Research Of Biodiesel Preparation With Solid Acid Catalysts From Waste Food Oils

In this paper, a series of solid superacid catalyst was prepared by the coprecipitation-impregnation method under different conditions.The catalytic properties of the samples were evaluated through biodiesel preparation of waste oil and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and BET surface area measurement. Various reaction parameters influencing the synthesis were discussed and the optimum conditions were established. By observing the activity of SO42-/MxOy solid superacid, rare earth-modified solid superacid, SO42-/ZrO2-Al2O3 and SO42-/SnO2-Al2O3, two higher activity solid acid catalysts were selected: SO42-/ZrO2-Al2O3 and SO42-/SnO2-Al2O3.The results show that the best preparation conditions of SO42-/ZrO2-Al2O3 were as follows: the optimal Al2O3 doping was 5%, the impregnant concentration was 0.5mol/L, calcination at 600℃for 4h. Under the optimum reaction conditions obtained as follows: 10:1 of molar ratio of methanol to waste oils, catalyst dosage 4wt% of oil mass used, 230℃of reaction temperature, 9 hours of reaction time, the yield of the biodiesel can reach 81.42%. And the results show that among all the prepared SO42-/SnO2-Al2O3 samples, the one that was calcined at 550℃, the calcination time was 4h, Al2O3 doping was 5%,and the impregnant concentration was 1.0mol/L has the highest production rate. When alcohol-oil ratio at 8:1, the dosage at 4%, 250℃of reaction temperature and the reaction time at 3h, the yield of biodiesel can be as high as 78.95%.Characterization by XRD and IR analysis showed that, the incorporation of Al2O3 into SO42-/ZrO2 stabilizes the tetragonal zirconia compound, and the calcination at 600℃increases the reactivity of the catalyst by producing a greater fraction of active tetragonal zirconia with a larger surface area. And the introduction of Al2O3 into SO42-/SnO2 strengthens the diffraction peak for the active constituents. It can be seen from the FT-IR spectra that superacid structures are formed in the catalysts and the acidity is strengthened remarkably and the activated centre of the catalyst were increasesed.