CaO catalysts supported on ZSM-5 zeolite for biodiesel production via transesterification of rapeseed oil

This paper deals with the effect of Si/Al ratio and form of zeolite support on the catalytic properties of the CaO catalysts in transesterification reaction of rapeseed oil with methanol. The reaction was conducted at 180 and 220 °C. To get the intended purposes of the work a various calcium oxide (CaO) catalysts supported on the ammonium and hydrogen forms of ZSM-5 zeolites with different Si/Al ratios were prepared by impregnation method. The results showed that the most active zeolite-based catalyst was 10%CaO/ZSM-5 (Si/Al = 50) system in the transesterification reaction at both temperatures 180 and 220 °C, which exhibited triglycerides (TG) conversion equal to 72.7 and 95.2% and fatty acid methyl esters (FAME) yield of 56.9 and 91.1%, respectively. High reactivity of this catalyst is explained by its acid-base properties, crystallite size of active phase, large external surface area and uniform distribution of the CaO on catalyst surface compared to the other investigated CaO systems supported on ZSM-5 zeolites. In addition, the analysis of the product obtained in the transesterification process carried out on the 10% CaO/ZSM-5 (Si/Al = 280) catalyst at 220 °C confirmed the presence of the following methyl esters of higher fatty acids: methyl oleate, methyl linoleate, methyl linolenate, methyl stearate, methyl eicosenoate, methyl palmitate, methyl palmitoleate, methyl nervonate and methyl arachidate.