Methyl transesterification of waste cooking oil using a laboratory synthesized reusable heterogeneous base catalyst: Process optimization and homogeneity study of catalyst

A novel heterogeneous base catalyst, potassium impregnated zinc oxide was synthesized via precipitation method. It was modified by impregnation method and was used for synthesis of biodiesel using waste cooking oil as feedstock. The synthesized catalyst was characterized using various sophisticated techniques. The catalyst having a K/Zn atomic ratio of 60:40 was calcined at 900 °C, provided the highest catalytic activity. Effect of different reaction parameters on biodiesel conversion efficiency were scrutinized. The experimental results showed that highest biodiesel conversion of 98% was achieved at optimized reaction conditions, at catalyst loading of 2.5 wt%, oil: methanol molar ratio of 1:18, 600 rpm and 65 °C for 50 min reaction time. Kinetics of the transesterification reaction was studied at varying reaction temperature (45–65 °C) and the reaction marked the highest rate constant at 65 °C. The activation energy of the reaction was 14.54 kJ/mol. The reusability and homogeneous contribution of the catalyst was examined and it was investigated that leaching of active components from catalyst into the reaction media was responsible for catalyst deactivation and homogeneity. The synthesis of biodiesel was ascertained by ATR-FTIR and NMR (1H and 13C) analysis.