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Matam SK, Silverwood IP, Boudjema L, O'Malley AJ, Catlow CRA. Methanol diffusion and dynamics in zeolite H-ZSM-5 probed by quasi-elastic neutron scattering and classical molecular dynamics simulations. Philos Trans A Math Phys Eng Sci 2023; 381:20220335. [PMID: 37691467 PMCID: PMC10493552 DOI: 10.1098/rsta.2022.0335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 03/31/2023] [Indexed: 09/12/2023]
Abstract
Zeolite ZSM-5 is a key catalyst in commercially relevant processes including the widely studied methanol to hydrocarbon reaction, and molecular diffusion in zeolite pores is known to be a crucial factor in controlling catalytic reactions. Here, we present critical analyses of recent quasi-elastic neutron scattering (QENS) data and complementary molecular dynamics (MD) simulations. The QENS experiments show that the nature of methanol diffusion dynamics in ZSM-5 pores is dependent both on the Si/Al ratio (11, 25, 36, 40 and 140), which determines the Brønsted acid site density of the zeolite, and that the nature of the type of motion observed may vary qualitatively over a relatively small temperature range. At 373 K, on increasing the ratio from 11 to 140, the observed mobile methanol fraction increases and the nature of methanol dynamics changes from rotational (in ZSM-5 with Si/Al of 11) to translational diffusion. The latter is either confined localized diffusion within a pore in zeolites with ratios up to 40 or non-localized, longer-range diffusion in zeolite samples with the ratio of 140. The complementary MD simulations conducted over long time scales (1 ns), which are longer than those measured in the present study by QENS (≈1-440 ps), at 373 K predict the occurrence of long-range translational diffusion of methanol in ZSM-5, independent of the Si/Al ratios (15, 47, 95, 191 and siliceous MFI). The rate of diffusion increases slightly by increasing the ratio from 15 to 95 and thereafter does not depend on zeolite composition. Discrepancies in the observed mobile methanol fraction between the MD simulations (100% methanol mobility in ZSM-5 pores across all Si/Al ratios) and QENS experiments (for example, ≈80% immobile methanol in ZSM-5 with Si/Al of 11) are attributed to the differences in time resolutions of the techniques. This perspective provides comprehensive information on the effect of acid site density on methanol dynamics in ZSM-5 pores and highlights the complementarity of QENS and MD, and their advantages and limitations. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.
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Affiliation(s)
- Santhosh K. Matam
- UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK
| | - Ian P. Silverwood
- UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
- ISIS Pulsed Neutron and Muon Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Lotfi Boudjema
- UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
- Department of Chemistry, University College London, 20 Gordon Street, London WC1E 6BT, UK
- ICGM, Université de Montpellier, CNRS, ENSCM, Montpellier, France
| | - Alexander J. O'Malley
- UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
- Institute for Sustainability, Department of Chemistry, University of Bath, Bath BA2 7AY, UK
| | - C. Richard A. Catlow
- UK Catalysis Hub, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Didcot OX11 0FA, UK
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, UK
- Department of Chemistry, University College London, 20 Gordon Street, London WC1E 6BT, UK
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2
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He Z, Wei Q, Liang C, Liu D, Ma J, Chen X, Song M. Unraveling the capture mechanism of gaseous As 2O 3 over H-zsm-5 zeolite from coal-fired flue gas: Experimental and theoretical insights. Chemosphere 2023:139243. [PMID: 37330063 DOI: 10.1016/j.chemosphere.2023.139243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 05/17/2023] [Accepted: 06/14/2023] [Indexed: 06/19/2023]
Abstract
Gaseous As2O3 discharged from coal-fired power plants results in severe detriments to the ecological environment. It is of great urgency to develop highly efficient As2O3 capture technology for reducing atmospheric arsenic contamination. Utilizing solid sorbents for gaseous As2O3 capture is a promising treatment for As2O3 capture. The zeolite of H-ZSM-5 was applied for As2O3 capture at high temperatures of 500-900 °C. Special attention was paid to clarifying its capture mechanism and identifying the influence of flue gas components via density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. Results revealed that due to high thermal stability with large specific areas, H-ZSM-5 demonstrated excellent arsenic capture at 500-900 °C. The captured arsenic consisted of As3+ and As5+ speciations, ascribed to As2O3 adsorption and oxidation. Moreover, As3+ and As5+ compounds were both through physisorption or chemisorption at 500-600 °C while dominant chemisorption at 700-900 °C. In particular, As3+ compounds were much more steadily fixed in products at all operating temperatures. Combining the characterization analysis and DFT calculations, it further verified that both Si-OH-Al groups and external Al species of H-ZSM-5 could chemisorb As2O3, and the latter exhibited much stronger affinities via orbital hybridization and electron transfer. The introduced O2 could facilitate As2O3 oxidation and fixation in H-ZSM-5, especially at a lower concentration of 2%. Additionally, H-ZSM-5 possessed great acid gas resistance for As2O3 capture under the concentration of NO or SO2 less than 500 ppm. AIMD simulations further identified that compared to NO and SO2, As2O3 was far more competitive and occupied the active sites of the Si-OH-Al groups and external Al species of H-ZSM-5. Overall, it demonstrated that H-ZSM-5 is a promising sorbent for As2O3 capture from coal-fired flue gas.
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Affiliation(s)
- Zhongli He
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
| | - Qi Wei
- High Performance Computing Department, National Supercomputing Center in Shenzhen, Shenzhen, 518000, China
| | - Cai Liang
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
| | - Daoyin Liu
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Jiliang Ma
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Xiaoping Chen
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Min Song
- Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
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Kirchberger FM, Liu Y, Plessow PN, Tonigold M, Studt F, Sanchez-Sanchez M, Lercher JA. Mechanistic differences between methanol and dimethyl ether in zeolite-catalyzed hydrocarbon synthesis. Proc Natl Acad Sci U S A 2022; 119:e2103840119. [PMID: 35046020 DOI: 10.1073/pnas.2103840119] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2021] [Indexed: 11/18/2022] Open
Abstract
Methanol conversion to hydrocarbons has emerged as a key reaction for synthetic energy carriers and light alkenes. The autocatalytic nature and complex reaction network make a mechanistic understanding very challenging and widely debated. Water is not only part of the overall conversion, it is also frequently used as diluent, influencing, in turn, activity, selectivity, and stability of the catalysts. Water directly and indirectly influences the processes that initiate the C–C formation via adjusting the chemical potential of methanol and dimethyl ether, with the latter being more efficient to generate highly reactive C1 species via hydride transfer. The insight shows paths to optimize the stability of catalysts and to tailor the product distribution for H-ZSM-5–based catalysts. Water influences critically the kinetics of the autocatalytic conversion of methanol to hydrocarbons in acid zeolites. At very low conversions but otherwise typical reaction conditions, the initiation of the reaction is delayed in presence of H2O. In absence of hydrocarbons, the main reactions are the methanol and dimethyl ether (DME) interconversion and the formation of a C1 reactive mixture—which in turn initiates the formation of first hydrocarbons in the zeolite pores. We conclude that the dominant reactions for the formation of a reactive C1 pool at this stage involve hydrogen transfer from both MeOH and DME to surface methoxy groups, leading to methane and formaldehyde in a 1:1 stoichiometry. While formaldehyde reacts further to other C1 intermediates and initiates the formation of first C–C bonds, CH4 is not reacting. The hydride transfer to methoxy groups is the rate-determining step in the initiation of the conversion of methanol and DME to hydrocarbons. Thus, CH4 formation rates at very low conversions, i.e., in the initiation stage before autocatalysis starts, are used to gauge the formation rates of first hydrocarbons. Kinetics, in good agreement with theoretical calculations, show surprisingly that hydrogen transfer from DME to methoxy species is 10 times faster than hydrogen transfer from methanol. This difference in reactivity causes the observed faster formation of hydrocarbons in dry feeds, when the concentration of methanol is lower than in presence of water. Importantly, the kinetic analysis of CH4 formation rates provides a unique quantitative parameter to characterize the activity of catalysts in the methanol-to-hydrocarbon process.
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Guo J, Ma YL, Yu JY, Gao YJ, Ma NX, Wu XY. Highly selective cleavage C-O ether bond of lignin model compounds over Ni/CaO- H-ZSM-5 in ethanol. BMC Chem 2019; 13:36. [PMID: 31384784 PMCID: PMC6661968 DOI: 10.1186/s13065-019-0557-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 03/15/2019] [Indexed: 11/10/2022] Open
Abstract
Herein, 2-(2-methoxyphenoxy)-1-phenylethanol (β-O-4), 2-methoxyphenyl anisole (α-O-4) and 4-phenoxyphenol (4-O-5) were selected as typical lignin model compounds. Given the effectiveness of traditional acid-base catalysts for lignin depolymerisation, a novel Ni/CaO-H-ZSM-5(60) catalyst was prepared to investigate the difficulty level of C-O bond of three model compounds cleavage in ethanol. It was observed that Ni/CaO-H-ZSM-5(60) had prominent performance on the C-O bond cleavage at very mild conditions (140 °C, 1 MPa H2). Among them, the C-O bond of α-O-4 and β-O-4 could be completely cleaved within 60 min. Although the C-O bond of 4-O-5 had high bond energy, 41.2% of conversion was occurred in 60 min. The introduction of CaO could regulate the acidity of H-ZSM-5 to enhance the ability to break C-O bonds. Moreover, the possible pathways of C-O ether bonds in three lignin model compounds cleavage were proposed in order to selectively obtain target products from the raw lignin degradation.
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Affiliation(s)
- J Guo
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
| | - Yu L Ma
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
| | - Jia Y Yu
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
| | - Yu J Gao
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
| | - Ning X Ma
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
| | - Xiao Y Wu
- State Key Laboratory of High-efficiency Coal Utilization and Green Chemical Engineering, College of Chemistry and Chemical Engineering, Ningxia University, Helanshan Rd. 539, Yinchuan, 750021 China
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Kubarev A, Breynaert E, Van Loon J, Layek A, Fleury G, Radhakrishnan S, Martens J, Roeffaers MBJ. Solvent Polarity-Induced Pore Selectivity in H-ZSM-5 Catalysis. ACS Catal 2017; 7:4248-4252. [PMID: 28713643 PMCID: PMC5504957 DOI: 10.1021/acscatal.7b00782] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 05/08/2017] [Indexed: 12/02/2022]
Abstract
Molecular-sized micropores of ZSM-5 zeolite catalysts provide spatial restrictions around catalytic sites that allow for shape-selective catalysis. However, the fact that ZSM-5 has two main pore systems with different geometries is relatively unexploited as a potential source of additional shape selectivity. Here, we use confocal laser-scanning microscopy to show that by changing the polarity of the solvent, the acid-catalyzed furfuryl alcohol oligomerization can be directed to selectively occur within either of two locations in the microporous network. This finding is confirmed for H-ZSM-5 particles with different Si/Al ratios and indicates a general trend for shape-selective catalytic reactions.
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Affiliation(s)
- Alexey
V. Kubarev
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Eric Breynaert
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Jordi Van Loon
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Arunasish Layek
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Guillaume Fleury
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Sambhu Radhakrishnan
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Johan Martens
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
| | - Maarten B. J. Roeffaers
- Center for Surface Chemistry
and Catalysis, KU Leuven, Celestijnenlaan 200F, 3001 Leuven, Belgium
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Neppolian B, Mine S, Horiuchi Y, Bianchi CL, Matsuoka M, Dionysiou DD, Anpo M. Efficient photocatalytic degradation of organics present in gas and liquid phases using Pt-TiO2/Zeolite (H-ZSM). Chemosphere 2016; 153:237-243. [PMID: 27016820 DOI: 10.1016/j.chemosphere.2016.03.063] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 02/16/2016] [Accepted: 03/14/2016] [Indexed: 06/05/2023]
Abstract
TiO2-encapsulated H-ZSM photocatalysts were prepared by physical mixing of TiO2 and zeolites. Pt was immobilized on the surface of the TiO2-encapsulated zeolite (H-ZSM) catalysts by a simple photochemical reduction method. Different weight ratios of both TiO2 and Pt were hybridized with H-ZSM and the catalytic performance of the prepared catalysts was investigated for 2-propanol oxidation in liquid phase and acetaldehyde in gas phase reaction. Around 5-10 wt% TiO2-encapsulated H-ZSM catalysts was found to be optimal amount for the effective oxidation of the organics. Prior to light irradiation, Pt-TiO2-H-ZSM showed considerable amount of catalytic degradation of 2-propanol in the dark, forming acetone as an intermediate. In this study, Pt has played a major and important role on the total oxidation of 2-propanol as well as acetaldehyde. As a result, no residual organics were present in the pores of the zeolites. The catalysts could be reused more than three times without losing their catalytic activity in both phases. The Pt-TiO2-H-ZSM photocatalysts could overcome the problem of strong adsorption of organics in the zeolite pores (after the reaction). Thus, Pt-TiO2-H-ZSM can be used as a potential catalyst for both liquid and gas phase oxidation of organic pollutants.
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Affiliation(s)
- B Neppolian
- SRM-Research Institute, SRM University, Kattankulathur, Chennai, India.
| | - Shinya Mine
- Department of Applied Chemistry, Osaka Prefecture University, Gakuen-Cho 1-1, Sakai, Osaka, 599-8531, Japan
| | - Yu Horiuchi
- Department of Applied Chemistry, Osaka Prefecture University, Gakuen-Cho 1-1, Sakai, Osaka, 599-8531, Japan
| | - C L Bianchi
- Department of Chemistry, University of Milan, Via Golgi 19, 20133 Milano, Italy.
| | - M Matsuoka
- Department of Applied Chemistry, Osaka Prefecture University, Gakuen-Cho 1-1, Sakai, Osaka, 599-8531, Japan
| | - D D Dionysiou
- Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, USA
| | - M Anpo
- Department of Applied Chemistry, Osaka Prefecture University, Gakuen-Cho 1-1, Sakai, Osaka, 599-8531, Japan
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