Utilization of rice husk silica as solid catalyst in the transesterification process for biodiesel production

Abstract

Biodiesel from palm oil is a promising renewable fuel for substitute petro-diesel either be used directly or as a diesel mixture. To improve reaction rate and biodiesel yield, adding a catalyst with excess alcohol is needed in transesterification process. The high content of silica in rice husks is very prospective for the development of a heterogeneous catalyst. The study was carried out to investigate catalytic activity of the silica from rice husk produced by the impregnation process and various calcination temperatures at various amounts of it in the transesterification process for biodiesel production. A preliminary study was carried out to determine the amount of catalyst in the transesterification process. The amount of catalyst producing the highest yield of biodiesel was used in the next study. In the main study, the catalyst from rice husk silica was synthesized through an impregnation process used 1 N KOH and calcination processes at 200, 300, 400, and 500 °C. The experimental result showed the crystallinity degree of the catalyst first increased and then decreased with increases in calcination temperatures. The calcination at 300 °C resulted in the highest surface area of the catalyst (7.21 m2/g). The biodiesel produced through transesterification process using catalyst from rice husk silica with impregnation of KOH 1N and calcination at 300 °C resulted in the highest methyl ester (94.39 %), total acid number of 0.09 mg KOH/g, total glycerol of 0.57 %, saponification number of 186.76 %, free glycerol of 0.01 %, and moisture content of 650.55 ppm.