Effect of bimodal porous silica on particle size and reducibility of cobalt oxide

Abstract

In this study, the effect of bimodal porous silica (BPS) on particle size and reducibility of cobalt oxide has been investigated. Unimodal porous silica (UPS) was used for comparison purposes. Both silica supports were impregnated with an aqueous solution of cobalt nitrate to obtain cobalt loadings of about 10 wt%. Pore structure, specific surface area, morphology and cobalt oxide crystallite size of the cobalt oxide loaded on porous silicas were systematically characterized by means of N2-sorption, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The reduction behavior profiles and the activation energy for the reducibility of the cobalt oxide were studied by dynamic thermal gravimetric under flow of H2. The average particle size of cobalt oxide loaded on the BPS sample was revealed to be slightly larger than that loaded on the UPS sample, likely because cobalt oxide particles were distributed both on mesopores and macropores. The reduction temperatures of the cobalt oxide loaded on the BPS sample were found to be evidentially lower than those of the cobalt oxide loaded on the UPS sample.