Synthesis, characterization and performance of silica impregnated calcium oxide as heterogeneous catalyst in biodiesel production

Currently, biodiesel is produced by performing a transesterification reaction with homogeneous base catalysts such as potassium hydroxide (KOH) or sodium hydroxide (NaOH) dissolved in methanol. This production process can provide high fatty acid methyl ester (FAME) yields under mild conditions. However, the homogeneous catalytic process suffers some drawbacks of an inevitable production of wastewater from washing process of catalyst residues and unreusability of the catalysts. Thus, in this study, it is proposed to synthesize and characterize a renewable low cost heterogeneous hybrid catalyst through utilization of waste material; rice husk and egg shell for transesterification reaction. The hybrid catalyst was synthesized via wet impregnation method and then characterized using fourier transform infrared spectroscopy, x-ray diffraction, surface area and pore size distribution and scanning electron microscopy. The composition of FAME was determined by gas chromatography analysis and the properties of biodiesel such as density, viscosity, acid value and calorific value were also analyzed. The result show that the calcium oxide (CaO) supported with silica is more effective for the production of biodiesel compared to CaO individually. Furthermore, the synthesized catalyst was able to be efficiently recyclable and repeatedly used up to 6 times. The fuel properties of biodiesel produced in this study were found to meet the specification of ASTM standards. Therefore, it can be concluded that the hybrid catalyst derived from waste materials can be an excellent catalyst in biodiesel production. In addition, developing new catalysts from rice husk and egg shell will not only solve the issue of disposal of these wastes but will also simplify the purification process, whereby the catalysts can be separated from the product more easily.