K-, CeO 2-, and Mn-promoted Ni/Al 2O 3 catalysts for stable CO 2 reforming of methane

Abstract

Reforming of methane with carbon dioxide into syngas over Ni/γ-Al 2O 3 catalysts modified by potassium, MnO and CeO 2 was studied. The catalysts were prepared by impregnation technique and were characterized by N 2 adsorption/desorption isotherm, BET surface area, pore volume, and BJH pore size distribution measurements, and by X-ray diffraction and scanning electron microscopy. The performance of these catalysts was evaluated by conducting the reforming reaction in a fixed bed reactor. The coke content of the catalysts was determined by oxidation conducted in a thermo-gravimetric analyzer. Incorporation of potassium and CeO 2 (or MnO) onto the catalyst significantly reduced the coke formation without significantly affecting the methane conversion and hydrogen yield. The stability and the lower amount of coking on promoted catalysts were attributed to partial coverage of the surface of nickel by patches of promoters and to their increased CO 2 adsorption, forming a surface reactive carbonate species. Addition of CeO 2 or MnO reduced the particle size of nickel, thus increasing Ni dispersion. For Ni–K/CeO 2–Al 2O 3 catalysts, the improved stability was further attributed to the oxidative properties of CeO 2. Results of the investigation suggest that stable Ni/Al 2O 3 catalysts for the carbon dioxide reforming of methane can be prepared by addition of both potassium and CeO 2 (or MnO) as promoters.