Transesterification Catalytic Performance of Mechanically Alloyed Eggshell Ash, Magnesium and Aluminum Oxides for Sustainable Biodiesel Production

Use of quicklime as a sole catalyst for transesterification is limited by poor chemical stability and post-reaction recovery. This study investigates the effect of dry milling time on the transesterification catalytic performance (activity and recovery) of mechanically alloyed MgO, Al2O3 and eggshell derived quicklime. Raw chicken eggshells were calcined at 900 °C. The resulting flaking eggshell ash was directly mixed and comminuted with MgO and Al2O3 in ball milling (BM) machine for 15, 30, 60, 90, 120 and 150 minutes. Each of the catalyst samples was analyzed for surface morphology and particle size distribution, and then utilized for biodiesel production. Analyses of catalyst samples showed that mean particle size reduced, while powder agglomeration advanced with milling time. Optimum catalytic performance was achieved with the composite alloyed for 120 minutes (Z120) and that resulted in fatty acid methyl ester (FAME) yield of 88.4% and catalyst recovery of 98.3%. Sample Z120 was further characterized by TEM, EDX, XRD and BET. Calcination of the composite catalyst enhanced its activity. Dry high energy BM of oxides can be utilized effectively for synthesis of composite catalysts.