Generation of Shape-Selectivity ofp-Xylene Formation in the Synthesized ZSM-5 Zeolites

Kim, Jong-Ho; Kunieda, Takehisa; Niwa, Miki

doi:10.1006/jcat.1997.1950

Cited by 85 publications

(54 citation statements)

References 22 publications

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“…Detailed research has been focused particularly on zeolite catalysts such as ZSM-5 and mordenite with micro-pore structures [85,86]. For toluene methylation with methanol over zeolite, the commonly accepted reaction scheme suggests that an activated form of methanol, the methyl cation, reacts with weakly adsorbed toluene [87,88]. In the cluster catalysis, this intermediate was expected by replacing the silica-alumina catalyst with the cluster moiety.…”

Section: Reaction Of Alcohol (Equationmentioning

confidence: 99%

Catalytic Reactions over Halide Cluster Complexes of Group 5–7 Metals

Nagashima

Kamiguchi

Chihara

2014

Metals

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Halide clusters of Group 5-7 metals develop catalytic activity above 150-250 °C, and the activity is retained up to 350-450 °C by taking advantage of their thermal stability, low vapor pressure, and high melting point. Two types of active site function: the solid Brønsted acid site and a coordinatively unsaturated site that catalyzes like the platinum metals do. Various types of catalytic reactions including new reactions and concerted catalyses have been observed over the clusters: hydrogenation, dehydrogenation, hydrogenolysis, isomerization of alkene and alkyne, and alkylation of toluene, amine, phenol, and thiol. Ring-closure reactions to afford quinoline, benzofuran, indene, and heterocyclic common rings are also catalyzed. Beckmann rearrangement, S-acylation of thiol, and dehydrohalogenation are also catalyzed. Although the majority of the reactions proceed over conventional catalysts, closer inspection shows some conspicuous features, particularly in terms of selectivity. Halide cluster catalysts are characterized by some aspects: cluster counter anion is too large to abstract counter cation from the protonated reactants, cluster catalyst is not poisoned by halogen and sulfur atoms. Among others, cluster catalysts are stable at high temperatures up to 350-450 °C. At high temperatures, apparent activation energy decreases, and hence weak acid can be a catalyst without decomposing reactants. OPEN ACCESSMetals 2014, 4 236

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Section: Reaction Of Alcohol (Equationmentioning

confidence: 99%

Catalytic Reactions over Halide Cluster Complexes of Group 5–7 Metals

Nagashima

Kamiguchi

Chihara

2014

Metals

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“…These modification methods can achieve high para-selectivity owing to deactivation of the external acid sites and/or regulating the pore-openings. However, the catalytic activity of ZSM-5 decreases by these modification methods [3] because its pore opening size is slightly reduced by these surface modification [10], resulting in an increase of a diffusion resistance in the pore.…”

Section: Introductionmentioning

confidence: 99%

“…MFI type aluminosilicate ZSM-5 has been often used for selective formation of p-xylene due to its suitable pore size which is intermediate between p-xylene and other isomers. In selective formation of p-xylene over H-ZSM-5, its intrinsic para-selectivity (denoted as a fraction of p-xylene in all produced xylene isomers) could be understood based on the differences in the intradiffusivity of xylene isomers within the pores [1][2][3]. However, while the separation factor of p-xylene was over 100 in the membrane separation [4], experimentally observed paraselectivity was not high in catalytic reactions, caused by less diffusion length within the pores due to a small crystal size and/or non-selective reaction such as isomerization occurring at the acid sites on the external surface of H-ZSM-5.…”

Section: Introductionmentioning

confidence: 99%

para-Selectivity of silicalite-1 coated MFI type galloaluminosilicate in aromatization of light alkanes

et al. 2015

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MFI type galloaluminosilicates (GaAlMFI) were coated with inert silicalite-1 layers. The silicalite-1 coating could improve the para-selectivity for xylene production in aromatization of propane. In the silicalite-1 coating step, low alkali concentration in the synthesis solution enhanced para-selectivity. A proton-exchange procedure also had an impact on the para-selectivity. Significant decrease of para-selectivity was observed over the silicalite-1 coated GaAlMFI with repeated proton-exchange. From the 71 Ga and 27 Al MAS NMR measurements, demetalation occurred during the proton-exchange process, and those metal species is likely to become catalytically active sites without para-selectivity. From the aromatization of propane and n-butane, para-selectivity in n-butane aromatization was found to be higher than that in propane aromatization. From the product distribution, naphthalene and its derivatives were easier to be produced in propane aromatization compared to n-butane aromatization. The formation of naphthalene and its derivatives may relate to decrease in the para-selectivity in propane aromatization.

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“…para-Xylene, a critical raw material for polyester manufacture, is the most lucrative petrochemical commodity in three xylene isomers [1][2][3][4]. The high profit of para-xylene production has created incentives for researchers to work on various aspects of the technologies.…”

Section: Introductionmentioning

confidence: 99%

“…Commonly used techniques include impregnation of with salts like boron, phosphorous or magnesium compounds [13][14][15], silanization by deposition of teraethyl orthosilicate [10,13], tuning the crystal size [3] and pre-coking [5].…”

Section: Introductionmentioning

confidence: 99%

A Facile Strategy to Prepare Shaped ZSM-5 Catalyst with Enhanced para-Xylene Selectivity and Stability for Toluene Methylation

Wang¹,

Chang²,

Liu³

et al. 2017

Preprint

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This work describes the catalytic performances of attapulgite/ZSM-5 extrudate in comparison to conventional alumina-bound ZSM-5 extrudate in toluene methylation. The novel attapulgite/ZSM-5 extrudate is prepared by using natural clay attapulgite as binder which introduces mobile alkaline species and macropores to the extrudate. In contrast to alumina-bound extrudate, this novel extrudate shows significantly higher para-selectivity and stability. By using characterization techniques, including in-situ XRD, SEM, NH3 temperature programmed desorption (TPD), thermogravimetric analysis and n-hexane/cyclohexane physical adsorption, the catalytic performance improvement of attapulgite/ZSM-5 extrudate is correlated with the neutralization of Brønsted acid sites by mobile alkaline species during calcination and reaction process. Moreover, a higher paraselectivity was obtained over attapulgite-bound modified ZSM-5 extrudate. The strategy of extruding ZSM-5 catalysts with attapulgite as binder is facile and universal. Such method paves a new way for preparation of shaped toluene methylation catalyst with enhanced para-selectivity and stability.

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Generation of Shape-Selectivity ofp-Xylene Formation in the Synthesized ZSM-5 Zeolites

Cited by 85 publications

References 22 publications

Catalytic Reactions over Halide Cluster Complexes of Group 5–7 Metals

Catalytic Reactions over Halide Cluster Complexes of Group 5–7 Metals

para-Selectivity of silicalite-1 coated MFI type galloaluminosilicate in aromatization of light alkanes

A Facile Strategy to Prepare Shaped ZSM-5 Catalyst with Enhanced para-Xylene Selectivity and Stability for Toluene Methylation

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