Synergistic effect of La<inf>2</inf>O<inf>3</inf>-Al<inf>2</inf>O<inf>3</inf> based catalysts for efficient biodiesel production

Abstract

Comprehensive synergistic effect of La2O3-Al2O3 on the catalytic performance of transesterification reaction of palm oil with methanol for biodiesel production was studied. The prepared catalyst possessed bifunctional acid-base properties. The well-balanced of acido-basic sites amounts over the catalyst at the La2O3 loading of 40 % and the calcined temperature of 600 °C gave the maximum fatty acid methyl ester (FAME) content of 93.12 %, under the optimum conditions of 1:30 molar ratio of oil to methanol, 200 °C reaction temperature, 39 bar reaction pressure, 5 wt% catalyst loading and 5 h reaction time. The catalyst exhibited reasonable stability. The partial leaching of La3+ ions and deposition of organics resulted in the loss of activity. The results showed that the catalyst generated new weak basic sites and more effective in the transesterification compared to strong basic sites as reported previously. The different strengths of new acid sites were also formed. The balancing of acid-base sites amount was a key to control the catalytic activity and the formation of side reactions. This gives critical guidance in further catalyst development for biodiesel production of waste oils or low-quality oils via simultaneous esterification and transesterification, which helps the biodiesel system being economical and scalable.