Zirconia Modification on Nanocrystalline Titania-Supported Cobalt Catalysts for Methanation
In this present study, the zirconia-modified different crystallite sizes of TiO2 (11, 13 and 16 nm) as support for the cobalt catalysts were investigated. The different TiO2 crystallites derived from the sol-gel method was obtained by varying the water:alkoxide molar ratio from 165 to 4 to gain the different nanocrystallite sizes of TiO2. Then, the TiO2 supports were used to yield various Co/TiO2 catalysts. It was found that the sizes of cobalt oxides species dispersed on TiO2 were corresponding to TiO2 sizes. Based on XPS study, the binding energy of Co 2p3/2 was not affected by the size of TiO2. The catalytic activity was measured via CO hydrogenation under methanation condition. In case of unmodified TiO2 support, the smaller TiO2 crystallites (Co/TiO2_11 nm) exhibited higher activity than other larger ones. Moreover, the zirconia modification also resulted in increased in activity for all samples. For both cases, it can be attributed to increased cobalt dispersion with small crystallite size of TiO2 support coupled with the zirconia modification as measured by CO chemisorption.