Catalytic Activity and Stability over Nanorod-Like Ordered Mesoporous Phosphorus-Doped Alumina Supported Palladium Catalysts for Methane Combustion

Nanorod-like phosphorus-doped ordered mesoporous γ-alumina (OMA), which has abundant ordered pore channels in the nanorods, was rapidly synthesized through a modified sol–gel strategy without use of any mineral acids. Highly dispersed Pd-based catalysts were synthesized by taking as-obtained phosphorus-doped OMA materials as carriers for methane combustion. The crystallization temperature of γ-Al 2 O 3 was increased by phosphorus doping. The surface acidity properties of γ-Al 2 O 3 were modified upon phosphorus incorporation, which had a significant effect on catalyst activities, and this influence was much more conspicuous for the supports calcined at high temperature. The incorporation of phosphorus adjusted the distribution of palladium active species and the reducibility of catalysts, synergistically affecting the low-temperature catalytic performance. Pd/6P-OMA catalyst demonstrated enhanced low-temperature catalytic properties and stability in the 13-cycle stability and long-term stability tests. During the reaction cycles, the total CH 4 conversion temperature for Pd/6P-OMA catalyst was as low as 345 °C, which could be reduced to 321 °C via hydrogen reduction treatment. In comparison with the catalyst without dopant, the Pd/6P-OMA catalyst also exhibited higher hydrothermal stability in the presence of excess water vapor in the feed.