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Ma Q, Fu T, Wang Z, Li C, Wu X, Yang N, Li Z. Hollow Zeolite Nanoreactor with Double Shells for Methanol Aromatization: Explicit Recognition on Catalytic Function of Inverse Elemental Zone and Shell-Cavity. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2308502. [PMID: 38168120 DOI: 10.1002/smll.202308502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 12/04/2023] [Indexed: 01/05/2024]
Abstract
Core@shell catalyst composited of dual aluminosilicate zeolite can effectively regulate the distribution of acid sites to control hydrocarbon conversion process for the stable formation of target product. However, the diffusion restriction reduces the accessibility of inner active sites and affects synergy between core and shell. Herein, hollow ZSM-5 zeolite nanoreactor with inverse aluminum distribution and double shells are prepared and employed for methanol aromatization. It is demonstrated that the intershell cavity alleviated the steric hindrance from zeolites channel and provided more paths and pore entrance for guest molecule. Correspondingly, olefin intermediates generated from methanol over the external shell are easier to adsorb at internal acid sites for further reactions. Importantly, the diffusion of generated aromatic macromolecules to the external surface is also promoted, which slows down the formation of internal coke, and ensures the use of internal acid sites for aromatization. The aromatics selectivity of the nanoreactor remained at 8% after 154 h, while that of solid core@shell catalyst decreased to 2% after 75 h. This finding promises broader insight to improve internal active site utilization of core@shell catalyst at the diffusion level and can be great aid in the flexible design of multifunctional nanoreactors to enhance the relay efficiency.
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Affiliation(s)
- Qian Ma
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Tingjun Fu
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Zhuo Wang
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Caiyan Li
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Xueqing Wu
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Ning Yang
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
| | - Zhong Li
- State Key Laboratory of Clean and Efficient Coal Utilization, College of Chemical Engineering and Technology, Taiyuan University of Technology, Taiyuan, Shanxi, 030024, China
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2
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Chen Y, Ma X, Hack JH, Zhang S, Peng A, Dombrowski JP, Voth GA, Tokmakoff A, Kung MC, Kung HH. Molecular Tuning of Reactivity of Zeolite Protons in HZSM-5. J Am Chem Soc 2024; 146:10342-10356. [PMID: 38574341 DOI: 10.1021/jacs.3c12680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
In acidic HZSM-5 zeolite, the reactivity of a methanol molecule interacting with the zeolite proton is amenable to modification via coadsorbing a stochiometric amount of an electron density donor E to form the [(E)(CH3OH)(HZ)] complex. The rate of the methanol in this complex undergoing dehydration to dimethyl ether was determined for a series of E with proton affinity (PA) ranging from 659 kJ mol-1 for C6F6 to 825 kJ mol-1 for C4H8O and was found to follow the expression: Ln(Rate) - Ln(RateN2) = β(PA - PAN2)γ, where E = N2 is the reference and β and γ are constants. This trend is probably due to the increased stability of the solvated proton in the [(E)(CH3OH)(HZ)] complex with increasing PA. Importantly, this is also observed in steady-state flow reactions when stoichiometric quantities of E are preadsorbed on the zeolite. As demonstrated with E being D2O, the effect on methanol reactivity diminishes when E is present in excess of the [(E)(CH3OH)(HZ)] complex. It is proposed that the methanol dehydration reaction involves [(E)(CH3OH)(CH3OH)(HZ)] as the transition state, which is supported by the isotopologue distribution of the initial dimethyl ether formed when a flow of CH3OH was passed over ZSM-5 containing one CD3OH per zeolite proton. The implication of this on the mechanism of catalytic methanol dehydration on HZSM-5 is discussed.
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Affiliation(s)
- Yaxin Chen
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
| | - Xinyou Ma
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
- Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - John H Hack
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Shuhao Zhang
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
| | - Anyang Peng
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
| | - James P Dombrowski
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
| | - Gregory A Voth
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
- Chicago Center for Theoretical Chemistry, The University of Chicago, Chicago, Illinois 60637, United States
| | - Andrei Tokmakoff
- Department of Chemistry, James Franck Institute, and Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, United States
| | - Mayfair C Kung
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
| | - Harold H Kung
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208-3120, United States
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3
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Ji Y, Chen K, Han X, Bao X, Hou G. Precise Structural and Dynamical Details in Zeolites Revealed by Coupling-Edited 1H- 17O Double Resonance NMR Spectroscopy. J Am Chem Soc 2024. [PMID: 38528765 DOI: 10.1021/jacs.3c14787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
Despite the extensive industrial and research interests in zeolites, their intrinsic catalytic nature is not fully understood due to the complexity of the hydroxyl-aluminum moieties. 17O NMR would provide irreplaceable opportunities for much-needed fine structural determination given the ubiquitous presence of oxygen atoms in nearly all species; however, the low sensitivity and quadrupolar nature of oxygen-17 make its NMR spectroscopic elucidation challenging. Here, we show that state-of-the-art double resonance solid-state NMR techniques have been combined with spectral editing methods based on scalar (through-bond) and dipolar (through-space) couplings, which allowed us to address the subtle protonic structures in zeolites. Notably, the often-neglected and undesired second-order quadrupolar-dipolar cross-term interaction ("2nd-QD interaction") can actually be exploited and can help gain invaluable information. Eventually, a comprehensive set of 1H-17O/1H-27Al double resonance NMR with J-/D-coupling spectral editing techniques have been designed in this work and enabled us to reveal atomic-scale precise structural and dynamical details in zeolites including: 1) The jump rate of the bridging acid site (BAS) proton is relatively low, i.e., far less than 100 s-1 at room temperature. 2) The Al-OH groups with 1H chemical shift at 2.6-2.8 ppm, at least for nonseverely dealuminated H-ZSM-5 catalysts, exhibit a rigid bridging environment similar to that of BAS. 3) The Si-OH groups at 2.0 ppm are not hydrogen bonded and undergo fast cone-rotational motion. The results in this study predict the 2nd-QD interaction to be universal for any rigid -17O-H environment, such as those in metal oxide surfaces or biomaterials.
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Affiliation(s)
- Yi Ji
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kuizhi Chen
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Xiuwen Han
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Xinhe Bao
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
| | - Guangjin Hou
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian 116023, China
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4
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Liu Q, van Bokhoven JA. Water structures on acidic zeolites and their roles in catalysis. Chem Soc Rev 2024; 53:3065-3095. [PMID: 38369933 DOI: 10.1039/d3cs00404j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
The local reaction environment of catalytic active sites can be manipulated to modify the kinetics and thermodynamic properties of heterogeneous catalysis. Because of the unique physical-chemical nature of water, heterogeneously catalyzed reactions involving specific interactions between water molecules and active sites on catalysts exhibit distinct outcomes that are different from those performed in the absence of water. Zeolitic materials are being applied with the presence of water for heterogeneous catalytic reactions in the chemical industry and our transition to sustainable energy. Mechanistic investigation and in-depth understanding about the behaviors and the roles of water are essentially required for zeolite chemistry and catalysis. In this review, we focus on the discussions of the nature and structures of water adsorbed/stabilized on Brønsted and Lewis acidic zeolites based on experimental observations as well as theoretical calculation results. The unveiled functions of water structures in determining the catalytic efficacy of zeolite-catalyzed reactions have been overviewed and the strategies frequently developed for enhancing the stabilization of zeolite catalysts are highlighted. Recent advancement will contribute to the development of innovative catalytic reactions and the rationalization of catalytic performances in terms of activity, selectivity and stability with the presence of water vapor or in condensed aqueous phase.
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Affiliation(s)
- Qiang Liu
- Institute for Chemical and Bioengineering, ETH Zurich, Vladimir Prelog Weg 1, 8093 Zurich, Switzerland.
| | - Jeroen A van Bokhoven
- Institute for Chemical and Bioengineering, ETH Zurich, Vladimir Prelog Weg 1, 8093 Zurich, Switzerland.
- Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
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5
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Zornes A, Abdul Rahman NB, Das OR, Gomez LA, Crossley S, Resasco DE, White JL. Impact of Low-Temperature Water Exposure and Removal on Zeolite HY. J Am Chem Soc 2024; 146:1132-1143. [PMID: 38156885 DOI: 10.1021/jacs.3c12437] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
Aqueous-phase postsynthetic modifications of the industrially important Y-type zeolite are commonly used to change overall acid site concentrations, introduce stabilizing rare-earth cations, impart bifunctional character through metal cation exchange, and tailor the distribution of Brønsted and Lewis acid sites. Zeolite Y is known to undergo framework degradation in the presence of both vapor- and liquid-phase water at temperatures exceeding 100 °C, and rare-earth exchanged and stabilized HY catalysts are commonly used for fluidized catalytic cracking due to their increased hydrothermal resilience. Here, using detailed spectroscopy, crystallography, and flow-reactor experiments, we reveal unexpected decreases in Brønsted acid site (BAS) density for zeolite HY following exposure even to room-temperature liquid water. These data indicate that aqueous-phase ion-exchange procedures commonly used to modify zeolite Y are impacted by the liquid water and its removal, even when fractional heating rates and inert conditions much less severe than standard practice are used for catalyst dehydration. X-ray diffraction, thermogravimetric, and spectroscopic analyses reveal that the majority of framework degradation occurs during the removal of a strongly bound water fraction in HY, which does not form when NH4Y is immersed in liquid water and which leads to reduced acidity in HY even when dehydration conditions much milder than those typically practiced are employed. Na+-exchanged HY prepared via room-temperature aqueous dissolution demonstrates that Brønsted acid sites are lost in excess of the theoretical maximum that is possible from sodium titration. The structural impact of low-temperature aqueous-phase ion-exchange methods complicates the interpretation of subsequent data and likely explains the wide variation in reported acid site concentrations and catalytic activity of HY zeolites with high-Al content.
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Affiliation(s)
- Anya Zornes
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Nabihan B Abdul Rahman
- School of Sustainable Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Omio Rani Das
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Laura A Gomez
- School of Sustainable Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Steven Crossley
- School of Sustainable Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Daniel E Resasco
- School of Sustainable Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Jeffery L White
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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6
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Salvia WS, Zhao TY, Chatterjee P, Huang W, Perras FA. Are the Brønsted acid sites in amorphous silica-alumina bridging? Chem Commun (Camb) 2023; 59:13962-13965. [PMID: 37930239 DOI: 10.1039/d3cc04237e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2023]
Abstract
Competing models exist to explain the differences in the activity of zeolites and amorphous silica-aluminas. Some postulate that silica-alumina contains dilute zeolitic bridging acid sites, while others favor a pseudo-bridging silanol model. We employed a selective isotope labeling strategy to assess the existence of Si-O(H)-Al bonds using NMR-based distance measurements.
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Affiliation(s)
- William S Salvia
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA.
| | - Tommy Yunpu Zhao
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA.
| | - Puranjan Chatterjee
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA.
| | - Wenyu Huang
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA.
| | - Frédéric A Perras
- Department of Chemistry, Iowa State University, Ames, IA 50011, USA
- Chemical and Biological Sciences Division, Ames National Laboratory, Ames, IA 50011, USA.
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7
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Schmithorst MB, Prasad S, Moini A, Chmelka BF. Direct Detection of Paired Aluminum Heteroatoms in Chabazite Zeolite Catalysts and Their Significance for Methanol Dehydration Reactivity. J Am Chem Soc 2023; 145:18215-18220. [PMID: 37552830 DOI: 10.1021/jacs.3c05708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2023]
Abstract
The distributions of heteroatoms within zeolite frameworks have important influences on the locations of exchangeable cations, which account for the diverse adsorption and reaction properties of zeolite catalysts. In particular for aluminosilicate zeolites, paired configurations of aluminum atoms separated by one or two tetrahedrally coordinated silicon atoms are important for charge-balancing pairs of H+ cations, which are active for methanol dehydration, or divalent metal cations, such as Cu2+, which selectively catalyze the reduction of NOx, both technologically important reactions. Such paired heteroatom configurations, however, are challenging to detect and probe, due to the typically nonstoichiometric compositions and nonperiodic distributions of aluminum atoms within aluminosilicate zeolite frameworks. Nevertheless, distinct configurations of paired framework aluminum atoms are unambiguously detected and resolved in solid-state 2D 27Al-29Si and 29Si-29Si NMR spectra, which are sensitive to the local environments of covalently bonded 27Al-O-29Si and 29Si-O-29Si moieties, respectively. Specifically, two H+-chabazite zeolites with the same bulk framework aluminum contents are shown to have different types and populations of closely paired aluminum species, which correlate with higher activity for methanol dehydration. The methodologies and insights are expected to be broadly applicable to analyses of heteroatom sites, their distributions, and adsorption and reaction properties in other zeolite framework types.
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Affiliation(s)
- Michael B Schmithorst
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
| | | | - Ahmad Moini
- BASF Corporation, Iselin, New Jersey 08830, United States
| | - Bradley F Chmelka
- Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States
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8
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Wang Z, Xiao D, Chen K, Lou C, Liang L, Xu S, Hou G. Identity, Evolution, and Acidity of Partially Framework-Coordinated Al Species in Zeolites Probed by TMP 31P-NMR and FTIR. ACS Catal 2023. [DOI: 10.1021/acscatal.3c00714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
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9
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Chau HK, Nguyen QP, Jerdy AC, Bui DP, Lobban LL, Wang B, Crossley SP. Role of Water on Zeolite-Catalyzed Dehydration of Polyalcohols and EVOH Polymer. ACS Catal 2023. [DOI: 10.1021/acscatal.2c05303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Han K. Chau
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Quy P. Nguyen
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Ana Carolina Jerdy
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Dai-Phat Bui
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Lance L. Lobban
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Bin Wang
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Steven P. Crossley
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
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10
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Pham TN, Nguyen V, Nguyen-Phu H, Wang B, Crossley S. Influence of Brønsted Acid Site Proximity on Alkane Cracking in MFI Zeolites. ACS Catal 2023. [DOI: 10.1021/acscatal.2c05291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Tram N. Pham
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Vy Nguyen
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Huy Nguyen-Phu
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Bin Wang
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
| | - Steven Crossley
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, Oklahoma73019, United States
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11
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Hu M, Wang C, Chu Y, Wang Q, Li S, Xu J, Deng F. Unravelling the Reactivity of Framework Lewis Acid Sites towards Methanol Activation on H‐ZSM‐5 Zeolite with Solid‐State NMR Spectroscopy. Angew Chem Int Ed Engl 2022; 61:e202207400. [DOI: 10.1002/anie.202207400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Indexed: 11/07/2022]
Affiliation(s)
- Min Hu
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Chao Wang
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Yueying Chu
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Qiang Wang
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Shenhui Li
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Jun Xu
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Feng Deng
- National Center for Magnetic Resonance in Wuhan State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Innovation Academy for Precision Measurement Science and Technology Chinese Academy of Sciences Wuhan 430071 P. R. China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
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12
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Chen K, Zornes A, Nguyen V, Wang B, Gan Z, Crossley SP, White JL. 17O Labeling Reveals Paired Active Sites in Zeolite Catalysts. J Am Chem Soc 2022; 144:16916-16929. [PMID: 36044727 DOI: 10.1021/jacs.2c05332] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Current needs for extending zeolite catalysts beyond traditional gas-phase hydrocarbon chemistry demand detailed characterization of active site structures, distributions, and hydrothermal impacts. A broad suite of homonuclear and heteronuclear NMR correlation experiments on dehydrated H-ZSM-5 catalysts with isotopically enriched 17O frameworks reveals that at least two types of paired active sites exist, the amount of which depends on the population of fully framework-coordinated tetrahedral Al (Al(IV)-1) and partially framework-coordinated tetrahedral Al (Al(IV)-2) sites, both of which can be denoted as (SiO)4-n-Al(OH)n. The relative amounts of Al(IV)-1 and Al(IV)-2 sites, and subsequent pairing, cannot be inferred from the catalyst Si/Al ratio, but depend on synthetic and postsynthetic modifications. Correlation experiments demonstrate that, on average, acidic hydroxyl groups from Al(IV)-1/Al(IV)-2 pairs are closer to one another than those from Al(IV)-1/Al(IV)-1 pairs, as supported by computational DFT calculations. Through-bond and through-space polarization transfer experiments exploiting 17O nuclei reveal a number of different acidic hydroxyl groups in varying Si/Al catalysts, the relative amounts of which change following postsynthetic modifications. Using room-temperature isotopic exchange methods, it was determined that 17O was homogeneously incorporated into the zeolite framework, while 17O → 27Al polarization transfer experiments demonstrated that 17O incorporation does not occur for extra-framework AlnOm species. Data from samples exposed to controlled hydrolysis indicates that nearest neighbor Al pairs in the framework are more susceptible to hydrolytic attack. The data reported here suggest that Al(IV)-1/Al(IV)-2 paired sites are synergistic sites leading to increased reactivity in both low- and high-temperature reactions. No evidence was found for paired framework/nonframework sites.
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Affiliation(s)
- Kuizhi Chen
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Anya Zornes
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Vy Nguyen
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Bin Wang
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Zhehong Gan
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Steven P Crossley
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Jeffery L White
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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13
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Wang C, Han Y, Tian M, Li L, Lin J, Wang X, Zhang T. Main-Group Catalysts with Atomically Dispersed In Sites for Highly Efficient Oxidative Dehydrogenation. J Am Chem Soc 2022; 144:16855-16865. [PMID: 36006855 DOI: 10.1021/jacs.2c04926] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transition metal oxides are well-known catalysts for oxidative dehydrogenation thanks to their excellent ability to activate alkanes. However, they suffer from an inferior alkene yield due to the trade-off between the conversion and selectivity induced by more reactive alkenes than alkanes, which obscures the optimization of catalysts. Herein, we attempt to overcome this challenge by activating a selective main-group indium oxide considered to be inactive for oxidative dehydrogenation in conventional wisdom. Atomically dispersed In sites with the local structure of [InOH]2+ anchored by substituting the protons of supercages in HY are enclosed to be active centers that enable the activation of ethane with a metal-normalized turnover number of almost one magnitude higher than those of their supported In2O3 counterparts. Furthermore, the structure of isolated [InOH]2+ sites could be stabilized by in situ formed H2O from the selective oxidation of hydrogen by In2O3 nanoparticles. As a result, the as-designed main-group In catalysts exhibit 80% ethene selectivity at 80% ethane conversion, thus achieving 60% ethene yield due to active isolated [InOH]2+ sites and selective In2O3 nanoparticles, outperforming state-of-the-art transition metal oxide catalysts. This study unlocks new opportunities for the utilization of main-group elements and could pave the way toward a more rational design of catalysts for highly efficient selective oxidation catalysis.
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Affiliation(s)
- Chaojie Wang
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China.,University of Chinese Academy of Sciences, 19(A) Yuquan Road, Shijingshan District, Beijing 100049, People's Republic of China
| | - Yujia Han
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China.,University of Chinese Academy of Sciences, 19(A) Yuquan Road, Shijingshan District, Beijing 100049, People's Republic of China
| | - Ming Tian
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
| | - Lin Li
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
| | - Jian Lin
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
| | - Xiaodong Wang
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
| | - Tao Zhang
- CAS Key Laboratory of Science and Technology on Applied Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, People's Republic of China
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14
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Hu M, Wang C, Chu Y, Wang Q, Li S, Xu J, Deng F. Unravelling the Reactivity of Framework Lewis Acid Sites towards Methanol Activation on H‐ZSM‐5 Zeolite with Solid‐State NMR Spectroscopy. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202207400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Min Hu
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
| | - Chao Wang
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
| | - Yueying Chu
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
| | - Qiang Wang
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
| | - Shenhui Li
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
| | - Jun Xu
- wuhan institute of physics and mathematics state key laboratory of magnetic resonance and atomic and molecular physics West No.30 Xiao Hong Shan 430071 Wuhan CHINA
| | - Feng Deng
- Innovation Academy for Precision Measurement Science and Technology CAS: Chinese Academy of Sciences Innovation Academy for Precision Measurement Science and Technology State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics CHINA
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15
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Liang L, Ji Y, Zhao Z, Quinn CM, Han X, Bao X, Polenova T, Hou G. Accurate heteronuclear distance measurements at all magic-angle spinning frequencies in solid-state NMR spectroscopy. Chem Sci 2021; 12:11554-11564. [PMID: 34567504 PMCID: PMC8409495 DOI: 10.1039/d1sc03194e] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Accepted: 07/20/2021] [Indexed: 11/21/2022] Open
Abstract
Heteronuclear dipolar coupling is indispensable in revealing vital information related to the molecular structure and dynamics, as well as intermolecular interactions in various solid materials. Although numerous approaches have been developed to selectively reintroduce heteronuclear dipolar coupling under MAS, most of them lack universality and can only be applied to limited spin systems. Herein, we introduce a new and robust technique dubbed phase modulated rotary resonance (PMRR) for reintroducing heteronuclear dipolar couplings while suppressing all other interactions under a broad range of MAS conditions. The standard PMRR requires the radiofrequency (RF) field strength of only twice the MAS frequency, can efficiently recouple the dipolar couplings with a large scaling factor of 0.50, and is robust to experimental imperfections. Moreover, the adjustable window modification of PMRR, dubbed wPMRR, can improve its performance remarkably, making it well suited for the accurate determination of dipolar couplings in various spin systems. The robust performance of such pulse sequences has been verified theoretically and experimentally via model compounds, at different MAS frequencies. The application of the PMRR technique was demonstrated on the H-ZSM-5 zeolite, where the interaction between the Brønsted acidic hydroxyl groups of H-ZSM-5 and the absorbed trimethylphosphine oxide (TMPO) were probed, revealing the detailed configuration of super acid sites.
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Affiliation(s)
- Lixin Liang
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Yi Ji
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Zhenchao Zhao
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
| | - Caitlin M Quinn
- Department of Chemistry and Biochemistry, University of Delaware Newark Delaware 19716 USA
| | - Xiuwen Han
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
| | - Xinhe Bao
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
| | - Tatyana Polenova
- Department of Chemistry and Biochemistry, University of Delaware Newark Delaware 19716 USA
| | - Guangjin Hou
- State Key Laboratory of Catalysis, National Laboratory for Clean Energy, 2011-Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Zhongshan Road 457 Dalian 116023 China
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16
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Cheng Y, Wang Y, Li S, Shen M, Huang H, Liao M, Peng J, Ding S, Chen X, Xu W, Yang S. Mechanism on redistribution synthesis of dichlorodimethylsilane by AlCl 3/ZSM-5(3T)@γ-Al 2O 3 core-shell catalyst. J Mol Model 2021; 27:255. [PMID: 34410509 DOI: 10.1007/s00894-021-04859-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 07/28/2021] [Indexed: 11/27/2022]
Abstract
The redistribution method plays an important role in addressing the issue of organosilicon by-products in the direct synthesis of dichlorodimethylsilane, and the redistribution mechanism is still a topic of debate. The redistribution mechanism by the ZSM-5(3 T)@γ-Al2O3 core-shell catalyst and post-modified AlCl3/ZSM-5(3 T)@γ-Al2O3 catalyst was technically performed using the Density functional theory (DFT) at the level of B3LYP/6-311 + + G(3df,2pd). The results show that no. 1 active site of ZSM-5(3 T)@γ-Al2O3 core-shell structure has a significant effect on the activity of the catalyst. Indicating that the active center involved in the reaction is H provided by the Al-O-H bond, which is an obvious catalytic active center of Bronsted acid. Furthermore, the post-modified AlCl3/ZSM-5(3T)@γ-Al2O3 catalyst is in more favor of redistribution reaction comparing with the ZSM-5(3 T)@γ-Al2O3 core-shell catalyst. It ascribes to the robust Lewis site of aluminum chloride favorable modification. The redistribution synthesis mechanism of dichlorodimethylsilane on the ZSM-5(3 T)@γ-Al2O3 core-shell catalyst and post-modified AlCl3/ZSM-5(3 T)@γ-Al2O3 catalyst had been investigated by using the Density functional theory (DFT) method at the level of B3LYP/6-311 + + G(3df,2pd). The former active center was Bronsted acidic center, while the latter one was Lewis acidic center, ascribing to the Lewis site of aluminum chloride favorable modification. The catalytic activity of the post-synthesis AlCl3/ZSM-5(3 T)@γ-Al2O3 catalyst completely was consistent with experimental results.
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Affiliation(s)
- Yongbing Cheng
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Yan Wang
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Suying Li
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Mengsha Shen
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Hongkun Huang
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Mengyin Liao
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Jiaxi Peng
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Shunmin Ding
- Key Laboratory of Jiangxi Province for Environment and Energy Catalysis, College of Chemistry, Nanchang University, Nanchang, 330031, People's Republic of China
| | - Xi Chen
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China
| | - Wenyuan Xu
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China.
| | - Shaoming Yang
- School of Materials Science and Engineering, East China Jiaotong University, Nanchang, 330013, People's Republic of China.
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17
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Resasco DE, Crossley SP, Wang B, White JL. Interaction of water with zeolites: a review. CATALYSIS REVIEWS 2021. [DOI: 10.1080/01614940.2021.1948301] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Daniel E. Resasco
- University of Oklahoma, School of Chemical, Biological, and Materials Engineering, Norman, OK, USA
| | - Steven P. Crossley
- University of Oklahoma, School of Chemical, Biological, and Materials Engineering, Norman, OK, USA
| | - Bin Wang
- University of Oklahoma, School of Chemical, Biological, and Materials Engineering, Norman, OK, USA
| | - Jeffery L. White
- Oklahoma State University, School of Chemical Engineering, Stillwater, OK, USA
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18
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Developing quantitative synthesis-structure-function relations for framework aluminum arrangement effects in zeolite acid catalysis. J Catal 2021. [DOI: 10.1016/j.jcat.2021.04.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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19
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Pham TN, Nguyen V, Wang B, White JL, Crossley S. Quantifying the Influence of Water on the Mobility of Aluminum Species and Their Effects on Alkane Cracking in Zeolites. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01138] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Tram N. Pham
- School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Vy Nguyen
- School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Bin Wang
- School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Jeffery L. White
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Steven Crossley
- School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
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20
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Chen K, Gan Z, Horstmeier S, White JL. Distribution of Aluminum Species in Zeolite Catalysts: 27Al NMR of Framework, Partially-Coordinated Framework, and Non-Framework Moieties. J Am Chem Soc 2021; 143:6669-6680. [PMID: 33881305 PMCID: PMC8212420 DOI: 10.1021/jacs.1c02361] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The structure of aluminum-containing moieties in and within zeolite H-ZSM-5 catalysts is a complex function of the elemental composition of the catalyst, synthesis conditions, exposure to moisture, and thermal history. 27Al NMR data collected at field strengths ranging from 7.05 to 35.2 T, i.e., 1H Larmor frequencies from 300 to 1500 MHz, reveal that Al primarily exists as framework or partially coordinated framework species in commercially available dehydrated H-ZSM-5 catalysts with Si/Al ranging from 11.5 to 40. Quantitative direct-excitation and sensitivity-enhanced 27Al NMR techniques applied over the wide range of magnetic field strengths used in this study show that prior to significant hydrothermal exposure, detectable amounts of nonframework Al species do not exist. Two-dimensional 27Al multiple-quantum magic-angle spinning (MQMAS) along with 1H-27Al and 29Si-27Al dipolar correlation (D-HMQC) NMR experiments confirm this conclusion and show that generation of nonframework species following varying severities of hydrothermal exposure are clearly resolved from partially coordinated framework sites. The impact of hydration on the appearance and interpretation of conventional direct-excitation 27Al spectra, commonly used to assess framework and nonframework Al, is discussed. Aluminum sites in dehydrated catalysts, which are representative of typical operating conditions, are characterized by large quadrupole interactions and are best assigned by obtaining data at multiple field strengths. On the basis of the results here, an accurate initial assessment of Al sites in high-Al content MFI catalysts prior to any hydrothermal treatment can be used to guide reaction conditions, anticipate potential water impacts, and identify contributions from hydroxyl groups other than those associated with the framework bridging acid site.
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Affiliation(s)
- Kuizhi Chen
- author to whom correspondence should be addressed: ;
| | | | | | - Jeffery L. White
- School of Chemical Engineering, Oklahoma State University, Stillwater, OK 74078
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21
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Sakha MR, Soltanali S, Salari D, Rashidzadeh M, Halimitabrizi P. Synergistic effect of Fe and Ga incorporation into ZSM-5 to increase propylene production in the cracking of n-hexane utilizing a microchannel reactor. NEW J CHEM 2021. [DOI: 10.1039/d1nj01866c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Comprehensive investigation of the synergistic effect of incorporating Fe and Ga into ZSM-5 in cracking of hexane.
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Affiliation(s)
- Mohsen Rostami Sakha
- Reactor and Catalysis Research Lab., Department of Chemistry, University of Tabriz, Tabriz
- Iran
- Catalysis Technologies Development Division, Research Institute of Petroleum Industry (RIPI)
- Tehran
- Iran
| | - Saeed Soltanali
- Catalysis Technologies Development Division, Research Institute of Petroleum Industry (RIPI)
- Tehran
- Iran
| | - Darush Salari
- Reactor and Catalysis Research Lab., Department of Chemistry, University of Tabriz, Tabriz
- Iran
| | - Mehdi Rashidzadeh
- Catalysis Technologies Development Division, Research Institute of Petroleum Industry (RIPI)
- Tehran
- Iran
| | - Parya Halimitabrizi
- Reactor and Catalysis Research Lab., Department of Chemistry, University of Tabriz, Tabriz
- Iran
- Department of Chemical and Petroleum Engineering, University of Tabriz, Tabriz
- Iran
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22
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Chen K, Horstmeier S, Nguyen VT, Wang B, Crossley SP, Pham T, Gan Z, Hung I, White JL. Structure and Catalytic Characterization of a Second Framework Al(IV) Site in Zeolite Catalysts Revealed by NMR at 35.2 T. J Am Chem Soc 2020; 142:7514-7523. [PMID: 32233465 DOI: 10.1021/jacs.0c00590] [Citation(s) in RCA: 47] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ultrahigh field 27Al{1H} 2D correlation NMR experiments demonstrate that at least two framework Al(IV) sites with hydroxyl groups can exist in acidic zeolite catalysts in their dehydrated and catalytically active states. In addition to the known Al(IV) at the framework bridging acid site (BAS), a new site created by a second tetrahedral Al atom and its hydroxyl group protons in zeolite HZSM-5 is clearly resolved at 35.2 T field strengths, enabled by recently developed series-connected hybrid (SCH) magnet technology. Coupled with computational modeling, extensive 27Al MQMAS experiments at multiple field strengths, and 1H MAS NMR experiments, these data indicate that this second tetrahedrally coordinated Al site (denoted Al(IV)-2) experiences an increased chemical shift and unique quadrupolar parameters relative to the BAS in both dehydrated and hydrated states. These new experimental data, supported by computational and catalytic reaction work, indicate that the second site arises from partially bonded framework (SiO)4-n-Al(OH)n species that significantly increase catalyst reactivity in benzene hydride-transfer and n-hexane cracking reactions. Al(IV)-2 sites result either from framework crystallization defects or from incomplete postsynthetic hydrolysis of a framework Al, prior to the formation of extraframework Al. Populations of this second acidic proton site created by the Al(IV)-2 species are shown to be controlled via postsynthetic catalyst treatments, should be general to different catalyst structures, and significantly enhance catalyst reactivity in the cited probe reactions when they are present. The results herein communicate the highest magnetic field strength data on active zeolite catalyst structures to date and enable for the first time the detection of Al and H association on a dry HZSM-5 catalyst, i.e., under conditions representative of typical end-use processes.
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Affiliation(s)
- Kuizhi Chen
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Sarah Horstmeier
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Vy T Nguyen
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Bin Wang
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Steven P Crossley
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Tram Pham
- School of Chemical, Materials, and Biological Engineering, University of Oklahoma, Norman, Oklahoma 73019, United States
| | - Zhehong Gan
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Ivan Hung
- National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States
| | - Jeffery L White
- School of Chemical Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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