Mechanism of iron doping promoting high temperature deNOx and anti-water vapor and SO2 poisoning of ZrW(Fe)Ox

Abstract

Driven by the strategy of reducing pollution and CO2, high temperature deNOx catalyst has become a major demand for current gas-fired exhaust purification. A series of Fe-doped ZrWOx complex oxides (Z1W0.2Fx) were prepared by solution evaporation and co-firing method, and effects of Fe doping on their high-temperature deNOx activity, N2 selectivity and anti-water vapor and SO2 poisoning were mainly investigated and the promotion mechanism of Fe doping was analyzed and discussed. Results showed that Fe doping significantly improved NH3-SCR of NO over the Z1W0.2Fx within 350–450 °C, mainly due to the redox properties of Fe2O3 itself. Appropriate Fe doping increased specific surface area and enhanced surface acidity of Z1W0.2Fx, the Z1W0.2F0.007 possessed the optimal catalytic performance for deNOx, with NO conversion more than 90 % and N2 selectivity more than 95 % at 400–650 °C. Moreover, compared to the blank sample of Z1W0.2, Fe doping remarkably enhanced anti-water vapor and SO2 poisoning of Z1W0.2Fx. Due to the competitive adsorption between H2O and NH3 at low temperature, water vapor has a slight influence on deNOx activity at 400 °C. Interestingly, water vapor notably improved deNOx activity and N2 selectivity at above 450 °C, because water vapor promoted the formation of hydroxyl groups and thus accelerated the Eley-Rideal deNOx at high temperature. SO2 had no influence on the deNOx performance of Z1W0.2Fx. Furthermore, both Lewis and Bronsted acid sites coexisted on the surface of Z1W0.2Fx, and the NH3-SCR of NO over Z1W0.2Fx at high temperature followed both Langmuir-Hinshelwood and Eley-Rideal reaction mechanisms.