Mobil Zeolite Catalysts for Monomers

Kaeding, Warren W.; Barile, George C.; Wu, Margaret

doi:10.1080/01614948408064727

Cited by 72 publications

(25 citation statements)

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“…para-selectivity is %25.0% all over the temperature range investigated. This persisting low selectivity of the as-synthesized HZSM-5 zeolite can be attributed to the presence of the unselective acid sites [15] which cause a secondary isomerization of p-xylene to take place on the catalyst's surface whereby the small difference in the diffusivities between the para-xylene and its isomers leads to a decrease in the para-selectivity [14,32]. The para-selectivity can be classified under controlling selectivity or/and transition state shape selectivity [33].…”

Section: Toluene Conversion and Total Xylene Productionmentioning

confidence: 93%

“…Post synthesis modification methods, described as pore size engineering [13], are proposed to tailor the properties of zeolites to achieve high selectivity. Catalyst modifications such as pore blocking and surface coating [14], which increase the intracrystalline diffusional resistance and inhibit the secondary isomerization of p-xylene on the external surface of the crystallite, respectively, have been employed in industrial practice [15] to enhance para-xylene selectivity. A typical shape-selective toluene disproportionation reaction occurs in the zeolitic pores of H-ZSM-5 to generate xylenes and benzene.…”

Section: Introductionmentioning

confidence: 99%

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Catalytic para-xylene maximization. Part X: Toluene disproportionation on HF promoted H-ZSM-5 catalysts

Aboul-Gheit

Aboul-Enein

Ghoneim

et al. 2012

Egyptian Journal of Petroleum

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H-ZSM-5 zeolite catalysts were doped with 2%, 3% and 4%HF to be used for investigating their activities and selectivities for xylenes production and for para-xylene maximization at temperatures of 300-500°C via toluene disproportionation. This doping caused pore size modification of the H-ZSM-5 catalyst. The reaction was carried out in a fixed bed flow type reactor. The ratio of produced para-xylene relative to its thermodynamic composition reached as high as 3.29 at 300°C on the 4%HF doped H-ZSM-5 catalyst although this catalyst possessed the lowest amount of the largest pores (3.0-5.7 nm) and the smallest pores (0.4-1.7 nm). The overall activities of the catalysts were decreased with an increase in HF doping because of diffusion restriction. The kinetics of the reaction were simply treated and found to give E a and DS * values compatible with the characterization data of the catalysts.

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Section: Toluene Conversion and Total Xylene Productionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Catalytic para-xylene maximization. Part X: Toluene disproportionation on HF promoted H-ZSM-5 catalysts

Aboul-Gheit

Aboul-Enein

Ghoneim

et al. 2012

Egyptian Journal of Petroleum

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“…(15)) [177] Much literature has appeared on the catalytic ring-attachment isomerization of o-and m-xylenes and the catalytic intermolecular transalkylation (disproportionation) of toluene to produce p-xylene [90,178,179], which is used in its oxidation to form terephthalic acid. Mordenite and ZSM-5 are currently the best catalysts for those catalytic reactions [180][181][182]. On the other hand, very little has been reported on the reactions of diethylbenzenes, even though p-diethylbenzene is an industrial source of p-divinylbenzene.…”

Section: Methodsmentioning

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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“…For ZSM-8, however, the number of strong sites per framework A1 (Choudhary and Akolekar, 1989) and the rate of catalyst deactivation due to deposition of large hydrocarbon molecules in zeolite channels (Akolekar and Choudhary, 1987;Akolekar, 1987) are found to be higher. Also the diffusion of cyclohexane (Chon et al, 1985) in H-ZSM-8 is found to be faster.Extensive studies have been reported on ZSM-5-type zeolites for the sorption/diffusion properties (Ruthven, 1984; Choudhary and Srinivasan, 1986a, b) and also on the zeolite modified with MgO, P,O,, and B,O, (Kaeding and Butter, 1980;Kaeding et al, 1984;Mamman, 1988). For ZSM-5, intracrystalline species like MgO can produce a two order of magnitude change in diffusivity and also significant changes in catalytic properties (Olson and Haag, 1984).…”

mentioning

confidence: 98%

Diffusion of cumene in H‐ZSM‐8 and modified H‐ZSM‐8 Zeolites

Choudhary

Mamman

1990

AIChE Journal

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ZSM-8 zeolite is a medium-pore (pore size = 0.6 nm) high-silica zeolite, belonging to a pentad family of zeolites, introduced by Mobil Oil Corporation in 1971. The X-ray diffraction spectrum of ZSM-8 is somewhat similar to that of ZSM-5, which is a very widely investigated zeolite, except for a splitting in the highest peak in the region 28 = 22-25O observed for ZSM-8 (Lechert, 1984). Earlier studies (Akolekar and Choudhary, 1987) have indicated that the influence of degree of Hi -exchange and calcination temperature on strong acid sites and catalytic activity and paraselectivity (in hydrocarbon conversion and alcohol-to-aromatics conversion reactions) of ZSM-8 are quite similar to those observed for ZSM-5. For ZSM-8, however, the number of strong sites per framework A1 (Choudhary and Akolekar, 1989) and the rate of catalyst deactivation due to deposition of large hydrocarbon molecules in zeolite channels (Akolekar and Choudhary, 1987;Akolekar, 1987) are found to be higher. Also the diffusion of cyclohexane (Chon et al., 1985) in H-ZSM-8 is found to be faster.Extensive studies have been reported on ZSM-5-type zeolites for the sorption/diffusion properties (Ruthven, 1984; Choudhary and Srinivasan, 1986a, b) and also on the zeolite modified with MgO, P,O,, and B,O, (Kaeding and Butter, 1980;Kaeding et al., 1984;Mamman, 1988). For ZSM-5, intracrystalline species like MgO can produce a two order of magnitude change in diffusivity and also significant changes in catalytic properties (Olson and Haag, 1984).No detailed investigation on the diffusion in ZSM-8 and modified ZSM-8 zeolites has been reported so far. The present investigation was undertaken with the objective of studying the influence of cations ( H + or N a + ) and modification by MgO, P,O,, and B,O, on the diffusion in ZSM-8-type zeolite, using a model sorbate (viz., Cumene).Correapndcncc concerning this paper should be addrcsd to V. R. Choudhary. Experimental StudiesThe preparation and characterization of H-ZSM-8 and H . N a -Z S M -8 zeolites (Si/AI = 29.6 and crystal size = 3.5pm) have been described earlier (Akolekar and Choudhary, 1987). The degrees of H+-exchange of the H-ZSM-8 and H . Na-ZSM-8 zeolites were 0.96 and 0.08, respectively. The magnesium, phosphorous and boron modified H-ZSM-8 zeolites have been prepared by contacting the H-ZSM-8 zeolite with aqueous solutions of magnesium acetate, ortho-phosphoric acid, and boric acid (all BDH AnalaR), respectively, at room temperature for two weeks while shaking the flask containing the zeolite and the solution occasionally. The zeolite was then filtered using a Gooch crucible and washed quickly to remove the material impregnated on the external surface of the zeolite crystals. The zeolite was then dried in a vacuum oven at 373 K for 12 h, calcined in air at 773 K for 12 h and analyzed for its magnesium, phosphorous or boron content by atomic absorption spectroscopy or spectrophotometry. All the zeolites were pressed (without any binder) and crushed into particles of about 0.2 mm size. This has not cau...

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Mobil Zeolite Catalysts for Monomers

Cited by 72 publications

References 4 publications

Catalytic para-xylene maximization. Part X: Toluene disproportionation on HF promoted H-ZSM-5 catalysts

Catalytic para-xylene maximization. Part X: Toluene disproportionation on HF promoted H-ZSM-5 catalysts

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

Diffusion of cumene in H‐ZSM‐8 and modified H‐ZSM‐8 Zeolites

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