The promotion effect of hydrogen spillover on CH4 reforming with CO2 over Rh/MCF catalysts

Abstract

The mesocellular silica foams (MCF) supported rhodium catalysts, prepared by wetness impregnation method, were tested in CH4 reforming with CO2. Hydrogen temperature-programmed desorption (H2-TPD) analysis showed that hydrogen spillover occurs on MCF loaded with highly dispersed rhodium. The turnover frequency of CH4 (TOFCH4(s−1)) increased with the strength rise of spilt-over hydrogen. The promotion mechanism was investigated by controlled atmosphere 13C and 1H MAS NMR. The spilt-over hydrogen atoms were found to adsorb on the bridged oxygen sites (SiOSi) of MCF and to form surface terminal silanol groups. Meanwhile, in the reforming reaction steps, CH4 dissociation into CH3* and CH3O* decomposition into CH2O* occurred. The results confirmed that hydrogen atoms can spill over from highly dispersed rhodium species to the neighboring bridged oxygen atoms of MCF, which promotes the reaction by facilitating rate determining steps of CH4 dissociation and CHxO*(x=2, 3) intermediates decomposition on metal surface.