Synthesis of biodiesel catalyzed by rare earth solid superacid SO42-/SnO2-CeO2.

Biodiesel was synthesized by industrial palmitic acid and methanol,using solid superacid catalyst SO42-/SnO2-CeO2 which was prepared by sol-gel method.Effects of the mole fraction of CeO2 in SnO2-CeO2,the calcination temperature and the time of calcination,the concentration of sulphuric acid,the mass ratio of methanol to industrial palmitic acid,the catalyst dosage and the reaction time on the esterification were investigated.The results showed that SO42-/SnO2-CeO2 exhibited better activity under the conditions of the dosage of CeO2(based on total mole of SnO2-CeO2) of 5%,the calcination temperature of 550 ℃,the calcination time of 3 h,and the concentration of sulfuric acid solution of 2.0 mol/L.The orthogonal test results showed that the optimal reaction conditions of synthesizing biodiesel were as follows: the mass ratio of methanol to palmitic acid was 15∶25,the catalyst quantity was 4.0% of the palmitic acid,the reaction time was 4 h,the esterification rate was 95.4%.Analysis result of GC-MS showed that the ester products were mainly hexadecanoic acid methyl ester and 10-octadecenoic acid methyl ester.