In‐Situ EPR Study of the Effect of SO₂ Poisoning and Regeneration of Cu‐CHA Catalysts

A series of copper (Cu) exchanged chabazite zeolite with different Cu content were investigated to elucidate the effect of SO 2 poisoning and regeneration of the Cu species. The distribution and redox ability of Cu species were determined by in situ electron paramagnetic resonance (EPR) measurements. After exposure of the catalyst to SO 2 , a large amount of redox active Cu sites disappeared and were replaced with redox inactive sulfated Cu species. The redox window, that is, the amount of Cu able to change oxidation state in the catalyst decreased significantly and was only partially regained by regeneration of the catalyst. This work provides a deeper knowledge of the effect of sulfation and regeneration of the copper sites by characterizing the redox activity of the individual Cu sites.