Photocatalytic Steam Reforming of Methane over Semiconductor Photocatalysts and Fischer-Tropsch Synthesis over Supported Cobalt Catalysts

In this review, I introduce our group's development of improved catalysts for use in photocatalytic steam reforming of methane and in Fischer-Tropsch synthesis. Although methane is a promising alternative to petro-leum, its use as a chemical feedstock is currently limited. This is because methane is a very stable hydrocarbon and its conversion usually requires high temperatures, which not only increases operating costs but also causes severe catalyst deactivation. In our first set of studies, we examined the use of photoenergy and photocatalysts at low temperature for methane conversion. We found that hydrogen could be efficiently produced from methane and water at room temperature by using semiconductor photocatalysts such as platinum-loaded, lanthanum-doped sodium tantalate (Pt/NaTaO3:La). In our second set of studies, we examined noble metal-free, cobalt-based cata-lysts as an inexpensive means of catalyzing Fischer-Tropsch synthesis. We found that the dispersion and elec-tronic state of cobalt metal particles could be precisely controlled by optimizing the crystal phase and pore struc-ture of the support, by carefully choosing the type and amount of promoter, and by selecting an appropriate catalyst preparation method, which together afforded catalysts with high catalytic activity for the formation of long-chain hydrocarbons with five or more carbon atoms.