Preparation of Cr2O3-promoted copper catalysts on rice husk ash by incipient wetness impregnation

Rice husk ash (RHA) was utilized as the support material for manufacturing Cr2O3-promoted copper catalyst by incipient wetness impregnation. With constant copper loading at 15 wt%, the effects of Cr content varying from 0 to 5 wt% on surface properties and catalytic activity were investigated. In addition to RHA, commercial silica gel was also used as catalyst support for comparison to study the effect of support material. Surface characterizations were examined extensively by XRD, TPR, SEM, N2 sorption, and H2-N2O titration, while catalytic activities were studied using ethanol dehydrogenation. The results indicate that copper dispersion is enhanced by the initial increase in Cr2O3 promoter content up to 2 wt%, while it then deteriorates gradually upon further increase in promoter content. It has been suggested that an optimal Cr content around 2 wt% not only enhances catalytic activity but also retards catalyst deactivation. Generally speaking, catalyst deactivation results predominantly from copper sintering. Despite the lower BET surface area, RHA is superior to commercial silica gel as a candidate for catalyst support in this work, because the surface of the former may possess more unique pores, while the majority of surface pores on the latter are interconnected and thus can be clogged easily.