Effect of calcination temperature on the activity of solid Ca/Al composite oxide-based alkaline catalyst for biodiesel production

A solid Ca/Al composite oxide-based alkaline catalyst containing Ca12Al14O33 and CaO was prepared by chemical synthesis and thermal activation from sodium aluminate solution and calcium hydroxide emulsion. The effect of calcination temperatures ranging from 120 degrees C to 1000 degrees C on activity of the catalyst was investigated. The catalyst calcined at 600 degrees C showed the highest activity with >94% yield of fatty acid methyl esters (i.e. biodiesel) when applied to the transesterification of rapeseed oil at a methanol:oil molar ratio of 15:1 at 65 degrees C for 3 h. Structure and properties of the catalyst were studied and the characterizations with XRD, TGA, FTIR, BET, and SEM demonstrated that the performance of the catalyst was closely related to its specific surface area and crystalline structure. In particular, the generation of crystalline Ca12Al14O33 improved the catalytic activity due its synergistic effect with CaO. (C) 2012 Elsevier Ltd. All rights reserved.