The Study of C3H6 Impact on Selective Catalytic Reduction by Ammonia (NH3-SCR) Performance over Cu-SAPO-34 Catalysts

In present work, the catalytic performance of Cu-SAPO-34 catalysts with or without propylene during the NH3-SCR process was conducted, and it was found that the de-NOx activity decreased during low temperature ranges (<350 °C), but obviously improved within the range of high temperatures (>350 °C) in the presence of propylene. The XRD, BET, TG, NH3-TPD, NOx-TPD, in situ DRIFTS and gas-switch experiments were performed to explore the propylene effect on the structure and performance of Cu-SAPO-34 catalysts. The bulk characterization and TG results revealed that neither coke deposition nor the variation of structure and physical properties of catalysts were observed after C3H6 treatment. Generally speaking, at the low temperatures (<350 °C), active Cu2+ species could be occupied by propylene, which inhibited the adsorption and oxidation of NOx species, confining the SCR reaction rate and causing the deactivation of Cu-SAPO-34 catalysts. However, with the increase of reaction temperatures, the occupied Cu2+ sites would be recovered and sequentially participate into the NH3-SCR reaction. Additionally, C3H6-SCR reaction also showed the synergetic contribution to the improvement of NOx conversion at high temperature (>350 °C).

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

Processes ◽

10.3390/pr9111966 ◽

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

Catalysis Science & Technology ◽

10.1039/d1cy02089g ◽

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...

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

Materials ◽

10.3390/ma11081307 ◽

2018 ◽

Vol 11 (8) ◽

pp. 1307 ◽

Cited By ~ 11

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.

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

Catalysts ◽

10.3390/catal11030361 ◽

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.

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A strategy for constructing highly efficient Co3O4-C@SiO2 nanofibers catalytic membrane for NOx-SCR and dust removal

10.22541/au.163256441.11527447/v1 ◽

2021 ◽

Author(s):

Huixian Zhou ◽

Yutang Kang ◽

Hui zhong ◽

Bin Chen ◽

Shuanglu Ma ◽

...

Keyword(s):

High Performance ◽

Gas Permeability ◽

Catalytic Performance ◽

Filtration Efficiency ◽

Co3o4 Nanoparticles ◽

Catalytic Membrane ◽

Nh3 Scr ◽

Nanofiber Membranes ◽

And Performance

The strategy of constructing catalytic membrane has a significant influence on its structure and performance. In this work, Co3O4-Cx@SiO2 nanofiber membranes (NFMs) were fabricated by an in-situ growth–pyrolysis–oxidation strategy. The Co3O4-Cx catalyst derived from ZIF-67 was wrapped around nanofibers, which helps to maintain a stable membrane structure, then suppressing the reduction of gas permeability. Among the Co3O4-Cx catalyst, the carbon skeleton can prevent the agglomeration of Co3O4 nanoparticles, obtaining an ultra-fine Co3O4 nanoparticles with high dispersibility, redox property and surface area. The obtained Co3O4-C300@SiO2 NFM exhibits excellent filtration efficiency and low pressure drop for PM2.5 (99.99% and 55 Pa) and outstanding catalytic performance with T90 of 245 °C for NH3-SCR, which is 40.3% higher than that of Co3O4@SiO2 NFM. This work might provide a universal strategy for the preparation of catalytic membrane with high-performance.

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Effect of Ce-modified Fe/ZSM-5 zeolite for selective catalytic reduction of NOx by ammonia

E3S Web of Conferences ◽

10.1051/e3sconf/202021803032 ◽

2020 ◽

Vol 218 ◽

pp. 03032

Author(s):

Chenxi Li ◽

Fanwei Meng ◽

Qing Ye

Keyword(s):

Selective Catalytic Reduction ◽

Photoelectron Spectroscopy ◽

Catalytic Reduction ◽

Catalytic Performance ◽

Acid Sites ◽

Impregnation Method ◽

Adsorption Ability ◽

In Situ Drifts ◽

X Ray

A series of xCe-Fe/ZSM-5 (x = 0, 0.25, 0.5 wt%) samples were prepared by the impregnation method, and the catalytic activity was evaluated by the selective catalytic reduction of NOx with ammonia (NH3-SCR). The physicochemical properties of prepared samples were characterized by various techniques such as X-ray diffraction (XRD), Brunner-Emmet-Teller (BET) measurement, hydrogen temperatureprogrammed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), ammonia temperatureprogrammed desorption (NH3-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). XRD and BET results demonstrated that Ce and Fe species were uniform dispersed on the surface of the ZSM-5 zeolite and the micropore structure of ZSM-5 was still maintained. H2-TPR analysis indicated that the doping of Ce created more isolated Ce4+ and Fe3+ on the surface of catalysts, and the abundant Ce4+ and Fe3+ could enhance the reduction ability of catalysts. XPS analysis suggested that the doping of Ce could generate more oxygen vacancies, thereby increasing the number of chemisorption oxygen. According to the in-situ DRIFTS and NH3-TPD results, Ce species provided more acidic sites, which is beneficial to the NH3 adsorption ability of ZSM-5 zeolite. Additionally, the abundant chemisorption oxygen, medium and strong Brønsted acid sites, excellent NH3 adsorption ability and outstanding reduction property are beneficial to the NH3-SCR reaction. Among all prepared samples, the 0.25Ce-Fe/ZSM-5 sample possessed the widest reaction temperature window and the best catalytic performance (NO conversion over 98% at 350-450 °C), which was associated with the abundant acid sites and remarkable adsorption ability of NH3, outstanding redox ability and abundant chemisorption oxygen after the doping of Ce.

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Copper-Iron Bimetal Ion-Exchanged SAPO-34 for NH3-SCR of NOx

Catalysts ◽

10.3390/catal10030321 ◽

2020 ◽

Vol 10 (3) ◽

pp. 321 ◽

Cited By ~ 1

Author(s):

Tuan Doan ◽

Phong Dam ◽

Khang Nguyen ◽

Thanh Huyen Vuong ◽

Minh Thang Le ◽

...

Keyword(s):

Active Sites ◽

Catalytic Reduction ◽

Catalytic Performance ◽

Physical Structure ◽

Acid Sites ◽

Tetraethylammonium Hydroxide ◽

Nh3 Scr ◽

Nox Conversion ◽

Temperature Window ◽

Scr Of Nox

SAPO-34 was prepared with a mixture of three templates containing triethylamine, tetraethylammonium hydroxide, and morpholine, which leads to unique properties for support and production cost reduction. Meanwhile, Cu/SAPO-34, Fe/SAPO-34, and Cu-Fe/SAPO-34 were prepared through the ion-exchanged method in aqueous solution and used for selective catalytic reduction (SCR) of NOx with NH3. The physical structure and original crystal of SAPO-34 are maintained in the catalysts. Cu-Fe/SAPO-34 catalysts exhibit high NOx conversion in a broad temperature window, even in the presence of H2O. The physicochemical properties of synthesized samples were further characterized by various methods, including XRD, FE-SEM, EDS, N2 adsorption-desorption isotherms, UV-Vis-DRS spectroscopy, NH3-TPD, H2-TPR, and EPR. The best catalyst, 3Cu-1Fe/SAPO-34 exhibited high NOx conversion (> 90%) in a wide temperature window of 250–600 °C, even in the presence of H2O. In comparison with mono-metallic samples, the 3Cu-1Fe/SAPO-34 catalyst had more isolated Cu2+ ions and additional oligomeric Fe3+ active sites, which mainly contributed to the higher capacity of NH3 and NOx adsorption by the enhancement of the number of acid sites as well as its greater reducibility. Therefore, this synergistic effect between iron and copper in the 3Cu-1Fe/SAPO-34 catalyst prompted higher catalytic performance in more extensive temperature as well as hydrothermal stability after iron incorporation.

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Remarkable Enhancement In The N2- Selectivity of NH3-SCR Over The CeNb3Fe0.3/TiO2 Catalyst In The Presence of Chlorobenzene

10.21203/rs.3.rs-607574/v1 ◽

2021 ◽

Author(s):

Pengchao Zang ◽

Jun Liu ◽

Xiaoqing Liu ◽

Guojie Zhang ◽

Jianjun Chen ◽

...

Keyword(s):

Sol Gel ◽

Catalytic Performance ◽

Acid Sites ◽

Oxidation Activity ◽

In Situ Drifts ◽

Nh3 Scr ◽

Adsorbed Oxygen Species ◽

Initial Stage ◽

Lower Temperature

Abstract The simultaneous removal of NOx and dioxins is the frontier of environmental catalysis, which is still in the initial stage and poses several challenges. In this study, a series of CeNb3Fex/TiO2 (x = 0, 0.3, 0.6, and 1.0) catalysts were prepared by the sol-gel method and examined for the synergistic removal of NOx and chlorobenzene. The CeNb3Fe0.3/TiO2 catalyst exhibits an optimum catalytic performance, with an NOx conversion greater than 95 % at 260-380 °C. It also exhibited an optimal CB oxidation activity, in which CB promoted both the NOx conversion and N2 selectivity below 250 °C. Moreover, the more favourable ratios of Ce4+ to Ce3+, and plentiful surface adsorbed oxygen species are the reasons why CeNb3Fe0.3/TiO2 catalyst has better catalytic activity than other catalysts at lower temperature. Simultaneously, owing to the modulation of Fe to the redox properties of Ce and Nb, the large number of oxygen vacancies and acid sites, the CeNb3Fe0.3/TiO2 catalyst is is beneficial to NOx reduction and CB oxidation. Further, the results of in situ DRIFTS study reveal the NH3-SCR reactions over CeNb3Fex/TiO2 catalysts are mainly controlled by the L-H mechanism (< 200 °C) and E-R mechanism (> 200 °C), respectively.

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

Catalysts ◽

10.3390/catal11050618 ◽

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.

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

Catalysts ◽

10.3390/catal11010055 ◽

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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