Deactivation induced by metal sulfate over MnCeOx catalyst in NH3-SCR reaction at low temperature

Sulfate adsorption is one of the factors that cause the poisoning of catalyst in the low-temperature NH3 selective catalytic reduction reaction (NH3-SCR). In this paper, by controlling the co-adsorption time of SO2 and O2 at 150 °C, a range of sulfated MnCeOx catalysts with different contents of metal sulfate species were prepared to reveal the influence of metal sulfate species content on the catalytic performances and reaction mechanisms at low temperature. The catalytic activity below 250 °C rapidly decreases with increasing metal sulfate species content. The results of characterizations shed light on the reduction of specific surface area, Mn4+ and Ce3+ content, and redox ability of MnCeOx owing to the formation of metal sulfate species. Further experiments reveal that metal sulfate species preferentially absorb on MnOx domains rather than on CeO2 domains, and the adsorbed metal sulfate species can suppress the Eley-Rideal and the Langmuir–Hinshelwood reaction mechanisms over the sulfated MnCeOx. All the above results are detrimental to the activity of sulfated MnCeOx in the low-temperature NH3-SCR reaction.