Effect of SiO2 pore size on partial hydrogenation of rapeseed oil-derived FAMEs

Palladium (Pd) supported on different SiO2 pore sizes: Q3, Q10, Q30, and Q50 with pore diameters of 3, 5, 30, and 50 nm, respectively, were studied for the partial hydrogenation of rapeseed oil-derived fatty acid methyl esters (FAMEs). The supports and catalysts were characterized by BET, NH3-adsorption, and CO-chemisorption technique. Highest turn over frequency (TOF) was found for Pd/Q30, while Pd/Q3 exhibited the lowest TOF. The reaction rate constants for each hydrogenation step, consequently from C18:3 to C18:2, C18:1, and C18:0, i.e., k(1). k(2), and k(3), respectively, were determined by POLYMATH Professional 6.2 and could explain the effect of SiO2 pore size on pore diffusion of FAMEs reactant and contact probability between reactant molecules and active sites. Moreover, pore size of the SiO2 support also affected on selectivity toward trans-monounsaturated FAME. The Pd/Q3 catalyst presented the lowest trans-monounsaturated FAME selectivity due to its smallest pore size and acidic properties. In addition, it was found that 0.5h of hydrogenation time using Pd/Q10, Pd/Q30, and Pd/Q50 could improve the oxidative stability to > 10 h. (C) 2012 Elsevier B.V. All rights reserved.