On the Mechanism of Toluene Disproportionation in a Zeolite Environment

Xiong, Yusheng; Rodewald, Paul G.; Chang, Clarence D.

doi:10.1021/ja00142a007

Cited by 65 publications

(47 citation statements)

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“…For the sake of simplicity, the scheme is limited to the formation of 25DMT. This mechanism is in accordance with the proposals made for aromatic hydrocarbons disproportionation [32,[35][36][37][38][39]. In the initial step, an adsorbed molecule of 2MT reacts with an acidic proton of the zeolite to lose a methyl hydrogen and form H 2 and a 2-thienylcarbenium ion (4-I) which can react with another 2MT molecule.…”

Section: Disproportionation Mechanismsupporting

confidence: 88%

Transformation of thiophenic compounds over acidic zeolites

Boita

Moreau

Richard

et al. 2006

Applied Catalysis A: General

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Section: Disproportionation Mechanismsupporting

confidence: 88%

Transformation of thiophenic compounds over acidic zeolites

Boita

Moreau

Richard

et al. 2006

Applied Catalysis A: General

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“…However, the initial activity of TNU-9 is quite high compared to that of large-pore H-mordenite and H-beta, and especially to that of medium-pore H-ZSM-5, which is almost inactive at 300°C. Considering that the intersecting 10-ring pore system of ZSM-5 does not allow the formation of the bulky transition state at this temperature [38][39][40], it appears that the bimolecular toluene disproportionation over H-TNU-9 may occur mainly on the Brönsted acid sites within the large 12-ring cavities rather than within the two main 10-ring channels along the b axis. We also note that H-TNU-9 deactivates less rapidly than H-MCM-22.…”

Section: Physicochemical and Catalytic Properties Of Tnu-9mentioning

confidence: 97%

“…This can be rationalized by considering that the longest pore diameter (6.0 Å ) of the channel A in TNU-9 is large enough to allow for the egress of 1,2,4-TMB (5.5 9 6.7 Å ) while still hindering the easy exit of the other two isomers (5.9 9 6.6 Å ). When m-xylene isomerizes to p-and o-xylenes, on the other hand, 10-ring pore zeolites are known to give higher p/o ratios than 12-ring pore zeolites, due to differences in the diffusion of both isomers through the narrow channels of the former zeolites, i.e., product shape selectivity [37][38][39][40][41][42][43][44][45]. As listed in Table 4, H-TNU-9 gives an initial p/o ratio of 3.6 that is in the expected range for medium-pore zeolites.…”

Section: Physicochemical and Catalytic Properties Of Tnu-9mentioning

confidence: 99%

Use of Flexible Diquaternary Structure-directing Agents in Zeolite Synthesis: Discovery of Zeolites TNU-9 and TNU-10 and Their Catalytic Properties

Hong

2008

Catal Surv Asia

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This review summarizes our recent work on zeolite syntheses in the presence of linear diquaternary alkylammonium ions, with the object of controlling the conformations of these flexible, hydrophilic organic structure-directing agents by varying the type and concentration of inorganic components in synthesis mixtures. After describing how we have been concerned about the search for novel zeolite structures through this synthetic strategy, we discuss the cooperative structure-directing effects of 1,4-bis(N-methylpyrrolidinium)butane and specific levels of Na + ions and lattice negative charges introduced by Al substitution on the crystallization of new medium-pore zeolites TNU-9 and TNU-10. The physicochemical and catalytic properties of these two materials are also outlined.

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“…Toluene transformation is well documented in the literature [5][6][7][8]. Toluene transformation can occur through two major mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Disproportionation and Methylation of Toluene with Methanol Over Zeolite Catalysts

2010

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Zeolites TNU-9, SSZ-33, mordenite (MOR) and ZSM-5 were evaluated for their activities in toluene disproportionation and methylation reaction of toluene with methanol. The medium-pore zeolite TNU-9 was found to possess the highest conversion in toluene disproportionation as compared with SSZ-33, mordenite and ZSM-5 based catalyst. Zeolite mordenite with the highest Si/Al ratio of 135.9 (the lowest concentration of active sites) exhibited the highest toluene conversion and maximum xylene yield in toluene methylation. On mordenite, the presence of channel intersections allows more reaction space for the formation of bulky intermediates and/or products and the 12-ring channels on the other hand, allow diffusion without trapping, since the channel diameter is large enough. In toluene methylation, xylene selectivity at the same conversion level follows the order: ZSM-5 [ TNU-9 [ MOR [ SSZ-33, which implies that xylene selectivity is directly related to the size of channels from medium to large pore zeolites. The medium-pore zeolite ZSM-5, with 10-ring channels, shows the lowest reactivity for further alkylation of xylene, while mordenite with 12-ring channel shows the highest reactivity for further alkylation of xylene.

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On the Mechanism of Toluene Disproportionation in a Zeolite Environment

Cited by 65 publications

References 0 publications

Transformation of thiophenic compounds over acidic zeolites

Transformation of thiophenic compounds over acidic zeolites

Use of Flexible Diquaternary Structure-directing Agents in Zeolite Synthesis: Discovery of Zeolites TNU-9 and TNU-10 and Their Catalytic Properties

Disproportionation and Methylation of Toluene with Methanol Over Zeolite Catalysts

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