High-temperature selective catalytic reduction of NO with NH3: Optimization of ZrO2 and WO3 complex oxides
The catalyst for selective catalytic reduction of NO x at high temperatures is significantly demanded by current gas-fired exhaust purification. In this work, the complex oxides composed of two different structures of ZrO 2 -WO 3 and WO 3 /ZrO 2 with zirconium as the main component were prepared for NH 3 -SCR of NO at high temperatures by blending method and equal volume impregnation method, respectively. Combined with XRD, NH 3 -TPD, FE-SEM, BET and in situ DRIFTS characterization, the effects of component optimization of two kinds of ZrO 2 and WO 3 complex oxides on the performance for NH 3 -SCR of NO were mainly studied. The optimal compatibility of ZrO 2 and WO 3 complex oxides was determined, and the corresponding N 2 selectivity and anti-interference ability of water vapor and SO 2 were further investigated. Results showed that the performance of ZrO 2 -WO 3 prepared by blending method for NH 3 -SCR of NO was significantly better than that of WO 3 /ZrO 2 prepared by impregnation method. The ZrO 2 -WO 3 containing 20% WO 3 has the best performance in NH 3 -SCR of NO with NO conversion higher than 90% and N 2 selectivity higher than 90% at 450–650 °C, and the performance was not affected by SO 2 , slightly affected by competitive adsorption of water vapor at 450 °C and not disturbed by water vapor above 500 °C. Further investigation showed that the NH 3 -SCR of NO over the ZrO 2 -WO 3 reaction followed both L-H and E-R mechanisms. Characterization analysis revealed that ZrO 2 -WO 3 has finer microscopic particles, larger specific surface area, higher acid amount and stronger acid strength than WO 3 /ZrO 2 .
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