REDUCTIVE REGENERATION OF SULFATED CUO AL2O3 CATALYST-SORBENTS IN HYDROGEN, METHANE AND STEAM/

A study of the reductive regeneration of sulfated 4.3% CuO/Al2O3 catal yst-sorbents suitable for the simultaneous removal of SO2 and NOx from flue gases was carried out with various reductants. H-2 demonstrated a propensity to form CuS (ca. 20% CuS at 400 degrees C) and subsequent formation of H2S above 550 degrees C. Surface aluminum sulfate specie s are slowly reduced with Hz to the sulfide at temperatures in excess of 450 degrees C. Subsequently, H2S forms at higher temperatures, whil e bulk aluminum sulfate species were found to reduce in H-2 directly t o Al2O3 with the formation of H2S above 550 degrees C. Although a much weaker reducing agent, regeneration with CH4 leads to significantly l ess CuS formation and no H2S production. The formation of CuS, which w as not reduced by CH4, occurred via the readsorption of product SO2 ga ses on the catalyst-sorbent. Interestingly, no CuS was formed when wat er vapor was added to the CH4 reductant gases and more SO2 evolved in these conditions.