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

摘要

Systematic studies were conducted to understand the influence of Tb doping on durability of Ni-based catalysts supported onto Ce_(0.75-x)Zr_(0.25)Tb_xO2 (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, H2-tem-perature-programmed reduction and Brunauer-Emmett-Teller analyses. These studies along with soot oxidation experiments confirmed that the existence of Tb~(3+) and/or Ce~(3+) ions made significant contribution to enhancing oxygen storage capacity (OSC) of the Tb doped CeO2-ZrO2 based materials, and among all the supports studied, Ce_(0.65)Zr_(0.25)Tb_(0.1)O2 (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 °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.