Comparative study of MCF-supported Ni-Zr and Ni-CaO catalysts for acetylation in biodiesel by-product utilization

Abstract. Malaysia's biodiesel production is expanding quickly, and the main by-product produced is surplus crude glycerol, which has limited application in local industries. Based on the current situation, the conversion of glycerol to higher-value products like acetin through acetylation is an attractive alternative. It has been demonstrated by previous research that the optimal temperature, catalyst type, and reaction time for acetylating glycerol are well-known. However, the effect of catalyst synthesis factors like metal loading still has limited research. Therefore, in this study mesostructured cellular foam (MCF) supported nickel (Ni) to zirconium (Zr) and nickel (Ni) to calcium oxide (CaO) catalysts were synthesised to investigate their performance on the glycerol conversion to acetins. Scanning electron microscopy-energy dispersive x-ray (SEM-EDX) analysis and Fourier transform infrared spectroscopy (FTIR) were done to study the physiochemical and morphological properties of the catalysts. The properties of the catalyst were then correlated with the catalytic activity in the glycerol acetylation with acetic acid reaction, where the impact of various metal loadings (0.5% Ni, 1.0% CaO and Zr) on the glycerol conversion and monoacetin concentration was examined. The reaction was conducted at a reaction duration of 60 minutes, reaction temperature of 115 ℃, 5 wt.% catalyst loading and glycerol/acetic acid molar ratio of 1:9. It was found that 0.5:1.0 Ni-CaO/MCF catalyst has the highest conversion of glycerol compared to other catalysts which is 82.70% while Ni-Zr/MCF catalyst has potential to produce a higher concentration of monoacetin compared to other catalysts which is around 69%. These findings show the significance of catalyst composition and surface properties in affecting product selectivity and conversion efficiency in glycerol conversion reactions.