Biodiesel Production from Palm Fatty Acids Distillate Using Tungstophosphoric Acid- and Cs-salt Immobilized-Silica

H3PW12O40/SiO2 and Cs1.5H1.5PW12O40/SiO2 composites with controllable acid loadings (5 - 15 wt% loading) were prepared by direct co-condensation sol-gel methods in the presence of triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) copolymer. Biodiesel production from palm fatty acids distillate (PFAD) having 93 % free fatty acids (FFA), a residual product from the refining of crude palm oil was investigated using these heterogeneous catalysts. The results demonstrated that under the same reaction conditions the catalytic activity of H3PW12O40/SiO2 was higher than Cs1.5H1.5PW12O40/SiO2 due to higher acidity. A study on effects of reaction temperature, time and catalyst amount has been performed. The FAME content was 96.7 % at a temperature of 85 °C, 15 h reaction time, a molar ratio of methanol to PFAD at 12:1 and catalyst 15 wt% based on PFAD. Graphical abstract