Mechanism of the selective catalytic reduction of NOx with CH4 on In/H-beta

In this paper, the mechanism of using an In/H-beta catalyst for the selective catalytic reduction of NO by CH4 (CH4-SCR) was investigated. For the mechanistic studies, the TPSR, TPD, and in situ DRIFT spectroscopy of In/H-beta were carried out to study the surface adsorption and the reactions of NO, NO + CH4, NO + O2, CH4 + O2, and NO + CH4 + O2 on the In/H-beta catalyst. These experimental results revealed the main reaction pathways and mechanisms of CH4-SCR on the In/H-beta catalyst. The TPD and in situ DRIFTS studies showed that the adsorption of the NO species was attributed to the Si–OH and (InO)+ sites whereas the activation of CH4 was mainly related to the (InO)+ active sites, which could transfer NO to nitrate, and CH4 to formate intermediate species, and thus it could be completely converted to CO2, H2O, and N2 in the presence of oxygen. The XPS results indicated that the (InO)+ played an important role in the highly efficient CH4-SCR performance.