Physico-chemical and catalytic properties of Ru–MCM-41 mesoporous molecular sieve catalyst: influence of Ru modification methods

Abstract

The MCM-41 mesoporous molecular sieve was modified with Ru using in-situ synthesis, ion-exchange and impregnation catalyst preparation methods. The physico-chemical properties of the Ru–MCM-41 synthesized catalysts were studied using characterisation techniques such as X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray micro-analysis, X-ray fluorescence, XPS and nitrogen adsorption. The hydrogenation of cinnamaldehyde was used as a test reaction to evaluate the catalytic properties of the Ru–MCM-41 catalysts. The in-situ synthesis, ion-exchange and impregnation methods used for the introduction of Ru did not influence the parent structure and phase purity of the MCM-41 mesoporous molecular sieve under suitable designed synthesis conditions. At the same time the method of Ru introduction in MCM-41 was found to influence the physico-chemical and catalytic properties. The Ru–MCM-41 catalyst synthesized using in-situ synthesis resulted in the largest Ru crystallite size, which provided highest selectivity to the desired product cinnamyl alcohol and lowest conversion of cinnamaldehyde in the hydrogenation. The Ru–MCM-41 catalyst prepared by impregnation showed sintering of Ru particles, and lower selectivity to cinnamyl alcohol than the in-situ synthesized Ru–MCM-41 catalyst. The Ru–MCM-41 mesoporous molecular sieve catalyst prepared by ion-exchange showed the highest conversion of cinnamaldehyde, however formation of cinnamyl alcohol was not observed.