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Chen H, Wang B, Zhang B, Chen J, Gui J, Shi X, Yan W, Li J, Li L. Deep removal of trace C 2H 2 and CO 2 from C 2H 4 by using customized potassium-exchange mordenite. Chem Sci 2023; 14:7068-7075. [PMID: 37389266 PMCID: PMC10306095 DOI: 10.1039/d3sc02147e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 05/26/2023] [Indexed: 07/01/2023] Open
Abstract
Adsorptive separation using porous materials is a promising approach for separating alkynes/olefins due to its energy efficiency, while the deep removal of trace amounts of C2H2 and CO2 from C2H4 is still very challenging for a commercial adsorbent. Herein, we report a low-cost inorganic metal cation-mediated mordenite (MOR) zeolite with the specific location and distribution of K+ cations acting as a goalkeeper for accurately controlling diffusion channels, as evidence of the experimental and simulation results. Deep purification of C2H4 from ternary CO2/C2H2/C2H4 mixtures was first realized on K-MOR with exceptional results, achieving a remarkable polymer-grade C2H4 productivity of 1742 L kg-1 for the CO2/C2H2/C2H4 mixture. Our approach which only involves adjusting the equilibrium ions, is both promising and cost-effective, and opens up new possibilities for the use of zeolites in the industrial light hydrocarbon adsorption and purification process.
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Affiliation(s)
- Hongwei Chen
- College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 China
| | - Binyu Wang
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University 2699 Qianjin Street Changchun 130012 China
| | - Bin Zhang
- College of Chemistry, Taiyuan University of Technology Taiyuan 030024 China
| | - Jiuhong Chen
- College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 China
| | - Jiabao Gui
- College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 China
| | - Xiufeng Shi
- College of Chemistry, Taiyuan University of Technology Taiyuan 030024 China
| | - Wenfu Yan
- State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University 2699 Qianjin Street Changchun 130012 China
| | - Jinping Li
- College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 China
| | - Libo Li
- College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 China
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Al-Nahari S, Dib E, Cammarano C, Saint-Germes E, Massiot D, Sarou-Kanian V, Alonso B. Impact of Mineralizing Agents on Aluminum Distribution and Acidity of ZSM-5 Zeolites. Angew Chem Int Ed Engl 2023; 62:e202217992. [PMID: 36541742 PMCID: PMC10108163 DOI: 10.1002/anie.202217992] [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: 12/06/2022] [Revised: 12/20/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022]
Abstract
Intensive research on improving the catalytic properties of zeolites is focused on modulating their acidity and the distribution of associated Al sites. Herein, by studying a series of ZSM-5 zeolites over a broad range of Al content, we demonstrate how the nature of the mineralizing agent (F- or OH- ) used in hydrothermal syntheses directly impacts Al sites distribution. The proportions of Al sites, probed by 27 Al NMR, depend on the Si/Al ratio for F- , but remain identical for OH- (from Si/Al=30 to 760). This leads to contrasting variations in weak and strong acidities. Such opposite effect of mineralizers is explained by the spatial location of negative charges and the resulting balance between short- and long-range electrostatic interactions. This understanding paves the way for additional and simple opportunities to control zeolites' acidity.
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Affiliation(s)
- Shadi Al-Nahari
- ICGM, Université de Montpellier, CNRS, ENSCM, 34293, Montpellier cedex 5, France
| | - Eddy Dib
- LCS, Normandie Univ, ENSICAEN, UNICAEN, CNRS, 14000, Caen, France
| | - Claudia Cammarano
- ICGM, Université de Montpellier, CNRS, ENSCM, 34293, Montpellier cedex 5, France
| | - Etienne Saint-Germes
- ICGM, Université de Montpellier, CNRS, ENSCM, 34293, Montpellier cedex 5, France
| | | | | | - Bruno Alonso
- ICGM, Université de Montpellier, CNRS, ENSCM, 34293, Montpellier cedex 5, France
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Insight into Crystallization Features of MOR Zeolite Synthesized via Ice-Templating Method. Catalysts 2022. [DOI: 10.3390/catal12030301] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Hydrothermal, solvothermal or ionothermal routes are usually employed for the synthesis of zeolite, which is often accompanied by a high energy consumption, high cost and low efficiency. We have developed a novel route for the rapid and high yield synthesis of mordenite (MOR) zeolite via an ice-templating method. In comparison with traditional hydrothermal synthesis, not only the high yield, but also the superior crystallinity, large reduction in water level and reaction pressure, simple device and conventional silica sources by this route can have great potential for the commercial production of pure MOR zeolite. Moreover, the changed bonding environment of silicon atoms in MOR zeolite, that is, a relative decrease in the tetrahedrally coordinated Si–O–Si bond, and accordingly, an increase in the T–OH (T = Si, Al) groups and Si–O–Al sites, remarkably enhances its acid strength.
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Cao K, Fan D, Zeng S, Fan B, Chen N, Gao M, Zhu D, Wang L, Tian P, Liu Z. Organic-free synthesis of MOR nanoassemblies with excellent DME carbonylation performance. CHINESE JOURNAL OF CATALYSIS 2021. [DOI: 10.1016/s1872-2067(20)63777-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Simancas R, Chokkalingam A, Elangovan SP, Liu Z, Sano T, Iyoki K, Wakihara T, Okubo T. Recent progress in the improvement of hydrothermal stability of zeolites. Chem Sci 2021; 12:7677-7695. [PMID: 34168820 PMCID: PMC8188473 DOI: 10.1039/d1sc01179k] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Accepted: 04/27/2021] [Indexed: 01/14/2023] Open
Abstract
Zeolites have been successfully employed in many catalytic reactions of industrial relevance. The severe conditions required in some processes, where high temperatures are frequently combined with the presence of steam, highlight the need of considering the evolution of the catalyst structure during the reaction. This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.
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Affiliation(s)
- Raquel Simancas
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
| | - Anand Chokkalingam
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
| | - Shanmugam P Elangovan
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
| | - Zhendong Liu
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
- Institute of Engineering Innovation, The University of Tokyo 2-11-16 Yayoi, Bunkyo-ku Tokyo 113-8656 Japan
| | - Tsuneji Sano
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
| | - Kenta Iyoki
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
| | - Toru Wakihara
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
- Institute of Engineering Innovation, The University of Tokyo 2-11-16 Yayoi, Bunkyo-ku Tokyo 113-8656 Japan
| | - Tatsuya Okubo
- Department of Chemical System Engineering, The University of Tokyo 7-3-1 Hongo, Bunkyo-ku Tokyo 13-8656 Japan
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Shelyapina MG, Yocupicio-Gaxiola RI, Zhelezniak IV, Chislov MV, Antúnez-García J, Murrieta-Rico FN, Galván DH, Petranovskii V, Fuentes-Moyado S. Local Structures of Two-Dimensional Zeolites-Mordenite and ZSM-5-Probed by Multinuclear NMR. Molecules 2020; 25:E4678. [PMID: 33066351 PMCID: PMC7587376 DOI: 10.3390/molecules25204678] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 10/10/2020] [Accepted: 10/13/2020] [Indexed: 11/19/2022] Open
Abstract
Mesostructured pillared zeolite materials in the form of lamellar phases with a crystal structure of mordenite (MOR) and ZSM-5 (MFI) were grown using CTAB as an agent that creates mesopores, in a one-pot synthesis; then into the CTAB layers separating the 2D zeolite plates were introduced by diffusion the TEOS molecules which were further hydrolyzed, and finally the material was annealed to remove the organic phase, leaving the 2D zeolite plates separated by pillars of silicon dioxide. To monitor the successive structural changes and the state of the atoms of the zeolite framework and organic compounds at all the steps of the synthesis of pillared MOR and MFI zeolites, the nuclear magnetic resonance method (NMR) with magic angle spinning (MAS) was applied. The 27Al and 29Si MAS NMR spectra confirm the regularity of the zeolite frameworks of the as synthetized materials. Analysis of the 1H and 13C MAS NMR spectra and an experiment with variable contact time evidence a strong interaction between the charged "heads" -[N(CH3)3]+ of CTAB and the zeolite framework at the place of [AlO4]- location. According to 27Al and 29Si MAS NMR the evacuation of organic cations leads to a partial but not critical collapse of the local zeolite structure.
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Affiliation(s)
- Marina G. Shelyapina
- Department of Nuclear Physics Research Methods, Saint-Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia; (I.V.Z.); (M.V.C.)
| | - Rosario I. Yocupicio-Gaxiola
- Center for Scientific Research and Higher Education at Ensenada (CICESE), Ensenada, Baja California 22860, Mexico;
| | - Iuliia V. Zhelezniak
- Department of Nuclear Physics Research Methods, Saint-Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia; (I.V.Z.); (M.V.C.)
| | - Mikhail V. Chislov
- Department of Nuclear Physics Research Methods, Saint-Petersburg State University, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia; (I.V.Z.); (M.V.C.)
| | - Joel Antúnez-García
- Center for Nanoscience and Nanotechnology, National Autonomous University of Mexico (CNyN, UNAM), Ensenada, Baja California 22860, Mexico; (J.A.-G.); (F.N.M.-R.); (D.H.G.); (V.P.); (S.F.-M.)
| | - Fabian N. Murrieta-Rico
- Center for Nanoscience and Nanotechnology, National Autonomous University of Mexico (CNyN, UNAM), Ensenada, Baja California 22860, Mexico; (J.A.-G.); (F.N.M.-R.); (D.H.G.); (V.P.); (S.F.-M.)
| | - Donald Homero Galván
- Center for Nanoscience and Nanotechnology, National Autonomous University of Mexico (CNyN, UNAM), Ensenada, Baja California 22860, Mexico; (J.A.-G.); (F.N.M.-R.); (D.H.G.); (V.P.); (S.F.-M.)
| | - Vitalii Petranovskii
- Center for Nanoscience and Nanotechnology, National Autonomous University of Mexico (CNyN, UNAM), Ensenada, Baja California 22860, Mexico; (J.A.-G.); (F.N.M.-R.); (D.H.G.); (V.P.); (S.F.-M.)
| | - Sergio Fuentes-Moyado
- Center for Nanoscience and Nanotechnology, National Autonomous University of Mexico (CNyN, UNAM), Ensenada, Baja California 22860, Mexico; (J.A.-G.); (F.N.M.-R.); (D.H.G.); (V.P.); (S.F.-M.)
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Chen M, Sun Q, Yang X, Yu J. A dual-template method for the synthesis of bimetallic CuNi/SSZ-13 zeolite catalysts for NH3-SCR reaction. INORG CHEM COMMUN 2019. [DOI: 10.1016/j.inoche.2019.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Snyder BER, Vanelderen P, Schoonheydt RA, Sels BF, Solomon EI. Second-Sphere Effects on Methane Hydroxylation in Cu-Zeolites. J Am Chem Soc 2018; 140:9236-9243. [DOI: 10.1021/jacs.8b05320] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Benjamin E. R. Snyder
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Pieter Vanelderen
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
- Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven − University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Robert A. Schoonheydt
- Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven − University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Bert F. Sels
- Department of Microbial and Molecular Systems, Centre for Surface Chemistry and Catalysis, KU Leuven − University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
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Gao S, Zhu X, Li X, Wang Y, Zhang Y, Xie S, An J, Chen F, Liu S, Xu L. Thermodynamic study of direct amination of isobutylene to tert-butylamine. CHINESE JOURNAL OF CATALYSIS 2017. [DOI: 10.1016/s1872-2067(16)62550-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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10
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Moliner M, Martínez C, Corma A. Multiporige Zeolithe: Synthese und Anwendungen bei der Katalyse. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201406344] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Moliner M, Martínez C, Corma A. Multipore zeolites: synthesis and catalytic applications. Angew Chem Int Ed Engl 2015; 54:3560-79. [PMID: 25664421 DOI: 10.1002/anie.201406344] [Citation(s) in RCA: 168] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Indexed: 11/06/2022]
Abstract
In the last few years, important efforts have been made to synthesize so-called "multipore" zeolites, which contain channels of different dimensions within the same crystalline structure. This is a very attractive subject, since the presence of pores of different sizes would favor the preferential diffusion of reactants and products through those different channel systems, allowing unique catalytic activities for specific chemical processes. In this Review we describe the most attractive achievements in the rational synthesis of multipore zeolites, containing small to extra-large pores, and the improvements reported for relevant chemical processes when these multipore zeolites have been used as catalysts.
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Affiliation(s)
- Manuel Moliner
- Instituto de Tecnología Química, Universidad Politécnica de Valencia, Consejo Superior de Investigaciones Científicas (UPV-CSIC), Valencia, 46022 (Spain)
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12
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Preparation and Performance of Mordenite Zeolite Membrane Using Fluoride Route. CHINESE JOURNAL OF CATALYSIS 2013. [DOI: 10.3724/sp.j.1088.2012.20436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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13
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Dědeček J, Sobalík Z, Wichterlová B. Siting and Distribution of Framework Aluminium Atoms in Silicon-Rich Zeolites and Impact on Catalysis. CATALYSIS REVIEWS-SCIENCE AND ENGINEERING 2012. [DOI: 10.1080/01614940.2012.632662] [Citation(s) in RCA: 265] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Yasui-Hiraiwa M, Hongo T, Hayashi H, Takaishi T, Nataka S, Yamazaki A. Phase Transition and Thermal Behavior Change of Low Silica X Zeolite at [Al] = 90. CHEM LETT 2010. [DOI: 10.1246/cl.2010.1242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Li X, Kita H, Zhu H, Zhang Z, Tanaka K. Synthesis of long-term acid-stable zeolite membranes and their potential application to esterification reactions. J Memb Sci 2009. [DOI: 10.1016/j.memsci.2009.04.054] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Georgieva I, Benco L, Tunega D, Trendafilova N, Hafner J, Lischka H. Multiple adsorption of NO on cobalt-exchanged chabazite, mordenite, and ferrierite zeolites: A periodic density functional theory study. J Chem Phys 2009; 131:054101. [DOI: 10.1063/1.3182850] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
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Benco L, Bucko T, Hafner J, Toulhoat H. Periodic DFT calculations of the stability of Al/Si substitutions and extraframework Zn2+ cations in mordenite and reaction pathway for the dissociation of H2 and CH4. J Phys Chem B 2007; 109:20361-9. [PMID: 16853635 DOI: 10.1021/jp0530597] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The local stability of Al atoms replacing Si in the zeolite framework is compared for all inequivalent tetrahedral (T) sites in mordenite. For Al/Si substitutions in two T sites the stable location of the compensating extraframework Zn(2+) cation forming a Lewis acid site is determined. In the most stable Zn-MOR structures Zn(2+) is located in a small ring (5MR, 6MR) containing two Al/Si substitutions. In less stable structures the Al atoms are placed at larger distances from each other and Zn(2+) interacts with only one Al site. The simulated adsorption of H(2) and CH(4) shows that adsorption strength decreases with increasing stability of the Zn(2+) Lewis site. A higher adsorption strength is observed for Zn(2+) deposited in the 5MR than for the 6MR. The reactivity of a series of stable Zn(2+) Lewis sites is tested via the dissociative adsorption of H(2) and CH(4). The heterolytic dissociation of the adsorbed molecule on the extraframework Zn(2+) cation produces a proton and an anion. The anion binds to Zn(2+) and proton goes to the zeolite framework, restoring a Brønsted acid site. Because bonding of the anion to Zn(2+) is almost energetically equivalent for Zn(2+) in any of the extraframework positions the dissociation is governed by stabilizing bonding of the proton to the framework. Those structures which can exothermically accommodate the proton represent reaction pathways. Due to the repulsion between the proton and Zn(2+) the most favorable proton-accepting O sites are not those of the ring where Zn(2+) is deposited, but O sites close to the ring. Large differences are observed for neighboring positions in a- and b-directions and those oriented along the c-vector. Finally, among the stable Zn(2+) Lewis sites not all represent reaction pathways for dehydrogenation. For all of them the dissociation of H(2) is an exothermic process. In structures exhibiting the highest reactivity the Al/Si substitutions are placed at a large distance and the Zn(2+) cation interacts with O-atoms next to Al in the T4 site of the 5MR. This Lewis site is strong enough to break the C-H bond in the CH(4) molecule.
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Affiliation(s)
- L Benco
- Institut für Materialphysik and Center for Computational Materials Science, Universität Wien, Sensengasse 8, A-1090 Vienna, Austria.
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Niwa M, Suzuki K, Katada N, Kanougi T, Atoguchi T. Ammonia IRMS-TPD Study on the Distribution of Acid Sites in Mordenite. J Phys Chem B 2005; 109:18749-57. [PMID: 16853412 DOI: 10.1021/jp051304g] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using an IRMS-TPD (temperature programmed desorption) of ammonia, we studied the nature, strength, crystallographic location, and distribution of acid sites of mordenite. In this method, infrared spectroscopy (IR) and mass spectroscopy (MS) work together to follow the thermal behavior of adsorbed and desorbed ammonia, respectively; therefore, adsorbed species were identified, and their thermal behavior was directly connected with the desorption of ammonia during an elevation of temperature. IR-measured TPD of the NH4(+) cation was similar to MS-measured TPD, thus showing the nature of Brønsted acidity. From the behavior of OH bands, it was found that the Brønsted acid sites consisted of two kinds of OH bands at high and low wavenumbers, ascribable to OH bands situated on 12- and 8-member rings (MR) of mordenite structure, respectively. The amount and strength of these Brønsted hydroxyls were measured quantitatively based on a theoretical equation using a curve fitting method. Up to ca. 30% of the exchange degree, NH4(+) was exchanged with Na+ on the 12-MR to arrive at saturation; therefore, in this region, the Brønsted acid site was situated on the large pore of 12-MR. The NH4(+) cation was then exchanged with Na+ on 8-MR, and finally exceeded the amount on 12-MR. In the 99% NH4-mordenite, Brønsted acid sites were located predominantly on the 8-MR more than on the 12-MR. Irrespective of the NH4(+) exchange degree, the strengths deltaH of Brønsted OH were 145 and 153 kJ mol(-1) on the 12- and 8-MR, respectively; that is, the strength of Brønsted acid site on the 8-MR was larger than that on the 12-MR. A density functional theory (DFT) calculation supported the difference in the strengths of the acid sites. Catalytic cracking activity of the Brønsted acid sites on the 8-MR declined rapidly, while that on the 12-MR was remarkably kept. The difference in strength and/or steric capacity may cause such a difference in the life of a catalyst.
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Affiliation(s)
- Miki Niwa
- Department of Materials Science, Faculty of Engineering, Tottori University 4-101, Koyama-minami, Tottori, 680-8552 Japan.
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Korányi TI, Nagy JB. Distribution of Aluminum in Different Periodical Building Units of MOR and BEA Zeolites. J Phys Chem B 2005; 109:15791-7. [PMID: 16853005 DOI: 10.1021/jp051793k] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Various commercial, homemade, and dealuminated mordenites (MOR) and beta (BEA) zeolites as well as cobalt modified BEAs have been characterized by 29Si- and 27Al solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The quantitative contributions of Si(nAl) and Si(OH)x sites to the NMR signal intensities were calculated from the various Si/Al ratios and relative 29Si and 27Al NMR signal intensities assuming a special distribution of aluminum in different periodical building units of the zeolite framework. A different dealumination and silanol formation mechanism for MOR and BEA was suggested. We conclude that we are able to distinguish the Si(OH)x groups that are original defect sites or produced in a dealumination or calcination process.
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Affiliation(s)
- Tamás I Korányi
- Department of Molecular Spectroscopy, Institute of Structural Chemistry, Chemical Research Center of the Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary.
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22
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Direct synthesis of high-silica mordenite and its thermal stability. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s0167-2991(04)80806-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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