Alumina-supported copper oxide materials were examined for their capacity to adsorb SO2 from a SO2/O-2/He gas stream at relatively low temperature (150 degreesC). The adsorbent (8 wt % copper oxide) was treated with a series of different compounds to examine the promoting effect of chloride and other halides and alkali metals. The results show that chloride has a strong promoting influence on both the rate of adsorption and the total capacity for SO2 on copper oxide on alumina adsorbents. When chloride is used to promote adsorbents formed using copper oxide as a precursor, the mode of promotion is apparently one wherein the chloride acts to facilitate the wetting of the alumina surface by the copper oxide and/or copper sulfate species. The result is the formation of extended networks of copper oxide that are stable for many adsorption/regeneration cycles. Adsorbents formed in this fashion are more reactive for sulfur dioxide adsorption than adsorbents containing similar amounts of well-dispersed copper oxide formed using copper nitrate as a precursor.