Influence of Terbium Doping on Oxygen Storage Capacity of Ceria-Zirconia Supports: Enhanced Durability of Ni Catalysts for Propane Steam Reforming

Abstract

Systematic studies were conducted to understand the influence of Tb doping on durability of Ni-based catalysts supported onto Ce0.75-xZr0.25TbxO2 (CZT (x) , x = 0.0-0.2), prepared by glycine-nitrate process. Ni metals were deposited onto the as-synthesized supports using a solvothermal method. The prepared supports and catalysts were characterized by a number of ex-situ techniques including X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, H-2-temperature-programmed reduction and Brunauer-Emmett-Teller analyses. These studies along with soot oxidation experiments confirmed that the existence of Tb3+ and/or Ce3+ ions made significant contribution to enhancing oxygen storage capacity (OSC) of the Tb doped CeO2-ZrO2 based materials, and among all the supports studied, Ce0.65Zr0.25Tb0.1O2 (x = 0.1, CZT (0.1) ) showed the highest OSC. To assess the performance of these catalysts, steam reforming reactions of propane were further carried out on the Ni supported catalysts (Ni/CZT (x) ) at a steam-to-carbon ratio of 1.5, a gas hourly spaced velocity of 45,000 h(-1), and a reaction temperature of 700 A degrees C. Consistent with the determined OSC of the catalysts, the durabilities of the Ni/CZT (x) catalysts were found to be increased in the order of Ni/CZT (0.1) > Ni/CZT (0.15) > Ni/CZT (0.2) > Ni/CZT (0.05) > Ni/CZ. In particular, the activity of Ni/CZT (0.1) was maintained to be > 99 % of propane conversion at least for 200 h without significant deactivation.