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Tang Y, Li Y, Feng Tao F. Activation and catalytic transformation of methane under mild conditions. Chem Soc Rev 2021; 51:376-423. [PMID: 34904592 DOI: 10.1039/d1cs00783a] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
In the last few decades, worldwide scientists have been motivated by the promising production of chemicals from the widely existing methane (CH4) under mild conditions for both chemical synthesis with low energy consumption and climate remediation. To achieve this goal, a whole library of catalytic chemistries of transforming CH4 to various products under mild conditions is required to be developed. Worldwide scientists have made significant efforts to reach this goal. These significant efforts have demonstrated the feasibility of oxidation of CH4 to value-added intermediate compounds including but not limited to CH3OH, HCHO, HCOOH, and CH3COOH under mild conditions. The fundamental understanding of these chemical and catalytic transformations of CH4 under mild conditions have been achieved to some extent, although currently neither a catalyst nor a catalytic process can be used for chemical production under mild conditions at a large scale. In the academic community, over ten different reactions have been developed for converting CH4 to different types of oxygenates under mild conditions in terms of a relatively low activation or catalysis temperature. However, there is still a lack of a molecular-level understanding of the activation and catalysis processes performed in extremely complex reaction environments under mild conditions. This article reviewed the fundamental understanding of these activation and catalysis achieved so far. Different oxidative activations of CH4 or catalytic transformations toward chemical production under mild conditions were reviewed in parallel, by which the trend of developing catalysts for a specific reaction was identified and insights into the design of these catalysts were gained. As a whole, this review focused on discussing profound insights gained through endeavors of scientists in this field. It aimed to present a relatively complete picture for the activation and catalytic transformations of CH4 to chemicals under mild conditions. Finally, suggestions of potential explorations for the production of chemicals from CH4 under mild conditions were made. The facing challenges to achieve high yield of ideal products were highlighted and possible solutions to tackle them were briefly proposed.
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Affiliation(s)
- Yu Tang
- Institute of Molecular Catalysis and In situ/operando Studies, College of Chemistry, Fuzhou University, Fujian, 350000, China.
| | - Yuting Li
- Department of Chemical and Petroleum Engineering, University of Kansas, KS 66045, USA.
| | - Franklin Feng Tao
- Department of Chemical and Petroleum Engineering, University of Kansas, KS 66045, USA.
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2
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Ehsani Tilami S, Pourali SM, Samadi-Maybodi A. Effects of microwave irradiation and seeding on low-temperature size-controlled nanozeolite P synthesis. INORG NANO-MET CHEM 2020. [DOI: 10.1080/24701556.2020.1841232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
| | - S. Masoomeh Pourali
- Analytical Department, Faculty of Chemistry, University of Mazandaran, Babolsar, Iran
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3
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Che Q, Xie X, Ma Q, Wang J, Zhu Y, Shi R, Yang P. Coordination environment evolution of Co( ii) during dehydration and re-crystallization processes of KCoPO 4·H 2O towards enhanced electrocatalytic oxygen evolution reaction. RSC Adv 2020; 10:14972-14978. [PMID: 35497144 PMCID: PMC9052093 DOI: 10.1039/d0ra01813a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/06/2020] [Indexed: 11/30/2022] Open
Abstract
Development of efficient and stable electrodes for electrocatalytic oxygen evolution reaction (OER) is essential for energy storage and conversion applications, such as hydrogen generation from water splitting, rechargeable metal–air batteries and renewable fuel cells. Alkali metal cobalt phosphates show great potential as OER electrocatalysts. Herein, an original electrode design strategy is reported to realize an efficient OER electrocatalyst through engineering the coordination geometry of Co(ii) in KCoPO4·H2O by a facile dehydration process. Experimental result indicated that the dehydration treatment is accompanied by a structural transformation from orthorhombic KCoPO4·H2O to hexagonal KCoPO4, involving a concomitant coordination geometry evolution of Co(ii) from octahedral to tetrahedral configuration. More significantly, the local structural evolution leads to an advantageous electronic effect, i.e. increased Co–O covalency, resulting in an enhanced intrinsic OER activity. To be specific, the as-produced KCoPO4 can deliver a current density of 10 mA cm−2 at a low overpotential of 319 mV with a small Tafel slope of 61.8 mV dec−1 in alkaline electrolyte. Thus, this present research provides a new way of developing alkali metal transition-metal phosphates for efficient and stable electrocatalytic oxygen evolution reaction. Coordination environment evolution of potassium cobalt phosphate towards enhanced electrocatalytic oxygen evolution reaction.![]()
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Affiliation(s)
- Quande Che
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
| | - Xiaobin Xie
- School of Materials Science and Engineering
- Wuhan University of Technology
- Wuhan 430070
- P. R. China
| | - Qian Ma
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
| | - Junpeng Wang
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
| | - Yuanna Zhu
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
| | - Ruixia Shi
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
| | - Ping Yang
- School of Materials Science and Engineering
- University of Jinan
- Jinan 250022
- P. R. China
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4
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Bravo-Suárez JJ, Srinivasan PD. Design characteristics of in situ and operando ultraviolet-visible and vibrational spectroscopic reaction cells for heterogeneous catalysis. CATALYSIS REVIEWS 2017. [DOI: 10.1080/01614940.2017.1360071] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Juan J. Bravo-Suárez
- Department of Chemical & Petroleum Engineering, The University of Kansas, Lawrence, Kansas, USA
- Center for Environmentally Beneficial Catalysis, The University of Kansas, Lawrence, Kansas, USA
| | - Priya D. Srinivasan
- Department of Chemical & Petroleum Engineering, The University of Kansas, Lawrence, Kansas, USA
- Center for Environmentally Beneficial Catalysis, The University of Kansas, Lawrence, Kansas, USA
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5
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Simmance K, van Beek W, Sankar G. Time resolved in situ X-ray diffraction study of crystallisation processes of large pore nanoporous aluminophosphate materials. Faraday Discuss 2015; 177:237-47. [PMID: 25683746 DOI: 10.1039/c4fd00179f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Time resolved high-resolution X-ray powder diffraction was utilized to obtain detailed changes in the crystal structure parameters during the hydrothermal crystallization process of the nanoporous aluminophosphate AlPO-5 (AFI) structure. This in situ study offered not only the influence of metal ions on the onset of crystallization and estimation of the activation energy of the process, but also allowed us to determine in detail the changes in lattice parameters during this process. More importantly the time-resolved study clearly showed the lattice expansion in the divalent metal ions substituted system right from the on-set of crystallization process, compared to the one without any dopant ions, which suggest that an amorphous or poorly crystalline network is formed prior to crystallization that contains the large divalent ions (compared to Al(iii), the substituting element), which is in agreement with the combined XAS/XRD study reported earlier. A mechanism based on this and the earlier study is suggested.
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Affiliation(s)
- Kerry Simmance
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
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6
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Guo X, Wang L, Yue S, Wang D, Lu Y, Song Y, He J. Single-Crystalline Organic–Inorganic Layered Cobalt Hydroxide Nanofibers: Facile Synthesis, Characterization, and Reversible Water-Induced Structural Conversion. Inorg Chem 2014; 53:12841-7. [DOI: 10.1021/ic501812n] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Xiaodi Guo
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Lianying Wang
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Shuang Yue
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Dongyang Wang
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Yanluo Lu
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Yufei Song
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
| | - Jing He
- State Key Laboratory of Chemical
Resource Engineering, Beijing University of Chemical Technology, Box 98, 15 Beisanhuan Dong Lu, Beijing 100029, P. R. China
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8
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Patlolla A, Carino EV, Ehrlich SN, Stavitski E, Frenkel AI. Application of Operando XAS, XRD, and Raman Spectroscopy for Phase Speciation in Water Gas Shift Reaction Catalysts. ACS Catal 2012. [DOI: 10.1021/cs300414c] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. Patlolla
- Department of Physics, Yeshiva University, New York, New York 10016, United
States
| | - E. V. Carino
- Department of Chemical
Engineering, University of Delaware, Newark,
Delaware 19716, United
States
| | - S. N. Ehrlich
- National Synchrotron
Light Source, Brookhaven National Laboratory, Upton, New York 11973,
United States
| | - E. Stavitski
- National Synchrotron
Light Source, Brookhaven National Laboratory, Upton, New York 11973,
United States
| | - A. I. Frenkel
- Department of Physics, Yeshiva University, New York, New York 10016, United
States
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9
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Samadi-Maybodi A, Nejad-Darzi SKH, Tafazzoli M. 27Al and 31P NMR Investigations of Soluble Aluminophosphate Species in Alcohol–Water Mixtures. J SOLUTION CHEM 2012. [DOI: 10.1007/s10953-012-9839-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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10
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Aerts A, Kirschhock CEA, Martens JA. Methods for in situ spectroscopic probing of the synthesis of a zeolite. Chem Soc Rev 2010; 39:4626-42. [PMID: 20949188 DOI: 10.1039/b919704b] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Unraveling the crystallization mechanism of zeolites remains an increasingly important challenge in chemistry. During the last decade, in situ spectroscopic methods have provided an unprecedented level of detail of the underlying molecular mechanisms and their kinetics. Magnetic resonance, vibrational and X-ray absorption techniques have emerged as principal tools for the in situ observation of crystallization. In this tutorial review, we discuss how these in situ methods have contributed to our understanding of the complex and diverse molecular processes that govern zeolite crystallization.
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Affiliation(s)
- Alexander Aerts
- Centre for Surface Chemistry and Catalysis, K.U. Leuven, Heverlee, Belgium
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11
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Brückner A. In situ electron paramagnetic resonance: a unique tool for analyzing structure-reactivity relationships in heterogeneous catalysis. Chem Soc Rev 2010; 39:4673-84. [PMID: 20886170 DOI: 10.1039/b919541f] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electron Paramagnetic Resonance (EPR) offers widespread opportunities for monitoring catalytically relevant species that contain unpaired electrons under conditions close to those of heterogeneous catalytic gas and liquid phase reactions. In this tutorial review, after introducing basic theoretical and experimental principles of the technique, selected examples of typical applications are discussed that comprise (1) transition metal ions in paramagnetic valence states such as vanadium, (2) radical anions such as O˙(-) formed on oxide surfaces and (3) electrons in ferromagnetic particles such as nickel as well as in conduction bands of organic conductors such as polyaniline.
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Affiliation(s)
- Angelika Brückner
- Leibniz-Institut für Katalyse, Albert-Einstein-Str., 29a, D-18059 Rostock, Germany.
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12
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Fan F, Feng Z, Li C. UV Raman spectroscopic studies on active sites and synthesis mechanisms of transition metal-containing microporous and mesoporous materials. Acc Chem Res 2010; 43:378-87. [PMID: 20028121 DOI: 10.1021/ar900210g] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Microporous and mesoporous materials are widely used as catalysts and catalyst supports. Although the incorporation of transition metal ions into the framework of these materials (by isomorphous substitution of Al and Si) is an effective means of creating novel catalytic activity, the characterization of the transition metal species within these materials is difficult. Both the low concentration of the highly dispersed transition metal and the coexistence of extraframework transition metal species present clear challenges. Moreover, the synthetic mechanisms that operate under the highly inhomogeneous conditions of hydrothermal synthesis are far from well understood. A useful technique for addressing these challenges is UV Raman spectroscopy, which is a powerful technique for catalyst characterization and particularly for transition metal-containing microporous and mesoporous materials. Conventional Raman spectroscopy, using visible and IR wavelengths, often fails to provide the information needed for proper characterization as a result of fluorescence interference. But shifting the excitation source to the UV range addresses this difficulty: interference from fluorescence (which typically occurs at 300-700 nm or greater) is greatly diminished. Moreover, signal intensity is enhanced because Raman intensity is proportional to the fourth power of the scattered light frequency. In this Account, we review recent advances in UV Raman spectroscopic characterization of (i) highly dispersed transition metal oxides on supports, (ii) transition metal ions in the framework of microporous and mesoporous materials, and (iii) the synthetic mechanisms involved in making microporous materials. By taking advantage of the strong UV resonance Raman effect, researchers have made tremendous progress in the identification of isolated transition metal ions incorporated in the framework of microporous and mesoporous materials such as TS-1, Ti-MCM-41, Fe-ZSM-5, and Fe-SBA-15. The synthetic mechanisms involved in creating microporous materials (such as Fe-ZSM-5 and zeolite X) have been investigated with resonance and in situ UV Raman spectroscopy. The precursors and intermediates evolved in the synthesis solution and gels can be sensitively detected and followed during the course of zeolite synthesis. This work has resulted in a greater understanding of the structure of transition metal-containing microporous and mesoporous materials, providing a basis for the rational design and synthesis of microporous and mesoporous catalysts.
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Affiliation(s)
- Fengtao Fan
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics
- Graduate University
| | - Zhaochi Feng
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics
| | - Can Li
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics
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13
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O'Brien MG, Beale AM, Weckhuysen BM. The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids. Chem Soc Rev 2010; 39:4767-82. [DOI: 10.1039/c0cs00088d] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Simmance K, Sankar G, Bell RG, Prestipino C, Beek WV. Tracking the formation of cobalt substituted ALPO-5 using simultaneous in situ X-ray diffraction and X-ray absorption spectroscopy techniques. Phys Chem Chem Phys 2010; 12:559-62. [DOI: 10.1039/b920245e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Fan F, Feng Z, Sun K, Guo M, Guo Q, Song Y, Li W, Li C. In Situ UV Raman Spectroscopic Study on the Synthesis Mechanism of AlPO-5. Angew Chem Int Ed Engl 2009; 48:8743-7. [DOI: 10.1002/anie.200903601] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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16
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Fan F, Feng Z, Sun K, Guo M, Guo Q, Song Y, Li W, Li C. In Situ UV Raman Spectroscopic Study on the Synthesis Mechanism of AlPO-5. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200903601] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Samadi-Maybodi A, Nejad-Darzi SKH, Bijanzadeh H. (31)P and (27)Al NMR studies of aqueous (2-hydroxyethyl) trimethylammonium solutions containing aluminum and phosphorus. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2009; 72:382-389. [PMID: 19041278 DOI: 10.1016/j.saa.2008.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Revised: 08/25/2008] [Accepted: 10/09/2008] [Indexed: 05/27/2023]
Abstract
Phosphorus-31 and aluminum-27 nuclear magnetic resonance techniques have been used to characterize the distribution of soluble aluminophosphate species in aqueous solutions of (2-hydroxyethyl) trimethylammonium chloride (2-HETMACl), phosphoric acid, and aluminum sulfate. Soluble aluminophosphate cations obtain from reactions of hexaaqua aluminum cations [A1(H(2)O)(6)](3+), with phosphate ligands (i.e., H(3)PO(4), H(2)PO(4)(-), and acid dimers H(6)P(2)O(8) and H(5)P(2)O(7)(-)). (31)P NMR and (27)Al NMR spectroscopies are very powerful techniques for characterization of the species present in the solution. A number of solutions containing different mole ratio of Al/P were prepared. The assignment of the peaks to aluminate connectivities is attempted, clarifying earlier works and producing information on the equilibrium between various aluminum-containing species (different aluminophosphate complexes). At least seven separated resonances were observed by (31)P NMR spectroscopy indicating presence of different complexes in aluminum phosphate solutions.
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18
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Jentoft FC. Chapter 3 Ultraviolet–Visible–Near Infrared Spectroscopy in Catalysis. ADVANCES IN CATALYSIS 2009. [DOI: 10.1016/s0360-0564(08)00003-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Dong M, Wang G, Qin Z, Wang J, Liu T, Yuan S, Jiao H. A Comparative Investigation of Co2+ and Mn2+ Incorporation into Aluminophosphates by in Situ XAS and DFT Computation. J Phys Chem A 2007; 111:1515-22. [PMID: 17269754 DOI: 10.1021/jp066408l] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The incorporation processes of Mn2+ and Co2+ into the framework of aluminophosphate molecular sieve AlPO4-5, at the onset of crystallization, were investigated by in situ synchrotron X-ray absorption spectroscopy (XAS) and density functional theory (DFT) computation. The results indicated that the syntheses of MnAPO-5 and CoAPO-5 were different in the incorporation mechanism of metal ions. For the synthesis of CoAPO-5, Co2+ transferred from an octahedral into tetrahedral structure with crystal formation, while, for MnAPO-5, the Mn2+ transition to the tetrahedral structure was much more difficult and it occurred after the appearance of long-range ordered microporous structure. The DFT computations of model intermediates involved in the synthesis process suggested that much higher transformation energy of [Mn(OP(OH)3)4]2+ than that of [Co(OP(OH)3)4]2+ was responsible for the diversity of the incorporation behaviors.
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Affiliation(s)
- Mei Dong
- State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, P. R. China
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20
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Beale AM, van der Eerden AMJ, Grandjean D, Petukhov AV, Smith AD, Weckhuysen BM. Monitoring the coordination of aluminium during microporous oxide crystallisation by in situ soft X-ray absorption spectroscopy. Chem Commun (Camb) 2006:4410-2. [PMID: 17057860 DOI: 10.1039/b610080e] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An in situ cell, which is capable of obtaining time resolved soft X-ray data (200 eV < E < 3000 eV) under hydrothermal conditions has been developed and used to study the self-assembly processes occurring during microporous aluminophosphate crystallization.
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Affiliation(s)
- Andrew M Beale
- Inorganic Chemistry and Catalysis group, Department of Chemistry, Utrecht University, Sorbonnelaan 16, 3508 TC, Utrecht, The Netherlands
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21
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Beale AM, van der Eerden AMJ, Jacques SDM, Leynaud O, O'Brien MG, Meneau F, Nikitenko S, Bras W, Weckhuysen BM. A Combined SAXS/WAXS/XAFS Setup Capable of Observing Concurrent Changes Across the Nano-to-Micrometer Size Range in Inorganic Solid Crystallization Processes. J Am Chem Soc 2006; 128:12386-7. [PMID: 16984167 DOI: 10.1021/ja062580r] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A novel combined SAXS/WAXS/XAFS setup for studying the self-assembly processes occurring during the crystallization of porous materials, such as ZnAlPO-34, is described. In a single experiment, it has been possible to obtain congruent and time-resolved information on aggregation processes in the synthesis gel, the incorporation process of Zn2+ ions in the framework, and the formation of the crystalline material.
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Affiliation(s)
- Andrew M Beale
- Inorganic Chemistry and Catalysis, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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Goldfarb D. High field ENDOR as a characterization tool for functional sites in microporous materials. Phys Chem Chem Phys 2006; 8:2325-43. [PMID: 16710481 DOI: 10.1039/b601513c] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The determination of the details of the spatial and electronic structure of functional sites (centers) in any system, be it in materials chemistry or in biology, is the first step towards understanding their function. When such sites happen to be paramagnetic in any point of their activity cycle, the tool box offered by a variety of high resolution electron paramagnetic resonance (EPR) spectroscopic techniques becomes very attractive for their characterization. This tool box has been considerably expanded by the developments in high field (HF) EPR in general, and HF electron nuclear double resonance (ENDOR), in particular. These have led to numerous new applications in the fields of biology, physics, chemistry and materials sciences. This overview focuses specifically on recent applications of pulsed HF ENDOR spectroscopy to microporous materials, such as zeotype materials, presenting the new opportunities it offers. First, a brief description of the theoretical basis required for the analysis of the HF ENDOR spectrum is given, followed by a description of the pulsed techniques used to record spectra and assign the signals, along with a brief presentation of the required instrumentation. Next, specific applications are given, including transition metal ions and complexes exchanged into zeolite cages, transition metal substitution into frameworks of zeolites, aluminophosphate molecular sieves, and silicious mesoporous materials, the interaction of NO with Lewis sites in zeolite cages and trapped S. We end with a discussion of the advantages and the shortcomings of the method and conclude with a future outlook.
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Affiliation(s)
- Daniella Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel.
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Grandjean D, Beale AM, Petukhov AV, Weckhuysen BM. Unraveling the Crystallization Mechanism of CoAPO-5 Molecular Sieves under Hydrothermal Conditions. J Am Chem Soc 2005; 127:14454-65. [PMID: 16218641 DOI: 10.1021/ja054014m] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hydrothermal crystallization of CoAPO-5 molecular sieves has been studied using time-resolved in-situ SAXS/WAXS, UV-vis, Raman, and XAS. Data collected during heating to 180 degrees C allowed the observation of different steps occurring during the transformation of the amorphous gel into a crystalline material from a macroscopic and atomic perspective. Raman spectroscopy detected the initial formation of Al-O-P bonds, whereas SAXS showed that these gel particles had a broad size distribution ranging from ca. 7 to 20 nm before crystallization began. WAXS showed that this crystallization was sharp and occurred at around 160 degrees C. Analysis of the crystallization kinetics suggested a one-dimensional growth process. XAS showed that Co(2+) transformed via a two-stage process during heating involving (i) a gradual transformation of octahedral coordination into tetrahedral coordination before the appearance of Bragg peaks corresponding to AFI, suggesting progressive incorporation of Co(2+) into the poorly ordered Al-O-P network up to ca. 150 degrees C, and (ii) a rapid transformation of remaining octahedral Co(2+) at the onset of crystallization. Co(2+) was observed to retard crystallization of AFI but provided valuable information regarding the synthesis process by acting as an internal probe. A three-stage, one-dimensional crystallization mechanism is proposed: (i) an initial reaction between aluminum and phosphate units forming a primary amorphous phase, (ii) progressive condensation of linear Al-O-P chains forming a poorly ordered structure separated by template molecules up to ca. 155 degrees C, and (iii) rapid internal reorganization of the aluminophosphate network leading to crystallization of the AFI crystal structure.
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Affiliation(s)
- Didier Grandjean
- Department of Inorganic Chemistry and Catalysis, Debye Institute, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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Bergwerff JA, Visser T, Leliveld BRG, Rossenaar BD, de Jong KP, Weckhuysen BM. Envisaging the Physicochemical Processes during the Preparation of Supported Catalysts: Raman Microscopy on the Impregnation of Mo onto Al2O3 Extrudates. J Am Chem Soc 2004; 126:14548-56. [PMID: 15521775 DOI: 10.1021/ja040107c] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Raman microscopy has been applied to study the preparation of shaped Mo/Al(2)O(3) catalysts. The speciation of different Mo complexes over gamma-Al(2)O(3) support bodies was followed in time after pore volume impregnation with aqueous solutions containing different Mo complexes. The addition of NO(3-) to the impregnation solutions allows for a quantitative Raman analysis of the distribution of different complexes over the catalyst bodies as this ion can be used as an internal standard. After impregnation with an acidic ammonium heptamolybdate (AHM) solution, the strong interaction between Mo(7)O(24)(6-) and Al(2)O(3) results in slow transport of this complex through the support and extensive formation of Al(OH)(6)Mo(6)O(18)(3-) near the outer surface of the support bodies. This may be prevented by decreasing the interaction between Mo and Al(2)O(3). In this way, transport is facilitated and a homogeneous distribution of Mo is obtained on a reasonable time scale. A decrease in interaction between Mo and Al(2)O(3) can be achieved by using alkaline impregnation solutions or by the addition of complexing agents, such as citrate and phosphate, to the impregnation solution. In general, time-resolved in situ Raman microscopy can be a valuable tool to study the physicochemical processes during the preparation of supported catalysts.
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Affiliation(s)
- Jaap A Bergwerff
- Department of Inorganic Chemistry and Catalysis, Debye Institute, Utrecht University, Sorbonnelaan 16 3508 TB Utrecht, The Netherlands
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Hartmann M, Kevan L. Substitution of transition metal ions into aluminophosphates and silicoaluminophosphates: characterization and relation to catalysis. RESEARCH ON CHEMICAL INTERMEDIATES 2002. [DOI: 10.1163/15685670260469357] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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