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Showing papers on "Selective catalytic reduction published in 2021"


Journal ArticleDOI
TL;DR: CeTiOx with nanotube structure was used for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx as mentioned in this paper, in which more than 98 % NO conversion can be achieved in the range of 180−390°C with 100 % N2 selectivity.
Abstract: Cerium and titanium oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx. However, the poor SO2 or H2O tolerance and stability limit their practical applications. Herein, CeTiOx with nanotube structure (CeTiOx-T) was prepared by hydrothermal method and used for NH3-SCR reaction. CeTiOx-T shows the excellent catalytic activity, SO2 and H2O tolerance and stability, in which more than 98 % NO conversion can be achieved in the range of 180−390 °C with 100 % N2 selectivity. The characterizations verify that CeTiOx-T exhibits amorphous structure due to the strong interaction between Ce and Ti to form short-range ordered Ce-O-Ti species. As results, CeTiOx-T displays the larger BET surface area, more surface Bronsted acid amounts and chemisorbed oxygen, leading to its higher NH3-SCR performance. In situ DRIFTS results suggest the SCR reaction mainly follow L-H and E-R mechanisms at low and high temperature for over CeTiOx-T, respectively.

149 citations


Journal ArticleDOI
15 Apr 2021-Fuel
TL;DR: In this paper, the effects of Fe2O3 based diesel oxidation catalyst and selective catalytic reduction catalyst on the engine characteristic of diesel engine fueled with biodiesels and diesel in the experimental study were investigated.

116 citations


Journal ArticleDOI
TL;DR: In this paper, a review summarizes major advances in Cu-SSZ-13 applied to the NH3-SCR reaction, including the state of copper species, standard and fast SCR reaction mechanism, hydrothermal deactivation mechanism, poisoning resistance and synthetic methodology.
Abstract: Zeolites, as efficient and stable catalysts, are widely used in the environmental catalysis field. Typically, Cu-SSZ-13 with small-pore structure shows excellent catalytic activity for selective catalytic reduction of NO x with ammonia (NH3-SCR) as well as high hydrothermal stability. This review summarizes major advances in Cu-SSZ-13 applied to the NH3-SCR reaction, including the state of copper species, standard and fast SCR reaction mechanism, hydrothermal deactivation mechanism, poisoning resistance and synthetic methodology. The review gives a valuable summary of new insights into the matching between SCR catalyst design principles and the characteristics of Cu2+-exchanged zeolitic catalysts, highlighting the significant opportunity presented by zeolite-based catalysts. Principles for designing zeolites with excellent NH3-SCR performance and hydrothermal stability are proposed. On the basis of these principles, more hydrothermally stable Cu-AEI and Cu-LTA zeolites are elaborated as well as other alternative zeolites applied to NH3-SCR. Finally, we call attention to the challenges facing Cu-based small-pore zeolites that still need to be addressed.

98 citations


Journal ArticleDOI
TL;DR: In this paper, two-dimensional metal-organic frameworks (MOFs), called copper-terephthalate, and CuO@C were investigated as catalysts for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent.
Abstract: Two-dimensional (2D) metal-organic frameworks (MOFs), called copper-terephthalate, and CuO@C were investigated as catalysts for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent. Copper-terephthalate frameworks were synthesized using the solvothermal method. While, CuO@C was synthesized using carbonization of copper-terephthalate at temperature of 400 °C, 500 °C, 600 °C, and 700 °C. Both materials displayed a complete reduction of 4-NP to 4-aminophenol (4-AP) in a short time (3 min) with a rate of 15.1× 10−3 min−1, and 6.0× 10−3 min-1 at room temperature for CuBDC, and CuO@C, respectively. The materials could be used for more than five times without obvious fading in their catalytic activities. The mechanism of the reduction was also discussed. The materials are promising for catalytic applications such as organic synthesis via the reduction of the nitro groups.

98 citations


Journal ArticleDOI
TL;DR: In this paper, the NH3-SCR (selective catalytic reduction of NO with NH3) catalysts that can work stably at low temperatures are presented. But the authors focus on the treatment of flue gas from non-electric industries.
Abstract: The urgent need for the treatment of flue gas from non-electric industries has stimulated great interest in developing NH3-SCR (selective catalytic reduction of NO with NH3) catalysts that can work stably at low temperatures (

87 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that the 3.5-mol% W-substituted vanadium oxide exhibits higher NOx removal ability than the TiO2 supported vanadia catalyst in the presence of water.
Abstract: NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100–150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5–20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h−1 gcat−1). Lewis acid sites of W-substituted vanadium oxide are converted to Bronsted acid sites under a wet condition while the distribution of Bronsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Bronsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Bronsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor. NH3 selective catalytic reduction is an important technique for NOx removal but water vapor critically inhibits the reaction at a low temperature. Here the authors show bulk W-substituted VOx exhibits higher NOx removal ability than the TiO2 supported vanadia catalyst in the presence of water.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the authors focus on the theory and practice of designing metal oxide catalysts for selective catalytic reduction with ammonia (NH3-SCR) in coal-fired flue gas and diesel vehicle exhaust on a large scale.

61 citations


Journal ArticleDOI
TL;DR: The efficiency, reaction conditions, effect factors, and reaction mechanism of NO oxidation from the aspects of liquid- phase oxidation, gas-phase oxidation, plasma technology, and catalytic oxidation are summarized.
Abstract: Due to the increasingly strict emission standards of NOx on various industries, many traditional flue gas treatment methods have been gradually improved. Except for selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) methods to remove NOx from flue gas, theoxidation method is paying more attention to NOx removal now because of the potential to simultaneously remove multiple pollutants from flue gas. This paper summarizes the efficiency, reaction conditions, effect factors, and reaction mechanism of NO oxidation from the aspects of liquid-phase oxidation, gas-phase oxidation, plasma technology, and catalytic oxidation. The effects of free radicals and active components of catalysts on NO oxidation and the combination of various oxidation methods are discussed in detail. The advantages and disadvantages of different oxidation methods are summarized, and the suggestions for future research on NO oxidation are put forward at the end. The review on the NO removal by oxidation methods can provide new ideas for future studies on the NO removal from flue gas.

56 citations


Journal ArticleDOI
TL;DR: The selective catalytic reduction (SCR) of NOx with ammonia is an effective method to remove NOx from stationary and mobile sources as discussed by the authors, and has been studied extensively as low-temper...
Abstract: The selective catalytic reduction (SCR) of NOx with ammonia is an effective method to remove NOx from stationary and mobile sources. Cerium oxides (CeOx) have been studied extensively as low-temper...

55 citations


Journal ArticleDOI
TL;DR: In this paper, a hybrid catalytic system comprised of metal oxide and Cu or Fe exchanged zeolite components represents a potential advancement of state-of-the-art for selective catalytic reduction of NOx by ammonia, including an elegant solution to the current challenge of improving the low-temperature efficiency of SCR catalysts.
Abstract: A hybrid catalytic system comprised of metal oxide and Cu or Fe exchanged zeolite components represents a potential advancement of state-of-the-art for selective catalytic reduction (SCR) of NOx by ammonia, including an elegant solution to the current challenge of improving the low-temperature efficiency of SCR catalysts. The idea is to enable in-situ NO oxidation over metal oxide component and concomitant fast SCR over zeolite component in the so-called “bifunctional mechanism”. This review is presented in the wake of growing interest in this innovative catalytic system. We begin this review by presenting key parameters that contribute to the synergy between metal oxide and zeolite components. Then, we discuss the materials selection for both components and their possible interactions in the system, followed by a summary of recent NH3-SCR investigations over multiple metal oxide–zeolite pairs and additional discussion on pairing techniques potentially explorable in upcoming studies. We end the review by providing the perspectives on future challenges in the development of this catalytic system.

54 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied the potential of ZnCu-MOF-74 for catalytic CO2 reduction in a nanosized channel decorated with readily accessible and homogeneously distributed Zn and Cu metal sites.
Abstract: Selective catalytic reduction of CO2 to methanol has tremendous importance in the chemical industry. It mitigates two critical issues in the modern society, the overwhelming climate change and the dependence on fossil fuels. The most used catalysts are currently based on mixed copper and zinc phases, where the high surface of active copper species is a critical factor for the catalyst performance. Motivated by the recent breakthrough in the controllable synthesis of bimetallic MOF-74 materials by ball milling, we targeted to study the potential of ZnCu-MOF-74 for catalytic CO2 reduction. Here, we tested whether the nanosized channels decorated with readily accessible and homogeneously distributed Zn and Cu metal sites would be advantageous for the catalytic CO2 reduction. Unlike the inactive monometallic Cu-MOF-74, ZnCu-MOF-74 shows moderate catalytic activity and selectivity for the methanol synthesis. Interestingly, the postsynthetic mechanochemical treatment of desolvated ZnCu-MOF-74 resulted in amorphization and a significant increase in both the activity and selectivity of the catalyst despite the destruction of the well-ordered and porous MOF-74 architecture. The results emphasize the importance of defects for the MOF catalytic activity and the potential of amorphous MOFs to be considered as heterogeneous catalysts. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and 13C magic angle-spinning nuclear magnetic resonance (MAS NMR) were applied to establish quantitative structure-reactivity relationships. The apparent activation energy of rate reaction kinetics has indicated different pathway mechanisms, primarily through reverse water-gas shift (RWGS). Prolonged time on stream productivity, stability and deactivation were assessed, analysing the robustness or degradation of metal-organic framework nanomaterials. Scalable MOF production processes are making the latter more appealing within emerging industrial decarbonisation, in particular for carbon capture and utilisation (CCU) or hydrogen carrier storage. Acknowledging scale, the costs of fabrication are paramount.

Journal ArticleDOI
TL;DR: In this paper, three zeolites with different structures (mazzit, faujasite and MFI) were prepared by hydrothermal way, and then were used to stabilize the Fe and Ni nanoparticles using ion exchange followed by treatment with a solution of NaBH4 as reducing agent.

Journal ArticleDOI
TL;DR: In this article, a dielectric barrier discharge (DBD) plasma-enhanced NH3-selective catalytic reduction (NH3-SCR) of NOx over a Cu-Mn/SAPO-34 catalyst at low temperatures was presented.
Abstract: In this work, a dielectric barrier discharge (DBD) plasma-enhanced NH3-selective catalytic reduction (NH3-SCR) of NOx over a Cu-Mn/SAPO-34 catalyst at low temperatures (

Journal ArticleDOI
TL;DR: In this article, a series of Mn/CeSiOx catalysts were synthesized to investigate the Ce/Si ratios and morphology effect of the Mn/SiOx support for selective catalytic reduction (SCR) of NO with NH3 at low temperature.

Journal ArticleDOI
TL;DR: In this article, a series of cobalt-doped MnFeOx ternary mixed oxides catalysts with a hierarchically ordered structure (Hierc-MnFe1-δCoδOx, δ ǫ = 0.2, 0.4 and 0.6) were developed and applied for NH3-SCR of NOx at low temperature.

Journal ArticleDOI
TL;DR: It was established that the developed methodology allows for the production of NPs with different morphologies and compositions in a safe and simple manner and a detailed reduction pathway mechanism for the catalytic reduction of 4-nitrophenol and nitrobenzene has been proposed.

Journal ArticleDOI
Xueke Shi1, Jiaxiu Guo1, Ting Shen1, Aidong Fan1, Shandong Yuan1, Jianjun Li1 
TL;DR: Cerium modified La-Mn oxides for NH3-SCR at low temperature is prepared by one-step synthesis method and characterized in this paper, where the results showed that the perovskite La-mns oxides at A-bit doped by Ce is more favorable for NOx removal than B-bit doping and achieves about 80% conversion of NOx at 120°C and about 100% in the range temperature of 180-220°C as well as good SO2 and/or H2O resistance.

Journal ArticleDOI
TL;DR: In this paper, a low vanadia loading was synthesized, in which crystalline V2O5 was deposited on a TiO2 support that had been pretreated at a high temperature.
Abstract: Vanadia-based catalysts have been widely used for catalyzing various reactions, including their long-standing application in the deNOx process. It has been commonly considered that various vanadium species dispersed on supports with a large surface area act as the catalytically active sites. However, the role of crystalline V2O5 in selective catalytic reduction of NOx with NH3 (NH3-SCR) remains unclear. In this study, a catalyst with low vanadia loading was synthesized, in which crystalline V2O5 was deposited on a TiO2 support that had been pretreated at a high temperature. Surprisingly, the catalyst, which had a large amount of crystalline V2O5, showed excellent low-temperature NH3-SCR activity. For the first time, crystalline V2O5 on low-vanadium-loading catalysts was found to be transformed to polymeric vanadyl species by the adsorption of NH3. The generated active polymeric vanadyl species played a crucial role in NH3-SCR, leading to remarkably enhanced catalytic performance at low temperatures. This new finding provides a fundamental understanding of the metal oxide-catalyzed chemical reaction and has important implications for the development and commercial applications of NH3-SCR catalysts.

Journal ArticleDOI
TL;DR: In this article, a new thulium modified Mn/TiO2 catalyst was proposed to remove NO at low temperature, where the TiO2 with relatively high specific surface area (184.3 m2/g) is used as carrier to support the active component MnOx, and Tm is utilized as promoter to modify the MnOx.

Journal ArticleDOI
TL;DR: This work would lead to a new strategic design of Ti3+ self-doped catalysts with fine structure and that can efficiently improve low-temperature SCR performance.

Journal ArticleDOI
TL;DR: The results manifest that CuO modification effectively enhances low-temperature catalytic activity and anti-K poisoning ability of CeTiOx catalyst by protecting the reduction ability and the surface acidity as well as weakening the adsorption strength of NOx.

Journal ArticleDOI
TL;DR: A promotion effect of support on the alkali and sulfur resistance is unraveled, which could promote the adsorption of SO2 on the TiO2 and reduce the toxicity of the active component (MnO2).

Journal ArticleDOI
TL;DR: In this article, a series of yolk-shell structured catalysts with core-shell structure were obtained via simple hydrothermal treatment, and the redox capacity can be effectively improved through co-existence of Ce and Mn.

Journal ArticleDOI
01 Jan 2021
TL;DR: In this paper, an approach that combines X-ray absorption spectroscopy with microtomography is introduced and showcased for the selective catalytic reduction of NOx with ammonia over a Cu-SSZ-13 washcoated monolith catalyst.
Abstract: Nitrogen oxide (NOx) emissions are a major source of pollution, demanding ever-improving performance from catalytic after-treatment systems. However, catalyst development is often hindered by limited understanding of the catalyst at work, exacerbated by widespread use of model catalysts rather than technical catalysts, and by global rather than spatially resolved characterization tools. Here we combine operando X-ray absorption spectroscopy with microtomography to perform three-dimensional chemical imaging of the chemical state of copper species in a Cu-SSZ-13 washcoated monolith catalyst during NOx reduction. Gradients in copper oxidation state and coordination environment, resulting from an interplay of NOx reduction with adsorption–desorption of NH3 and mass transport phenomena, were revealed at micrometre spatial resolution while simultaneously determining catalytic performance. Crucially, direct three-dimensional visualization of complex reactions on non-model catalysts is feasible only by the use of operando X-ray spectrotomography, which can improve our understanding of structure–activity relationships, including the observation of mass and heat transport effects. Obtaining spatially resolved spectroscopic information for catalysts under working conditions remains challenging. Here, an approach that combines X-ray absorption spectroscopy with microtomography is introduced and showcased for the selective catalytic reduction of NOx with ammonia over a Cu-SSZ-13 washcoated monolith catalyst.

Journal ArticleDOI
TL;DR: The transient reaction demonstrated that the doped W species on Mn3CeW0.3Ox could inhibit the N2O produced by the Langmuir-Hinshelwood mechanism, which was suggested to inhibit the charge imbalance and reducibility of tungsten.

Journal ArticleDOI
TL;DR: In this paper, the low-temperature catalytic performance of Cu-ion-exchanged SSZ-52 catalysts for the selective catalytic reduction of NOx by NH3 (NH3-SCR) is investigated.
Abstract: The low-temperature catalytic performance of Cu-ion-exchanged SSZ-52 catalysts (with different amounts of ion-exchanged Cu) for the selective catalytic reduction of NOx by NH3 (NH3-SCR) is investigated. The Cu-ion-exchanged SSZ-52 catalysts are prepared by a new method by using fumed silica as the silicon source. Among the synthesized Cux-SSZ-52 catalyst series, Cu2.4-SSZ-52 exhibits the highest NH3-SCR activity. In addition, the de-NOx performance of Cu2.4-SSZ-52 is superior to that of Cu2.4-SSZ-13. Moreover, the catalytic performance of Cu2.4-SSZ-52 reduces only slightly after hydrothermal aging at 750 °C. The microporous structure, redox ability, acidity properties as well as the location and nature of the Cu species and the reactant adsorption process of the support and Cux-SSZ-52 catalysts are investigated in detail. Overall, the findings show that the unique structure and cages of SSZ-52 are responsible for its excellent catalytic performance.

Journal ArticleDOI
TL;DR: In this article, the authors review the ongoing development of selective catalytic reduction (SCR) systems with focus on the efficient evaporation and decomposition of the injected spray for a homogeneous ammonia distribution in front of the SCR catalyst.

Journal ArticleDOI
TL;DR: In this paper, two types of surface reaction properties have been shown to be involved in the W-Ce (VWCeTi) and Sb-ce (VSbCeTi), and they were found to have a positive effect on catalytic ABS/AS decomposition.
Abstract: The challenge for selective catalytic reduction (SCR) of NO with NH3 is to develop a proven catalyst with satisfactory performance and sulfur resistance at low temperatures. Two types of surface reaction properties have been shown to be involved in the W-Ce (VWCeTi) and Sb-Ce (VSbCeTi) systems. That is, active species have improved catalytic activity and the decomposition of ammonium bisulfate (ABS)/ammonium sulfate (AS) by the functionalization as well as the surface reactive oxygen (surface lattice oxygen/highly dispersed oxygen). The Sb-Ce system resulted in greater catalyst surface functionalization, generated the bulk-like cerium sulfate species and improved the active site by the sulfate effect. This system promoted the release of more reactive oxygen and surface lattice oxygen by enhancing the interaction between Sb and Ce to form more active species, which was found to have a positive effect on catalytic ABS/AS decomposition.

Journal ArticleDOI
TL;DR: In this paper, the effect of K deposition on the catalytic activi cation of NH3-SCR catalysts has been investigated and shown to be a complex yet unresolved issue restricting catalytic activity.
Abstract: Alkali metal poisoning has been a complex yet unresolved issue restricting the catalytic activity of NH3–SCR catalysts in industry to date. Herein, the effect of K deposition on the catalytic activ...

Journal ArticleDOI
Hongbing Dan1, Yan Song1, Yan Xu, Yue Gao1, Wenjia Kong1, Ying Huang, Qinyan Yue1, Baoyu Gao1 
TL;DR: In this article, a novel and highly reactive Cu nanoparticles (CuNPs) embedded straw-graphene composite (Cu-SG) was synthesized via a facile and green one-pot hydrothermal route and then used for p-nitrophenol (PNP) reduction in the presence of NaBH4 from an aqueous medium.