CO2 Reforming of CH4 over SiO2-Supported Ni Catalyst: Effect of Sn as Support and Metal Promoter

Ni (10 wt %) catalysts supported on SiO2 and on SiO2 doped with 1 and 4 wt % Sn and a Sn-doped Ni catalyst supported on silica were prepared by microwave-assisted precipitation methods. The catalysts, analyzed by TPR, XRD, and XPS techniques, were tested in the dry reforming of methane (DRM) with CO2. The reaction was conducted at atmospheric pressure in a temperature range of 450-800 degrees C with a feed gas mixture containing CH4 and CO2 in a 1:1 ratio in He. The effect of the catalyst pre-reduction temperatures of 550 and 750 degrees C was considered. As compared to the bare Ni-SiO2 catalysts, doping silica with 4 wt % Sn, corresponding to a Sn/Ni molar ratio of 0.2, substantially decreased the amount of deposited carbon but determined a consistent loss of activity. In the presence of a lower amount of tin (Sn/Ni = 0.05), with a lower amount of formed carbon, the catalyst was still less active and less stable as compared to bare Ni-SiO2. On the contrary, changing the sequence of metal addition, i.e., adding 1 wt % Sn to Ni-SiO2, slightly improved the activity and the catalytic stability at 650 degrees C during 24 h on stream, also reducing the carbon formation. The structural characterizations before and after the reaction were in accord with a better structural stability of the nickel particle when doped by tin. The nickel ensemble dilution upon NixSny alloy formation, as detected by XRD, hindered formation of surface carbon.