Reductive regeneration of sulfated CuO/Al2O3 catalyst-sorbent in ammonia

Reductive regeneration of a sulfated CuO/Al2O3 catalyst-sorbent suitable for simultaneous SO2 and NO, removal from flue gases was carried out in 5 vol.% NH3/Ar. Effect of regeneration temperature on SO2 removal activity of the regenerated catalyst-sorbent was investigated. Chemical morphology and physical structure of the catalyst-sorbent before and after the regeneration were characterized using elemental analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and physical absorption. The results show that copper sulfate, the main copper species in the sulfated catalyst-sorbent, can be effectively regenerated at 350-450 degreesC. Aluminum sulfate, resulted from the reaction between Al2O3 and SO2 in flue gas, is unreductable under the conditions, which leads to reduced SO2 removal activity of the regenerated catalyst-sorbent compared to the fresh catalyst-sorbent. The main copper species after the regeneration at 400 degreesC is Cu3N. The nonexistance of copper sulfide suggests that over-reduction occurring in H-2 is avoided in NH3. BET surface area and pore size distribution of the regenerated catalyst-sorbent are almost the same as that of the fresh one when the reduction temperature is 400 degreesC or higher. Besides as a reductand, ammonia also reacts with SO2 formed in the regeneration to form hydroxyamine sulfate at the outlet of the reactor. (C) 2003 Elsevier Science B.V. All rights reserved.