Investigation of methanol conversion over high-Si beta zeolites and the reaction mechanism of their high propene selectivity
11 Dec 2017-Catalysis Science & Technology (The Royal Society of Chemistry)-Vol. 7, Iss: 24, pp 5882-5892
TL;DR: In this paper, a large pore high-Si beta zeolites (Si/Al = 136 to 340) were synthesized by a HF-assisted method, and their catalytic performance for the conversion of methanol to propene was explored.
About: This article is published in Catalysis Science & Technology.The article was published on 2017-12-11. It has received 27 citations till now. The article focuses on the topics: Propene & Catalysis.
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TL;DR: Recent progress in MTO catalyst development is summarized, focusing on the advances in the optimization of SAPO-34 catalysts, together with the development efforts on catalysts with preferential ethylene or propylene selectivity.
Abstract: Methanol conversion to olefins, as an important reaction in C1 chemistry, provides an alternative platform for producing basic chemicals from nonpetroleum resources such as natural gas and coal. Methanol-to-olefin (MTO) catalysis is one of the critical constraints for the process development, determining the reactor design, and the profitability of the process. After the construction and commissioning of the world's first MTO plant by Dalian Institute of Chemical Physics, based on high-efficiency catalyst and fluidization technology in 2010, more attention has been attracted for a deep understanding of the reaction mechanism and catalysis principle, which has led to the continuous development of catalysts and processes. Herein, the recent progress in MTO catalyst development is summarized, focusing on the advances in the optimization of SAPO-34 catalysts, together with the development efforts on catalysts with preferential ethylene or propylene selectivity.
174 citations
TL;DR: It is shown that formaldehyde is present during MTO with an average concentration of ~0.2 C% across the ZSM-5 catalyst bed up to a MeOH conversion of 70%.
Abstract: Formaldehyde is an important intermediate product in the catalytic conversion of methanol to olefins (MTO). Here we show that formaldehyde is present during MTO with an average concentration of ~0.2 C% across the ZSM-5 catalyst bed up to a MeOH conversion of 70%. It condenses with acetic acid or methyl acetate, the carbonylation product of MeOH and DME, into unsaturated carboxylate or carboxylic acid, which decarboxylates into the first olefin. By tracing its reaction pathways of 13C-labeled formaldehyde, it is shown that formaldehyde reacts with alkenes via Prins reaction into dienes and finally to aromatics. Because its rate is one order of magnitude higher than that of hydrogen transfer between alkenes on ZSM-5, the Prins reaction is concluded to be the major reaction route from formaldehyde to produce dienes and aromatics. In consequence, formaldehyde increases the yield of ethene by enhancing the contribution of aromatic cycle. The recognition of the importance of HCHO in methanol to olefins (MTO) makes it imperative to quantify its concentration in the reaction and distribution over the catalyst bed. Here the authors quantify the concentration level of HCHO and its distribution along the catalyst bed in MTO, and explores its role in methanol conversion.
107 citations
TL;DR: In this article, a comprehensive analysis of active sites in zeolite frameworks is presented, focusing on the active sites generated by the Al incorporation in the framework and the inclusion of other heteroatoms.
Abstract: The exceptional catalytic performance of zeolites is due to the presence of active sites in a shape-selective environment, i.e., in micropores with molecular dimensions. The present review provides a comprehensive analysis of active sites in zeolite frameworks. It is focused on the active sites generated by the Al incorporation in the framework. The inclusion of other heteroatoms in the zeolite framework is also addressed. After the introduction of zeolite-type materials and a discussion of the structure-properties relationship in zeolites the central part of the review is devoted to i) the analytical methods and their complementarity for the evaluation of the number, strength, and position of active sites and ii) the in situ and post-synthesis methods of acid sites assessment and control. The data presented herein provide guidelines for making zeolite materials by design in terms of acidity.
63 citations
TL;DR: In this paper, the authors investigated the initiation mechanism of methanol-to-olefins process for different zeotype materials, H-SSZ-13, HZSM-5, HBEA and H-SAPO-34 using density functional theory.
Abstract: In this contribution, we investigate the initiation mechanism of the methanol-to-olefins process for the different zeotype materials, H-SSZ-13, H-ZSM-5, H-BEA and H-SAPO-34 using density functional theory. While the energetics differ between these materials, variations are systematic so that the relative ordering of the barriers remains the same. We hence predict that the initiation mechanism follows an identical path in all materials with similar rate-limiting steps. We show that the observed trends that have been found for the reaction barriers can be explained by differences in acidity and van-der-Waals interactions of the materials.
42 citations
TL;DR: In this article, the performance of a ZSM-11 zeolite catalyst in the conversion of methanol to olefins (MTO) is closely related to the location of aluminum (Al) in the lattice sites.
41 citations
References
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TL;DR: In this paper, a brief summary of the key issues for the methanol-to-olefins (MTO) reaction is given, including studies on the reaction mechanism, molecular sieve synthesis and crystallization mechanism, catalyst and its manufacturing scale-up, reactor selection and reactor scaleup, process demonstration, and commercialization.
Abstract: The methanol-to-olefins (MTO) reaction is an interesting and important reaction for both fundamental research and industrial application. The Dalian Institute of Chemical Physics (DICP) has developed a MTO technology that led to the successful construction and operation of the world’s first coal to olefin plant in 2010. This historical perspective gives a brief summary on the key issues for the process development, including studies on the reaction mechanism, molecular sieve synthesis and crystallization mechanism, catalyst and its manufacturing scale-up, reactor selection and reactor scale-up, process demonstration, and commercialization. Further challenges on the fundamental research and the directions for future catalyst improvement are also suggested.
1,174 citations
TL;DR: In this article, the reaction mechanism with respect to both catalyst deactivation and product formation in the conversion of methanol to hydrocarbons over zeolite H-ZSM-5 was examined.
848 citations
TL;DR: Using other microporous catalysts that are selective for light olefins, methanol-to-olefin (MTO) catalysis may soon become central to the conversion of natural gas to polyolefins.
Abstract: The process of converting methanol to hydrocarbons on the aluminosilicate zeolite HZSM-5 was originally developed as a route from natural gas to synthetic gasoline. Using other microporous catalysts that are selective for light olefins, methanol-to-olefin (MTO) catalysis may soon become central to the conversion of natural gas to polyolefins. The mechanism of methanol conversion proved to be an intellectually challenging problem; 25 years of fundamental study produced at least 20 distinct mechanisms, but most did not account for either the primary products or a kinetic induction period. Recent experimental and theoretical work has firmly established that methanol and dimethyl ether react on cyclic organic species contained in the cages or channels of the inorganic host. These organic reaction centers act as scaffolds for the assembly of light olefins so as to avoid the high high-energy intermediates required by all “direct” mechanisms. The rate of formation of the initial reaction centers, and hence the d...
844 citations
TL;DR: In this paper, the authors have shown that the combined use of fast magic-angle spinning and bidimensional multiple-quantum (MQ) spectroscopy can refocus these anisotropies.
Abstract: Whereas solid state isotropic spectra can be obtained from spin-'/2 nuclei by fast magic-angle spinning (MAS), this methodology fails when applied on half-integer quadrupoles due to the presence of non-negligible secondorder anisotropic effects. Very recently, however, we have shown that the combined use of MAS and bidimensional multiple-quantum (MQ) spectroscopy can refocus these anisotropies; the present paper discusses theoretical and experimental aspects of this novel MQMAS methodology and illustrates its application on a series of sodium salts. It is shown that even under fixed magnetic field operation, a simple model-free inspection of the peaks in a bidimensional MQMAS NMR spectrum can separate the contributions of isotropic chemical and isotropic quadrupolar shifts for different chemical sites. Moreover the anisotropic line shapes that can be resolved from these spectra are almost unaffected by excitation distortions and can thus be used to discern the values of a site's quadrupolar coupling constant and asymmetry parameter. The conditions that maximize the MQMAS signal-to-noise ratio for a ~pin-~/z are then explored with the aid of a simple analytical model, which can also be used to explain the absence of distortions in the anisotropic line shapes. The MQMAS method thus optimized was applied to the high-resolution 23Na NMR analysis of the multi-site ionic compounds NazTeO3, Na2S03, Na3P5010, and Na2HP04; extensions of the MQMAS NMR methodology to the quantitative analysis of inequivalent sites are also discussed and demonstrated.
809 citations
TL;DR: In this paper, 13C-Methanol and 12C ethene were co-reacted over SAPO-34 in a flow system at 400°C using argon as a carrier (diluent) gas.
597 citations