Alcohol synthesis by hydrogenation of fatty acid methyl esters on supported Ru-Sn and Rh-Sn catalysts

Alcohol synthesis by hydrogenation of methyl laurate or methyl palmitate was studied using binary catalysts such as Ru-Sn and Rh-Sn supported on Al(2)O(3), SiO(2), or ZrO(2). The catalyst was suspended in the neat ester, and the reaction was carried out at 300 degrees C and 6.0 MPa of H(2) in an autoclave. Binary catalysts were prepared by the conventional impregnation method and characterized by XRD, isothermal nitrogen adsorption-desorption, and CO-adsorption. Among the catalysts studied, supported Rh-Sn catalyst showed the highest alcohol yield, and a major by-product was a lengthy ester formed by an ester-exchange reaction between the original ester and the formed alcohol itself. The molar ratio of noble metal to tin greatly influenced the catalytic performance. Support with a low surface area, for example alpha-Al(2)O(3), was favorable for the alcohol synthesis compared with that with a high surface area. It was revealed that the ester-exchange reaction occurred without catalyst just by heating at temperatures higher than 200 degrees C. The results showed that to achieve a high alcohol yield, it is important to prepare catalysts of high activity to hydrogenate the lengthy ester formed in situ. (C) 2009 Elsevier B.V. All rights reserved.