The purpose of this dissertation is to introduce the new supercritical methanol process combining metal catalyst to produce quality-improved biodiesel from highly unsaturated feedstock.
In chapter Ⅲ, conventional hydrogenation of highly unsaturated biodiesel over copper catalyst was performed to evaluate the catalytic performance for reducing the degree of unsaturation of biodiesel and to confirm the fuel quality of hydrogenated biodiesel. It was found that 8%-Cu/SiO2 catalyst exhibited high catalytic performance for reducing the polyunsaturated fatty acid methyl esters without increasing the saturated fatty acid methyl esters, and quality-improved biodiesel was obtained even after three cycles of 8%-Cu/SiO2 catalyst reuse. In chapter Ⅳ, to overcome the weakness in two-step process of conventional copper-catalyzed hydrogenation of biodiesel, a supercritical one-pot process combining transesterification and partial hydrogenation of highly unsaturated feedstock was proposed to test its technical feasibility. Results showed that hydrogenation proceeded simultaneously during the transesterification of soybean oil in supercritical methanol, and hydrogenation occurred during the reaction despite the absence of hydrogen gas. Furthermore, key properties of the partially hydrogenated methyl esters were improved and complied with standard specifications for biodiesel. In chapter Ⅴ, the activity and selectivity of Cu/SiO2 for supercritical one-pot process combining transesterification and partial hydrogenation of highly unsaturated feedstock were statistically optimized using response surface methodology. The catalyst amount and Cu loading were chosen as variables affecting the supercritical one-pot reactions, and the optimal catalyst amount and Cu loading were predicted. The experimental results showed that the highest FAME and methyl oleate contents were acquired by 4.456% of Cu loading and 4.6225 wt.% catalyst, and the activity of this optimized Cu/SiO2 catalyst was maintained after three cycles. Finally, in chapter Ⅵ, the effects of operating parameters of supercritical one-pot process were evaluate to give more detailed information on this process. For this purpose, supercritical one-pot reactions over 4.456%-Cu/SiO2 catalyst were carried out by varying the temperatures of 280-320 oC, times of 5-40 min, molar ratios of 15-60 and pressures of 80-250 bar, and corresponding results were further analyzed in terms of kinetics. It was found from the results that Cu/SiO2 catalyst had activities for not only partial hydrogenation, but also transesterification, and the rate of transesterification is faster than hydrogenation in the supercritical one-pot process.
The results of these studies are expected to contribute to extending the research area of supercritical methanol process for high-quality biodiesel production.