Novel insights for simultaneous NOx and CO Removal: Cu+-Sm3+-Ov-Ti4+ asymmetric active site promoting NH3-SCR coupled with CO oxidation reaction

Abstract

Ammonia selective catalytic reduction (NH3-SCR) coupled with CO oxidation is a promising approach for simultaneous removal of NOx and CO. However, finding a bifunctional catalyst that can effectively facilitate both reactions remains a significant challenge. This study investigates the enhancing effect of Cu+-Sm3+-Ov-Ti4+ asymmetric active sites on the oxidation reaction of NH3-SCR coupled with CO oxidation. The traditional Cu/TiO2 catalyst can achieve a maximum NOx conversion of 75 % at 225 °C, while the CuSmOTi catalyst can achieve 100 % NOx conversion at 200 °C. The successful construction of the asymmetric active site leads to an increase in Cu+ content, producing abundant oxygen vacancies, accelerating the redox cycle in the reaction process, and improving the adsorption capacity of CO. Additionally, compared with the 8.4 % Cu dispersion on the Cu/TiO2 catalyst, the Cu dispersion on the SmCuOTi catalyst is as high as 75.0 %, which improves the reduction performance of the catalyst. A large number of Lewis acid sites optimize the activation and adsorption of the catalyst to the reactants. In-situ DRIFTS analysis indicates that the NH3-SCR reaction on the CuSmOTi catalyst primarily follows the (E-R) mechanism, while CO oxidation follows the (MvK) mechanism. Moreover, the formation of a significant number of amide intermediates during the reaction process enhances the N2 selectivity. These findings present a novel concept of utilizing asymmetric active sites in NH3-SCR coupled with CO oxidation reactions, provides valuable insights for achieving the complete removal of nitrogen oxides and carbon monoxide in the case of “0″ by-products.