Transition metal ions regulate the catalytic performance of Ti0.8M0.2Ce0.2O2+x for the NH3-SCR of NO: the acidic mechanism

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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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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Synergistic effect and mechanism of FeO and CeO co-doping on the superior catalytic performance and SO2 tolerance of Mn-Fe-Ce/ACN catalyst in low-temperature NH3-SCR of NO

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2021.106360 ◽

2021 ◽

Vol 9 (6) ◽

pp. 106360

Author(s):

Lijun Jiang ◽

Ya Liang ◽

Weizao Liu ◽

Hongli Wu ◽

Tahani Aldahri ◽

...

Keyword(s):

Low Temperature ◽

Synergistic Effect ◽

Catalytic Performance ◽

Co Doping ◽

Nh3 Scr ◽

Scr Of No ◽

So2 Tolerance

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

Materials ◽

10.3390/ma13020475 ◽

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.

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Synergistic effect of VOx and MnOx surface species for improved performance of V2O5/Ce0.5Ti0.5−xMnxO2−δ catalysts in low-temperature NH3-SCR of NO

Catalysis Science & Technology ◽

10.1039/c8cy02193g ◽

2018 ◽

Vol 8 (24) ◽

pp. 6360-6374 ◽

Cited By ~ 7

Author(s):

Thanh Huyen Vuong ◽

Stephan Bartling ◽

Ursula Bentrup ◽

Henrik Lund ◽

Jabor Rabeah ◽

...

Keyword(s):

Low Temperature ◽

Synergistic Effect ◽

Catalytic Performance ◽

Surface Species ◽

Nh3 Scr ◽

Redox Couples ◽

Scr Of No ◽

Improved Performance

Inserting adjacent Mn3+/Mn2+ and VO3+/VO2+ redox couples in Ce1−xTixO2 improves catalytic performance.

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Effect of the calcination temperature of cerium–zirconium mixed oxides on the structure and catalytic performance of WO3/CeZrO2 monolithic catalyst for selective catalytic reduction of NOx with NH3

RSC Advances ◽

10.1039/c7ra03054a ◽

2017 ◽

Vol 7 (39) ◽

pp. 24177-24187 ◽

Cited By ~ 15

Author(s):

Haidi Xu ◽

Mengmeng Sun ◽

Shuang Liu ◽

Yuanshan Li ◽

Jianli Wang ◽

...

Keyword(s):

Low Temperature ◽

Selective Catalytic Reduction ◽

Lewis Acid ◽

Mixed Oxides ◽

Catalytic Reduction ◽

Catalytic Performance ◽

Acid Sites ◽

Lewis Acid Sites ◽

Reduction Of Nox ◽

Calcined Temperature

The calcined temperature of the carrier obviously affected SCR activity of catalysts, WO3/Ce0.68Zr0.32O2-500 showed the best low-temperature NH3-SCR activity due to its more Lewis acid sites and stronger redox property.

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The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

Catalysis Letters ◽

10.1007/s10562-018-2333-4 ◽

2018 ◽

Vol 148 (4) ◽

pp. 1228-1235 ◽

Cited By ~ 10

Author(s):

Rui Wu ◽

Ningqiang Zhang ◽

Xiaojun Liu ◽

Lingcong Li ◽

Liyun Song ◽

...

Keyword(s):

Low Temperature ◽

Catalytic Reduction ◽

Physicochemical Characteristics ◽

Acid Sites ◽

Keggin Structure ◽

Lewis Acid Sites ◽

Nh3 Scr ◽

Strong Acidity ◽

Ft Ir ◽

Brønsted And Lewis Acid

Abstract Heteropolyacids and their salts have been effectively used in selective catalytic reduction because of the Keggin structure and extraordinarily strong acidity. Catalysts with and without the Keggin structure were synthesized to further investigate the effects of heteropolyoxometallate on low temperature NH3–SCR. XRD, BET, Raman, H2–TPR, NH3–TPD, FT-IR, and SO2–TPD techniques were used to characterize the physicochemical characteristics of the catalysts. Results indicate that catalysts with the Keggin structure had more surface Brönsted and Lewis acid sites, and these catalysts had significantly improved performances in the SCR reaction and in SO2 poisoning resistance. Graphical Abstract

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The Role of Nitrate on the Sol-Gel Spread Self-Combustion Process and Its Effect on the NH3-SCR Activity of Magnetic Iron-Based Catalyst

Catalysts ◽

10.3390/catal10030314 ◽

2020 ◽

Vol 10 (3) ◽

pp. 314

Author(s):

Xing Ning ◽

Zhi-bo Xiong ◽

Bin Yang ◽

Wei Lu ◽

Shui-mu Wu

Keyword(s):

Nitric Acid ◽

Citric Acid ◽

Sol Gel ◽

Nox Reduction ◽

Combustion Process ◽

Catalytic Performance ◽

Metal Nitrate ◽

Acid Sites ◽

Complexing Agent ◽

Nh3 Scr

Sol-gel spread self-combustion is the burning of the complexing agent in dried gel and the oxidant. Meanwhile, high temperature takes place during the combustion process, which is harmful to the pore structure of the catalyst. The nitrate from metal nitrate precursors as an oxidant could participate in the spread of the self-combustion process. Therefore, the influence of nitrate from metal nitrate on the spread self-combustion of an iron–cerium–tungsten citric acid gel and its catalytic performance of NOx reduction were investigated by removing nitrate via the dissolution of washing co-precipitation with citric acid and re-introducing nitric acid into the former solution. It was found that the removal of nitrate contributes to enhancing the NH3–SCR activity of the magnetic mixed oxide catalyst. The NOx reduction efficiency was close to 100% for Fe85Ce10W5–CP–CA at 250 °C while the highest was only 80% for the others. The results of thermal analysis demonstrate that the spread self-combustion process of citric acid dried gel is enhanced by re-introducing nitric acid into the citric acid dissolved solution when compared with the removal of nitrate. In addition, the removal of nitrate helps in the formation of γ-Fe2O3 crystallite in the catalyst, refining the particle size of the catalyst and increasing its pore volume. The removal of nitrate also contributes to the formation of Lewis acid sites and Brønsted acid sites on the surface of the catalyst compared with the re-introduction of nitric acid. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) demonstrates that both Eley–Rideal (E–R) and Langmuir–Hinshelwood (L–H) mechanisms exist over Fe85Ce10W5–CP–CA at 250 °C with E–R as its main mechanism.

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