Bulk tungsten-substituted vanadium oxide for low-temperature NOx removal in the presence of water

Y NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100-150 degrees C) and in the presence of water (similar to 20vol%). The 3.5mol% W-substituted vanadium oxide shows >99% (dry) and similar to 93% (wet, 5-20 vol% water) NO conversion at 150 degrees C (250 ppm NO, 250 ppm NH3, 4% O-2, SV=40000mLh(-1) g(cat)(-1)). Lewis acid sites of W-substituted vanadium oxide are converted to BrOnsted acid sites under a wet condition while the distribution of BrOnsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on BrOnsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 degrees C. The high redox ability and reactivity of BrOnsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor.