Biodiesel II: A new concept of biodiesel production - transesterification with supercritical methanol

Abstract

Biodiesel is defined as a fuel that might be used as a pure biofuel or at high concentration in mineral oil derivatives, in accordance with specific quality standards for transport applications. The main raw material used for biodiesel production is rapeseed, which contains mono-unsaturated (about 60%) and also, in a lower quantity, poly-unsaturated fatty acids (C 18:1 and C 18:3), as well as some amounts of undesired saturated fatty acids (palmitic and stearic acids). Other raw materials have also been used in the research and industrial production of biodiesel (palm-oil, sunflower-oil, soybean-oil, waste plant oil, animal fats, etc). The historical background of the biodiesel production, installed industrial capacities, as well as Directives of the European Parliament and of the Council (May 2003) regarding the promotion of the use of biofuels or other renewable fuels for transport are discussed in the first part of this article (Chem. Ind. 58 (2004)). The second part focused on some new concepts and the future development of technology for biodiesel production based on the use of non-catalytic transesterification under supercritical conditions. A literature review, as well as original results based on the transesterification of animal fats, plant oil and used plant oil were discussed. Obtained results were compared with the traditional concept of transesterification based on base or acid catalysis. Experimental investigations of transesterification with supercritical methanol were performed in a 2 dm3 autoclave at 140 bar pressure and at 300°C with molar ratio of methanol to triglycerides of about 41. The degree of esterification strongly depends on the density of supercritical methanol and on the possibility of reaction occurring in one phase.

U prvom članku serije na temu biodizela analizirana je proizvodnja biodizela u proteklih 20 godina, ukupno instalirani kapaciteti za proizvodnju biodizela u Evropi, trenutno iskorišćenje postojećih kapaciteta, usvojena direktiva Evropske zajednice u 2003. o supstituciji dizela mineralnog porekla dobijenog iz nafte sa biodizelom koja treba da bude primenjena do 2010. U prvom članku su navedeni standardi koji su usvojeni u nekim državama trenutno najvećim proizvođačima biodizela [1]. U drugom članku ove serije posvećene problematici biodizela analizira se nov postupak dobijanja biodizela primenom direktne konverzije trigiicerida u odgovarajuće estre masnih kiselina korišćenjem metanola u natkritčnim uslovima. U radu se, između ostalog, prikazuju originalni rezultati natkriticne transesterifikacije trigiicerida sa metanoiom izvdeni sa trigiiceridima životinjskog porekla (svinjska mast), uljem suncokreta i korišćenog biljnog ulja kao polazne sirovine za proizvodnju biogoriva odnosno biodizela.