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 Ce_0.75−xZr_0.25Tb_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-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, Ce_0.65Zr_0.25Tb_0.1O₂ (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 °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.

Graphical Abstract