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

Catalysts ◽  
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.

scholarly journals A study on the selective catalytic reduction of NOx by ammonia on sulphated iron-based catalysts

RSC Advances ◽  
2020 ◽  
Vol 10 (67) ◽  
pp. 40948-40959
Author(s):  
Caixia Liu ◽  
Huijun Wang ◽  
Yalian Bi ◽  
Ziyin Zhang
Keyword(s):  
Selective Catalytic Reduction ◽  
High Temperatures ◽  
Catalytic Reduction ◽  
Reduction Of Nox ◽  
Iron Based ◽  
Iron Based Catalysts

The roles of Fe3+ and SO42− are different at low and high temperatures due to their interaction. It is the appropriate contents of Fe3+ and SO42− that can result in high NH3-SCR activity at varying temperatures.

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.

Recent advances in the preparation of zeolites for the selective catalytic reduction of NOx in diesel engines

2019 ◽  
Vol 4 (6) ◽  
pp. 975-985 ◽  
Author(s):  
Ling Zhang ◽  
Qinming Wu ◽  
Xiangju Meng ◽  
Ulrich Müller ◽  
Mathias Feyen ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Diesel Engines ◽  
Catalytic Reduction ◽  
Pore Sizes ◽  
Recent Advances ◽  
Small Pore ◽  
Reduction Of Nox ◽  
Scr Of Nox

Metal-exchanged zeolites with small pore sizes have attracted much attention in recent years due to their application in the selective catalytic reduction (SCR) of NOx in diesel engines.

scholarly journals Synthesis of SSZ-13 Zeolite in the Presence of N,N,N-Dimethylethylcyclohexyl Ammonium for Selective Catalytic Reduction of NOx

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Dang Van Long ◽  
Le Thanh Son ◽  
Pham Dinh Trong
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
The United States ◽  
Structure Directing Agent ◽  
Mobile Sources ◽  
Nox Conversion ◽  
Scr Catalysts ◽  
Small Pore ◽  
Reduction Of Nox ◽  
Scr Of Nox

Abstract: Since NOx emission requirements from stationary and mobile sources are more strictly regulated in the United States, Europe, and other countries; researchers have conducted many studies to improve the performance of selective catalytic reduction (SCR) catalysts to meet more and more stringent emission standards. Herein, we reported the synthesis of small pore zeolite (Cu)-SSZ-13 using N,N,N-dimethylethylcyclohexylammonium as the structure directing agent. The catalytic activity of the fresh and hydrothermal aged copper exchanged supported on SSZ-13 catalyst was investigated in the SCR of NOx using NH3 as a reductant. Cu-SSZ-13 possessing a high SCR performance (NOx conversion reached approximately 100% at 250oC), and high hydrothermal stability in combination with an easy synthesis route is considered to be a potential catalyst for SCR application. Keywords: Zeolite, SSZ-13, synthesis, SCR, NOx.

scholarly journals 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 ◽  
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.

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.

scholarly journals NH3-Selective Catalytic Reduction of NOx to N2 over Ceria Supported WOx Based Catalysts: Influence of Tungsten Content

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 950
Author(s):  
Imane El Arrouji ◽  
Cuirong Chen ◽  
Jamil Toyir ◽  
Cherif Larabi ◽  
Kai C. Szeto ◽  
...  
Keyword(s):  
High Temperature ◽  
Catalyst Surface ◽  
Catalytic Reduction ◽  
Tungstophosphoric Acid ◽  
Tungsten Content ◽  
Nh3 Scr ◽  
Tungsten Clusters ◽  
Reduction Of Nox ◽  
Series Of Experiments ◽  
Scr Of Nox

A series of HPW/CeO2 catalysts generated from 12-tungstophosphoric acid, H3PW12O40 (HPW), supported on ceria and presenting different tungsten loadings (2, 4.5, 9, 16, and 40 wt% W) were prepared and characterized by N2 physisorption, XRD, IR, Raman, and UV-Vis. The different characterization techniques suggested that low loading of tungsten resulted in mainly isolated sites, while high tungsten loading produced polymeric or tungsten clusters. Those materials exhibited high activity in NH3-SCR of NOx into N2. Moreover, the series of experiments indicated that low loading in tungsten (2% HPW/CeO2) displayed the highest activity with a remarkable N2 selectivity (99%) at medium-high temperature (300–515 °C), owing to the high amount of monomeric tungstate coverage on the catalyst surface.

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