agreement between calculated and experimental data.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Fuel",
title = "Decrease of free fatty acid content in vegetable oil using silica supported ferric sulfate catalyst",
pages = "602-595",
volume = "97",
doi = "10.1016/j.fuel.2012.03.039"
}

Dokic, M., Kesic, Z., Krstić, J., Jovanović, D. M.,& Skala, D.. (2012). Decrease of free fatty acid content in vegetable oil using silica supported ferric sulfate catalyst. in Fuel
Elsevier Sci Ltd, Oxford., 97, 595-602.
https://doi.org/10.1016/j.fuel.2012.03.039

Dokic M, Kesic Z, Krstić J, Jovanović DM, Skala D. Decrease of free fatty acid content in vegetable oil using silica supported ferric sulfate catalyst. in Fuel. 2012;97:595-602.
doi:10.1016/j.fuel.2012.03.039 .

Dokic, Marko, Kesic, Zeljka, Krstić, Jugoslav, Jovanović, Dušan M., Skala, Dejan, "Decrease of free fatty acid content in vegetable oil using silica supported ferric sulfate catalyst" in Fuel, 97 (2012):595-602,
https://doi.org/10.1016/j.fuel.2012.03.039 . .

TY  - JOUR
AU  - Lazarević, Slavica
AU  - Janković-Častvan, Ivona
AU  - Onjia, Antonije
AU  - Krstić, Jugoslav
AU  - Janaćković, Đorđe
AU  - Petrović, Rada
PY  - 2011
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1850
AB  - Inverse gas chromatography at infinite and finite surface coverages was applied to evaluate the surface properties of an iron-modified sepiolite sorbent, Fe-sepiolite. The adsorptions of different nonpolar and polar probes were measured in the infinite-dilution regime, in the temperature range 483-513 K. For the organic probes used, the thermodynamic parameters (free energy, enthalpy, and entropy) of adsorption and the dispersive and specific components of the free energy of adsorption were determined and are discussed in terms of specific reactions that can occur on the adsorbent surface. Following the approach of Gutmann (The Donor Acceptor Approach to Molecular Interactions; Plenum Press: New York, 1978), acid/base surface characteristics were determined. The adsorption isotherms of n-hexane, benzene, chloroform, and tetrahydrofuran were used to estimate the specific surface areas, isosteric heats of adsorption, and adsorption energy distributions for the adsorption of organic molecules.
PB  - Amer Chemical Soc, Washington
T2  - Industrial & Engineering Chemistry Research
T1  - Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography
EP  - 11475
IS  - 20
SP  - 11467
VL  - 50
DO  - 10.1021/ie200595n
ER  - 

@article{
author = "Lazarević, Slavica and Janković-Častvan, Ivona and Onjia, Antonije and Krstić, Jugoslav and Janaćković, Đorđe and Petrović, Rada",
year = "2011",
abstract = "Inverse gas chromatography at infinite and finite surface coverages was applied to evaluate the surface properties of an iron-modified sepiolite sorbent, Fe-sepiolite. The adsorptions of different nonpolar and polar probes were measured in the infinite-dilution regime, in the temperature range 483-513 K. For the organic probes used, the thermodynamic parameters (free energy, enthalpy, and entropy) of adsorption and the dispersive and specific components of the free energy of adsorption were determined and are discussed in terms of specific reactions that can occur on the adsorbent surface. Following the approach of Gutmann (The Donor Acceptor Approach to Molecular Interactions; Plenum Press: New York, 1978), acid/base surface characteristics were determined. The adsorption isotherms of n-hexane, benzene, chloroform, and tetrahydrofuran were used to estimate the specific surface areas, isosteric heats of adsorption, and adsorption energy distributions for the adsorption of organic molecules.",
publisher = "Amer Chemical Soc, Washington",
journal = "Industrial & Engineering Chemistry Research",
title = "Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography",
pages = "11475-11467",
number = "20",
volume = "50",
doi = "10.1021/ie200595n"
}

Lazarević, S., Janković-Častvan, I., Onjia, A., Krstić, J., Janaćković, Đ.,& Petrović, R.. (2011). Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography. in Industrial & Engineering Chemistry Research
Amer Chemical Soc, Washington., 50(20), 11467-11475.
https://doi.org/10.1021/ie200595n

Lazarević S, Janković-Častvan I, Onjia A, Krstić J, Janaćković Đ, Petrović R. Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography. in Industrial & Engineering Chemistry Research. 2011;50(20):11467-11475.
doi:10.1021/ie200595n .

Lazarević, Slavica, Janković-Častvan, Ivona, Onjia, Antonije, Krstić, Jugoslav, Janaćković, Đorđe, Petrović, Rada, "Surface Characterization of Iron-Modified Sepiolite by Inverse Gas Chromatography" in Industrial & Engineering Chemistry Research, 50, no. 20 (2011):11467-11475,
https://doi.org/10.1021/ie200595n . .

TY  - JOUR
AU  - Jokić, Bojan
AU  - Drmanić, Saša
AU  - Radetić, Tamara
AU  - Krstić, Jugoslav
AU  - Petrović, Rada
AU  - Orlović, Aleksandar
AU  - Janaćković, Đorđe
PY  - 2010
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1661
AB  - Submicron carbon spherical particles were obtained by polycondensation of resorcinol and formaldehyde in a solution and subsequent ultrasonic spray pyrolysis of the prepared sol. Microscopic characterization indicates the regular spherical shape of the obtained particles and sphere diameters in 200-700 nm range. The carbon spheres are amorphous as confirmed by electron diffraction, EELS, XRD and HREM characterization. Activation procedure was performed with H2O in a nitrogen flow for 15 and 30 min at 800 degrees C. The activation procedure preserved the initial spherical shapes of the particles while the particle porosity and specific surface area were increased. The amount of surface oxygen functionalities was also increased by activation procedure as indicated by FTIR analysis.
PB  - Elsevier, Amsterdam
T2  - Materials Letters
T1  - Synthesis of submicron carbon spheres by the ultrasonic spray pyrolysis method
EP  - 2176
IS  - 20
SP  - 2173
VL  - 64
DO  - 10.1016/j.matlet.2010.06.066
ER  - 

@article{
author = "Jokić, Bojan and Drmanić, Saša and Radetić, Tamara and Krstić, Jugoslav and Petrović, Rada and Orlović, Aleksandar and Janaćković, Đorđe",
year = "2010",
abstract = "Submicron carbon spherical particles were obtained by polycondensation of resorcinol and formaldehyde in a solution and subsequent ultrasonic spray pyrolysis of the prepared sol. Microscopic characterization indicates the regular spherical shape of the obtained particles and sphere diameters in 200-700 nm range. The carbon spheres are amorphous as confirmed by electron diffraction, EELS, XRD and HREM characterization. Activation procedure was performed with H2O in a nitrogen flow for 15 and 30 min at 800 degrees C. The activation procedure preserved the initial spherical shapes of the particles while the particle porosity and specific surface area were increased. The amount of surface oxygen functionalities was also increased by activation procedure as indicated by FTIR analysis.",
publisher = "Elsevier, Amsterdam",
journal = "Materials Letters",
title = "Synthesis of submicron carbon spheres by the ultrasonic spray pyrolysis method",
pages = "2176-2173",
number = "20",
volume = "64",
doi = "10.1016/j.matlet.2010.06.066"
}

Jokić, B., Drmanić, S., Radetić, T., Krstić, J., Petrović, R., Orlović, A.,& Janaćković, Đ.. (2010). Synthesis of submicron carbon spheres by the ultrasonic spray pyrolysis method. in Materials Letters
Elsevier, Amsterdam., 64(20), 2173-2176.
https://doi.org/10.1016/j.matlet.2010.06.066

Jokić B, Drmanić S, Radetić T, Krstić J, Petrović R, Orlović A, Janaćković Đ. Synthesis of submicron carbon spheres by the ultrasonic spray pyrolysis method. in Materials Letters. 2010;64(20):2173-2176.
doi:10.1016/j.matlet.2010.06.066 .

Jokić, Bojan, Drmanić, Saša, Radetić, Tamara, Krstić, Jugoslav, Petrović, Rada, Orlović, Aleksandar, Janaćković, Đorđe, "Synthesis of submicron carbon spheres by the ultrasonic spray pyrolysis method" in Materials Letters, 64, no. 20 (2010):2173-2176,
https://doi.org/10.1016/j.matlet.2010.06.066 . .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Krstić, Jugoslav
AU  - Glišić, Sandra
AU  - Jovanović, Dušan
AU  - Skala, Dejan
PY  - 2010
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1600
AB  - In this study, catalysts for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as the active component on an alumina/silica support were synthesized using the sol-gel method, which was followed by drying the 'dense' wet gels with supercritical carbon dioxide to obtain the aerogels. The prepared catalysts were characterized by XRD analysis, FTIR spectroscopy and N2 physisorption at 77 K, and tested in the methanolysis of sunflower oil. The effects of reaction variables, such as reaction time, temperature and methanol to oil molar ratio, on the yield of FAME were investigated. The aerogel catalysts with K2CO3 as the active component on an alumina/silica support exhibited good activity in the methanolysis of sunflower oil. The leaching of potassium when the catalyst was in contact with pure methanol under the working conditions of methanolysis was also tested in this study, indicating that it occurred only at higher temperatures, while at lower ones, it was negligible.
AB  - U ovom radu katalizator za sintezu metil estara masnih kiselina (MEMK ili biodizel) sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču sintetizovan je sol-gel metodom nakon čega je dobijeni gel sušen uz prisustvo natkritičnog ugljen dioksida da bi se dobio aerogel. Za karakterizaciju sintetizovanih katalizatora korišćene su metode XRD, FTIR i N2 fizisorpcija na 77 K i katalizatori su testirani u reakciji metanolize suncokretovog ulja. Katalizator je testiran u reakciji metanolize suncekrotovog ulja i sintezi MEMK. Ispitan je uticaj različitih parametara kao što su vreme, temperatura i molarni odnos metanol : ulje na prinos MEMK. Aerogel katalizator sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču pokazao je dobru katalitičku aktivnost u reakciji metanolize suncokretovog ulja. Izluživanje kalijuma u kontaktu sa metanolom na radnim uslovima metanolize takođe je testirano u ovom radu, pokazujući da ono postoji na višim temperaturama, dok je na nižim zanemarljivo.
PB  - Serbian Chemical Society, Belgrade
T2  - Journal of the Serbian Chemical Society
T1  - Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts
T1  - Sinteza biodizela katalizovana alumosilikatnim aerogelom sa K2Co3
EP  - 801
IS  - 6
SP  - 789
VL  - 75
UR  - https://hdl.handle.net/21.15107/rcub_technorep_1600
ER  - 

@article{
author = "Lukić, Ivana and Krstić, Jugoslav and Glišić, Sandra and Jovanović, Dušan and Skala, Dejan",
year = "2010",
abstract = "In this study, catalysts for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as the active component on an alumina/silica support were synthesized using the sol-gel method, which was followed by drying the 'dense' wet gels with supercritical carbon dioxide to obtain the aerogels. The prepared catalysts were characterized by XRD analysis, FTIR spectroscopy and N2 physisorption at 77 K, and tested in the methanolysis of sunflower oil. The effects of reaction variables, such as reaction time, temperature and methanol to oil molar ratio, on the yield of FAME were investigated. The aerogel catalysts with K2CO3 as the active component on an alumina/silica support exhibited good activity in the methanolysis of sunflower oil. The leaching of potassium when the catalyst was in contact with pure methanol under the working conditions of methanolysis was also tested in this study, indicating that it occurred only at higher temperatures, while at lower ones, it was negligible., U ovom radu katalizator za sintezu metil estara masnih kiselina (MEMK ili biodizel) sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču sintetizovan je sol-gel metodom nakon čega je dobijeni gel sušen uz prisustvo natkritičnog ugljen dioksida da bi se dobio aerogel. Za karakterizaciju sintetizovanih katalizatora korišćene su metode XRD, FTIR i N2 fizisorpcija na 77 K i katalizatori su testirani u reakciji metanolize suncokretovog ulja. Katalizator je testiran u reakciji metanolize suncekrotovog ulja i sintezi MEMK. Ispitan je uticaj različitih parametara kao što su vreme, temperatura i molarni odnos metanol : ulje na prinos MEMK. Aerogel katalizator sa K2CO3 kao aktivnom komponentom na alumosilikatnom nosaču pokazao je dobru katalitičku aktivnost u reakciji metanolize suncokretovog ulja. Izluživanje kalijuma u kontaktu sa metanolom na radnim uslovima metanolize takođe je testirano u ovom radu, pokazujući da ono postoji na višim temperaturama, dok je na nižim zanemarljivo.",
publisher = "Serbian Chemical Society, Belgrade",
journal = "Journal of the Serbian Chemical Society",
title = "Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts, Sinteza biodizela katalizovana alumosilikatnim aerogelom sa K2Co3",
pages = "801-789",
number = "6",
volume = "75",
url = "https://hdl.handle.net/21.15107/rcub_technorep_1600"
}

Lukić, I., Krstić, J., Glišić, S., Jovanović, D.,& Skala, D.. (2010). Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts. in Journal of the Serbian Chemical Society
Serbian Chemical Society, Belgrade., 75(6), 789-801.
https://hdl.handle.net/21.15107/rcub_technorep_1600

Lukić I, Krstić J, Glišić S, Jovanović D, Skala D. Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts. in Journal of the Serbian Chemical Society. 2010;75(6):789-801.
https://hdl.handle.net/21.15107/rcub_technorep_1600 .

Lukić, Ivana, Krstić, Jugoslav, Glišić, Sandra, Jovanović, Dušan, Skala, Dejan, "Biodiesel synthesis using K2CO3/Al-O-Si aerogel catalysts" in Journal of the Serbian Chemical Society, 75, no. 6 (2010):789-801,
https://hdl.handle.net/21.15107/rcub_technorep_1600 .

TY  - JOUR
AU  - Tanasković, N.
AU  - Radovanović, Željko
AU  - Đokić, Veljko
AU  - Krstić, Jugoslav
AU  - Drmanić, Saša
AU  - Janaćković, Đorđe
AU  - Petrović, Rada
PY  - 2009
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1510
AB  - Mesoporous titania with well-crystallized anatase phase was synthesized by nonhydrolytic sol-gel process combined with solvothermal treatment. Titanium-isopropoxide, titanium-tetrachloride, and carbon-tetrachloride were used for synthesis under nitrogen atmosphere in a glove box. The obtained mixture was heated in an autoclave at 140 degrees C for 3 h and 30 h. XRD analysis showed that dry gels contained anatase phase with low crystallinity, while powders obtained by calcination of dry gels at 500 degrees C for 3 h consisted of pure anatase with high crystallinity. SEM analysis of dried gels and powders shows agglomerates of spherical particles of the size similar to 300 nm. The TEM micrographs confirmed the nanoscale size of the titania powders, with the primary particle size of about 20 nm. Titania powders exhibit maximum pore diameter of 13.2 nm and 9.5 nm for gelation time 3 h and 30 h, respectively. The photocatalytic activity of such synthesized titania is superior to that of commercial photocatalyst Degussa P-25.
PB  - Academic Press Ltd- Elsevier Science Ltd, London
T2  - Superlattices and Microstructures
T1  - Synthesis of mesoporous nanocrystalline titania powders by nonhydrolitic sol-gel method
EP  - 222
IS  - 1-2
SP  - 217
VL  - 46
DO  - 10.1016/j.spmi.2008.12.028
ER  - 

@article{
author = "Tanasković, N. and Radovanović, Željko and Đokić, Veljko and Krstić, Jugoslav and Drmanić, Saša and Janaćković, Đorđe and Petrović, Rada",
year = "2009",
abstract = "Mesoporous titania with well-crystallized anatase phase was synthesized by nonhydrolytic sol-gel process combined with solvothermal treatment. Titanium-isopropoxide, titanium-tetrachloride, and carbon-tetrachloride were used for synthesis under nitrogen atmosphere in a glove box. The obtained mixture was heated in an autoclave at 140 degrees C for 3 h and 30 h. XRD analysis showed that dry gels contained anatase phase with low crystallinity, while powders obtained by calcination of dry gels at 500 degrees C for 3 h consisted of pure anatase with high crystallinity. SEM analysis of dried gels and powders shows agglomerates of spherical particles of the size similar to 300 nm. The TEM micrographs confirmed the nanoscale size of the titania powders, with the primary particle size of about 20 nm. Titania powders exhibit maximum pore diameter of 13.2 nm and 9.5 nm for gelation time 3 h and 30 h, respectively. The photocatalytic activity of such synthesized titania is superior to that of commercial photocatalyst Degussa P-25.",
publisher = "Academic Press Ltd- Elsevier Science Ltd, London",
journal = "Superlattices and Microstructures",
title = "Synthesis of mesoporous nanocrystalline titania powders by nonhydrolitic sol-gel method",
pages = "222-217",
number = "1-2",
volume = "46",
doi = "10.1016/j.spmi.2008.12.028"
}

Tanasković, N., Radovanović, Ž., Đokić, V., Krstić, J., Drmanić, S., Janaćković, Đ.,& Petrović, R.. (2009). Synthesis of mesoporous nanocrystalline titania powders by nonhydrolitic sol-gel method. in Superlattices and Microstructures
Academic Press Ltd- Elsevier Science Ltd, London., 46(1-2), 217-222.
https://doi.org/10.1016/j.spmi.2008.12.028

Tanasković N, Radovanović Ž, Đokić V, Krstić J, Drmanić S, Janaćković Đ, Petrović R. Synthesis of mesoporous nanocrystalline titania powders by nonhydrolitic sol-gel method. in Superlattices and Microstructures. 2009;46(1-2):217-222.
doi:10.1016/j.spmi.2008.12.028 .

Tanasković, N., Radovanović, Željko, Đokić, Veljko, Krstić, Jugoslav, Drmanić, Saša, Janaćković, Đorđe, Petrović, Rada, "Synthesis of mesoporous nanocrystalline titania powders by nonhydrolitic sol-gel method" in Superlattices and Microstructures, 46, no. 1-2 (2009):217-222,
https://doi.org/10.1016/j.spmi.2008.12.028 . .

TY  - JOUR
AU  - Lukić, Ivana
AU  - Krstić, Jugoslav
AU  - Jovanović, D.
AU  - Skala, Dejan
PY  - 2009
UR  - http://TechnoRep.tmf.bg.ac.rs/handle/123456789/1432
AB  - The new type of catalyst for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as active component on alumina/silica support was synthesized using sol-gel method. Corresponding catalyst (xerogel) was prepared by 12 h drying the wet gel in air at 300 degrees C, 600 degrees C or 1000 degrees C at atmospheric pressure. The catalysts activity in the methanolysis of sunflower oil was compared to the activity of the pure K2CO3. The effects of various reaction variables on the yield of FAME were investigated. It was found that the temperature of 120 degrees C and methanol to oil molar ratio of 15: 1, are optimal conditions for FAME synthesis with synthesized catalyst. Repeated use of same amount of catalyst indicated that effect of potassium leaching obviously existed leading to decrease of catalyst activity.
PB  - Elsevier Sci Ltd, Oxford
T2  - Bioresource Technology
T1  - Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil
EP  - 4696
IS  - 20
SP  - 4690
VL  - 100
DO  - 10.1016/j.biortech.2009.04.057
ER  - 

@article{
author = "Lukić, Ivana and Krstić, Jugoslav and Jovanović, D. and Skala, Dejan",
year = "2009",
abstract = "The new type of catalyst for fatty acid methyl esters (FAME or biodiesel) synthesis with K2CO3 as active component on alumina/silica support was synthesized using sol-gel method. Corresponding catalyst (xerogel) was prepared by 12 h drying the wet gel in air at 300 degrees C, 600 degrees C or 1000 degrees C at atmospheric pressure. The catalysts activity in the methanolysis of sunflower oil was compared to the activity of the pure K2CO3. The effects of various reaction variables on the yield of FAME were investigated. It was found that the temperature of 120 degrees C and methanol to oil molar ratio of 15: 1, are optimal conditions for FAME synthesis with synthesized catalyst. Repeated use of same amount of catalyst indicated that effect of potassium leaching obviously existed leading to decrease of catalyst activity.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Bioresource Technology",
title = "Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil",
pages = "4696-4690",
number = "20",
volume = "100",
doi = "10.1016/j.biortech.2009.04.057"
}

Lukić, I., Krstić, J., Jovanović, D.,& Skala, D.. (2009). Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil. in Bioresource Technology
Elsevier Sci Ltd, Oxford., 100(20), 4690-4696.
https://doi.org/10.1016/j.biortech.2009.04.057

Lukić I, Krstić J, Jovanović D, Skala D. Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil. in Bioresource Technology. 2009;100(20):4690-4696.
doi:10.1016/j.biortech.2009.04.057 .

Lukić, Ivana, Krstić, Jugoslav, Jovanović, D., Skala, Dejan, "Alumina/silica supported K2CO3 as a catalyst for biodiesel synthesis from sunflower oil" in Bioresource Technology, 100, no. 20 (2009):4690-4696,
https://doi.org/10.1016/j.biortech.2009.04.057 . .