Effect of the Pd/MCM-41 Pore Size on the Catalytic Activity and cis–trans Selectivity for Partial Hydrogenation of Canola Biodiesel

Abstract

The effect of the pore size of Pd/MCM-41 on the catalytic activity and selectivity in partial hydrogenation of canola-oil-derived biodiesel was studied under mild reaction conditions. The catalysts with different pore sizes were obtained by varying the amount of aqueous ammonia added during the synthesis: Pd/MCM-41-a8, Pd/MCM-41-a5, and Pd/MCM-41-a3 with average pore diameters of 3.72, 3.99, and 7.55 nm, respectively. The supports and supported Pd catalysts were characterized by Brunauer–Emmett–Teller surface area analysis, X-ray powder diffraction, transmission electron microscopy, CO pulse chemisorption, and temperature-programmed desorption of ammonia. The highest hydrogenation activity was found for the largest pore catalyst, Pd/MCM-41-a3, as presented in term of the turnover frequency (TOF), whereas Pd/MCM41-a8 and Pd/MCM-41-a5 provided higher selectivity toward cis-monounsaturated fatty acid methyl ester (FAME), which was attributed to their limited pore dimension. The correlation between the cataly...