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

Abstract

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.