Catalysts for Selective Catalytic Reduction (SCR) and Related Reactions

A special issue of Catalysts (ISSN 2073-4344). This special issue belongs to the section "Industrial Catalysis".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 12854

Special Issue Editors

Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu 610064, China
Interests: heterogeneous catalysis; functional materials
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Guest Editor
School of Resources and Environment, Nanchang University, 999 Xuefu Road, Nanchang 330031, China
Interests: environmental functional materials; NOx and VOC removal

Special Issue Information

Dear Colleagues,

This is a Special Issue on “Catalysts for Selective Catalytic Reduction (SCR) and Related Reactions”, including selective catalytic reduction of NOx, passive NOx adsorption (PNA), NO oxidation, and selective catalytic oxidation of ammonia (NH3-SCO), the catalytic elimination of volatile organic compounds (VOCs), and the related reactions. This call includes both experimental results and computational calculations. We are interested in but not limited to the study of SCR activity and stability of catalysts via optimizing zeolites and mixed oxide-based catalysts. Particular focus is on the discovery of novel PNA and AdSCR catalysts to address issues related to NOx emission from diesel engines during the cold-start period. From a theoretical point of view, we highly encourage submissions that involve quantum theory in atoms and molecules to illustrate the microstructure of active sites over catalysts for SCR and related reactions.

Dr. Haidi Xu
Prof. Dr. Honggen Peng
Guest Editors

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Keywords

  • nitrogen oxides
  • SCR
  • PNA
  • AdSCR
  • NH3-SCO
  • zeolites
  • mixed oxides
  • VOCs

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Published Papers (8 papers)

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Research

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17 pages, 7953 KiB  
Article
Hard Template-Assisted Trans-Crystallization Synthesis of Hierarchically Porous Cu-SSZ-13 with Enhanced NH3-SCR Performance
by Fuzhen Yang, Ying Xin, Xiaoli Zhu, Ahui Tang, Long Yu, Dongxu Han, Junxiu Jia, Yaning Lu and Zhaoliang Zhang
Catalysts 2023, 13(8), 1217; https://doi.org/10.3390/catal13081217 - 16 Aug 2023
Cited by 3 | Viewed by 1733
Abstract
Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NOx with ammonia (NH3-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces [...] Read more.
Small porous Cu-SSZ-13 catalysts have recently been commercialized for the selective catalytic reduction of NOx with ammonia (NH3-SCR) on diesel vehicles. Unfortunately, the conventional Cu-SSZ-13 catalyst still confronts the challenge of diffusion limitations, which represent a major obstacle that reduces the catalyst’s SCR performance. Herein, a hierarchically porous SSZ-13 zeolite was synthesized via a trans-crystallization method assisted by the use of carbon black as a hard template in a short synthetic period, and the corresponding Cu-SSZ-13 catalysts with mesopores exhibited improved low-temperature activity and hydrothermal stability when compared with their microporous counterpart. A series of characterizations revealed that the mesopores are conducive to an increase in Cu loading while helping to stabilize the CHA structure and maintain the Cu species in their ionic form. More importantly, intra-particle diffusion limitations are reduced via the introduction of the mesopores owing to the shortened diffusion path inside the SSZ-13 zeolite, thus not only enhancing the active sites’ accessibility but also promoting the diffusion of the reactants and products. This work contributes to the design and synthesis of a high-performance Cu-SSZ-13 zeolite SCR catalyst for the removal of NOx emitted from diesel vehicles. Full article
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13 pages, 7252 KiB  
Article
Revealing the Roles of Cu/Ba on Ce-Based Passive NOx Adsorbers
by Mingming Pei, Yuxin Fan, Haidi Xu, Zhihua Lian, Wei Tan, Jianli Wang and Yaoqiang Chen
Catalysts 2023, 13(8), 1180; https://doi.org/10.3390/catal13081180 - 2 Aug 2023
Cited by 3 | Viewed by 1213
Abstract
At present, passive NOx adsorbers (PNAs) represent one of the most effective technologies for addressing NOx emissions from diesel engines during cold-start periods. Conventional PNAs, which primarily consist of noble metals (such as Pt, Pd, and Ag) loaded on metal oxides [...] Read more.
At present, passive NOx adsorbers (PNAs) represent one of the most effective technologies for addressing NOx emissions from diesel engines during cold-start periods. Conventional PNAs, which primarily consist of noble metals (such as Pt, Pd, and Ag) loaded on metal oxides or zeolites, share the common drawback of high production costs. Consequently, developing low-cost PNAs with outstanding NOx storage performance remains a significant challenge. In this study, a series of CuxBa5Ce adsorbents were synthesized using the impregnation method, and a monolithic adsorbent was employed to evaluate NOx storage and release performance. Techniques such as XRD, UV-Vis DRs, H2-TPR, XPS, and in situ DRIFTs confirmed the crucial roles of Cu and Ba in NOx storage and release. Specifically, the incorporation of Cu into CeO2 enhanced NOx storage performance. Moreover, in the Cu3Ba5Ce adsorbent, the addition of Ba not only introduced new storage sites and altered the stability of NOx adsorption species but also helped prevent the aggregation of CuO, thereby prolonging the complete NOx storage duration and satisfying desorption temperature requirements. The Cu3Ba5Ce adsorbent exhibited the most favorable NOx storage performance, including a complete NOx storage time of 135 s and a NOx storage efficiency exceeding 50% at 80 °C over a 10 min period. While PNAs loaded with noble metals, such as Pd/CeO2 and Pt/CeO2, exhibited NOx storage efficiencies below 50% after adsorbing for 5 min at 80 °C. Therefore, this research offered a crucial strategy for developing non-noble-metal-loaded, Ce-based PNAs. Full article
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12 pages, 5175 KiB  
Article
The Catalyst of Ruthenium Nanoparticles Decorated Silicalite-1 Zeolite for Boosting Catalytic Soot Oxidation
by Yuanfeng Li, Hao Guo, Jing Xiong, Yaxiao Ma, Xuanzhen Li, Peng Zhang, Sicheng Zhang and Yuechang Wei
Catalysts 2023, 13(8), 1167; https://doi.org/10.3390/catal13081167 - 30 Jul 2023
Cited by 5 | Viewed by 1380
Abstract
Herein, the Ruthenium nanoparticles (NPs) with the size of 12 nm were decorated on the hexagonal prism silicalite-1 (Ru/S-1) by the gas bubbling-assisted membrane reduction method (GBMR). The adsorption/activation properties are improved for reactant molecules due to the formation of an interfacial structure [...] Read more.
Herein, the Ruthenium nanoparticles (NPs) with the size of 12 nm were decorated on the hexagonal prism silicalite-1 (Ru/S-1) by the gas bubbling-assisted membrane reduction method (GBMR). The adsorption/activation properties are improved for reactant molecules due to the formation of an interfacial structure that enhances the interaction between the Ru NPs and S-1. The Ru/S-1 catalyst displays the highest catalytic activity (T50 = 356 °C) and CO2 selectivity (SCO2m = 99.9%). Moreover, no obvious deactivation was observed over the Ru/S-1 catalyst even after five cycles, and the values of T50 and SCO2m after cycling five times are similar to the fresh catalyst. The Ru/S-1 catalyst with excellent catalytic performance can be compared with a series of noble metal catalysts for soot oxidation. The catalytic mechanism of the Ru/S-1 catalyst was revealed by in situ characterization for soot oxidation. The interfacial effect between Ru NPs and S-1 plays an important role in the conversion of NO to NO2 during soot oxidation. Preparation of Ru/S-1 catalyst provides a hopeful way to obtain considerably low-cost and highly stable auto-exhaust treatment catalysts. Full article
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13 pages, 7008 KiB  
Article
A Comparative Study on the Effect of Surface and Bulk Sulfates on the High-Temperature Selective Catalytic Reduction of NO with NH3 over CeO2
by Chong Tan, Zhiwen Gu, Songil Sin, Jiawei Ji, Yan Wang, Baiyun Zhu, Lijun Cheng, Chunkai Huang, Lulu Li, Hongliang Zhang and Changjin Tang
Catalysts 2023, 13(8), 1162; https://doi.org/10.3390/catal13081162 - 28 Jul 2023
Cited by 1 | Viewed by 1022
Abstract
Herein, two CeO2 samples dominantly decorated with surface and bulk sulfates were constructed and their distinct effects on high-temperature NH3-SCR were investigated by strictly controlling the sulfate content at a comparable level. The obtainment of surface and bulk sulfates was [...] Read more.
Herein, two CeO2 samples dominantly decorated with surface and bulk sulfates were constructed and their distinct effects on high-temperature NH3-SCR were investigated by strictly controlling the sulfate content at a comparable level. The obtainment of surface and bulk sulfates was revealed using a designed leaching experiment, and further evidenced by the characterization results from XPS and H2-TPR. In comparison with CeO2 modified with bulk sulfates (B-CeS), sufficient acid sites with strong intensity were generated on CeO2 modified with surface sulfates (S-CeS). In addition, due to electron-withdrawing effect from S=O in sulfate species, NH3 oxidation over S-CeS was greatly suppressed, providing an additional contribution to enhanced performance in high-temperature NH3-SCR. Full article
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15 pages, 7877 KiB  
Article
Engineering Surface Properties of CuO/Ce0.6Zr0.4O2 Catalysts for Efficient Low-Temperature Toluene Oxidation
by Mingyue Wang, Qiulin Zhang, Meilin Zou, Jingge Wang, Danrui Zhu, Jiaying Liu, Junwei Wang, Yang Zuo, Jianjun Chen and Ping Ning
Catalysts 2023, 13(5), 866; https://doi.org/10.3390/catal13050866 - 10 May 2023
Cited by 2 | Viewed by 1436
Abstract
The development of superior low-temperature catalytic performance and inexpensive catalysts for the removal of volatile organic compounds (VOCs) is crucial for their industrial application. Herein, CuO/Ce0.6Zr0.4O2 catalysts calcinated at different temperatures (Cu/CZ-X, X represented calcination temperature) were prepared [...] Read more.
The development of superior low-temperature catalytic performance and inexpensive catalysts for the removal of volatile organic compounds (VOCs) is crucial for their industrial application. Herein, CuO/Ce0.6Zr0.4O2 catalysts calcinated at different temperatures (Cu/CZ-X, X represented calcination temperature) were prepared and used to eliminate toluene. It can be found that Cu/CZ-550 presented the highest low-temperature catalytic activity, with the lowest temperature (220 °C) 50% conversion of toluene, the highest normalized reaction rate (3.1 × 10−5 mol·g−1·s−1 at 180 °C) and the lowest apparent activation energy value (86.3 ± 4.7 kJ·mol−1). Systematically, the surface properties analysis results showed that the optimum redox property, abundant oxygen vacancies, and plentiful surface Ce3+ species over Cu/CZ-550 were associated with the strong interaction between Cu and support could significantly favor the adsorption and activation of toluene, thus resulting in its superior catalytic performance. Full article
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16 pages, 3619 KiB  
Article
Cobalt-/pH-Modified V2O5-MoO3/TiO2 Catalyst with Enhanced Activity for the Low-Temperature Selective Catalytic Reduction Process
by Ruonan Wang, Yanli Zhang, Xing Fan and Jian Li
Catalysts 2023, 13(5), 844; https://doi.org/10.3390/catal13050844 - 6 May 2023
Cited by 4 | Viewed by 1585
Abstract
Currently, the elimination of gaseous pollutants—particularly nitrogen oxides—has emerged as a significant concern. Among various deNOx technologies, selective catalytic reduction (SCR) has gained prominence as the primary approach for NOx abatement, owing to its superior performance. In this study, novel low-temperature [...] Read more.
Currently, the elimination of gaseous pollutants—particularly nitrogen oxides—has emerged as a significant concern. Among various deNOx technologies, selective catalytic reduction (SCR) has gained prominence as the primary approach for NOx abatement, owing to its superior performance. In this study, novel low-temperature SCR catalysts were developed by regulating the pH value and doping cobalt based on a V2O5-MoO3/TiO2 (VMT) catalyst. The results show an increased SCR performance with 82.8% and 91.1% for catalysts after pH (=10) modification (VMT-10) and (1 wt%) Co/pH (=10) modification (1CoVMT-10), respectively. H2-TPR, NH3-TPD, XPS and DRIFTS confirmed that the pH regulation transformed polymerization V species into isolated V5+=O, thus leading to an increase in the number of acid sites, which enhanced the NH3 and NO2 adsorption capacity. Furthermore, the DRIFTS study indicated that the NH3-SCR reaction over 1CoVMT-10 followed the E–R and L–H mechanism. Full article
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15 pages, 4575 KiB  
Article
Low-Temperature NH3-SCR Performance and In Situ DRIFTS Study on Zeolite X-Supported Different Crystal Phases of MnO2 Catalysts
by Lin Chen, Shan Ren, Tao Chen, Xiaodi Li, Mingming Wang, Zhichao Chen and Qingcai Liu
Catalysts 2023, 13(4), 682; https://doi.org/10.3390/catal13040682 - 31 Mar 2023
Viewed by 1530
Abstract
In this study, a series of zeolite-X-supported different crystal phases of MnO2 (α-MnO2, β-MnO2, γ-MnO2, and σ-MnO2) catalysts were prepared via a solid-state diffusion method and high-heat treatment method to explore their low-temperature NH [...] Read more.
In this study, a series of zeolite-X-supported different crystal phases of MnO2 (α-MnO2, β-MnO2, γ-MnO2, and σ-MnO2) catalysts were prepared via a solid-state diffusion method and high-heat treatment method to explore their low-temperature NH3-SCR performance. All of the catalysts featured typical octahedral zeolite X structures and manganese dioxides species of various crystal types dispersed across the support surface. Throughout the entire temperature range of the reaction, γ-MnO2/X catalyst had the highest NO conversion. Additionally, β-MnO2/X, γ-MnO2/X, and σ-MnO2/X catalysts had nearly 100% of N2 selectivity, whereas the α-MnO2/X catalyst had the lowest N2 selectivity (about 90%) below 125 °C. Moreover, the γ-MnO2/X catalyst demonstrated superior acidity capacity and reduction ability compared with the other three catalysts. All the catalysts contained the essential intermediates NH2NO and NH4NO3 species, which are essential to the SCR reaction. More acid sites and nitrate species existed on the γ-MnO2/X catalyst than on the other catalysts, thereby boosting the SCR reaction. Full article
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Review

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23 pages, 3749 KiB  
Review
Research Progress on Metal Oxides for the Selective Catalytic Reduction of NOx with Ammonia
by Lanyi Wang, Shengran Zhou, Mengxia You, Di Yu, Chunlei Zhang, Siyu Gao, Xuehua Yu and Zhen Zhao
Catalysts 2023, 13(7), 1086; https://doi.org/10.3390/catal13071086 - 11 Jul 2023
Cited by 6 | Viewed by 2249
Abstract
Nitrogen oxides emitted from diesel vehicle exhaust seriously endanger the atmospheric environment and human health, which have attracted people’s attention. Among numerous nitrogen oxide (NOx) removal technologies, photocatalytic removal of NOx and SCR have received widespread attention. The photocatalytic treatment [...] Read more.
Nitrogen oxides emitted from diesel vehicle exhaust seriously endanger the atmospheric environment and human health, which have attracted people’s attention. Among numerous nitrogen oxide (NOx) removal technologies, photocatalytic removal of NOx and SCR have received widespread attention. The photocatalytic treatment of NOx technology is a good choice due to its mild reaction conditions and low costs. Moreover, NH3-SCR has been widely used in denitration technology and plays an important role in controlling NOx emissions. In NH3-SCR technology, the development of high-efficiency catalysts is an important part. This paper summarizes the research progress of metal oxide catalysts for NH3-SCR reactions, including V-based catalysts, Mn-based catalysts, Fe-based catalysts, Ce-based catalysts, and Cu-based catalysts. Meanwhile, the detailed process of the NH3-SCR reaction was also introduced. In addition, this paper also describes a possible SO2 poisoning mechanism and the stability of the catalysts. Finally, the problems and prospects of metal oxide catalysts for NOx removal were also proposed. Full article
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