H-Gallosilicate (MFI) Propane Aromatization Catalyst: Influence of Si/Ga Ratio on Acidity, Activity and Deactivation Due to Coking

Choudhary, Vasant R.; Kinage, Anil K.; Sivadinarayana, C.; Devadas, P.; Sansare, S.D.; Guisnet, M.

doi:10.1006/jcat.1996.0004

Cited by 87 publications

(44 citation statements)

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“…On the contrary, a significant fraction of the Ga atoms was located at extraframework positions in the [Ga]MFI zeolites. The relatively low fraction of Ga atoms inserted into the MFI zeolite framework is consistent with the findings of Choudhary et al . Notably, the samples were calcined two times, once to remove the organic template and the second to remove ammonia after ion‐exchange of the Na form.…”

Section: Resultsmentioning

confidence: 99%

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

et al. 2017

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The influence of framework substituents (Al3+, Ga3+, Fe3+ and B3+) and morphology (bulk vs. nanometer‐sized sheets) of MFI zeolites on the acidity and catalytic performance in the methanol‐to‐hydrocarbons (MTH) reaction was investigated. The Brønsted acid density and strength decreased in the order Al(OH)Si>Ga(OH)Si>Fe(OH)Si≫B(OH)Si. Pyridine 15N NMR spectra confirmed the differences in the Brønsted and Lewis acid strengths but also provided evidence for site heterogeneity in the Brønsted acid sites. Owing to the lower efficiency with which tervalent ions can be inserted into the zeolite framework, sheet‐like zeolites exhibited lower acidity than bulk zeolites. The sheet‐like Al‐containing MFI zeolite exhibited the greatest longevity as a MTH catalyst, outperforming its bulk [Al]MFI counterpart. Although the lower acidity of bulk [Ga]MFI led to a better catalytic performance than bulk [Al]MFI, the sheet‐like [Ga]MFI sample was found to be nearly inactive owing to lower and heterogeneous Brønsted acidity. All Fe‐ and B‐substituted zeolite samples displayed very low catalytic performance owing to their weak acidity. Based on the product distribution, the MTH reaction was found to be dominated by the olefins‐based catalytic cycle. The small contribution of the aromatics‐based catalytic cycle was larger for bulk zeolite than for sheet‐like zeolite, indicating that shorter residence time of aromatics can explain the lower tendency toward coking and enhanced catalyst longevity.

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Section: Resultsmentioning

confidence: 99%

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

et al. 2017

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High‐Yield Synthesis of [2] Catenanes by Intramolecular Ring‐Closing Metathesis

Mohr

Sauvage

Grubbs

et al. 1997

Angew. Chem. Int. Ed. Engl.

251

101

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COMMUNICATIONS ethane (33.3 mol%) and nitrogen, with or without any additive (higher alkanes or olefins), as the feed at a space velocity of 6100+_ 100 cm3 g-' h-* w' ith a squarepulse technique descrlbed earlier [21]. The space velocity was measured at 0 "C and 1 atm. Conversion X in %, S,, in %, and yield of arene based on ethane conversion ( YArlCIHs) in %) were determined as follows: X = [{(wt% of reactant in the feed hydrocarbons) -(wt% of reactant in the product hydrocarbons)}/(wt% of reactant in the feed hydrocarbons)] x 100; S,, = [(wt% of arenes in the hydrocarbon products)/{l00 -wt% of reactant(s) in the hydrocarbon products]] x 100; YAr,Cz",, = (XS*,)/~OO.Angew (%en?. Int. G I EngI. 1997, 36, N o . 12 :(; VCH Ve~lrigsgesrilrcbfi~ mhH, 0-69451 Wi+diein?. I997 0570-OH33!Y7~3612-1309 S 17.56 +.SO 0 Experimental Section General procedure for ruthenium benzylidene catalyzed RCM : Under exclusion from air and moisture, 1 (5 mol%) in CH,CI, was added to a 0.01 M solution of the diolefin (typically 200 to 900 mg) in CH,CI,. After the mixture was stirred for 6 h at room temperature, additional catalyst (5 mol%) was added, and stirring continued for 6 h. The solvent was then removed under reduced pressure, and the crude reaction mixture purified by repeated column chromatography (silica gel, CH,CI,/ MeOH 9614 viv) to yield the [2]catenates as burgundy solids. All compounds were characterized by NMR spectrscopy, FAB-MS, and elemental analysis.

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“…This is consistent with our earlier observations for zeolites with di †erent Si/Ga ratios. 7 The crystallization rate was also found to be strongly inÑuenced by the ( Fig. 1(b)) and c)) ratios of the gel.…”

Section: Inñuence Of Gel Composition and Phmentioning

confidence: 92%

Hydrothermal synthesis of gallosilicate (MFI) zeolite: factors influencing crystallization kinetics and crystal size/growth

Choudhary

Kinage

1998

J. Chem. Technol. Biotechnol.

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: The kinetics of the hydrothermal synthesis of gallosilicate (MFI) zeolite (under autogeneous pressure at 180¡C) from a gel containing a source of silica (Na-trisilicate or fumed silica), gallium nitrate, templating agent (TPA-Br or TPA-OH), deionized water and sulfuric acid have been thoroughly investigated in order to understand the inÑuence of various synthesis parameters (viz. gel composition, source of silica, template, method of gel preparation and pH of gel) on the crystallization kinetics and crystal size/growth of the zeolite. The zeolite samples were characterized for their crystallinity by XRD and crystal size and morphology by SEM. The crystallization rate and crystal size of the zeolite were found to be strongly inÑuenced by the above synthesis parameters.1998 SCI (

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H-Gallosilicate (MFI) Propane Aromatization Catalyst: Influence of Si/Ga Ratio on Acidity, Activity and Deactivation Due to Coking

Cited by 87 publications

References 0 publications

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

High‐Yield Synthesis of [2] Catenanes by Intramolecular Ring‐Closing Metathesis

Hydrothermal synthesis of gallosilicate (MFI) zeolite: factors influencing crystallization kinetics and crystal size/growth

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H-Gallosilicate (MFI) Propane Aromatization Catalyst: Influence of Si/Ga Ratio on Acidity, Activity and Deactivation Due to Coking

Cited by 87 publications

References 0 publications

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al3+, Ga3+, Fe3+, B3+) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al3+, Ga3+, Fe3+, B3+) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

High‐Yield Synthesis of [2] Catenanes by Intramolecular Ring‐Closing Metathesis

Hydrothermal synthesis of gallosilicate (MFI) zeolite: factors influencing crystallization kinetics and crystal size/growth

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On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction

On the Role of Acidity in Bulk and Nanosheet [T]MFI (T=Al³⁺_, Ga³⁺, Fe³⁺, B³⁺) Zeolites in the Methanol‐to‐Hydrocarbons Reaction