Editorial

3 pages, 197 KiB

Open AccessEditorial

Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook

by Jean-François Lamonier and Annemie Bogaerts

Catalysts 2022, 12(7), 720; https://doi.org/10.3390/catal12070720 - 30 Jun 2022

Viewed by 966

This Special Issue collects three reviews, eight articles, and two communications related to the design of catalysts for environmental applications, such as the transformation of several pollutants into harmless or valuable products [...] Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

Research

Jump to: Editorial, Review

19 pages, 5850 KiB

Open AccessFeature PaperArticle

Modified Red Mud Catalyst for Volatile Organic Compounds Oxidation

by Gaurav Pande, Subramanian Selvakumar, Carmen Ciotonea, Jean-Marc Giraudon, Jean-François Lamonier and Vidya S. Batra

Catalysts 2021, 11(7), 838; https://doi.org/10.3390/catal11070838 - 10 Jul 2021

Cited by 9 | Viewed by 2209

Abstract

Red mud waste from the aluminium industry was modified by leaching using hydrochloric acid or oxalic acid with additives, followed by precipitation or evaporation. The prepared catalysts were characterized in detail and tested for toluene total oxidation. The samples prepared by precipitation of [...] Read more.

Red mud waste from the aluminium industry was modified by leaching using hydrochloric acid or oxalic acid with additives, followed by precipitation or evaporation. The prepared catalysts were characterized in detail and tested for toluene total oxidation. The samples prepared by precipitation of the leachate by adding a base gave a much better performance in catalytic oxidation than the ones prepared by just evaporating the leachate. These improved performances can be correlated to the enhanced textural and redox properties of the catalysts due to the better dispersion and higher enrichment of Fe oxides at their surface. The best performing catalyst had a light-off temperature of around 310 °C and complete oxidation took place at around 380 °C. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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11 pages, 3112 KiB

Open AccessArticle

Removal of VOCs by Ozone: n-Alkane Oxidation under Mild Conditions

by Alina I. Mytareva, Igor S. Mashkovsky, Sergey A. Kanaev, Dmitriy A. Bokarev, Galina N. Baeva, Alexander V. Kazakov and Alexander Yu. Stakheev

Catalysts 2021, 11(4), 506; https://doi.org/10.3390/catal11040506 - 16 Apr 2021

Cited by 10 | Viewed by 2867

Abstract

Volatile organic compounds (VOCs) have a negative effect on both humans and the environment; therefore, it is crucial to minimize their emission. The conventional solution is the catalytic oxidation of VOCs by air; however, in some cases this method requires relatively high temperatures. [...] Read more.

Volatile organic compounds (VOCs) have a negative effect on both humans and the environment; therefore, it is crucial to minimize their emission. The conventional solution is the catalytic oxidation of VOCs by air; however, in some cases this method requires relatively high temperatures. Thus, the oxidation of short-chain alkanes, which demonstrate the lowest reactivity among VOCs, starts at 250–350 °C. This research deals with the ozone catalytic oxidation (OZCO) of alkanes at temperatures as low as 25–200 °C using an alumina-supported manganese oxide catalyst. Our data demonstrate that oxidation can be significantly accelerated in the presence of a small amount of O₃. In particular, it was found that n-C₄H₁₀ can be readily oxidized by an air/O₃ mixture over the Mn/Al₂O₃ catalyst at temperatures as low as 25 °C. According to the characterization data (SEM-EDX, XRD, H₂-TPR, and XPS) the superior catalytic performance of the Mn/Al₂O₃ catalyst in OZCO stems from a high concentration of Mn₂O₃ species and oxygen vacancies. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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15 pages, 2999 KiB

Open AccessArticle

Adsorption of VOCs Is a Key Step in Plasma-Catalyst Coupling: The Case of Acetone onto TiO₂ vs. CeO₂

by Xianjie Wang, Christelle Barakat, Zixian Jia, Manolis N. Romanias, Frédéric Thévenet and Antoine Rousseau

Catalysts 2021, 11(3), 350; https://doi.org/10.3390/catal11030350 - 09 Mar 2021

Cited by 5 | Viewed by 1981

Abstract

If a number of literature studies point at the positive role of coupling materials with non-thermal plasma, particularly for Volatile Organic Compounds (VOC) removal, most of them focus on the direct plasma-material interaction to understand the coupling. However, a key contribution relies in [...] Read more.

If a number of literature studies point at the positive role of coupling materials with non-thermal plasma, particularly for Volatile Organic Compounds (VOC) removal, most of them focus on the direct plasma-material interaction to understand the coupling. However, a key contribution relies in the VOC–material interaction. Therefore, this study focuses on the adsorption step of targeted VOCs to provide a new insight on plasma–material coupling. The adsorption of acetone, used as probe VOC, is explored on two widespread coupling materials: TiO₂ and CeO₂. First, their behaviors are compared regarding acetone uptake. This process is reactive and creates other organic species than acetone on both surfaces. Second, the metal oxide behaviors are compared regarding ozone uptake. Interestingly, under typical VOC treatment configuration, i.e., with organics on their surfaces, ozone uptake is driven by the adsorbed organics, not directly by the metal oxides anymore. Finally, the ozonation of both materials, preliminary exposed to acetone, is explored through the evolution of the adsorbed organics and the corresponding mineralization, i.e., CO and CO₂ formation. It evidences that the reactive adsorption of VOCs plays a key role in making the surface organics ready for an efficient oxidation and mineralization under post-plasma exposure. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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13 pages, 3052 KiB

Open AccessArticle

Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

by Apolo Nambo, Veerendra Atla, Sivakumar Vasireddy, Vivekanand Kumar, Jacek B. Jasinski, Sreedevi Upadhyayula and Mahendra Sunkara

Catalysts 2021, 11(2), 175; https://doi.org/10.3390/catal11020175 - 28 Jan 2021

Cited by 4 | Viewed by 2351

Abstract

In this paper, nanowire-supported catalysts loaded with nickel are shown to be coke resistant compared to nanoparticle-supported catalysts. Specifically, Ni-loaded titania-based nanowire catalysts were tested with the dry methane reforming process in a laboratory-scale continuous packed-bed atmospheric reactor. The CO₂ conversion rate [...] Read more.

In this paper, nanowire-supported catalysts loaded with nickel are shown to be coke resistant compared to nanoparticle-supported catalysts. Specifically, Ni-loaded titania-based nanowire catalysts were tested with the dry methane reforming process in a laboratory-scale continuous packed-bed atmospheric reactor. The CO₂ conversion rate stayed above 90% for over 30 h on stream under coke-promoting conditions, such as high flow rates, low temperatures, and a high ratio of CH₄ to CO₂. The coke (C_xH_y, x>>y) on the spent catalyst surface for both nanowire- and nanoparticle-supported catalysts was characterized by TGA, temperature-programmed reduction (TPR), and electron microscopy (SEM/TEM/EDS), and it was revealed that the types of carbon species present and their distribution over the morphology-enhanced materials played a major role in the deactivation. The CO₂ conversion activity of Ni supported on titania nanoparticles was reduced from ~80% to less than 72% in 30 h due to the formation of a graphitic coke formation. On the other hand, Ni particles supported on nanowires exhibited cube-octahedral morphologies, with a high density of non- (111) surface sites responsible for the increased activity and reduced graphitic coke deposition, giving a sustained and stable catalytic activity during a long time-on-stream experiment. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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12 pages, 2022 KiB

Open AccessArticle

The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al₂O₃ Catalysts

by Guanghao Cheng, Gurong Shen, Jun Wang, Yunhao Wang, Weibo Zhang, Jianqiang Wang and Meiqing Shen

Catalysts 2021, 11(1), 99; https://doi.org/10.3390/catal11010099 - 13 Jan 2021

Cited by 5 | Viewed by 2030

Abstract

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al₂O₃ catalysts. Comparing to γ-Al₂O₃, θ-Al₂O₃ can [...] Read more.

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al₂O₃ catalysts. Comparing to γ-Al₂O₃, θ-Al₂O₃ can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh³⁺ and Rh⁴⁺, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (E_app) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al₂O₃ and Rh/θ-Al₂O₃. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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21 pages, 6405 KiB

Open AccessFeature PaperArticle

Formaldehyde Total Oxidation on Manganese-Doped Hydroxyapatite: The Effect of Mn Content

by Dayan Chlala, Jean-Marc Giraudon, Madona Labaki and Jean-François Lamonier

Catalysts 2020, 10(12), 1422; https://doi.org/10.3390/catal10121422 - 04 Dec 2020

Cited by 9 | Viewed by 2471

Abstract

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO₂). Methods [...] Read more.

An aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO₂). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N₂ physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO₂ phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO₂ per mole of Mn of 0.042 h⁻¹ at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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10 pages, 2075 KiB

Open AccessCommunication

A Highly Active Au/In₂O₃-ZrO₂ Catalyst for Selective Hydrogenation of CO₂ to Methanol

by Zhe Lu, Kaihang Sun, Jing Wang, Zhitao Zhang and Changjun Liu

Catalysts 2020, 10(11), 1360; https://doi.org/10.3390/catal10111360 - 23 Nov 2020

Cited by 34 | Viewed by 4671

Abstract

A novel gold catalyst supported by In₂O₃-ZrO₂ with a solid solution structure shows a methanol selectivity of 70.1% and a methanol space–time yield (STY) of 0.59 g_MeOH h⁻¹ g_cat⁻¹ for CO₂ hydrogenation to [...] Read more.

A novel gold catalyst supported by In₂O₃-ZrO₂ with a solid solution structure shows a methanol selectivity of 70.1% and a methanol space–time yield (STY) of 0.59 g_MeOH h⁻¹ g_cat⁻¹ for CO₂ hydrogenation to methanol at 573 K and 5 MPa. The ZrO₂ stabilizes the structure of In₂O₃, increases oxygen vacancies, and enhances CO₂ adsorption, causing the improved activity. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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20 pages, 4974 KiB

Open AccessFeature PaperArticle

Abatement of Toluene Using a Sequential Adsorption-Catalytic Oxidation Process: Comparative Study of Potential Adsorbent/Catalytic Materials

by Shilpa Sonar, Jean-Marc Giraudon, Savita Kaliya Perumal Veerapandian, Rim Bitar, Karen Leus, Pascal Van Der Voort, Jean-François Lamonier, Rino Morent, Nathalie De Geyter and Axel Löfberg

Catalysts 2020, 10(7), 761; https://doi.org/10.3390/catal10070761 - 08 Jul 2020

Cited by 7 | Viewed by 3710

Abstract

A novel strategy for toluene abatement was investigated using a sequential adsorption-regeneration process. Commercial Hopcalite (CuMn₂O_x, Purelyst101MD), Ceria nanorods, and UiO-66-SO₃H, a metal–organic framework (MOF), were selected for this study. Toluene was first adsorbed on the material [...] Read more.

A novel strategy for toluene abatement was investigated using a sequential adsorption-regeneration process. Commercial Hopcalite (CuMn₂O_x, Purelyst101MD), Ceria nanorods, and UiO-66-SO₃H, a metal–organic framework (MOF), were selected for this study. Toluene was first adsorbed on the material and a mild thermal activation was performed afterwards in order to oxidize toluene into CO₂ and H₂O. The materials were characterized by XRD, N₂ adsorption-desorption analysis, H₂-TPR and TGA/DSC. The best dynamic toluene adsorption capacity was observed for UiO-66-SO₃H due to its hierarchical porosity and high specific surface area. However, in terms of balance between storage and catalytic properties, Hopcalite stands out from others owing to its superior textural/chemical properties promoting irreversible toluene adsorption and outstanding redox properties, allowing a high activity and CO₂ selectivity in toluene oxidation. The high conversion of toluene into CO₂ which easily desorbs from the surface during heating treatment shows that the sequential adsorption-catalytic thermal oxidation can encompass a classical oxidation process in terms of efficiency, CO₂ yield, and energy-cost saving, providing that the bifunctional material displays a good stability in repetitive working conditions. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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26 pages, 5919 KiB

Open AccessArticle

Catalytic Oxidation of Dimethyl Disulfide over Bimetallic Cu–Au and Pt–Au Catalysts Supported on γ-Al₂O₃, CeO₂, and CeO₂–Al₂O₃

by Tuomas K. Nevanperä, Satu Ojala, Tiina Laitinen, Satu Pitkäaho, Sami Saukko and Riitta L. Keiski

Catalysts 2019, 9(7), 603; https://doi.org/10.3390/catal9070603 - 13 Jul 2019

Cited by 10 | Viewed by 4900

Abstract

Dimethyl disulfide (DMDS, CH₃SSCH₃) is an odorous and harmful air pollutant (volatile organic compound (VOC)) causing nuisance in urban areas. The abatement of DMDS emissions from industrial sources can be realized through catalytic oxidation. However, the development of active [...] Read more.

Dimethyl disulfide (DMDS, CH₃SSCH₃) is an odorous and harmful air pollutant (volatile organic compound (VOC)) causing nuisance in urban areas. The abatement of DMDS emissions from industrial sources can be realized through catalytic oxidation. However, the development of active and selective catalysts having good resistance toward sulfur poisoning is required. This paper describes an investigation related to improving the performance of Pt and Cu catalysts through the addition of Au to monometallic “parent” catalysts via surface redox reactions. The catalysts were characterized using ICP-OES, N₂ physisorption, XRD, XPS, HR-TEM, H₂-TPR, NH₃-TPD, CO₂-TPD, and temperature-programmed ¹⁸O₂ isotopic exchange. The performance of the catalysts was evaluated in DMDS total oxidation. In addition, the stability of a Pt–Au/Ce–Al catalyst was investigated through 40 h time onstream. Cu–Au catalysts were observed to be more active than corresponding Pt–Au catalysts based on DMDS light-off experiments. However, the reaction led to a higher amount of oxygen-containing byproduct formation, and thus the Pt–Au catalysts were more selective. H₂-TPR showed that the higher redox capacity of the Cu-containing catalysts may have been the reason for better DMDS conversion and lower selectivity. The lower amount of reactive oxygen on the surface of Pt-containing catalysts was beneficial for total oxidation. The improved selectivity of ceria-containing catalysts after the Au addition may have resulted from the lowered amount of reactive oxygen as well. The Au addition improved the activity of Al₂O₃-supported Cu and Pt. The Au addition also had a positive effect on SO₂ production in a higher temperature region. A stability test of 40 h showed that the Pt–Au/Ce–Al catalyst, while otherwise promising, was not stable enough, and further development is still needed. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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12 pages, 4543 KiB

Open AccessCommunication

Mild Ammonia Synthesis over Ba-Promoted Ru/MPC Catalysts: Effects of the Ba/Ru Ratio and the Mesoporous Structure

by Masayasu Nishi, Shih-Yuan Chen and Hideyuki Takagi

Catalysts 2019, 9(5), 480; https://doi.org/10.3390/catal9050480 - 23 May 2019

Cited by 19 | Viewed by 4290

Abstract

A series of novel mesoporous carbon-supported, Ba-promoted, Ru catalysts with Ba/Ru ratios of 0.1–1.6 and a Ru loading of 10 wt% (denoted as 0.1–1.6Ba-10Ru/MPC) were prepared via stepwise impregnation of Ru and Ba precursors on the mesoporous carbon materials. The catalysts were applied [...] Read more.

A series of novel mesoporous carbon-supported, Ba-promoted, Ru catalysts with Ba/Ru ratios of 0.1–1.6 and a Ru loading of 10 wt% (denoted as 0.1–1.6Ba-10Ru/MPC) were prepared via stepwise impregnation of Ru and Ba precursors on the mesoporous carbon materials. The catalysts were applied to mild ammonia synthesis and compared to reference materials, including an analog of the prepared catalyst with a Ba/Ru ratio of 1.6 and a Ru loading of 10 wt% (denoted as 1.6Ba-10Ru/AC). Characterization by X-ray diffraction (XRD), nitrogen physisorption, and electronic microscopy revealed that the 0.1–1.6Ba-10Ru/MPC catalysts contained Ru particles (approximately 2 nm) that were well-dispersed on the mesoporous structure and nanostructured Ba(NO₃)₂ species. These species decomposed into amorphous BaO_x species, acting as a promoter on the metallic Ru particles forming catalytically active sites for ammonia synthesis. All the 0.1–1.6Ba-10Ru/MPC catalysts showed a synergistic effect of the active Ba and Ru species, which were stabilized in the mesoporous carbon framework with fast molecular diffusion and could effectively catalyze mild ammonia synthesis (280–450 °C and 0.99 MPa) even under intermittently variable conditions, particularly for those with Ba/Ru ratios of >0.5. In contrast, the 1.6Ba-10Ru/AC analog showed poor activity and stability for ammonia synthesis due to the sintering of Ba and Ru particles on the outer surface of the microporous carbon framework, resulting in low molecular diffusion and weak synergistic effect of the catalytically active sites. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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Review

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78 pages, 14445 KiB

Open AccessFeature PaperReview

Tungsten-Based Catalysts for Environmental Applications

by Fabien Can, Xavier Courtois and Daniel Duprez

Catalysts 2021, 11(6), 703; https://doi.org/10.3390/catal11060703 - 02 Jun 2021

Cited by 49 | Viewed by 12243

Abstract

This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties [...] Read more.

This review aims to give a general overview of the recent use of tungsten-based catalysts for wide environmental applications, with first some useful background information about tungsten oxides. Tungsten oxide materials exhibit suitable behaviors for surface reactions and catalysis such as acidic properties (mainly Brønsted sites), redox and adsorption properties (due to the presence of oxygen vacancies) and a photostimulation response under visible light (2.6–2.8 eV bandgap). Depending on the operating condition of the catalytic process, each of these behaviors is tunable by controlling structure and morphology (e.g., nanoplates, nanosheets, nanorods, nanowires, nanomesh, microflowers, hollow nanospheres) and/or interactions with other compounds such as conductors (carbon), semiconductors or other oxides (e.g., TiO₂) and precious metals. WO_x particles can be also dispersed on high specific surface area supports. Based on these behaviors, WO₃-based catalysts were developed for numerous environmental applications. This review is divided into five main parts: structure of tungsten-based catalysts, acidity of supported tungsten oxide catalysts, WO₃ catalysts for DeNO_x applications, total oxidation of volatile organic compounds in gas phase and gas sensors and pollutant remediation in liquid phase (photocatalysis). Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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35 pages, 8485 KiB

Open AccessFeature PaperReview

Methane to Methanol through Heterogeneous Catalysis and Plasma Catalysis

by Shangkun Li, Rizwan Ahmed, Yanhui Yi and Annemie Bogaerts

Catalysts 2021, 11(5), 590; https://doi.org/10.3390/catal11050590 - 01 May 2021

Cited by 17 | Viewed by 7108

Abstract

Direct oxidation of methane to methanol (DOMTM) is attractive for the increasing industrial demand of feedstock. In this review, the latest advances in heterogeneous catalysis and plasma catalysis for DOMTM are summarized, with the aim to pinpoint the differences between both, and to [...] Read more.

Direct oxidation of methane to methanol (DOMTM) is attractive for the increasing industrial demand of feedstock. In this review, the latest advances in heterogeneous catalysis and plasma catalysis for DOMTM are summarized, with the aim to pinpoint the differences between both, and to provide some insights into their reaction mechanisms, as well as the implications for future development of highly selective catalysts for DOMTM. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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24 pages, 2055 KiB

Open AccessFeature PaperReview

Poisoning of SCR Catalysts by Alkali and Alkaline Earth Metals

by Luciana Lisi and Stefano Cimino

Catalysts 2020, 10(12), 1475; https://doi.org/10.3390/catal10121475 - 16 Dec 2020

Cited by 32 | Viewed by 5713

Abstract

SCR still represents the most widely applied technique to remove nitrogen oxides from flue gas from both stationary and mobile sources. The catalyst lifetime is greatly affected by the presence of poisoning compounds in the exhaust gas that deactivate the catalysts over time [...] Read more.

SCR still represents the most widely applied technique to remove nitrogen oxides from flue gas from both stationary and mobile sources. The catalyst lifetime is greatly affected by the presence of poisoning compounds in the exhaust gas that deactivate the catalysts over time on stream. The progressive and widespread transition towards bio-derived fuels is pushing research efforts to deeply understand and contrast the deactivating effects of some specific poisons among those commonly found in the emissions from combustion processes. In particular, exhaust gases from the combustion of bio-fuels, as well as from municipal waste incineration plants and marine engines, contain large amounts of alkali and alkaline earth metals that can severely affect the acid, redox, and physical properties of the SCR catalysts. This review analyzes recent studies on the effects of alkali and alkaline earth metals on different types of SCR catalysts divided into three main categories (conventional V₂O₅-WO₃/TiO₂, supported non-vanadium catalysts and zeolite-based catalysts) specifically focusing on the impact of poisons on the reaction mechanism while highlighting the different type of deactivation affecting each group of catalysts. An overview of the different regeneration techniques aimed at recovering as much as possible the original performance of the catalysts, highlighting the pros and cons, is given. Finally, current research trends aiming to improve the tolerance towards alkali-poisoning of SCR catalysts are reported. Full article

(This article belongs to the Special Issue Feature Papers to Celebrate “Environmental Catalysis”—Trends & Outlook)

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