A mesh-type Cu-Mn-CeO
x/Al
2O
3/Al alumite catalyst was employed to investigate the selective reduction of NO with C
3H
6 in the presence of SO
2 and H
2O. The effect of SO
2 on the de-NO
x activity closely depended on SO
2 concentration and temperature. At a low temperature (673 K), SO
2 of 50 ppm greatly improved the NO
x reduction, but a further increase in SO
2 concentration (up to 500 ppm) caused a rapid catalyst deactivation. As temperature increased to 723 K, the catalyst deactivation caused by 500 ppm SO
2 disappeared, and further the presence of SO
2 also produced a remarkable promotion in the de-NO
x activity. The effect of SO
2 was observed to be an irreversible course associated with irreversible chemical phase transition. The presence of SO
2 was considered to inhibit the over-oxidation of the organic-intermediates by oxygen, and to make the organic-intermediates more available for the NO
x reduction. However, a high concentration of SO
2 inhibited not only this over-oxidation but also propene activation, and led to catalyst deactivation. The inhibition of SO
2 in the propene activation, mainly attributed to the over-adsorption of SO
2, could be weakened as temperature increases. Although the presence of water vapor depressed the de-NO
x activity, this change was almost reversible. In comparison with the separate presence of SO
2, the coexistence of H
2O and SO
2 more dramatically improved the NO
x reduction. It was considered possible that the coexisting H
2O diluted SO
2 to lessen the inhibition effect of SO
2 on activating propene.
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