Thesis (M.Eng.)--Chulalongkorn University, 2008

The study focused on effect of Ga-modified Al₂O₃,TiO₂ and SiO₂ supports on characteristics and catalytic properties of supported cobalt catalyst during CO hydrogenation. Ga was first impregnated onto the supports to produce Ga-modified supports containing 0.2 and 1 wt% of Ga in the final catalyst. Then, Co catalysts having 20 wt% of Co were prepared from those supports by the incipient wetness impregnation method. CO hydrogenation (H₂/CO = 10/1) was also performed to determine the overall activity and selectivity. It revealed that the activities of Co/Al₂O₃ catalysts were higher than those of the Co/SiO2 catalysts. However, activity depended on acid sites of catalyst. Ga modification on Al₂O₃ supports resulted in increased activities. On contrary, addition of Ga onto SiO₂ decreased activities. It was found that Ga modification had a significant impact on the catalyst properties. The reduced Co metal atoms determined by the H₂ chemisorption increased with Ga modification on Al₂O₃, but decreased with Ga modification on SiO₂. However, Ga modification on Al₂O₃ and SiO₂ supports decrease the catalyst deactivation. For the TiO₂ -supported Co catalyst, it was found that the activity decreased dramatically. This was probably due to the catalysts had sulphur on the surface as impurities