Stability and enhanced low-temperature NH3-SCR activity of supported vanadate catalysts in a microwave field

Abstract

Low-temperature selective catalytic reduction (SCR) of NO by NH₃ over supported NdV/Ti-x% (x = 1, 5, and 10) catalysts has been assessed in a microwave field. The NO conversion of NdV/Ti-10% catalyst reached above 85% in three cycles at temperatures ranging from 120 to 200 °C, with a N₂ selectivity of ca. 90%. The catalysts before and after activity evaluation were characterized by means of XRD, TEM, H₂-TPR, TPD, in situ DRIFTs etc. The results suggested that the catalysts exhibited excellent stability in the microwave field. It also showed that catalysts after microwave irradiation possessed an enhanced formation of oxygen species, monodentate nitrite and bridging bidentate nitrates on the catalysts' surface, which favored the generation of gaseous NO₂ to promote the “fast SCR” process. Additionally, the results implied that oxygen species activation and NO oxidation to NO₂ over the catalyst were favored in the microwave field, which facilitated NH₃-SCR reaction at low temperatures.