Cerium Oxide-Based Sorbents for Regenerative Hot Reformate Gas Desulfurization

摘要

The activity and stability of lanthanum- or copper-containing cerium oxide sorbents for hot reformate gas desulfurization were investigated in this work.Reformate gas,derived from the catalytic partial oxidation or autothermal reforming of heavy fuels such as JP-8,is rich in hydrogen and CO and may also contain up to 500 ppmv H_2S.Desulfurization at temperatures in the range of 650-800degC is required before using the fuel gas in solid oxide fuel cells.In this work,regenerable cerium oxide-based sorbents were used in desulfurization.The sorbents were prepared with high surface area by the urea coprecipitation/gelation method,followed by slow heating and calcination in air at 650degC for 4 h.Lanthanum doping (up to 50 at.%) was determined to be effective in moderating the surface area loss of cerium oxide (ceria) in H_2S-free reformate gas at 800degC.On the other hand,severe sintering occurred when copper was used as an additive,even in amounts as low as 10 at.% copper in ceria.However,the copper-containing ceria had the best sulfidation kinetics among the ceria-based sorbents.Sorbents were evaluated in cyclic sulfidation/regeneration tests at 650 and 800degC,using a simulated reformate gas mixture in sulfidation,and a 3% O_2-He gas mixture for regeneration.Using very high space velocities,we determined that sulfidation could be limited to the sorbent surface.The surface sulfur capacity of the sorbents was stable in cyclic sulfidation/regeneration under these conditions.