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

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1307 ◽  
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.

Time-resolved in situ DRIFTS study on NH3–SCR of NO on CeO2/TiO2 catalyst

2022 ◽  
Author(s):  
Jie Yang ◽  
Shan Ren ◽  
Mingming Wang ◽  
Zhicaho Chen ◽  
Lin Chen ◽  
...  
Keyword(s):  
Nitrogen Oxides ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Time Resolved ◽  
In Situ Drifts ◽  
Tio2 Catalyst ◽  
Nh3 Scr ◽  
Scr Of No

Ce–Ti catalysts were considered as promising replacement for V–Ti based catalysts for selective catalytic reduction (SCR) of nitrogen oxides (NO and NO2) with NH3. In this work, CeO2/TiO2 catalyst was...

scholarly journals Well-Defined Surface Tungstenocarbyne complex through the Reaction of [W(≡CtBu)(CH2tBu)3] with CeO2 : a highly and stable precatalyst for NOx reduction with NH3 ≡

2021 ◽  
Author(s):  
Cherif Larabi ◽  
Cuirong chen ◽  
Nicolas Merle ◽  
marc charlin ◽  
Kai Chung Szeto ◽  
...  
Keyword(s):  
Organometallic Chemistry ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Active Phase ◽  
High Dispersion ◽  
Nh3 Scr ◽  
Reduction Of Nox ◽  
Surface Organometallic Chemistry

A novel well-defined precatalyst for ammonia selective catalytic reduction of NOx (NH3-SCR), [W(CtBu)(CH2tBu)3]/CeO2, was prepared by surface organometallic chemistry and characterized. Due to the high dispersion of the active phase,...

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

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2534
Author(s):  
Yaping Zhang ◽  
Peng Wu ◽  
Ke Zhuang ◽  
Kai Shen ◽  
Sheng Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Selective Catalytic Reduction ◽  
Volume Fraction ◽  
Catalytic Reduction ◽  
Surface Measurement ◽  
X Ray ◽  
Nox Conversion ◽  
Nh3 Adsorption ◽  
Reduction Of Nox

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.

In Situ-DRIFTS Study of Selective Catalytic Reduction of NOx by NH3 over Cu-Exchanged SAPO-34

ACS Catalysis ◽  
2013 ◽  
Vol 3 (5) ◽  
pp. 871-881 ◽  
Author(s):  
Di Wang ◽  
Li Zhang ◽  
Krishna Kamasamudram ◽  
William S. Epling
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
In Situ Drifts ◽  
Reduction Of Nox

scholarly journals Insight into the Promoting Role of Er Modification on SO2 Resistance for NH3-SCR at Low Temperature over FeMn/TiO2 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 618
Author(s):  
Huan Du ◽  
Zhitao Han ◽  
Xitian Wu ◽  
Chenglong Li ◽  
Yu Gao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Catalyst Surface ◽  
Impregnation Method ◽  
In Situ Drifts ◽  
Tio2 Catalyst ◽  
Nh3 Scr ◽  
Nh3 Adsorption ◽  
So2 Resistance ◽  
Fast Scr

Er-modified FeMn/TiO2 catalysts were prepared through the wet impregnation method, and their NH3-SCR activities were tested. The results showed that Er modification could obviously promote SO2 resistance of FeMn/TiO2 catalysts at a low temperature. The promoting effect and mechanism were explored in detail using various techniques, such as BET, XRD, H2-TPR, XPS, TG, and in-situ DRIFTS. The characterization results indicated that Er modification on FeMn/TiO2 catalysts could increase the Mn4+ concentration and surface chemisorbed labile oxygen ratio, which was favorable for NO oxidation to NO2, further accelerating low-temperature SCR activity through the “fast SCR” reaction. As fast SCR reaction could accelerate the consumption of adsorbed NH3 species, it would benefit to restrain the competitive adsorption of SO2 and limit the reaction between adsorbed SO2 and NH3 species. XPS results indicated that ammonium sulfates and Mn sulfates formed were found on Er-modified FeMn/TiO2 catalyst surface seemed much less than those on FeMn/TiO2 catalyst surface, suggested that Er modification was helpful for reducing the generation or deposition of sulfate salts on the catalyst surface. According to in-situ DRIFTS the results of, the presence of SO2 in feeding gas imposed a stronger impact on the NO adsorption than NH3 adsorption on Lewis acid sites of Er-modified FeMn/TiO2 catalysts, gradually making NH3-SCR reaction to proceed in E–R mechanism rather than L–H mechanism. DRIFTS.

scholarly journals Numerical Investigation on the Intraphase and Interphase Mass Transfer Limitations for NH3-SCR over Cu-ZSM-5

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1966
Author(s):  
Shiyong Yu ◽  
Jichao Zhang
Keyword(s):  
Pressure Drop ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Catalytic Performance ◽  
No Oxidation ◽  
Relative Pressure ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Nh3 Adsorption ◽  
Media Channels

A systematic modeling approach was scrutinized to develop a kinetic model and a novel monolith channel geometry was designed for NH3 selective catalytic reduction (NH3-SCR) over Cu-ZSM-5. The redox characteristic of Cu-based catalysts and the variations of NH3, NOx concentration, and NOx conversion along the axis in porous media channels were studied. The relative pressure drop in different channels, the variations of NH3 and NOx conversion efficiency were analyzed. The model mainly considers NH3 adsorption and desorption, NH3 oxidation, NO oxidation, and NOx reduction. The results showed that the model could accurately predict the NH3-SCR reaction. In addition, it was found that the Cu-based zeolite catalyst had poor low-temperature catalytic performance and good high-temperature activity. Moreover, the catalytic reaction of NH3-SCR was mainly concentrated in the upper part of the reactor. In addition, the hexagonal channel could effectively improve the diffusion rate of gas reactants to the catalyst wall, reduce the pressure drop and improve the catalytic conversion efficiencies of NH3 and NOx.

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