DRIFTS Study on Adsorption and Activation of CH4 and CO2 over Ni/SiO2 Catalyst with Various Ni Particle Sizes

Abstract

Abstract The adsorption and activation of CH4 and CO2 over the Ni/SiO2 catalyst with different Ni particle sizes were investigated by diffuse reflectance infrared Fourier transform spectroscopy. CHx species (x = 1–3) were observed over the catalysts when CH4 was adsorbed on the surface. The CH3O species was also detected as the result of the reaction of CHx species with surface hydroxyl groups. The dissociation of CH4 depended intensively on the Ni particle size. CH4 dissociated more easily over the Ni/SiO2 catalyst with Ni particles of diameter approximately 8 nm. Dissociation of CO2 over Ni/SiO2 was very difficult, whereas the adsorbed H that resulted from CH4 dissociation promoted the dissociation of CO2. Small Ni particles might be helpful for hydrogen spillover to the support for CO2 activation. With respect to the coadsorption of CH4 and CO2, the monodentate carbonate species was observed over the Ni/SiO2 catalyst with a small Ni particle size, which indicated that small Ni particles could promote the reaction of CO2 with surface oxygen species.