Chemical and spatial promotional effects of bimodal pore catalysts for methane dry reforming

SiO2, ZrO2 and Al2O3 bimodal pore supports were prepared by incipient-wetness impregnation of silica gel, with SiO2, ZrO2 and Al2O3 sol respectively. The obtained bimodal pore supports showed two different kinds of pores, new mesopores and original macropores, simultaneously. The increased BET surface areas and the decreased pore volumes of bimodal pore supports, compared to those of the original silica gel, proved that the nano particles of precursor sols indeed entered into the macrospores of silica gel and aggregated to form mesopores by self-organization at the calcination step. Platinum supported onto these supports were applied in carbon dioxide reforming of methane (dry reforming). It was found that SiO2 bimodal catalyst was better than unimodal ones due to high metal dispersion and fast intra-pellet diffusion of reactants as well as products. Among all bimodal catalysts, ZrO2 and Al2O3 bimodal catalysts exhibited higher activity and stability contributed by both the spatial promotional effect of bimodal pore structure and intrinsical chemical effect of ZrO2 and Al2O3, at the same time.