The Effect of S02 and H20 on the SCR-C3H6 of NO over a Transition Metals Supported Mesh-type Alumite Catalyst

Abstract

A mesh-type Cu-Mn-CeOx/Al2O3/Al alumite catalyst was employed to investigate the selective reduction of NO with C3H6 in the presence of SO2 and H2O. The effect of SO2 on the de-NOx activity closely depended on SO2 concentration and temperature. At a low temperature (673 K), SO2 of 50 ppm greatly improved the NOx reduction, but a further increase in SO2 concentration (up to 500 ppm) caused a rapid catalyst deactivation. As temperature increased to 723 K, the catalyst deactivation caused by 500 ppm SO2 disappeared, and further the presence of SO2 also produced a remarkable promotion in the de-NOx activity. The effect of SO2 was observed to be an irreversible course associated with irreversible chemical phase transition. The presence of SO2 was considered to inhibit the over-oxidation of the organic-intermediates by oxygen, and to make the organic-intermediates more available for the NOx reduction. However, a high concentration of SO2 inhibited not only this over-oxidation but also propene activation, and led to catalyst deactivation. The inhibition of SO2 in the propene activation, mainly attributed to the over-adsorption of SO2, could be weakened as temperature increases. Although the presence of water vapor depressed the de-NOx activity, this change was almost reversible. In comparison with the separate presence of SO2, the coexistence of H2O and SO2 more dramatically improved the NOx reduction. It was considered possible that the coexisting H2O diluted SO2 to lessen the inhibition effect of SO2 on activating propene.