1
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Dummer NF, Willock DJ, He Q, Howard MJ, Lewis RJ, Qi G, Taylor SH, Xu J, Bethell D, Kiely CJ, Hutchings GJ. Methane Oxidation to Methanol. Chem Rev 2022; 123:6359-6411. [PMID: 36459432 PMCID: PMC10176486 DOI: 10.1021/acs.chemrev.2c00439] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The direct transformation of methane to methanol remains a significant challenge for operation at a larger scale. Central to this challenge is the low reactivity of methane at conditions that can facilitate product recovery. This review discusses the issue through examination of several promising routes to methanol and an evaluation of performance targets that are required to develop the process at scale. We explore the methods currently used, the emergence of active heterogeneous catalysts and their design and reaction mechanisms and provide a critical perspective on future operation. Initial experiments are discussed where identification of gas phase radical chemistry limited further development by this approach. Subsequently, a new class of catalytic materials based on natural systems such as iron or copper containing zeolites were explored at milder conditions. The key issues of these technologies are low methane conversion and often significant overoxidation of products. Despite this, interest remains high in this reaction and the wider appeal of an effective route to key products from C-H activation, particularly with the need to transition to net carbon zero with new routes from renewable methane sources is exciting.
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Affiliation(s)
- Nicholas F. Dummer
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
| | - David J. Willock
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
| | - Qian He
- Department of Materials Science and Engineering, National University of Singapore, Singapore117575, Singapore
| | - Mark J. Howard
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
| | - Richard J. Lewis
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
| | - Guodong Qi
- National Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan430071, P. R. China
- University of Chinese Academy of Sciences, Beijing100049, P. R. China
| | - Stuart H. Taylor
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
| | - Jun Xu
- National Center for Magnetic Resonance in Wuhan, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan430071, P. R. China
- University of Chinese Academy of Sciences, Beijing100049, P. R. China
| | - Don Bethell
- Department of Chemistry, University of Liverpool, Crown Street, LiverpoolL69 7ZD, United Kingdom
| | - Christopher J. Kiely
- Department of Materials Science and Engineering, Lehigh University, 5 East Packer Avenue, Bethlehem, Pennsylvania18015, United States
| | - Graham J. Hutchings
- Max Planck−Cardiff Centre on the Fundamentals of Heterogeneous Catalysis FUNCAT, Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, CardiffCF10 3AT, United Kingdom
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2
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Bols ML, Devos J, Rhoda HM, Plessers D, Solomon EI, Schoonheydt RA, Sels BF, Dusselier M. Selective Formation of α-Fe(II) Sites on Fe-Zeolites through One-Pot Synthesis. J Am Chem Soc 2021; 143:16243-16255. [PMID: 34570975 DOI: 10.1021/jacs.1c07590] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
α-Fe(II) active sites in iron zeolites catalyze N2O decomposition and form highly reactive α-O that selectively oxidizes unreactive hydrocarbons, such as methane. How these α-Fe(II) sites are formed remains unclear. Here different methods of iron introduction into zeolites are compared to derive the limiting factors of Fe speciation to α-Fe(II). Postsynthetic iron introduction procedures on small pore zeolites suffer from limited iron diffusion and dispersion leading to iron oxides. In contrast, by introducing Fe(III) in the hydrothermal synthesis mixture of the zeolite (one-pot synthesis) and the right treatment, crystalline CHA can be prepared with >1.6 wt % Fe, of which >70% is α-Fe(II). The effect of iron on the crystallization is investigated, and the intermediate Fe species are tracked using UV-vis-NIR, FT-IR, and Mössbauer spectroscopy. These data are supplemented with online mass spectrometry in each step, with reactivity tests in α-O formation and with methanol yields in stoichiometric methane activation at room temperature and pressure. We recover up to 134 μmol methanol per gram in a single cycle through H2O/CH3CN extraction and 183 μmol/g through steam desorption, a record yield for iron zeolites. A general scheme is proposed for iron speciation in zeolites through the steps of drying, calcination, and activation. The formation of two cohorts of α-Fe(II) is discovered, one before and one after high temperature activation. We propose the latter cohort depends on the reshuffling of aluminum in the zeolite lattice to accommodate thermodynamically favored α-Fe(II).
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Affiliation(s)
- Max L Bols
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
| | - Julien Devos
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
| | - Hannah M Rhoda
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Dieter Plessers
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
| | - Edward I Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Robert A Schoonheydt
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
| | - Bert F Sels
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
| | - Michiel Dusselier
- Department of Microbial and Molecular Systems, KU Leuven, 3001 Heverlee, Belgium
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3
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Yamashita K, Liu Z, Iyoki K, Chen CT, Miyagi S, Yanaba Y, Yamauchi Y, Okubo T, Wakihara T. Synthetic and natural MOR zeolites as high-capacity adsorbents for the removal of nitrous oxide. Chem Commun (Camb) 2021; 57:1312-1315. [PMID: 33480896 DOI: 10.1039/d0cc07511f] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
N2O is typically present as a trace gas in chemical processes, but its emission causes serious environmental issues. We herein demonstrate that ion-exchanged mordenite zeolites (framework code: MOR) can exhibit high capacities for N2O adsorption under ambient conditions. In particular, a natural MOR zeolite gives an adsorption capacity as high as 0.34 mmol-N2O per g-zeolite (1 atm, 25 °C), representing the best performing material among all zeolite-based adsorbents reported so far. The results contribute toward a comprehensive understanding of the structure-activity relationship and offer insights to establishing a zeolite-based adsorption system for enriching or removing N2O.
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Affiliation(s)
- Keita Yamashita
- Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
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4
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Aranifard S, Bell AT, Keil FJ, Heyden A. Kinetic modeling of nitrous oxide decomposition on Fe-ZSM-5 in the presence of nitric oxide based on parameters obtained from first-principles calculations. Catal Sci Technol 2021. [DOI: 10.1039/d1cy00252j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A variety of experiments for the N2O decomposition over Fe-ZSM-5 catalysts have been simulated in the presence and absence of small amounts of nitric oxide and water vapor.
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Affiliation(s)
- Sara Aranifard
- Department of Chemical Engineering
- University of South Carolina
- Columbia
- USA
| | - Alexis T. Bell
- Department of Chemical and Biomolecular Engineering
- University of California Berkeley
- Berkeley
- USA
| | - Frerich J. Keil
- Department of Chemical Reaction Engineering
- Hamburg University of Technology
- 21073 Hamburg
- Germany
| | - Andreas Heyden
- Department of Chemical Engineering
- University of South Carolina
- Columbia
- USA
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5
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Xu X, Kumar Megarajan S, Xia X, Toghan A, Feldhoff A, Zhang Y, Jiang H. Effect of reduction temperature on the structure and catalytic performance of mesoporous Ni–Fe–Al 2O 3 in oxidative dehydrogenation of ethane. NEW J CHEM 2020. [DOI: 10.1039/d0nj02618b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The effects of reduction temperature on the structure and catalytic performance of mesoporous Ni–Fe–Al2O3 are investigated for the first time.
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Affiliation(s)
- Xia Xu
- Key Laboratory of Biofuels
- Qingdao Institute of Bioenergy and Bioprocess Technology
- Chinese Academy of Sciences
- Qingdao 266101
- China
| | - Suresh Kumar Megarajan
- Key Laboratory of Biofuels
- Qingdao Institute of Bioenergy and Bioprocess Technology
- Chinese Academy of Sciences
- Qingdao 266101
- China
| | - Xuefa Xia
- Key Laboratory of Biofuels
- Qingdao Institute of Bioenergy and Bioprocess Technology
- Chinese Academy of Sciences
- Qingdao 266101
- China
| | - Arafat Toghan
- Chemistry Department
- Faculty of Science
- South Valley University
- Qena 83523
- Egypt
| | - Armin Feldhoff
- Institute of Physical Chemistry and Electrochemistry
- Leibniz University of Hannover
- Hannover 30167
- Germany
| | - Yan Zhang
- Key Laboratory of Biofuels
- Qingdao Institute of Bioenergy and Bioprocess Technology
- Chinese Academy of Sciences
- Qingdao 266101
- China
| | - Heqing Jiang
- Key Laboratory of Biofuels
- Qingdao Institute of Bioenergy and Bioprocess Technology
- Chinese Academy of Sciences
- Qingdao 266101
- China
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6
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Yang J, Du B, Liu J, Krishna R, Zhang F, Zhou W, Wang Y, Li J, Chen B. MIL-100Cr with open Cr sites for a record N 2O capture. Chem Commun (Camb) 2018; 54:14061-14064. [PMID: 30451265 PMCID: PMC11170657 DOI: 10.1039/c8cc07679k] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
Nitrous oxide (N2O) is considered as the third most important greenhouse gas after carbon dioxide and methane and needs to be removed from air. Herein, we reported the metal-organic framework MIL-100Cr with open Cr sites for record N2O capture capacities of 5.78 mmol g-1 at 298 K and 8.25 mmol g-1 at 273 K, respectively. DFT calculations showed that the static binding energy of N2O on the open-Cr site is notably higher than that of N2, 72.5 kJ mol-1vs. 51.6 kJ mol-1, which enforces MIL-100Cr to exhibit extremely high N2O/N2 ideal adsorbed solution theory (IAST) gas separation selectivity up to 1000.
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Affiliation(s)
- Jiangfeng Yang
- Research Institute of Special Chemicals, College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China.
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7
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Shahami M, Dooley KM, Shantz DF. Steam-assisted crystallized Fe-ZSM-5 materials and their unprecedented activity in benzene hydroxylation to phenol using hydrogen peroxide. J Catal 2018. [DOI: 10.1016/j.jcat.2018.10.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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8
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Richards N, Nowicka E, Carter JH, Morgan DJ, Dummer NF, Golunski S, Hutchings GJ. Investigating the Influence of Fe Speciation on N 2O Decomposition Over Fe-ZSM-5 Catalysts. Top Catal 2018; 61:1983-1992. [PMID: 30930588 PMCID: PMC6411129 DOI: 10.1007/s11244-018-1024-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The influence of Fe speciation on the decomposition rates of N2O over Fe-ZSM-5 catalysts prepared by Chemical Vapour Impregnation were investigated. Various weight loadings of Fe-ZSM-5 catalysts were prepared from the parent zeolite H-ZSM-5 with a Si:Al ratio of 23 or 30. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. UV/Vis spectroscopy, surface area analysis, XPS and ICP-OES of the acid washed catalysts indicated a reduction of ca. 60% of Fe loading when compared to the parent catalyst with a 0.4 wt% Fe loading. The TOF of N2O decomposition at 600 °C improved to 3.99 × 103 s-1 over the acid washed catalyst which had a weight loading of 0.16%, in contrast, the parent catalyst had a TOF of 1.60 × 103 s-1. Propane was added to the gas stream to act as a reductant and remove any inhibiting oxygen species that remain on the surface of the catalyst. Comparison of catalysts with relatively high and low Fe loadings achieved comparable levels of N2O decomposition when propane is present. When only N2O is present, low metal loading Fe-ZSM-5 catalysts are not capable of achieving high conversions due to the low proximity of active framework Fe3+ ions and extra-framework ɑ-Fe species, which limits oxygen desorption. Acid washing extracts Fe from these active sites and deposits it on the surface of the catalyst as FexOy, leading to a drop in activity. The Fe species present in the catalyst were identified using UV/Vis spectroscopy and speculate on the active species. We consider high loadings of Fe do not lead to an active catalyst when propane is present due to the formation of FexOy nanoparticles and clusters during catalyst preparation. These are inactive species which lead to a decrease in overall efficiency of the Fe ions and consequentially a lower TOF.
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Affiliation(s)
- Nia Richards
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - Ewa Nowicka
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - James H. Carter
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - David J. Morgan
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - Nicholas F. Dummer
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - Stanislaw Golunski
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
| | - Graham J. Hutchings
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff, CF10 3AT UK
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9
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Meng L, Zhu X, Hensen EJM. Stable Fe/ZSM-5 Nanosheet Zeolite Catalysts for the Oxidation of Benzene to Phenol. ACS Catal 2017; 7:2709-2719. [PMID: 28413693 PMCID: PMC5389689 DOI: 10.1021/acscatal.6b03512] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 02/27/2017] [Indexed: 11/28/2022]
Abstract
Fe/ZSM-5 nanosheet zeolites of varying thickness were synthesized with di- and tetraquaternary ammonium structure directing agents and extensively characterized for their textural, structural, and catalytic properties. Introduction of Fe3+ ions in the framework of nanosheet zeolites was slightly less effective than in bulk ZSM-5 zeolite. Steaming was necessary to activate all catalysts for N2O decomposition and benzene oxidation. The higher the Fe content, the higher the degree of Fe aggregation was after catalyst activation. The degree of Fe aggregation was lower when the crystal domain size of the zeolite or the Fe content was decreased. These two parameters had a substantial influence on the catalytic performance. Decreasing the number of Fe sites along the b-direction strongly suppressed secondary reactions of phenol and, accordingly, catalyst deactivation. This together with the absence of diffusional limitations in nanosheet zeolites explains the much higher phenol productivity obtainable with nanostructured Fe/ZSM-5. Steamed Fe/ZSM-5 zeolite nanosheet synthesized using C22-6-3·Br2 (domain size in b-direction ∼3 nm) and containing 0.24 wt % Fe exhibited the highest catalytic performance. During the first 24 h on stream, this catalyst produced 185 mmolphenol g-1. Calcination to remove the coke deposits completely restored the initial activity.
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Affiliation(s)
- Lingqian Meng
- Inorganic Materials Chemistry,
Schuit Institute of Catalysis, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | | | - Emiel J. M. Hensen
- Inorganic Materials Chemistry,
Schuit Institute of Catalysis, Department of Chemical Engineering
and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
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10
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Xie P, Luo Y, Ma Z, Huang C, Miao C, Yue Y, Hua W, Gao Z. Catalytic decomposition of N2O over Fe-ZSM-11 catalysts prepared by different methods: Nature of active Fe species. J Catal 2015. [DOI: 10.1016/j.jcat.2015.07.010] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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11
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Yue Y, Liu H, Yuan P, Yu C, Bao X. One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3. Sci Rep 2015; 5:9270. [PMID: 25791958 PMCID: PMC4366855 DOI: 10.1038/srep09270] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/10/2015] [Indexed: 11/26/2022] Open
Abstract
Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3.
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Affiliation(s)
- Yuanyuan Yue
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China
| | - Haiyan Liu
- The Key Laboratory of Catalysis, China National Petroleum Corporation, China University of Petroleum, Beijing 102249, P. R. China
| | - Pei Yuan
- State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China
| | - Chengzhong Yu
- Australian Institute for Bioengineering and Nanotechnology, the University of Queensland, Brisbane St Lucia, QLD 4072, Australia
| | - Xiaojun Bao
- The Key Laboratory of Catalysis, China National Petroleum Corporation, China University of Petroleum, Beijing 102249, P. R. China
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12
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Lee JK, Kim YJ, Lee HJ, Kim SH, Cho SJ, Nam IS, Hong SB. Iron-substituted TNU-9, TNU-10, and IM-5 zeolites and their steam-activated analogs as catalysts for direct N2O decomposition. J Catal 2011. [DOI: 10.1016/j.jcat.2011.08.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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13
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Koekkoek AJJ, Degirmenci V, Hensen EJM. Dry gel conversion of organosilane templated mesoporous silica: from amorphous to crystalline catalysts for benzene oxidation. ACTA ACUST UNITED AC 2011. [DOI: 10.1039/c1jm10779h] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Smeets PJ, Woertink JS, Sels BF, Solomon EI, Schoonheydt RA. Transition-metal ions in zeolites: coordination and activation of oxygen. Inorg Chem 2010; 49:3573-83. [PMID: 20380459 PMCID: PMC2881549 DOI: 10.1021/ic901814f] [Citation(s) in RCA: 131] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Zeolites containing transition-metal ions (TMIs) often show promising activity as heterogeneous catalysts in pollution abatement and selective oxidation reactions. In this paper, two aspects of research on the TMIs Cu, Co, and Fe in zeolites are discussed: (i) coordination to the lattice and (ii) activated oxygen species. At low loading, TMIs preferably occupy exchange sites in six-membered oxygen rings (6MR), where the TMIs preferentially coordinate with the O atoms of Al tetrahedra. High TMI loadings result in a variety of TMI species formed at the zeolite surface. Removal of the extralattice O atoms during high-temperature pretreatments can result in autoreduction. Oxidation of reduced TMI sites often results in the formation of highly reactive oxygen species. In Cu-ZSM-5, calcination with O(2) results in the formation of a species, which was found to be a crucial intermediate in both the direct decomposition of NO and N(2)O and the selective oxidation of methane into methanol. An activated oxygen species, called alpha-O, is formed in Fe-ZSM5 and reported to be the active site in the partial oxidation of methane and benzene into methanol and phenol, respectively. However, this reactive alpha-O can only be formed with N(2)O, not with O(2). O(2)-activated Co intermediates in faujasite (FAU) zeolites can selectively oxidize alpha-pinene and epoxidize styrene. In Co-FAU, Co(III) superoxo and peroxo complexes are suggested to be the active cores, whereas in Cu and Fe-ZSM-5, various monomeric and dimeric sites have been proposed, but no consensus has been obtained. Very recently, the active site in Cu-ZSM-5 was identified as a bent [Cu-O-Cu](2+) core (Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 18908-18913). Overall, O(2) activation depends on the interplay of structural factors such as the type of zeolite and sizes of the channels and cages and chemical factors such as the Si/Al ratio and the nature, charge, and distribution of the charge-balancing cations. The presence of several different TMI sites hinders the direct study of the spectroscopic features of the active site. Spectroscopic techniques capable of selectively probing these sites, even if they only constitute a minor fraction of the total amount of TMI sites, are thus required. Fundamental knowledge of the geometric and electronic structures of the reactive active site can help in the design of novel selective oxidation catalysts.
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Affiliation(s)
- Pieter J. Smeets
- Center for Surface Chemistry and Catalysis, K.U.Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Julia S. Woertink
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
| | - Bert F. Sels
- Center for Surface Chemistry and Catalysis, K.U.Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
- Stanford Synchrotron Radiation Lab, Menlo Park, CA 94025, USA
| | - Robert A. Schoonheydt
- Center for Surface Chemistry and Catalysis, K.U.Leuven, Kasteelpark Arenberg 23, 3001 Leuven, Belgium
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15
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Li Y, Feng Z, Xin H, Fan F, Zhang J, Magusin PCMM, Hensen EJM, van Santen RA, Yang Q, Li C. Effect of Aluminum on the Nature of the Iron Species in Fe-SBA-15. J Phys Chem B 2006; 110:26114-21. [PMID: 17181265 DOI: 10.1021/jp0657641] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report the preparation of highly ordered mesoporous Fe-Al-SBA-15 with isolated extraframework Fe species under acidic conditions. The materials were characterized by means of UV resonance Raman spectroscopy, in conjunction with BET, XRD, TEM, UV-vis, H2-TPR, FT-IR, and 27Al MAS NMR spectroscopy. The addition of both Fe and Al to the synthesis gel of SBA-15 results in the formation of isolated extraframework Fe species located close to the framework Al ions and the Fe content an order of magnitude higher than that in Fe-SBA-15 synthesized without Al. The existence of anchored extraframework Fe species was confirmed by the presence of a strong absorption band at 270 nm, hydrogen reduction at relatively low temperature, and the presence of a resonance Raman band at 1140 cm(-1). The location of Fe in close proximity to framework Al nuclei is further supported by 27Al MAS NMR measurements. Two characteristic UV Raman bands at 510 cm(-1) and 1090 cm(-1) excited by 244-nm laser are assigned to Fe-O-Si symmetric and asymmetric stretching modes of isolated tetrahedral Fe ions in the silica framework for Fe-SBA-15. The resonance Raman band at 1140 cm(-1) excited by 325-nm laser is attributed to the asymmetric stretching mode of the isolated extraframework iron species in Fe-Al-SBA-15. The isolated Fe species close to framework Al species are stable in acidic HCl solution, whereas the majority of Fe species in Fe-SBA-15 can be easily removed.
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Affiliation(s)
- Ying Li
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
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16
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Yang G, Zhou D, Liu X, Han X, Bao X. Possible active sites in Fe/ZSM-5 zeolite for the direct benzene hydroxylation to phenol: 1. μ-Oxo[Fe,M] species (M=Fe,Al). J Mol Struct 2006. [DOI: 10.1016/j.molstruc.2006.03.059] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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17
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Krishna K, Makkee M. Preparation and Pretreatment Temperature Influence on Iron Species Distribution and N2O Decomposition in Fe–ZSM-5. Catal Letters 2006. [DOI: 10.1007/s10562-005-9628-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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18
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Kiwi-Minsker L, Bulushev DA, Renken A. Low temperature decomposition of nitrous oxide over Fe/ZSM-5: Modelling of the dynamic behaviour. Catal Today 2005. [DOI: 10.1016/j.cattod.2005.09.039] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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