Source of Selectivity of p-Xylene Formation in the Toluene Disproportionation over HZSM-5 Zeolites

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

doi:10.1006/jcat.1999.2686

Cited by 41 publications

(28 citation statements)

References 8 publications

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“…The steric restrictions in the channels also prevent the isomerization of the primary product by reentry into the channels. Kunieda et al reported an exponential decrease in p-selectivity for toluene disproportionation with an increase in conversion of 1,3,5, TIPB which is correlated with the external surface acidity for ZSM5 zeolites [30]. A similar relationship was also observed in the present study and is shown in Fig.…”

Section: Reaction Studies With Zsm5 Coated Monolithssupporting

confidence: 88%

Disproportionation of Toluene on Monoliths Washcoated with Metal Oxide Modified ZSM5

Mitra

Kunzru

2011

Catal Lett

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Monoliths washcoated with ZSM5 and metal oxide (MgO, CaO, La 2 O 3 or CeO 2 ) modified ZSM5 were prepared, characterized and studied for toluene disproportionation. An improvement in the yield of the desired p-xylene isomer was obtained by using monoliths coated with metal oxide-modified ZSM5. The enhancement in p-xylene yield depended on the type of modifier, metal loading and the washcoat thickness on the monolith. The 10% LaZSM5 coated monolith having an average washcoat thickness of 23 lm showed the highest p-xylene yield.

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Section: Reaction Studies With Zsm5 Coated Monolithssupporting

confidence: 88%

Disproportionation of Toluene on Monoliths Washcoated with Metal Oxide Modified ZSM5

Mitra

Kunzru

2011

Catal Lett

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“…Additionally, different preparation methods of the same zeolite can give rise to quite different properties, due to several additional effects such as, e.g., different particle morphologies [3], active site densities or different distribution of framework aluminum and, consequently, of protons from surface to bulk [4]. In most cases the role of shape selectivity and of pretreatments, such as dealumination, are still imperfectly known or under debate.…”

Section: Introductionmentioning

confidence: 99%

Effects of crystal size and Si/Al ratio on the surface properties of H-ZSM-5 zeolites

Armaroli

Simon

Digne

et al. 2006

Applied Catalysis A: General

178

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“…3 The number and strength of acid sites in a zeolite is closely linked to its catalytic properties with respect to activity, deactivation rate and product selectivity. 2,4 The location of acid sites is of equal fundamental importance since internal acid sites catalyse sizeselective reactions [5][6][7] and external acid sites catalyse non-sizeselective reactions [8][9][10] or can lead to deactivation of a reaction by coke formation. 11 For example, external acidity is very important in reactions involving molecular species with sizes much larger than the zeolite's typical pore size.…”

Section: Introductionmentioning

confidence: 99%

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

Bräuer

Situmorang

et al. 2017

RSC Adv.

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In this work, we have systematically investigated the effect of the Al content on the number and location of bridging hydroxyls (Brønsted acid sites) and terminal hydroxyls (terminal silanol sites) in ZSM-5 zeolites with varying silica-alumina ratio (SAR ¼ SiO 2 /Al 2 O 3 ) using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) without molar extinction coefficients. Two base probe molecules with different kinetic diameters, pyridine (5.7Å) and collidine (7.4Å), were used. The total content of Brønsted acid sites is obtained by elemental analysis of the proton form and sodium exchanged form of ZSM-5. To quantify the number of internal and external Brønsted acid sites the change in area of the Brønsted acid site peak in the O-H stretching region is then used; thus, the need for molar extinction coefficients to quantify Brønsted acid sites is thereby eliminated. The results reported here show that for ZSM-5 the number of external Brønsted sites, in absolute terms, increases with increasing total Al content, as evidenced by collidine adsorption. The number of terminal silanol acid sites was found to be proportional to the external surface area probed by argon sorption experiments. In summary, this work shows that the use of DRIFTS in conjunction with elemental analysis is a valid alternative to qualitatively and quantitatively probe the number and location of hydroxyl acid sites without the use of molar extinction coefficients and gives a comprehensive picture of the effect of Al content on number and location of hydroxyl acid species in ZSM-5 zeolites with varying SAR. The work contributes to advancing the range of characterisation protocols for solid acid catalysts.

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Source of Selectivity of p-Xylene Formation in the Toluene Disproportionation over HZSM-5 Zeolites

Cited by 41 publications

References 8 publications

Disproportionation of Toluene on Monoliths Washcoated with Metal Oxide Modified ZSM5

Disproportionation of Toluene on Monoliths Washcoated with Metal Oxide Modified ZSM5

Effects of crystal size and Si/Al ratio on the surface properties of H-ZSM-5 zeolites

Effect of Al content on number and location of hydroxyl acid species in zeolites: a DRIFTS quantitative protocol without the need for molar extinction coefficients

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