Insights into the superior resistance of In-Co3O4-Ga2O3/H-Beta to SO2 and H2O in the selective catalytic reduction of NOx by CH4.

The existence of sulfur dioxide and water vapor in the flue gas generated from waste-to-energy stations could lead to catalyst deactivation, which has adverse effects on NOx removal. It is thus particularly important to study the reaction mechanism of catalyst resistance to poisoning. Herein, we report the mechanism of In-Co3O4-Ga2O3/H-Beta catalyst to SO2 and H2O resistance in the selective catalytic reduction (SCR) of NOx by CH4. The catalyst could achieve 74.6% NOx removal efficiency in the presence of 100 ppm SO2 and 5% H2O. In this catalyst, Co3O4 is attributed to enhancing the reversible poisoning of SO2 and CH4 activation and increasing the number of Brønsted acid sites by decomposing H2O. However, the InO+ active center was still eroded by a small amount of water vapor, leading to a reduction in NOx removal efficiency. The addition of Ga2O3 primarily provided an important intermediate NO2 for CH4-SCR reaction and reduced the aggregates of Co3O4 to increase the exposure of indium sites, and could reduce a part of SO2 to S2-. This study provides a good candidate for preparing catalysts with superior resistance towards SO2 and H2O for CH4-SCR.