Impact of the Silica Support Structure on Liquid-Phase Hydrogenation on Pd Catalysts

Abstract

The effect of the silica support structure on the characteristics and catalytic properties in liquid-phase hydrogenation of 1-hexene over two types of silica (amorphous SiO2 and MCM-41) supported Pd catalysts was studied under mild conditions. The catalysts were characterized by atomic adsorption (AA), N2 physisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO pulse chemisorption, and temperature-programmed reduction (TPR). The highest hydrogenation activity was found for the larger pore MCM-41 (dpore = 9 nm) supported Pd catalysts. Use as a catalyst support of a smaller pore size MCM-41, a small-pore amorphous SiO2, and a commercial large-pore SiO2 led to lower Pd dispersions. The results suggest that Pd was inside the pores of the large-pore MCM-41 and SiO2, and to a lesser extent for the small-pore MCM-41. However, almost no Pd appears to have been inside the pores of the small-pore SiO2, the support with the greatest percent of pores <3 nm. There was no evidence of any pore ...