Abstract: Ni/γ-Al2O3catalysts prepared by three different ways, general reduction (GR), plasma reduction after calcination (PR), and plasma direct reduction without calcination (PDR), were investigated by temperature-programmed desorption (TPD) with H2 and CO2,X-raydiffraction, and N2 adsorption. The results showed that H2 was adsorbed mainly on the Ni active sites, whereas CO2 was adsorbed mainly on the strong alkaline sites of the support. Compared with that on the GR catalyst, H2 and CO2 adsorbed on the PR and PDR catalysts increased a lot, and the desorption temperature of H2 decreased by 55 and 69 ℃, respectively. An estimation based on assumption of H2 showed that the dispersions of GR, PR, and PDR catalysts were 26%, 32%, and 58%, respectively. The catalysts reduced by plasma had better dispersion, more alkaline sites, and lower H2 desorption temperature. Plasma reduction that was performed at a low temperature for a short time could preserve the structure of the support and improve the dispersion of the active sites, which were responsible for the good performance of these catalysts.

Key words: temperature-programmed desorption, plasma reduction, nickel, alumina, supported catalyst, methane, carbon dioxide, reforming