Regenerable mixed metal oxide sorbents for coal gas desulfurization at moderate temperatures

This paper reports on research conducted at the Institute of Gas Technology (IGT) for the development of durable metal oxide-based sorbents for fluidized-bed desulfurization of coal-derived fuel gases in the moderate temperature range of 350–550°C, which is currently of industrial interest. This study has systematically considered copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) oxides as bases for developing regenerable sorbents. The sorbent formulations prepared, their sulfidation performance and regenerability, and the physical and chemical properties of a select group of sorbents are presented and discussed. The results from multi-cycle evaluation tests of a few sorbents in a packed-bed reactor are also presented. The results of attrition resistance tests carried out according to the ASTM D 5757-95 method are also presented and their implications discussed in detail. Sorbents based on copper oxide were found to possess the best combination of high attrition resistance and sulfidation reactivity, sulfur removal efficiency, and pre-breakthrough conversion in the moderate temperature range of 350–550°C. Encouraging results were also obtained with sorbents based on manganese oxide; however, their regeneration necessitates very high temperatures that cannot be accommodated by current desulfurization systems requiring regeneration ignition temperatures of approximately 550°C. No sorbent based on iron oxide was found to have sufficient reactivity in the moderate temperature range.