Preparation of heterogeneous catalyst for biodlesel synthesis

Abstract

Certain disadvantages of conventional processes of biodiesel, i.e. fatty acid methyl esters (FAME) synthesis could be avoided by applying new technologies which are based on using heterogeneous catalyst. In this study a new type of heterogeneous catalyst with potassium-oxide or zinc-oxide as active component on alumina/silica support was synthesized using sol-gel method which was followed by drying: at elevated temperature and atmospheric pressure (xerogel) or with the supercritical carbon dioxide (aerogel). Prepared catalysts were used in the methanolysis of sunflower oil. The effects of various reaction variables such as reaction time, temperature and methanol to oil molar ratio on the yield of FAME were investigated. The catalysts were characterized with XRD, FTIR and BET surface area analysis. The results indicated that active component is the main reason for the catalytic activity towards the reaction. It has been determined that the temperature of 393 K and methanol:oil molar ratio of 15:1, are optimal conditions for fatty acid methyl esters synthesis with potassium-oxide as active component of the heterogeneous catalyst. At these conditions, after 15 min the yield of fatty acid methyl esters was above 92%.