Synthesis and Properties of Zeolite Omega

Cole, J. F.; Kouwenhoven, Herman W.

doi:10.1021/ba-1973-0121.ch053

Cited by 26 publications

(8 citation statements)

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“…This channel system is inaccessible from the 12MR channel . It is also showed that the access to the column of gmelinite cages is very restricted due to complicated diffusion paths . It has been shown that MAZ has two non‐equivalent crystallographic sites (T1 and T2) .…”

Section: Direct Ch4 To Ch3oh Conversion Over Zeolitesmentioning

confidence: 99%

Advanced X‐ray Absorption Spectroscopy Analysis to Determine Structure‐Activity Relationships for Cu‐Zeolites in the Direct Conversion of Methane to Methanol

et al. 2020

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An industrial process for direct conversion of methane to methanol (DMTM) would revolutionize methane as feedstock for the chemical industry and it would be a cherished contribution to climate change mitigation. At the present stage, it is a rather remote perspective, but the search for the materials that would make it possible and economically viable, is very active. Cu‐exchanged zeolites have been shown to cleave the C−H bond of methane at low temperatures (≤200 °C), and has been extensively studied for the stepwise DMTM conversion over the last decades. The determination of the speciation of CuxOy‐species in zeolites and the understanding of their role in the reaction mechanism has been heavily debated. Lately, advanced X‐ray absorption spectroscopy (XAS) analysis has been standing out as a powerful technique for investigating the behavior of Cu in zeolites. In this review we focus on the in situ and operando studies of changes in the electronic and structural properties of Cu, during the different steps of the DMTM conversion uncovered by XAS, which have led to new and insightful information about the complex behavior of Cu‐zeolites in the DMTM process.

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Section: Direct Ch4 To Ch3oh Conversion Over Zeolitesmentioning

confidence: 99%

Advanced X‐ray Absorption Spectroscopy Analysis to Determine Structure‐Activity Relationships for Cu‐Zeolites in the Direct Conversion of Methane to Methanol

et al. 2020

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“…Zeolite omega, a synthetic analogue of the natural mineral mazzite, consists of gmelinite cages which are linked in columns parallel to the c‐axis to produce main channels with 12‐membered rings . It is used as a catalyst in various fields such as olefin hydration, aromatic isomerization and alkylation, alkane isomerization and refractory gas oil hydrocracking . Tetramethylammonium (TMA) cations, which may be trapped in the gmelinite cages during crystal growth, are the conventional structure‐directing agents for the synthesis of zeolite omega .…”

Section: Introductionmentioning

confidence: 99%

“…It is used as a catalyst in various fields such as olefin hydration, aromatic isomerization and alkylation, alkane isomerization and refractory gas oil hydrocracking . Tetramethylammonium (TMA) cations, which may be trapped in the gmelinite cages during crystal growth, are the conventional structure‐directing agents for the synthesis of zeolite omega . Nevertheless, TMA cations may not be essential for this synthesis, zeolite omega could be obtained in the absence of them by employing other organic compounds.…”

Section: Introductionmentioning

confidence: 99%

Solvothermal conversion of magadiite into zeolite omega in a glycerol–water system

Cui

Wang

Liu

et al. 2013

J of Chemical Tech & Biotech

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BACKGROUND Zeolite omega is used as a catalyst in various fields. Expensive tetramethylammonium cations are the conventional structure‐directing agents for the synthesis of zeolite omega. In this work, glycerol was used as both solvent and structure‐directing agent instead of expensive quaternary ammonium compounds. Zeolite omega has been obtained through conversion of magadiite in this glycerol–water system. The effects of various parameters such as reaction time, temperature, alkalinity and glycerol content were discussed. RESULTS Pure zeolite omega could be obtained at 120°C for 10 days with the reactants molar composition of 14 SiO2: Al2O3: 10 Na2O: 169 H2O: 200 glycerol. Water content plays an important role in the solvothermal conversion of magadiite to zeolite omega. CONCLUSION The zeolite omega obtained from this system is a rather pure phase free from impurities. A preferential location of the Al atoms in the six‐membered rings of the gmelinites in zeolite omega was observed. A method including extraction and calcination was introduced to remove organic species by which highly ordered pore structure of zeolite was well retained. The present work develops a novel synthesis method for zeolite omega. © 2013 Society of Chemical Industry

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“…These, in turn, are determined by the catalyst preparation process [7,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36]. Most of the papers under discussion provide only scant information on the catalyst preparation and characterization, so that it is not possible to evaluate the contributions of each of the critical parameters to the resultant (de)hydrogenation efficiency.…”

Section: Does Selectivity Relate To the Relative (De)hydrogenation Efmentioning

confidence: 99%

“…An equitable comparison between the performance of MAZand MOR-type zeolites turned out to be remarkably complicated, for the accessibility [21][22][23][24][25][26][27], density, and strength [7,28,29] of the Brønsted acid sites all appear critically dependent on the zeolite synthesis [23,[30][31][32][33][34] and modification [23,35,36] processes. After nearly a decade of research, it was concluded that the improvement of MAZ-over MORtype zeolites was too small to merit commercialization of the former [29,37].…”

Section: Introductionmentioning

confidence: 99%

The selectivity of -hexane hydroconversion on MOR-, MAZ-, and FAU-type zeolites

Calero

Schenk

Dubbeldam

et al. 2004

Journal of Catalysis

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Analyses of a series of published n-hexane hydroisomerization product slates suggest that MAZ-type zeolites yield more dimethylbutane and less methylpentane than either FAU-or MOR-type zeolites. Molecular simulations do not corroborate the traditional view that these selectivity differences are specifically related to the MAZ-, FAU-, or MOR-type zeolite topology. A scrutiny of the literature indicates that reported variation in selectivity relates to a variation in the efficiency of the (de)hydrogenation function relative to the acid function. The FAU-type zeolite catalyst had the most efficient hydrogenation function. The efficiency of the hydrogenation function on the MAZ-type zeolite was low enough to significantly enhance the 2,3-dimethylbutane yield relative to the methylpentane yield, but not low enough to decrease the 2,2-dimethylbutane yield. The efficiency of the hydrogenation function on the MOR-type zeolite was low enough to do both. Only at a sufficiently high n-hexane hydroconversion does the catalyst with the most efficient hydrogenation function exhibit the highest dimethylbutane yield. This new perspective on the reported hexane hydroconversion selectivities suggests that a FAU-type zeolite catalyst with a highly efficient hydrogenation function is best suited for n-hexane hydroisomerization. The FAU topology has the highest porosity which should afford the highest activity without impairing selectivity.  2004 Elsevier Inc. All rights reserved.

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Synthesis and Properties of Zeolite Omega

Cited by 26 publications

References 0 publications

Advanced X‐ray Absorption Spectroscopy Analysis to Determine Structure‐Activity Relationships for Cu‐Zeolites in the Direct Conversion of Methane to Methanol

Advanced X‐ray Absorption Spectroscopy Analysis to Determine Structure‐Activity Relationships for Cu‐Zeolites in the Direct Conversion of Methane to Methanol

Solvothermal conversion of magadiite into zeolite omega in a glycerol–water system

The selectivity of -hexane hydroconversion on MOR-, MAZ-, and FAU-type zeolites

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