Biodiesel production using CaO impregnated with silica as catalyst

Abstract

Currently, biodiesel is produced by performing a transesterification reaction with homogeneous base catalysts such as KOH or NaOH dissolved in methanol. This production process can provide high 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 ash (RHA) and egg shell (ES) for transesterification reaction. The hybrid RHA-ES was synthesized via a wet impregnation method. Then, the synthesized hybrid catalyst was characterized using BET and SEM analysis. The effectiveness of the hybrid catalyst will be tested on biodiesel yield. From BET results, surface area of hybrid catalyst was found to have higher surface area than CaO catalyst. It could be due to the strong interaction of the CaO with silica support, which reduced the surface diffusion of Ca, inhibited sintering and stabilized the surface of CaO [Omar and Amin, 2011]. Furthermore, this result was supported by SEM image, whereby the significant agglomeration of the silica particles with a heterogeneous distribution was observed on the surface of CaO catalysts. In the transesterification study, it was found that the CaO supported with silica had a higher yield of methyl ester than CaO individually. This might be due to the solid state reaction between silica compound and the surface of CaO in the activation process, whereby the silica could have inserted in the vacant sites of CaO. Therefore, it can be concluded that the hybrid RHA-ES catalyst derived from waste materials can be an excellent catalyst in biodiesel production.