초임계 메탄올을 이용한 바이오디젤 제조에 관한 연구

Abstract

The aim of this research is to establish a database on the high efficient and evironment-friendly process for biodiesel production via non-catalytic supercritical process. In chapter Ⅲ, thermal decomposition of various fatty acid methyl esters (FAMEs) in supercritical methanol was assessed to investigate degradation characteristics and examine the thermal stability of biodiesel. It was found that if FAMEs have shorter chain lengths and are more saturated, they have higher thermal stability in supercritical methanol. All FAMEs remained stable at 330 ℃ or below. Based on these results, it was recommend that transesterification reactions in supercritical methanol should be carried out below 330 ℃, the temperature at which thermal decomposition of FAMEs begins to occur, to optimize high-yield biodiesel production. In chapter Ⅳ, a gas chromatographic method was developed to determine the content of FAMEs in biodiesel prepared by a supercritical process. This new gas chromatographic method using HP-88 column can be used to accurately determine the content of FAMEs in biodiesel prepared by a supercritical process. In chapter Ⅴ, the effects of reaction parameters on the transesterification of various vegetable oils in supercritical methanol were investigated to design the optimum reaction conditions. High levels of FAMEs in the biodiesel was obtained under the following reaction conditions: 335 ℃, 20 MPa, a molar ratio of methanol to oil of 45:1, an agitation speed of 500 rpm, and a reaction time of 15 min. A kinetic study on the transesterification of various vegetable oils in supercritical methanol was also performed to evaluate the reactivity of various raw materials with supercritical methanol. As a result, with more highly saturated raw material, the reaction rate was faster. Finally, in chapter Ⅵ, in order to obtain optimal conditions maximizing the methyl esters content, the relationships between the FAMEs content and reaction parameters were evaluated and the reaction process was statistically optimized using response surface methodology. The optimum processing conditions were 330 ℃ 21 MPa, 16 min, and 50 mol/mol. The response value in the biodiesel for these conditions was 93.6% methyl esters. These researches are expected to provide useful information to optimize the reaction conditions for biodiesel production using supercritical methanol.