Browsing by Author "Xu, Yifan"

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Catalytic performance and SO2 tolerance of tetragonal-zirconia-based catalysts for low-temperature selective catalytic reduction
(2016-09-14)
Liu, Rong
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Ji, Lingchen
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Xu, Yifan
;
Ye, Fei
;
Jia, Feng
MnOx-CeO2/t-ZrO2 catalyst was prepared by impregnation of nanotetragonal zirconia. The NO conversion of 5 wt% MnOx-CeO2/t-ZrO2 catalyst was 68.1% at 100 degrees C while that of 30 wt% MnOx-CeO2/t-ZrO2 catalyst was 97.4%. The x-ray diffraction, Brunner-Emmet-Teller measurements (BET), and H-2-TPR showed surface properties of the prepared catalysts were good for selective catalytic reduction reactions. X-ray photoelectron spectroscopy analysis indicated that Mn4+ and Ce4+ oxidation states were predominant on the surface of the catalyst and so was lattice oxygen which was conducive to Lewis acid sites. NH3-TPD test results demonstrated that Lewis acid sites are predominant on the surface of catalyst. The presence of SO2 reduced the catalyst activity. The realized conversion dramatically decreased to 47% from nearly 100% after 8 h. Characterization of fresh and spent catalysts indicated the deterioration of active component and deposition of NH4HSO4 or (NH4)(2)SO4 contribute to SO2 poisoning.
Effect of ZrO2 Crystal Structures on the Catalytic Performance of MnOx-CeO2/ZrO2 for Selective Reduction of NO with NH3 at Low Temperature
(2017-12-01)
Xu, Yifan
;
Liu, Rong
;
Jia, Feng
;
Ji, Lingchen
;
Ye, Fei
A series of manganese oxide and cerium oxide catalysts supported on monoclinic zirconia (m-ZrO2), tetragonal zirconia (t-ZrO2) and cubic zirconia (c-ZrO2) were prepared by a wet-impregnation method. The catalytic performance and SO2 tolerance for the selective reduction (SCR) of NOx with NH3 were investigated. Measurements were carried out in a fixed-bed reactor. The results suggested that both SCR activity (NO conversion on the catalysts) and SO2 tolerance of the prepared catalysts decreased in the following order: 5 wt.% MnOx-CeO2/c-ZrO2(5c) > 5 wt.% MnOx-CeO2/t-ZrO2(5t) > 5 wt.% MnOx-CeO2/m-ZrO2(5m) Surface properties are discussed by using XRD, BET, SEM, XPS, TPR, TPD and TG-DTA, FT-IR. 5 wt.% MnOx-CeO2/c-ZrO2 catalyst exhibited the best redox property and the highest adsorption capacity for NH3 while 5 wt.% MnOx-CeO2/m-ZrO2 and 5 wt.% MnOx-CeO2/t-ZrO2 catalysts exhibited relatively poor performance. Also, there existed the largest density of acid sites and highest strength of acidity when c-ZrO2 was used as carrier. The deterioration of active component and deposition of NH4HSO4, (NH4)(2)SO4 or metallic sulfites were identified as the main causes of SO2 poisoning.
Influence of transition metal (Fe, Co, and Ag) doping on the MnOx-CeO2/Ti-bearing blast furnace slag catalyst for selective catalytic reduction of NOx with NH3 at low temperature
(2017-10-07)
Liu, Rong
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Xu, Yifan
;
Ye, Fei
;
Jia, Feng
;
Xu, Rui
Ti-Bearing blast furnace slag has been found to be suitable as the support of the selective catalytic reduction (SCR) catalysts. Mn-Ce-M (M = Fe, Co, Ag)/Slag catalysts prepared using a solution impregnation method for the low-temperature selective catalytic reduction (SCR) of NO with NH3 under the influence of transition metals were investigated in this study. The experiments suggested that the addition of Co can greatly enhance the SCR activity and the addition of Fe can broaden the SCR temperature range (NO conversion > 90%), while the addition of Ag reduced the SCR activity. The XRD and SEM analyses revealed that for the Co and Fe doped catalysts, the active components were well dispersed, while the Ag doped catalyst had agglomeration and sintering. The XPS results revealed that the Fe and Co doped catalysts had relatively higher ratios of Mn4+/Mn3+, Ce3+/Ce4+ and O-alpha/O-alpha + O-beta. TPR results showed that the redox properties were enhanced after adding Co and Fe. NH3-TPD was also studied to investigate the acid sites over the surface of the catalysts. And the addition of Co and Fe increased strong acid sites on the surface of the catalyst. However, the strength of acid sites over the surface of the Ag doped catalyst was too high to cause the desorption of NH3.
Manganese-cerium oxide (MnOx-CeO2) catalysts supported by titanium-bearing blast furnace slag for selective catalytic reduction of nitric oxide with ammonia at low temperature
(2017-01-01)
Xu, Yifan
;
Liu, Rong
;
Ye, Fei
;
Jia, Feng
;
Ji, Lingchen
A series of manganese-cerium oxide (MnOx-CeO2) catalysts supported by Ti-bearing blast furnace slag were prepared by wet impregnation and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. The slag-based catalyst exhibited high nitrogen oxide removal (deNOx) activity and wide effective temperature range. Under the condition of NO = 500 ppm, NH3 = 500 ppm, O-2 = 7-8 vol%, and total flow rate = 1600 mL/min, the Mn-Ce/Slag catalyst exhibited a NO conversion higher than 95% in the range of 180-260 degrees C. The activity of Mn/Slag catalysts was greatly enhanced with the addition of CeO2. The results indicated that Ti-bearing blast furnace slag had suitable phase composition as good support of SCR catalyst. Implications: Ti-bearing blast furnace slag is a kind of industrial waste in China. Much slag was underused and piling up, which could cause many environmental issues, such as enormous waste of titanium and groundwater and soil contamination by heavy metals in leachates. The utilization of slag as the support of SCR catalyst will not only make use of solid waste but also cut down the NOx emitted from power plant.