Effect of SO2 on the Selective Catalytic Reduction of NOx over V2O5-CeO2/TiO2-ZrO2 Catalysts

The effect of SO2 on the selective catalytic reduction of NOx by NH3 over V2O5-0.2CeO2/TiO2-ZrO2 catalysts was studied through catalytic activity tests and various characterization methods, like Brunner−Emmet−Teller (BET) surface measurement, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), hydrogen temperature-programmed desorption (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS). The results showed that the catalyst exhibited superior SO2 resistance when the volume fraction of SO2 was below 0.02%. As the SO2 concentration further increased, the NOx conversion exhibited some degree of decline but could restore to the original level when stopping feeding SO2. The deactivation of the catalyst caused by water in the flue gas was reversible. However, when 10% H2O was introduced together with 0.06% SO2, the NOx conversion was rapidly reduced and became unrecoverable. Characterizations indicated that the specific surface area of the deactivated catalyst was significantly reduced and the redox ability was weakened, which was highly responsible for the decrease of the catalytic activity. XPS results showed that more Ce3+ was generated in the case of reacting with SO2. In situ DRIFTS results confirmed that the adsorption capacity of SO2 was enhanced obviously in the presence of O2, while the SO2 considerably refrained the adsorption of NH3. The adsorption of NOx was strengthened by SO2 to some extent. In addition, NH3 adsorption was improved after pre-adsorbed by SO2 + O2, indicating that the Ce3+ and more oxygen vacancy were produced.

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In Situ DRIFTS Studies of NH3-SCR Mechanism over V2O5-CeO2/TiO2-ZrO2 Catalysts for Selective Catalytic Reduction of NOx

Materials ◽

10.3390/ma11081307 ◽

2018 ◽

Vol 11 (8) ◽

pp. 1307 ◽

Cited By ~ 11

Author(s):

Yaping Zhang ◽

Xiupeng Yue ◽

Tianjiao Huang ◽

Kai Shen ◽

Bin Lu

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Nox Reduction ◽

Oxygen Storage ◽

In Situ Drifts ◽

Nh3 Scr ◽

Nh3 Adsorption ◽

Reduction Of Nox ◽

Zro2 Catalyst

TiO2-ZrO2 (Ti-Zr) carrier was prepared by a co-precipitation method and 1 wt. % V2O5 and 0.2 CeO2 (the Mole ratio of Ce to Ti-Zr) was impregnated to obtain the V2O5-CeO2/TiO2-ZrO2 catalyst for the selective catalytic reduction of NOx by NH3. The transient activity tests and the in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) analyses were employed to explore the NH3-SCR (selective catalytic reduction) mechanism systematically, and by designing various conditions of single or mixing feeding gas and pre-treatment ways, a possible pathway of NOx reduction was proposed. It was found that NH3 exhibited a competitive advantage over NO in its adsorption on the catalyst surface, and could form an active intermediate substance of -NH2. More acid sites and intermediate reaction species (-NH2), at lower temperatures, significantly promoted the SCR activity of the V2O5-0.2CeO2/TiO2-ZrO2 catalyst. The presence of O2 could promote the conversion of NO to NO2, while NO2 was easier to reduce. The co-existence of NH3 and O2 resulted in the NH3 adsorption strength being lower, as compared to tests without O2, since O2 could occupy a part of the active site. Due to CeO2’s excellent oxygen storage-release capacity, NH3 adsorption was weakened, in comparison to the 1 wt. % V2O5-0.2CeO2/TiO2-ZrO2 catalyst. If NOx were to be pre-adsorbed in the catalyst, the formation of nitrate and nitro species would be difficult to desorb, which would greatly hinder the SCR reaction. All the findings concluded that NH3-SCR worked mainly through the Eley-Rideal (E-R) mechanism.

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Poisoning Effects of Alkali and Alkaline Earth Metal Doping on Selective Catalytic Reduction of NO with NH3 over the Nb-Ce/Zr-PILC Catalysts

Catalysts ◽

10.3390/catal11030329 ◽

2021 ◽

Vol 11 (3) ◽

pp. 329

Author(s):

Chenxi Li ◽

Jin Cheng ◽

Qing Ye ◽

Fanwei Meng ◽

Xinpeng Wang ◽

...

Keyword(s):

Selective Catalytic Reduction ◽

Alkaline Earth ◽

Catalytic Reduction ◽

Earth Metal ◽

Alkaline Earth Metal ◽

X Ray ◽

Nh3 Adsorption ◽

Temperature Programmed ◽

Redox Ability

The poisoning effects of alkali metals (K and Na) and alkaline earth metals (Ca and Mg) on catalytic performance of the 2Nb4Ce/Zr-PILC catalyst for the selective catalytic reduction of NOx with NH3 (NH3-SCR) were investigated, and physicochemical properties of the catalysts were characterized by means of the X-ray diffraction XRD (XRD), Brunner−Emmet−Teller (BET), hydrogen temperature-programmed reduction (H2-TPR), X-ray Photoelectron Spectroscopy (XPS), ammonia temperature-programmed desorption (NH3-TPD), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) techniques. Doping of M (M = K, Na, Ca, and Mg) deactivated the 2Nb4Ce/Zr-PILC catalyst according to the sequence of 0.8 K > 0.8 Na > 0.8 Ca > 0.8 Mg (M/Ce molar ratio = 0.8). The characterization results showed that the decreases in redox ability, NH3 adsorption, Ce3+/Ce4+ atomic ratio, and amount of the chemisorbed oxygen (Oβ) were the important factors influencing catalytic activities of the alkali metal-and alkaline earth metal-doped samples. Consequently, compared with the Mg- and Ca-doped samples, doping of K caused the 2Nb4Ce/Zr-PILC sample to possess the lowest redox ability, NH3 adsorption, and amount of the Oβ species, which resulted in an obvious deactivation effect.

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Selective Catalytic Reduction of NOx by Ammonia over Fe-ZSM-5 Catalyst

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.230 ◽

2012 ◽

Vol 550-553 ◽

pp. 230-233

Author(s):

Luo Ning Ma ◽

Hong Xia Qu ◽

Qin Zhong ◽

Jie Zhang ◽

Qi Sheng Tang

Keyword(s):

Catalytic Activity ◽

Selective Catalytic Reduction ◽

Hydrothermal Method ◽

Flue Gas ◽

Catalytic Reduction ◽

Iron Loading ◽

Nox Conversion ◽

Reduction Of Nox ◽

Different Levels

Fe-ZSM-5 catalysts were synthesized by hydrothermal method under different levels of iron loading. The result of XRD and TG/DTA showed that Fe-ZSM-5 catalysts were successfully obtained after calcination at 550 °C. The effects of Si/(Fe+Al) and Fe/Al ratio on the SCR performance of Fe-ZSM-5 catalyst were investigated in a simulated flue gas. When Si/(Fe+Al)=20 and Fe:Al=20 Fe-ZSM-5 catalyst showed excellent catalytic activity. Under the condition of 210 °C, [NH3]/[NO] of 1.2, [O2] of 6 vol%, [NOx] of 900×10-6, Si/(Fe+Al)=20 and Fe/Al=1, NOx conversion exceeds 98%. Besides, Fe-ZSM-5 catalyst was excellently resistant to SO2 and H2O in the SCR reaction.

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Cu- and Fe-speciation in a composite zeolite catalyst for selective catalytic reduction of NOx: insights from operando XAS

Catalysis Science & Technology ◽

10.1039/d0cy01654c ◽

2021 ◽

Author(s):

Ilia A. Pankin ◽

Houeida Issa Hamoud ◽

Kirill A. Lomachenko ◽

Søren Birk Rasmussen ◽

Andrea Martini ◽

...

Keyword(s):

Selective Catalytic Reduction ◽

Absorption Spectroscopy ◽

Zeolite Catalyst ◽

Catalytic Reduction ◽

Mechanical Mixture ◽

X Ray ◽

Fe Speciation ◽

Reduction Of Nox ◽

Operando Xas ◽

X Ray Absorption

Cu-SAPO-34 (Cu-CZC) and Fe-mordenite (Fe-MOR) and their mechanical mixture (50 : 50) have been exhaustively investigated by means of operando X-ray absorption spectroscopy under NH3-SCR conditions.

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Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: In situ Cu and S K-edge XAS studies

Catalysis Science & Technology ◽

10.1039/d1cy00975c ◽

2021 ◽

Author(s):

Vitaly Mesilov ◽

Sandra Dahlin ◽

Susanna Liljegren Bergman ◽

Peter Sams Hammershøi ◽

Shibo Xi ◽

...

Keyword(s):

Selective Catalytic Reduction ◽

Oxidation State ◽

Absorption Spectroscopy ◽

Catalytic Reduction ◽

Sulfur Poisoning ◽

X Ray ◽

Scr Catalysts ◽

X Ray Absorption

In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Sulfur in the oxidation state...

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Investigation of Sulfated Iron-Based Catalysts with Different Sulfate Position for Selective Catalytic Reduction of NOx with NH3

Catalysts ◽

10.3390/catal10091035 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1035

Author(s):

Baiyu Fan ◽

Ziyin Zhang ◽

Caixia Liu ◽

Qingling Liu

Keyword(s):

Selective Catalytic Reduction ◽

Catalyst Surface ◽

Catalytic Reduction ◽

Nh3 Adsorption ◽

Reduction Of Nox ◽

Iron Based ◽

Redox Ability ◽

Scr Of Nox ◽

Iron Based Catalysts

The Fe/(SZr) and S(Fe/Zr) sulfated iron-based catalysts, prepared by impregnation methods through changing the loading order of Fe2O3 and SO42− on ZrO2, were investigated on selective catalytic reduction (SCR) of NOx by ammonia. It was studied that the existent forms of Fe2O3 and SO42− on the surface of catalysts were affected by the loading order. The Fe/(SZr) catalyst surface had isolated Fe2O3 and SO42− species and followed both the L-H mechanism and the E-R mechanism, whereas the S(Fe/Zr) catalyst contained SO42− specie and sulfate only and mainly followed the E-R pathway. These factors affected the redox ability and NH3 adsorption, which might be key to the SCR reaction.

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