The present invention provides a regenerable catalyst composition suitable for entrapping SO.sub.x. The composition of the invention comprises a copper oxide having the formula (Cu/(A oxide) where A oxide is SiO.sub.2, Zr--SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2--Al.sub.2O.sub.3, ZrO.sub.2 and In.sub.2O.sub.3 or mixtures thereof. Copper loading may vary from about 10 to 60 mol % and is preferably about 25 mol %. The catalyst composition adsorbs SO.sub.x as metal sulfate under lean conditions and desorbs accumulated SO.sub.x as SO.sub.2 under rich conditions. Such reversible SO.sub.x trap are able to operate under conventional NO.sub.x trap operating conditions to prevent sulfur poisoning of the NO.sub.x trap. Furthermore, these traps may be regenerated under rich conditions at 300-450.degree. C. In another embodiment of the present invention, an irreversible SO.sub.x trap capable of collecting SO.sub.x under lean conditions is provided. The traps of this embodiment include praseodymia, zirconia-praseodymia and mixed manganese-yttria and mixtures thereof.