NH3-SCR Performance Research Articles

05/01487 Influence of nitrogen surface functionalities onthe catalytic activity of activated carbon in low temperature SCR of NO x with NH 3: Szymanski, G. S. et al. Catalysis Today, 2004, 90, (1–2), 51–59

The effect of synthesis methods on the activity of V/Ce/WTi catalysts was investigated for the selective catalytic reduction (SCR) of NOx by NH3. V/Ce/WTi-DP (deposition precipitation) catalyst showed excellent NH3-SCR performance, especially the better medium-temperature activity and the less N2O formation than V/Ce/WTi-IMP (impregnation). These catalysts were characterized by X-ray diffraction (XRD), Brumauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (H2-TPR), and in situ DRIFTS techniques. The XPS and H2-TPR results revealed that V/Ce/WTi-DP exhibited more surface Ce species, higher level of Oα and higher reducibility of Ce species. Reflected by in situ DRIFTS results, the deposition precipitation method (DP) contributed to a greater amount of weakly adsorbed NO2, monodentate nitrate and NH3 species with better reactive activity. Meanwhile, the cis-N2O22– species, an intermediate for N2O formation, was very limited. As a result, these advantages brought about the superior SCR activity and N2 selectivity for V/Ce/WTi-DP.

Heats of activation in decomposition of ammonia over catalysts differing in chemical composition. II. Cobalt-, nickel-, copper-, and zirconium-based catalysts

The catalyst for selective catalytic reduction of NOx at high temperatures is significantly demanded by current gas-fired exhaust purification. In this work, the complex oxides composed of two different structures of ZrO2-WO3 and WO3/ZrO2 with zirconium as the main component were prepared for NH3-SCR of NO at high temperatures by blending method and equal volume impregnation method, respectively. Combined with XRD, NH3-TPD, FE-SEM, BET and in situ DRIFTS characterization, the effects of component optimization of two kinds of ZrO2 and WO3 complex oxides on the performance for NH3-SCR of NO were mainly studied. The optimal compatibility of ZrO2 and WO3 complex oxides was determined, and the corresponding N2 selectivity and anti-interference ability of water vapor and SO2 were further investigated. Results showed that the performance of ZrO2-WO3 prepared by blending method for NH3-SCR of NO was significantly better than that of WO3/ZrO2 prepared by impregnation method. The ZrO2-WO3 containing 20% WO3 has the best performance in NH3-SCR of NO with NO conversion higher than 90% and N2 selectivity higher than 90% at 450–650 °C, and the performance was not affected by SO2, 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 NH3-SCR of NO over the ZrO2-WO3 reaction followed both L-H and E-R mechanisms. Characterization analysis revealed that ZrO2-WO3 has finer microscopic particles, larger specific surface area, higher acid amount and stronger acid strength than WO3/ZrO2.

On the relative velocity of blue and yellow light

In the present work, a serial of Cu0.02Fe0.2CeyTi1-yOx catalysts are prepared by sol-gel method and applied for NH3-SCR of NO, meanwhile Cu0.02Fe0.2Ce0.2Ti0.8Ox shows good low-temperature NH3-SCR performance with/without water and an outstanding water resistance. The bulk structure, redox ability, surface acidity and surface species of Cu0.02Fe0.2CeyTi1-yOx are measured and discussed by series of characterization in details to illuminate the reasons for the good low-temperature activity and water resistance. The Ce modification can tune the surface acidic distribution, improve the surface oxygen content and surface oxidation reduction cycle (Ce4+ + Fe2+ ↔ Ce3+ + Fe3+), which contribute the good activity. In addition, the effect of water on NH3-SCR performance over Cu0.02Fe0.2TiOx and Cu0.02Fe0·2Ce0·2Ti0.8Ox are investigated emphatically by in situ DRIFTS.