Wei Han

Alkali Metal Poisoning of a CeO2–WO3 Catalyst Used in the Selective Catalytic Reduction of NOx with NH3: an Experimental and Theoretical Study

The alkali metal-induced deactivation of a novel CeO(2)-WO(3) (CeW) catalyst used for selective catalytic reduction (SCR) was investigated. The CeW catalyst could resist greater amounts of alkali metals than V(2)O(5)-WO(3)/TiO(2). At the same molar concentration, the K-poisoned catalyst exhibited a greater loss in activity compared with the Na-poisoned catalyst below 200 °C. A combination of experimental and theoretical methods, including NH(3)-TPD, DRIFTS, H(2)-TPR, and density functional theory (DFT) calculations, were used to elucidate the mechanism of the alkali metal deactivation of the CeW catalyst in SCR reaction. Experiments results indicated that decreases in the reduction activity and the quantity of Brønsted acid sites rather than the acid strength were responsible for the catalyst deactivation. The DFT calculations revealed that Na and K could easily adsorb on the CeW (110) surface and that the surface oxygen could migrate to cover the active tungsten, and then inhibit the SCR of NO(x) with ammonia. Hot water washing is a convenient and effective method to regenerate alkali metal-poisoned CeW catalysts, and the catalytic activity could be recovered 90% of the fresh catalyst.

Mesoporous CexCo1−xCr2O4 spinels: synthesis, characterization and catalytic application in simultaneous removal of soot particulate and NO

Cerium-doped mesoporous spinel-type catalysts were prepared via a solution combustion synthesis method and were investigated for the catalytic combustion of soot and NO. Characterization studies using BET, XRD, SEM, TEM and catalytic activity tests confirmed that these catalysts effectively and simultaneously removed soot and NO, which are the two prevalent pollutants in diesel exhaust in the temperature range of 200–600 °C. The results from the characterization indicated that the deformation of a spinel structure might occur in the process of cerium substitution. This deformation would increase the oxygen mobility and affect the catalytic performance of cerium modified spinel-type catalysts.

DRIFT study on Cr2O3-SO42−/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3

Chromium oxides supported on TiO2 showed good activity for the selective catalytic reduction of NO by NH3. The catalytic activity of Cr2O3-SO42−/TiO2 catalyst was greatly enhanced by the addition of SO42− into TiO2 support. The catalyst surface properties were characterized with NH3-TPD(temperature programmed desorption) and H2-TPR(temperature programmed reduction). The sulphate on the catalyst surface could enhance the acidity and redox of the catalyst obviously. The reaction mechanism on this catalyst was researched in detail by in situ diffuse reflectance Fourier transform infrared(FTIR) spectroscope. Eley-Rideal and Langmuir-Hinshelwood mechanism existed simultaneously for selective catalytic reduction(SCR) reaction of NO over Cr2O3-SO42−/TiO2 catalyst.

DRIFT study on Cr2O3-SO4 2−/TiO2 catalyst for low temperature selective catalytic reduction of NO with NH3

Chromium oxides supported on TiO2 showed good activity for the selective catalytic reduction of NO by NH3. The catalytic activity of Cr2O3-SO42−/TiO2 catalyst was greatly enhanced by the addition of SO42− into TiO2 support. The catalyst surface properties were characterized with NH3-TPD(temperature programmed desorption) and H2-TPR(temperature programmed reduction). The sulphate on the catalyst surface could enhance the acidity and redox of the catalyst obviously. The reaction mechanism on this catalyst was researched in detail by in situ diffuse reflectance Fourier transform infrared(FTIR) spectroscope. Eley-Rideal and Langmuir-Hinshelwood mechanism existed simultaneously for selective catalytic reduction(SCR) reaction of NO over Cr2O3-SO42−/TiO2 catalyst.

DRIFT Study on Cr 2 O 3 -SO 4 2- /TiO 2 Catalyst for Low Temperature Selective Catalytic Reduction of NO with NH 3

Chromium oxides supported on TiO2 showed good activity for the selective catalytic reduction of NO by NH3. The catalytic activity of Cr2O3-SO42−/TiO2 catalyst was greatly enhanced by the addition of SO42− into TiO2 support. The catalyst surface properties were characterized with NH3-TPD(temperature programmed desorption) and H2-TPR(temperature programmed reduction). The sulphate on the catalyst surface could enhance the acidity and redox of the catalyst obviously. The reaction mechanism on this catalyst was researched in detail by in situ diffuse reflectance Fourier transform infrared(FTIR) spectroscope. Eley-Rideal and Langmuir-Hinshelwood mechanism existed simultaneously for selective catalytic reduction(SCR) reaction of NO over Cr2O3-SO42−/TiO2 catalyst.