Leaching of the active component of alumina supported sodium catalysts during the transesterification of soybean oil

Abstract

The transesterification reaction for biodiesel production using soybean oil with several alkali and alkaline metal hydroxides and alkoxides as liquid-phase catalysts has been studied. The hydroxides and alkoxides of sodium (Na) and potassium (K) are found to be the most active. Alumina (Al₂O₃) supported Na is subsequently considered for the synthesis of a suitable solid-phase catalyst. This catalyst was synthesized and characterized. An optimum Na loading of 10 wt% for biodiesel production is determined. This catalyst also show the maximum basicity. The effects of operating conditions for the transesterification reaction using the Al₂O₃ supported Na catalyst are also determined. In all of the reactions involving Al₂O₃ supported Na catalysts leaching of the active component has been observed and the reaction appeared to proceed as a liquid phase catalyzed reaction. The leached amount corresponded to about 20% of the Na present in the Al₂O₃ supported Na catalyst and is independent of the methanol amount. Thus, leaching is a serious consideration for supported Na catalysts.