Low-vanadium and high-activity SCR catalyst for low-temperature denitrification: Influence of vanadium precursor and surface vanadium concentration

Abstract

Nitrogen oxides (NOx), as the main pollutants of air pollution, cause serious harm to the ecological environment and human health. SCR technology is widely used as the most effective method for treating NOx. The core of SCR technology is SCR catalyst. The reaction temperature of traditional commercial catalysts is difficult to reach the optimal operating temperature range, so expanding the temperature window of V2O5/TiO2 catalysts to the low-temperature region while reducing vanadium loading is a key issue to be solved. A series of V2O5/TiO2 catalysts with different vanadium precursors and different vanadium loadings were prepared by solid-phase synthesis method. The physicochemical properties of the catalyst were analyzed by X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed desorption of ammonia and temperature programmed reduction of hydrogen. The denitrification activity of the catalyst was evaluated in a fixed bed reactor. The catalysts prepared with vanadyl oxalate (VOC2O4·xH2O) and vanadyl acetylacetonate (VO(acac)2) as vanadium precursors with a vanadium loading of 5% exhibited the highest denitrification activity, with a stable NOx conversion of 100% within the temperature range of 200–350 °. Compared with the catalysts prepared with ammonium metavanadate (NH4VO3) and vanadyl sulfate (VOSO4·xH2O) as the vanadium precursors, the maximum activity temperature of VOC2O4-V5Ti and VO(acac)2-V5Ti shifted towards the low-temperature region by about 150 °. Furthermore, the denitrification activity of catalyst with a low vanadium content (1%) prepared using VO(acac)2 precursor was even higher than that of catalyst with a high vanadium content (6%) prepared using NH4VO3 precursor. Using VOC2O4 and VO(acac)2 as vanadium precursors could effectively regulate the active sites and polymeric states on the catalysts, and promote the interaction of V atoms with different valence states to form more reductive V species (V4+), thus exhibiting excellent SCR reactivity. This study provided an effective method for the preparation of low-vanadium and high-activity denitrification catalysts at low temperatures.