scholarly journals The Deactivation Mechanism of the Mo-Ce/Zr-PILC Catalyst Induced by Pb for the Selective Catalytic Reduction of NO with NH3

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2641
Author(s):  
Chenxi Li ◽  
Jin Cheng ◽  
Qing Ye ◽  
Fanwei Meng ◽  
Xinpeng Wang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Surface Acidity ◽  
Catalyst Activity ◽  
Acid Sites ◽  
Nh3 Scr ◽  
Highly Active ◽  
Negative Effect ◽  
Redox Ability ◽  
Deactivation Mechanism

As a heavy metal, Pb is one component in coal-fired flue gas and is widely considered to have a strong negative effect on catalyst activity in the selective catalytic reduction of NOx by NH3 (NH3-SCR). In this paper, we investigated the deactivation mechanism of the Mo-Ce/Zr-PILC catalyst induced by Pb in detail. We found that NO conversion over the 3Mo4Ce/Zr-PILC catalyst decreased greatly after the addition of Pb. The more severe deactivation induced by Pb was attributed to low surface area, lower amounts of chemisorbed oxygen species and surface Ce3+, and lower redox ability and surface acidity (especially a low number of Brønsted acid sites). Furthermore, the addition of Pb inhibited the formation of highly active intermediate nitrate species generated on the surface of the catalyst, hence decreasing the NH3-SCR activity.

scholarly journals Promoting Effect of Ti Species in MnOx-FeOx/Silicalite-1 for the Low-Temperature NH3-SCR Reaction

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 566
Author(s):  
Jialiang Gu ◽  
Rudi Duan ◽  
Weibin Chen ◽  
Yan Chen ◽  
Lili Liu ◽  
...  
Keyword(s):  
Catalytic Reduction ◽  
Surface Acidity ◽  
Space Velocity ◽  
Acid Sites ◽  
Impregnation Method ◽  
Promoting Effect ◽  
Nh3 Scr ◽  
Nh3 Adsorption ◽  
Redox Ability

Manganese and iron oxides catalysts supported on silicalite-1 and titanium silicalite-1 (TS-1) are synthesized by the wet impregnation method for the selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR), respectively. The optimized catalyst demonstrates an increased NOx conversion efficiency of 20% below 150 °C, with a space velocity of 18,000 h−1, which can be attributed to the incorporation of Ti species. The presence of Ti species enhances surface acidity and redox ability of the catalyst without changing the structure of supporter. Moreover, further researches based on in situ NH3 adsorption reveal that Lewis acid sites linked to Mn4+ on the surface have a huge influence on the improvement of denitration efficiency of the catalyst at low temperatures.

Deactivation of Mn/TiO2 catalyst for NH3-SCR reaction: effect of phosphorous

RSC Advances ◽  
2016 ◽  
Vol 6 (14) ◽  
pp. 11226-11232 ◽  
Author(s):  
Ning-zhi Yang ◽  
Rui-tang Guo ◽  
Qing-shan Wang ◽  
Wei-guo Pan ◽  
Qi-lin Chen ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Reduction Of No ◽  
Tio2 Catalyst ◽  
Nh3 Scr ◽  
Deactivation Mechanism

The deactivation mechanism of phosphorous on a Mn/TiO2 catalyst for selective catalytic reduction of NO with NH3 was investigated in this study.

scholarly journals Preparation of Mesoporous Mn–Ce–Ti–O Aerogels by a One-Pot Sol–Gel Method for Selective Catalytic Reduction of NO with NH3

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 475
Author(s):  
Yabin Wei ◽  
Shuangling Jin ◽  
Rui Zhang ◽  
Weifeng Li ◽  
Jiangcan Wang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Lewis Acid ◽  
Catalytic Reduction ◽  
Sol Gel ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
One Pot ◽  
Gel Method ◽  
Nh3 Scr ◽  
Composite Aerogels

Novel Mn–Ce–Ti–O composite aerogels with large mesopore size were prepared via a one-pot sol–gel method by using propylene oxide as a network gel inducer and ethyl acetoacetate as a complexing agent. The effect of calcination temperature (400, 500, 600, and 700 °C) on the NH3–selective catalytic reduction (SCR) performance of the obtained Mn–Ce–Ti–O composite aerogels was investigated. The results show that the Mn–Ce–Ti–O catalyst calcined at 600 °C exhibits the highest NH3–SCR activity and lowest apparent activation energy due to its most abundant Lewis acid sites and best reducibility. The NO conversion of the MCTO-600 catalyst maintains 100% at 200 °C in the presence of 100 ppm SO2, showing the superior resistance to SO2 poisoning as compared with the MnOx–CeO2–TiO2 catalysts reported the literature. This should be mainly attributed to its large mesopore sizes with an average pore size of 32 nm and abundant Lewis acid sites. The former fact facilitates the decomposition of NH4HSO4, and the latter fact reduces vapor pressure of NH3. The NH3–SCR process on the MCTO-600 catalyst follows both the Eley–Rideal (E–R) mechanism and the Langmuir–Hinshelwood (L–H) mechanism.

scholarly journals Preparation and Performance of Cerium-Based Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 361
Author(s):  
Ming Cai ◽  
Xue Bian ◽  
Feng Xie ◽  
Wenyuan Wu ◽  
Peng Cen
Keyword(s):  
Nitrogen Oxides ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Surface Acidity ◽  
Catalytic Performance ◽  
Synthesis Methods ◽  
Preparation Methods ◽  
Nh3 Scr ◽  
Nox Control ◽  
And Performance

Selective catalytic reduction of nitrogen oxides with NH3 (NH3-SCR) is still the most commonly used control technology for nitrogen oxides emission. Specifically, the application of rare earth materials has become more and more extensive. CeO2 was widely developed in NH3-SCR reaction due to its good redox performance, proper surface acidity and abundant resource reserves. Therefore, a large number of papers in the literature have described the research of cerium-based catalysts. This review critically summarized the development of the different components of cerium-based catalysts, and characterized the preparation methods, the catalytic performance and reaction mechanisms of the cerium-based catalysts for NH3-SCR. The purpose of this review is to highlight: (1) the modification effect of the various metal elements for cerium-based catalysts; (2) various synthesis methods of the cerium-based catalysts; and (3) the physicochemical properties of the various catalysts and clarify their relations to catalytic performances, particularly in the presence of SO2 and H2O. Finally, we hope that this work can give timely technical guidance and valuable insights for the applications of NH3-SCR in the field of NOx control.

scholarly journals Comparison of physicochemical properties and selective catalytic reduction activities of CeMn/TiO2 catalysts with and without phosphorus additives

2021 ◽  
Author(s):  
Zeycan KESKİN
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalyst Activity ◽  
High Surface ◽  
High Surface Area ◽  
Phosphorus Loading ◽  
X Ray Diffraction ◽  
Reduction Activity ◽  
Highly Active ◽  
Loading Amount

Abstract Lubricant additives contain phosphorus, which has a fly ash effect. Phosphorus negatively affects catalyst activity. Determining the effects of phosphorus loading amount on the catalytic activity is important for the development of catalysts with high NOx reduction. This study focuses on the control of NOx emissions, one of the air pollutants released from the diesel engine. The catalysts used in the reduction of NOx emissions were synthesized by washcoating method. Ce and Mn contents of all catalysts were adjusted as 3%, while the phosphorus contents of poisoned catalysts were adjusted as 0.5% and 1%. For this purpose, cordierite with high surface area was used. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Brunauer-Emmett-Teller (BET), X-Ray diffraction (XRD) and ultraviolet visible spectroscopy (UV-Vis) analyzes. The NOx reduction activity of with and without phosphorus doped CeMn/TiO2 catalysts was investigated with the designed selective catalytic reduction system (SCR). NOx conversion ratios of the CeMn/TiO2 catalyst reached the high values of 84.6% at 280°C. After the phosphorus loading, the structure of the CeMn/TiO2 catalyst deteriorated, and the NOx conversion ratios decreased. 0.5P-CeMn/TiO2 and 1P-CeMn/TiO2 catalysts showed lower NOx conversion ratios compared to CeMn/TiO2 catalyst. CeMn-TiO2 catalyst was found highly active for SCR at all tests. Phosphorus loading caused deactivation of the catalyst and deactivation increased due to the increase in phosphorus loading amount.

scholarly journals Strikingly Distinctive NH3-SCR Behavior over Cu-SSZ-13 in the Presence of NO2

2021 ◽  
Author(s):  
Yulong Shan ◽  
Guangzhi He ◽  
Jinpeng Du ◽  
Yu Sun ◽  
Zhongqi Liu ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Nh3 Scr ◽  
Highly Active ◽  
Small Pore ◽  
Standard Scr ◽  
Catalyst Systems

Abstract Commercial Cu-exchanged small-pore SSZ-13 (Cu-SSZ-13) zeolite catalysts are highly active for the selective catalytic reduction (SCR) of NOx with NH3, but distinct from other catalyst systems, their activity is unexpectedly inhibited in the presence of NO2. Here, we combined kinetic experiments, in-situ/operando X-ray absorption spectroscopy, and density functional theory (DFT) calculations to obtain direct evidence that under reaction conditions, strong oxidation by NO2 forces Cu ions to exist mainly as fixed framework Cu2+ species (fw-Cu2+), which impede the formation of dynamic binuclear Cu+ species that serve as the main active sites for the standard SCR (SSCR) reaction. As a result, the SSCR reaction is significantly inhibited by NO2 in the zeolite system, and the NO2-involved SCR reaction occurs with an energy barrier higher than that of the SSCR reaction on dynamic binuclear sites. Moreover, the NO2-involved SCR reaction tends to occur at the Brønsted acid sites (BAS) rather than the fw-Cu2+ sites. This work clearly explains the strikingly distinctive selective catalytic behavior in the zeolite system.

scholarly journals Ce and Zr Modified WO3-TiO2 Catalysts for Selective Catalytic Reduction of NOx by NH3

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 375 ◽  
Author(s):  
Wenyi Zhao ◽  
Zhaoqiang Li ◽  
Yan Wang ◽  
Rongrong Fan ◽  
Cheng Zhang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
Engine Exhaust ◽  
Operation Temperature ◽  
Nh3 Scr ◽  
Catalyst Composition ◽  
Contour Lines

A series of Ce and/or Zr modified WO3-TiO2 catalysts were synthesized by the impregnation method, which were employed for NH3-SCR reaction. The T50 contour lines of NOx were used to quickly optimize catalyst composition, the Ce20Zr12.5WTi catalyst was considered to be the optimization result, and also exhibited excellent NH3-SCR activity and thermal stability with broad operation temperature window, which is a very promising catalyst for NOx abatement from diesel engine exhaust. The excellent catalytic performance is associated with the formation of Ce-Zr solid solution. The introduction of Zr to CeWTi catalyst facilitated the redox of Ce4+/Ce3+ and the formation of more acid sites, more Ce3+ ions, more oxygen vacancies, larger quantities of surface adsorbed oxygen species and NH3, which were beneficial for the excellent selective catalytic reduction (SCR) performance.

scholarly journals Promoting Effect of Mn on In Situ Synthesized Cu-SSZ-13 for NH3-SCR

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1375
Author(s):  
Jinpeng Du ◽  
Jingyi Wang ◽  
Xiaoyan Shi ◽  
Yulong Shan ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Acid Sites ◽  
Promoting Effect ◽  
Nh3 Scr ◽  
Temperature Programmed ◽  
Diffuse Reflectance Infrared ◽  
Redox Ability

The effect of Mn impregnation on the NH3-SCR (selective catalytic reduction of NOx by NH3) activity of in situ synthesized Cu-SSZ-13 was investigated in this work. It was found that Mn addition could efficiently improve the low-temperature activity of Cu-SSZ-13. The optimal amount of Mn was 5 wt.%, and NOx conversion was improved by more than 20% over a temperature range of 120 °C to 150 °C. SEM (scanning electron microscopy), XRD (X-ray diffraction), N2 adsorption-desorption, H2-TPR (temperature programmed reduction of H2), NH3-TPD (temperature programmed desorption of NH3) and in situ DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) experiments were conducted to investigate the changes in the zeolite structure, active sites, acid sites and reaction mechanism. The impregnated MnOx species caused a decline in the crystallinity of Cu-SSZ-13 but markedly improved the redox ability. Nitrate and nitrite species were observed in the Mn-modified Cu-SSZ-13, and the formation of these species was thought to cause the observed increase in low-temperature NH3-SCR activity. The results show that the addition of Mn is a promising method for promoting the low-temperature catalytic activity of Cu-SSZ-13.

The synergistic effects between Ce and Cu in CuyCe1−yW5Ox catalysts for enhanced NH3-SCR of NOx and SO2 tolerance

2019 ◽  
Vol 9 (3) ◽  
pp. 718-730 ◽  
Author(s):  
Jian-Wen Shi ◽  
Yao Wang ◽  
Ruibin Duan ◽  
Chen Gao ◽  
Baorui Wang ◽  
...  
Keyword(s):  
Metal Oxides ◽  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Synergistic Effects ◽  
Reduction Of No ◽  
Nh3 Scr ◽  
So2 Tolerance ◽  
Scr Of Nox

Non-manganese-based metal oxides are promising catalysts for the NH3-SCR (selective catalytic reduction) of NOx at low temperatures.

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