Biodiesel production from waste cooking oil catalyzed by solid acid SO42−/TiO2/La3+

A solid acid catalyst SO42−/TiO2/La3+ was prepared via sol-gel method using tetrabutyl titanate as TiO2 precursor. The catalyst simultaneously catalyzed esterification and transesterification resulting in the synthesis of biodiesel from waste cooking oil with high content of free fatty acids as feedstock. The optimization of reaction conditions was also performed. The maximum yield of more than 90% could be obtained under the optimized conditions that catalyst amount 5 wt. % of oil, 10:1 molar ratio (methanol to oil), temperature 110 °C, and esterification of 1 h. The catalyst can be reused for five times by activation without observing the decrease of its catalytic performance. The final products were purified by molecular distillation and detected by GC-MS. The content of fatty acid methyl esters was 96.16%.