scholarly journals Effects of Ce over TiO2 supported MnOx-based Catalyst for NOx Reduction by Ammonia

2020 ◽  
Vol 185 ◽  
pp. 04026
Author(s):  
Zhi Liu ◽  
Yunqi Liu
Keyword(s):  
Catalytic Reduction ◽  
Nox Reduction ◽  
Catalyst Design ◽  
No Oxidation ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Positive Role ◽  
Fast Scr ◽  
Insight Into

Ce modified MnOx-based catalysts have attracted much attention due to its high activity for selective catalytic reduction of NOx by NH3 (NH3-SCR) at low-temperatures. However, the most important role of Ce on the NH3-SCR performance of MnOx-based catalysts has not been confirmed. Herein, the typical Ce-Mn/TiO2 catalyst was synthesized through incipient-wetness impregnation method, the positive role of Ce on Ce-Mn/TiO2 catalyst in the NH3-SCR process was revealed by combining different activity tests (including NO oxidation and NH3 oxidation) and characterizations (including XRD, XPS and He-TPDMS experiments). It was found that the introduction of Ce can promote the dispersion of MnOx on TiO2 support. Meanwhile, the doping of Ce in MnOx can also increase the content of Mn4+ species. The Mn4+ species plays a crucial role in NO oxidation reaction, which can trigger the “Fast SCR” reaction and promote the conversion of NOx. This work provides insight into the catalyst design for NH3-SCR process at low-temperature.

scholarly journals The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

Catalysts ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 593 ◽  
Author(s):  
Chen Wang ◽  
Jun Wang ◽  
Jianqiang Wang ◽  
Zhixin Wang ◽  
Zexiang Chen ◽  
...  
Keyword(s):  
Catalytic Reduction ◽  
Acid Sites ◽  
Particulate Filter ◽  
Kinetic Temperature ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Hydrothermal Aging ◽  
Scr Catalysts ◽  
Na Ions

To reveal the role of impregnated sodium (Na) ions in Cu/SSZ-13 catalysts, Cu/SSZ-13 catalysts with four Na-loading contents were prepared using an incipient wetness impregnation method and hydrothermally treated at 600 °C for 16 h. The physicochemical property and selective catalytic reduction (SCR) activity of these catalysts were studied to probe the deactivation mechanism. The impregnated Na exists as Na+ on catalysts and results in the loss of both Brönsted acid sites and Cu2+ ions. Moreover, the high loading of Na ions destroy the framework structure of Cu/SSZ-13 and forms new phases (SiO2/NaSiO3 and amorphous species) when Na loading was higher than 1.0 mmol/g. The decreased Cu2+ ions finally transformed into CuxO, CuO, and CuAlOx species. The inferior SCR activity of Na impregnated catalysts was mainly due to the reduced contents of Cu2+ ions at kinetic temperature region. The reduction in the amount of acid sites and Cu2+ ions, as well as copper oxide species (CuxO and CuO) formation, led to low SCR performance at high temperature. Our study also revealed that the existing problem of the Na ions’ effect should be well-considered, especially at high hydrothermal aging when diesel particulate filter (DPF) is applied in upstream of the SCR applications.

scholarly journals The promotional role of Ce in Cu/ZSM-5 and in situ surface reaction for selective catalytic reduction of NOx with NH3

RSC Advances ◽  
2015 ◽  
Vol 5 (110) ◽  
pp. 90235-90244 ◽  
Author(s):  
Shuangshuang Lai ◽  
Dongmei Meng ◽  
Wangcheng Zhan ◽  
Yun Guo ◽  
Yanglong Guo ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Surface Reaction ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Reduction Of No ◽  
Reduction Of Nox

Ce doped Cu/ZSM-5 catalysts were prepared by the incipient-wetness-impregnation method, and the effect of Ce doping on the structure and the catalytic performance was investigated in detail for the selective catalytic reduction of NO with NH3

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.

Cu-Supported on Sodium-Treated Sepiolite for Selective Catalytic Reduction of NO by Propylene

2015 ◽  
Vol 1088 ◽  
pp. 569-572
Author(s):  
Zhi Hao Zhang ◽  
Yang Li ◽  
Yun Fang Qi ◽  
Qing Ye ◽  
Shu Lan Ji ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
High Performance ◽  
Catalytic Reduction ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Redox Species ◽  
Reduction Of No ◽  
Catalytic Activities ◽  
Scr Of No ◽  
Activity Center

Cu/Na-Sep samples were prepared by the incipient wetness impregnation method. These catalysts were characterized by means of XRF, XRD, and XPS techniques, and their catalytic activities were performed by the SCR of NO with propylene. The results show that the Cu/Na-Sep catalyst exhibited the high performance in the C3H6-SCR of NO. After investigation by XRD and XPS, the result showed that there are Cu2+/Cu+redox species as a reaction activity center over Cu/Na-Sep.

Activity of yFe-10Cu/H-Sep and xCu/H-Sep for the Selective Catalytic Reduction of NO with Propylene

2012 ◽  
Vol 518-523 ◽  
pp. 281-284
Author(s):  
Qing Ye ◽  
Hai Ping Wang ◽  
Hai Xia Zhao ◽  
Shui Yuan Cheng ◽  
Tian Fang Kang
Keyword(s):  
Catalytic Reduction ◽  
Catalytic Performance ◽  
High Dispersion ◽  
High Catalytic Activity ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Promotional Effect ◽  
Scr Of No ◽  
Metal Support Interaction ◽  
Metal Support

Cu supported on acid-treated sepiolite catalysts (xCu/H-Sep, x = 0  20.0 wt%) or Cu-Fe mixed supported on acid-treated sepiolite catalysts (yFe-10Cu/H-Sep, y = 0  20.0 wt%) were prepared by the incipient wetness impregnation method. The xCu/H-Sep and yFe-10Cu/H-Sep catalysts were characterized by means of XRD, BET, XRF, XPS, and H2-TPR techniques, and their catalytic activities were evaluated for the SCR of NO with propylene. XPS and XRD results indicate that there was the co-presence of Cu+-Cu2+ and Fe2+-Fe3+ over the surfaces of yFe-10Cu/H-Sep catalysts, and there was a strong interaction between Cu, Fe and sepiolite. High promotional effect of iron additive on the catalytic performance of Cu/H-Sep catalyst were found in C3H6-SCR of NO reaction. The highest activity of 65% NO conversion was obtained over 15Fe-10Cu/H-Sep catalyst at 280 oC under the condition of 1000 ppm NO, 1000 ppm C3H6, and 5% O2. The high catalytic activity of 15Fe-10Cu/H-Sep catalyst for NO reduction was due to its high reducibility to activate C3H6 to selectively reduce NO in the presence of excess O2. The high dispersion of copper oxides and strong metal-support interaction over 15Fe-10Cu/H-Sep catalyst also improve its catalytic performance.

Sleight of Hand? Practice Opacity, Third-party Responses, and the Interorganizational Diffusion of Controversial Practices

2012 ◽  
Vol 57 (4) ◽  
pp. 553-584 ◽  
Author(s):  
Forrest Briscoe ◽  
Chad Murphy
Keyword(s):  
Media Coverage ◽  
Third Party ◽  
Positive Role ◽  
Organizational Fields ◽  
Cultural Approach ◽  
Adoption Decisions ◽  
Conflicting Interests ◽  
Insight Into ◽  
Subsequent Diffusion

We examine the role of a practice’s opacity (versus transparency) in the interorganizational diffusion of organizational practices. Though the opacity of a practice is typically thought to impede diffusion, a political-cultural approach to institutions suggests that opacity can sometimes play a positive role. Given that adoption decisions are embedded in a web of conflicting interests, transparency may bring negative attention that, when observed by prospective adopters, inhibits them from following suit. Opacity, in contrast, helps avoid that cycle. Using the curtailment of health benefits for retirees among large U.S. employers (1989 to 2009), we compare the diffusion of transparent adoptions (i.e., partial or complete benefit cuts) with opaque adoptions (i.e., spending caps that trigger disenrollment). We find that transparent adoptions reduce subsequent diffusion of the practice to other organizations. This effect is fully mediated by negative media coverage, which is itself conditioned by the presence of opposition from interest groups. Opaque adoptions, in contrast, increase subsequent diffusion to other organizations and are facilitated by the involvement of professional experts. Thus, in addition to providing findings on practice opacity, our study contributes insight into how organizational fields shape diffusion by illuminating the role of third parties in the spread of controversial practices.

scholarly journals Insight into Platinum Poisoning Effect on Cu-SSZ-13 in Selective Catalytic Reduction of NOx with NH3

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 796
Author(s):  
Huawang Zhao ◽  
Lei Han ◽  
Yujie Wang ◽  
Jiandong Zheng
Keyword(s):  
Catalytic Reduction ◽  
No Oxidation ◽  
Oxidation Reactions ◽  
Hydrothermal Aging ◽  
N2o Formation ◽  
Poisoning Effect ◽  
Nh3 Oxidation ◽  
Reduction Of Nox ◽  
Parallel Reactions ◽  
Insight Into

Platinum’s (Pt) poisoning effect on Cu-SSZ-13 and its regeneration were investigated. The Pt enhanced the parallel reactions, such as NH3 oxidation and NO oxidation reactions, which decreased the deNOx activities. In the temperature range below 330 °C, the deactivation of Cu-SSZ-13 by Pt poisoning was primarily caused by the overconsumption of NH3, due to the enhanced NH3-selective oxidation reaction, while the formation of NOx in NH3 oxidation and NO oxidation into NO2 further aggravated the degradation when the temperature was above 460 °C. The non-selective NH3 oxidation and non-selective NOx catalytic reduction reactions resulted in increased N2O formation over Pt-doped samples. The transformation of Pt0 into PtOx after hydrothermal aging recovered the deNOx activities of the Pt-poisoned samples.

Modeling Species Inhibition of NO Oxidation in Urea-SCR Catalysts for Diesel Engine NOx Control

2010 ◽  
Author(s):  
Maruthi Devarakonda ◽  
Russell Tonkyn ◽  
Diana Tran ◽  
Jong Lee ◽  
Darrell Herling
Keyword(s):  
Low Temperature ◽  
Kinetic Models ◽  
Catalytic Reduction ◽  
No Oxidation ◽  
Dissociation Kinetics ◽  
Scr Catalysts ◽  
Fast Scr ◽  
Standard Scr ◽  
Heavy Duty Diesel ◽  
Nox Control

Urea-selective catalytic reduction (SCR) catalysts are regarded as the leading NOx aftertreatment technology to meet the 2010 NOx emission standards for on-highway vehicles running on heavy-duty diesel engines. However, issues such as low NOx conversion at low temperature conditions still exist due to various factors, including incomplete urea thermolysis, inhibition of SCR reactions by hydrocarbons and H2O. We have observed a noticeable reduction in the standard SCR reaction efficiency at low temperature with increasing water content. We observed a similar effect when hydrocarbons are present in the stream. This effect is absent under fast SCR conditions where NO ∼ NO2 in the feed gas. As a first step in understanding the effects of such inhibition on SCR reaction steps, kinetic models that predict the inhibition behavior of H2O and hydrocarbons on NO oxidation are presented in the paper. A one-dimensional SCR model was developed based on conservation of species equations and was coded as a C-language S-function and implemented in Matlab/Simulink environment. NO oxidation and NO2 dissociation kinetics were defined as a function of the respective adsorbate’s storage in the SCR catalyst. The corresponding kinetic models were then validated on temperature ramp tests that showed good match with the test data.

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