Study On Preparation Of Calcium Based Soild Base Catalyst And Its Application In Biodiesel Synthesis

With the gradual depletion of fossil fuels, environmental issues have become increasingly prominent, biodiesel that is a clean, renewable biomass energy has received extensive attention all over the world. Heterogeneous catalysts could make the production of biodiesel more environmentally friendly, and it will have important significance to prepare cheap heterogeneous catalysts with good performance for biodiesel production. In this research, two kinds of calcium oxide based solid base catalyst were prepared for synthesis of biodiesel from rapeseed oil, and the catalysts were characterized using a variety of modern characterization methods. The major results of this thesis were summarized as follows:1. A high catalytic activity catalyst KF/Ca O-La2O3 was prepared by impregnation method. The optimum preparation conditions of KF/Ca O-La2O3 are as follows: La2O3 additive amount 15 wt%, calcination temperature 600℃ and calcination time 3h. The crystal structure and morphology of the catalyst were characterized by XRD, N2 adsorption-desorption, SEM and TEM, and base strength was characterized by Hammett indicator method. Characterization showed: Ca O, KCa F3 and La OF were formed after calcination; the porous structure can be observed; BET surface area was 0.96m2/g, average pore size was 24.7nm; the hammett base strength was 15.0<H—<18.4. The effects of reaction conditions were investigated, and results indicate that when transesterification carried out at temperature 65℃ with a molar ratio of oil to methanol 12:1 and a catalyst dosage 4 wt% for 80 min, the highest FAME yield 97.3% could be achieved. The KF/Ca O-La2O3 can be separated from the product for reuse, and the FMAE yield was more 70% after reused of 5 times.2. KF/Ca O-MSP catalyst was prepared by impregnation method. The optimum preparation conditions of KF/Ca O-La2O3 are as follows: La2O3 additive amount 15 wt%, calcination temperature 600℃ and calcination time 3h. The crystal structure and morphology of the catalyst were characterized by XRD, N2 adsorption-desorption, SEM and TEM, and base strength was characterized by Hammett indicator method. Characterization showed: Ca O, KCa F3 and La OF were formed after calcination; the porous structure can be observed; BET surface area was 1.04m2/g, average pore size was 18.5nm; the hammett base strength was 9.8<H—<15.0. Under the optimum reaction conditions:reaction temperature 65℃, a molar ratio of oil to methanol 12:1, catalyst dosage 4 wt% and reaction time 2.5h, the highest FAME yield 95.3% could be achieved.3. In our research, between KF/Ca O-La2O3 and KF/Ca O-MSP, only KF/Ca O-La2O3 maintain the integrity of shape after transesterification reaction. Mechanical strength tests showed that the mechanical strength of KF/Ca O-La2O3 improved significantly compared with pure Ca O, and the experimental data follows well with the Weibull distribution. The average limited pressure of cylindrical KF/Ca O-La2O3 catalyst was 25.2Kg, and the Weibull modulus m was 6.37, which indicated that KF/Ca O-La2O3 has good mechanical strength performance with high strength reliability.4. Our research showed that the new crystal KCa F3 formed after calcium oxide based solid base catalyst loaded with KF was not an active crystal, which can not catalyze the transesterification reaction of oil and methanol.