Constructing highly active vanadyl species for efficient selective catalytic reduction of NOx

Abstract

Vanadia-based catalysts have been commercially applied for selective catalytic reduction with NH3 of NOx (NH3-SCR). Considering the biotoxicity of V2O5, V-based catalysts are demanded to exhibit high catalytic activity with low V2O5 loadings. However, at low vanadium contents, surface VOx primarily present in the form of monomers, which show poor low-temperature activity. Here, efficient low-vanadium-loading catalysts were designed via constructing highly reactive polymeric vanadyl species by introducing disparate forms of niobia species. Niobia species were found to promote the polymerization of surface VOx, and the disparate forms of niobia species had a key influence on the formation of polymeric vanadyl species. Crystalline Nb2O5 promoted the formation of polymeric vanadyl species, induced by a structural effect. By contrast, uniformly dispersed niobium species on the surface of a Nb-Ti-O solid solution support served as new anchoring sites for VOx and promoted a greater extent of polymerization of VOx species via electronic interactions among V, Nb and Ti. Ultimately, Nb-Ti-O solid solution-supported V2O5 exhibited much higher low-temperature reaction rates than TiO2-supported Nb2O5 and V2O5 due to more polymeric vanadyl species. This study provides new methods to design low-vanadium-loading catalysts, offering new perspectives for the modification of transition metal oxides to design efficient catalysts.