Transesterification of cooking palm oil via Mn-Al mixed oxides catalysts: effects of metal ratio / Siti Athirah Ramli … [et al.]

The abstract Biodiesel or fatty acid methyl ester (FAME) is an environmentally friendly fuel that is an alternative to diesel fuel. In this study, mixed oxides catalysts of Mn-Al were synthesised via the sol-gel method at various metal ratios and used in the transesterification of cooking palm oil (CPO) to produce FAME. The reactions were conducted in a batch reactor at a temperature of 55 °C, with a reaction time of 3 h and a catalyst loading of 2.5 wt%. The effects of Mn:Al metal weight ratios of 1:1, 1:2, 2:1, 0:1, and 1:0 were investigated based on the FAME density obtained from the reaction. The thermal stability and the presence of surface functional groups were investigated using thermal gravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR), respectively. The results show that the Mn-Al catalyst prepared at 1:2 metal weight ratio and calcined at 500 °C for 2 h obtained a FAME density of 862 kg/m3, which is the closest to standard palm oil biodiesel density. The catalysts with different metal ratios contained similar active surface functional groups. The TGA analysis of the Mn-Al metal ratio 1:2 showed no significant weight loss observed after 300 °C, indicating good thermal stability. The findings indicate that Mn-Al mixed oxides have the potential as heterogeneous catalyst in the transesterification of CPO to produce FAME.