scholarly journals Cu-IM-5 as the Catalyst for Selective Catalytic Reduction of NOx with NH3: Role of Cu Species and Reaction Mechanism

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 221
Author(s):  
Guangying Fu ◽  
Junwen Chen ◽  
Yuqian Liang ◽  
Rui Li ◽  
Xiaobo Yang ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Oxidation Activity ◽  
Paramagnetic Resonance ◽  
Nh3 Scr ◽  
Nh3 Oxidation ◽  
Diffuse Reflectance Infrared

The role of Cu species in Cu ion-exchanged IM-5 zeolite (Cu-IM-5) regarding the performance in selective catalytic reduction (SCR) of NOx with NH3 (NH3-SCR) and the reaction mechanism was studied. Based on H2 temperature-programmed reduction (H2-TPR) and electron paramagnetic resonance (EPR) results, Cu–O–Cu and isolated Cu species are suggested as main Cu species existing in Cu-IM-5 and are active for SCR reaction. Cu–O–Cu species show a good NH3-SCR activity at temperatures below 250 °C, whereas their NH3 oxidation activity at higher temperatures hinders the SCR performance. At low temperatures, NH4NO3 and NH4NO2 are key reaction intermediates. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) suggests a mixed Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanism over Cu-IM-5 at low temperatures.

scholarly journals A Study on Mn-Fe Catalysts Supported on Coal Fly Ash for Low-Temperature Selective Catalytic Reduction of NOX in Flue Gas

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1399
Author(s):  
Xiaoxu Duan ◽  
Jinxiao Dou ◽  
Yongqi Zhao ◽  
Salman Khoshk Rish ◽  
Jianglong Yu
Keyword(s):  
Reaction Mechanism ◽  
Fly Ash ◽  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Coal Fly Ash ◽  
Fixed Bed Reactor ◽  
Main Reaction ◽  
Nh3 Scr

A series of Mn0.15Fe0.05/fly-ash catalysts have been synthesized by the co-precipitation method using coal fly ash (FA) as the catalyst carrier. The catalyst showed high catalytic activity for low-temperature selective catalytic reduction (LTSCR) of NO with NH3. The catalytic reaction experiments were carried out using a lab-scale fixed-bed reactor. De-NOx experimental results showed the use of optimum weight ratio of Mn/FA and Fe/FA, resulted in high NH3-SCR (selective catalytic reduction) activity with a broad operating temperature range (130–300 °C) under 50000 h−1. Various characterization methods were used to understand the role of the physicochemical structure of the synthesized catalysts on their De-NOx capability. The scanning electron microscopy, physical adsorption-desorption, and X-ray photoelectron spectroscopy showed the interaction among the MnOx, FeOx, and the substrate increased the surface area, the amount of high valence metal state (Mn4+, Mn3+, and Fe3+), and the surface adsorbed oxygen. Hence, redox cycles (Fe3+ + Mn2+ ↔ Mn3+ + Fe2+; Fe2+ + Mn4+ ↔ Mn3+ + Fe3+) were co-promoted over the catalyst. The balance between the adsorption ability of the reactants and the redox ability can promote the excellent NOx conversion ability of the catalyst at low temperatures. Furthermore, NH3/NO temperature-programmed desorption, NH3/NO- thermo gravimetric-mass spectrometry (NH3/NO-TG-MS), and in-situ DRIFTs (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) results showed the Mn0.15Fe0.05/FA has relatively high adsorption capacity and activation capability of reactants (NO, O2, and NH3) at low temperatures. These results also showed that the Langmuir–Hinshelwood (L–H) reaction mechanism is the main reaction mechanism through which NH3-SCR reactions took place. This work is important for synthesizing an efficient and environmentally-friendly catalyst and demonstrates a promising waste-utilization strategy.

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.

scholarly journals Deactivation of Cu/SSZ-13 NH3-SCR Catalyst by Exposure to CO, H2, and C3H6

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 929 ◽  
Author(s):  
Auvray ◽  
Mihai ◽  
Lundberg ◽  
Olsson
Keyword(s):  
Flow Reactor ◽  
Catalytic Reduction ◽  
Plug Flow ◽  
Acid Sites ◽  
Drift Spectroscopy ◽  
Scr Catalyst ◽  
Nh3 Scr ◽  
Scr Catalysts ◽  
Nh3 Oxidation ◽  
Diffuse Reflectance Infrared

Lean nitric oxide (NOx)-trap (LNT) and selective catalytic reduction (SCR) are efficient systems for the abatement of NOx. The combination of LNT and SCR catalysts improves overall NOx removal, but there is a risk that the SCR catalyst will be exposed to high temperatures and rich exhaust during the LNTs sulfur regeneration. Therefore, the effect of exposure to various rich conditions and temperatures on the subsequent SCR activity of a Cu-exchanged chabazite catalyst was studied. CO, H2, C3H6, and the combination of CO + H2 were used to simulate rich conditions. Aging was performed at 800 °C, 700 °C, and, in the case of CO, 600 °C, in a plug-flow reactor. Investigation of the nature of Cu sites was performed with NH3-temperature-programed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) of probe molecules (NH3 and NO). The combination of CO and H2 was especially detrimental to SCR activity and to NH3 oxidation. Rich aging with low reductant concentrations resulted in a significantly larger deactivation compared to lean conditions. Aging in CO at 800 °C caused SCR deactivation but promoted high-temperature NH3 oxidation. Rich conditions greatly enhanced the loss of Brønsted and Lewis acid sites at 800 °C, indicating dealumination and Cu migration. However, at 700 °C, mainly Brønsted sites disappeared during aging. DRIFT spectroscopy analysis revealed that CO aging modified the Cu2+/CuOH+ ratio in favor of the monovalent CuOH+ species, as opposed to lean aging. To summarize, we propose that the reason for the increased deactivation observed for mild rich conditions is the transformation of the Cu species from Z2Cu to ZCuOH, possibly in combination with the formation of Cu clusters.

Promotional effect of iron oxide on the catalytic properties of Fe–MnOx/TiO2 (anatase) catalysts for the SCR reaction at low temperatures

2016 ◽  
Vol 6 (6) ◽  
pp. 1772-1778 ◽  
Author(s):  
Shengcai Deng ◽  
Ke Zhuang ◽  
Bolian Xu ◽  
Yuanhua Ding ◽  
Lei Yu ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Iron Oxide ◽  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Properties ◽  
Catalytic Reduction ◽  
Surface Interaction ◽  
Tio2 Anatase ◽  
Promotional Effect

The surface interaction of the iron-improved MnOx/TiO2 (anatase) catalyst for the selective catalytic reduction of nitric oxide was studied. The role of iron was investigated through detailed experiments.

scholarly journals The Latest Research Progress of NH3-SCR in the SO2 Resistance of the Catalyst in Low Temperatures for Selective Catalytic Reduction of NOx

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1034 ◽  
Author(s):  
Caixia Liu ◽  
Huijun Wang ◽  
Ziyin Zhang ◽  
Qingling Liu
Keyword(s):  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Complex Oxide ◽  
Research Progress ◽  
Preparation Methods ◽  
Nh3 Scr ◽  
So2 Resistance ◽  
Reduction Of Nox ◽  
Further Development

The selective catalytic reduction (SCR) has been widely used in industrial denitrification owing to its high denitrification efficiency, low operating costs, and simple operating procedures. However, coal containing a large amount of sulfur will produce SO2 during combustion, which makes the catalyst easy to be deactivated, thus limiting the application of this technology. This review summarizes the latest NH3-SCR reaction mechanisms and the deactivation mechanism of catalyst in SO2-containing flue gas. Some strategies are summarized for enhancing the poison-resistance through modification, improvement of support, the preparation of complex oxide catalyst, optimizing the preparation methods, and acidification. The mechanism of improving sulfur resistance of catalysts at low temperatures is summarized, and the further development of the catalyst is also prospected. This paper could provide a reference and guidance for the development of SO2 resistance of the catalyst at low temperatures.

The Effect of Si/Al Ratio on Selective Catalytic Reduction of NOx with NH3 over Pt/Al-SBA-15

2008 ◽  
Vol 135 ◽  
pp. 61-64
Author(s):  
Min Kang ◽  
Jae Hyun Park ◽  
Eun Duck Park ◽  
Ji Man Kim ◽  
Dae Jung Kim ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Reaction Temperature ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Pt Catalysts ◽  
Nh3 Scr ◽  
Nox Conversion ◽  
Reduction Of Nox

The selective catalytic reduction of NOx with NH3 (NH3-SCR) was investigated over Pt catalysts supported on various supports such as alumina, ZSM-5, SBA-15, and Al-SBA-15 with different amounts of alumina. Among them, Pt catalysts supported on Al-SBA-15 showed the higher NOx conversion at low temperatures than those of others. These also showed high NOx conversions over a wide reaction temperature. As the Si/Al ratio in Al-SBA-15 decreased, the NH3-SCR activity increased. This was closely related to the amount of strongly-adsorbed NH3.

Highly dispersed MnOx–FeOx supported by silicalite-1 for the selective catalytic reduction of NOx with NH3 at low temperatures

2020 ◽  
Vol 10 (16) ◽  
pp. 5525-5534 ◽  
Author(s):  
Jialiang Gu ◽  
Bingjun Zhu ◽  
Rudi Duan ◽  
Yan Chen ◽  
Shaoxin Wang ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Low Temperatures ◽  
Catalytic Reduction ◽  
Highly Dispersed ◽  
Reduction Of Nox

MnOx–FeOx-Loaded silicalite-1 catalysts exhibit high NOx conversion at low temperatures.

scholarly journals Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 55
Author(s):  
Katarzyna Świrk ◽  
Ye Wang ◽  
Changwei Hu ◽  
Li Li ◽  
Patrick Da Costa ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Supported Catalysts ◽  
Catalytic Performance ◽  
Experimental Conditions ◽  
One Pot ◽  
Nh3 Scr ◽  
Scr Of No ◽  
Temperature Programmed ◽  
Stationary Sources

Copper and iron promoted ZrO2 catalysts were prepared by one-pot synthesis using urea. The studied catalysts were characterized by XRD, N2 physisorption, XPS, temperature-programmed desorption of NH3 (NH3-TPD), and tested by the selective catalytic reduction by ammonia (NH3-SCR) of NO in the absence and presence of water vapor, under the experimental conditions representative of exhaust gases from stationary sources. The influence of SO2 on catalytic performance was also investigated. Among the studied catalysts, the Fe-Zr sample showed the most promising results in NH3-SCR, being active and highly selective to N2. The addition of SO2 markedly improved NO and NH3 conversions during NH3-SCR in the presence of H2O. The improvement in acidic surface properties is believed to be the cause.

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