The transformation of 1,2,4-trimethylbenzene A probe reaction to monitor external surface modifications of HZSM-5?

Röger, H.P.; Möller, K.P.; O’Connor, C.T.

doi:10.1016/s0927-6513(96)00081-8

Cited by 38 publications

(26 citation statements)

References 20 publications

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“…Das et al[4] also studied the toluene and TMB transformation reactions using zeolite beta. They obtained the highest yield of xylenes at temperature of 400 o C and toluene/TMB molar ratio of about 1:1.Over medium pore zeolites, TMB transformations revealed much lower yield of xylenes compared to that under large pore and high acidity zeolites [5][6][7][8]. Roger et al [7] studied the conversion of 1,2,4-TMB over HZSM5.…”

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“…They noted that the disproportionation of 1,2,4-TMB was followed by rapid paring dealkylation of the TeMBs. The bulky intermediates (TeMBs) that reinforced the diffusional resistances by pore mouth narrowing favored the paring reaction inside the zeolite crystals.The above literature survey indicates that most of the research on the TMB transformations has been carried out in fixed bed reactors [1][2][3][4][5][6][7][8]. Fluidized bed on the other hand 3 reveals the importance of diffusional effects in these reactions.…”

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1,2,4-Trimethylbenzene Transformation Reaction Compared with its Transalkylation Reaction with Toluene over USY Zeolite Catalyst

Al-Khattaf

Tukur

Al-Amer

2007

Ind. Eng. Chem. Res.

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Abstract1,2,4-Trimethyl benzene (TMB) transalkylation with toluene has been studied over USY-zeolite type catalyst using a riser simulator that mimics the operation of a fluidized-bed reactor. 50:50 wt% reaction mixtures of TMB and toluene were used for the transalkylation reaction. The range of temperature investigated was 400-500 o C and time on stream ranging from 3 to 15 seconds.The effect of reaction conditions on the variation of p-xylene to o-xylene products ratio (P/O), distribution of trimethylbenzene (TMB) isomers (1,3,5-to-1,2,3-) and values of xylene/tetramethylbenzenes (X/TeMB) ratios are reported. Comparisons are made between the results of the transalkylation reaction with the results of pure 1,2,4-TMB and toluene reactions earlier reported. Toluene that was found almost inactive, became reactive upon blending with 1,2,4-TMB. This shows that toluene would rather accept a methyl group to transform to xylene than to loose a methyl group to form benzene under the present experimental condition with pressures around ambient. The experimental results were modeled using quasi-steady state approximation. Kinetic parameters for the 1,2,4-TMB disappearance during the transalkylation reaction, and in its conversion into isomerization and disproportionation products were calculated using the catalyst activity decay function based on time on stream (TOS). The apparent activation energies were found to decrease as follows: E transalkylation > E isomerization > E disproportionation . February 2007Keywords: Trimethyl benzene transalkylation, toluene reaction, fluidized-bed reactor, USY-zeolite, xylene yield * Corresponding author. Tel.: +966-3-860-1429; Fax: +966-3-860-4234 e-mail address: skhattaf@kfupm.edu.sa 2 Introduction:The demand for xylenes as a raw material for polyester fibers and films continues to grow and drive the search to increase xylene production processes. In the year 1999, the world consumption of mixed xylene was about 24 million tons, and is expected to grow at a rate of 6.2% to 35.9 million tons by the year 2007. This indicates that xylenes are still gaining importance in the petrochemical market. Among the three xylene isomers, p-xylene is the most demanded and thus most expensive, followed by o-xylene.One common way for xylene production is the conversion of the lower value toluene (C 7 ) and trimethylbenzene (C 9 ) into xylenes via toluene disproportionation, trimethyl benzene (TMB) disproportionation and transalkylation with toluene. Thus, these processes offer a way to utilize the low cost toluene and TMB to produce much more attractive product xylene. TMB disproportionation, and toluene-TMB transalkylation. They found that the zeolite beta has excellent stability and transalkylation selectivity. In TMB disproportionation, blending toluene into feedstocks can shift the production selectivity of TeMB to xylene, whereas in toluene disproportionation, mixing TMB into feedstocks not only reduced the reaction temperatures but also raised the xylene yield. Das et al.[4] also studied the t...

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confidence: 99%

1,2,4-Trimethylbenzene Transformation Reaction Compared with its Transalkylation Reaction with Toluene over USY Zeolite Catalyst

Al-Khattaf

Tukur

Al-Amer

2007

Ind. Eng. Chem. Res.

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“…Over medium pore zeolites, TMB transformations revealed much lower yield of xylenes compared to that under large pore and high acidity zeolites [5][6][7][8] . Roger et al 7 studied the conversion of 1,2,4-TMB over HZSM5.…”

Section: May 2007mentioning

confidence: 86%

“…They found that the zeolite beta has excellent stability and transalkylation selectivity. The authors also demonstrated that xylene selectivity could be increased by blending toluene into feedstocks during the TMB disproportionation reaction.Over medium pore zeolites, TMB transformations revealed much lower yield of xylenes compared to that under large pore and high acidity zeolites [5][6][7][8] . Roger et al 7 studied the conversion of 1,2,4-TMB over HZSM5.…”

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Catalytic Transformation of 1,3,5-Trimethylbenzene over a USY Zeolite Catalyst

Tukur

Al-Khattaf

2007

Energy Fuels

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Catalytic transformation of 1,3,5-Trimethylbenzene (TMB) has been investigated over USY zeolite catalyst in a novel riser simulator at different operating conditions. The effect of reaction conditions on the variation of isomerization to disproportionation products ratio (I/D), distribution of trimethylbenzene (TMB) isomers, xylene/tetramethylbenzenes (X/TeMB) ratio and values of p-xylene/o-xylene (P/O) ratios are reported. Comparisons are made between the results of the 1,3,5-TMB and the earlier reported values of 1,2,4-TMB under similar conditions. Even though the kinetic diameters of these molecules slightly exceed the pore size of the USY zeolite (7.4Å), they still have access to the openings of the zeolite pore due to their flexibility. They are readily accommodated inside the zeolite channel system thereby allowing reaction to proceed. Surprisingly, 1,3,5-trimethylbenzene was found to be more reactive than 1,2,4-trimethylbenzene at temperatures above 450 o C and reaction times more than 5secs. The experimental results have been modeled using quasi-steady state approximation. Kinetic parameters for 1,2,4-and 1,3,5-TMB conversions into isomerization and disproportionation products were calculated using the catalyst activity decay function based on time on stream (TOS). The apparent activation energies were found to decrease as May 2007Keywords: Trimethyl benzene, isomerization, disproportionation, fluidized-bed reactor, ZSM-5, USY-zeolite, modeling, * Corresponding author. Tel.: +966-3-860-1429; Fax: +966-3-860-4234 e-mail address: skhattaf@kfupm.edu.sa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 investigated the transformation (isomerization and disproportionation) of trimethylbenzenes (TMBs) over LaY catalysts. In the disproportionation reaction, the transfer of one methyl group from TMBs led to the formation of equal amounts of xylene and tetramethylbenzene (TeMB) isomers. The authors reported that disproportionation appeared to be linearly related to the total conversion over most of the conversion range studied for both 1,2,4-and 1,3,5-TMB, whereas, for 1,2,3-TMB, isomerization was much more favored than disproportionation.Cejka et al. used zeolite beta to investigate its potential in xylene production reactions, including toluene disproportionation, TMB disproportionation, and toluene-TMB transalkylation. They found that the zeolite beta has excellent stability and transalkylation selectivity. The authors also demonstrated that xylene selectivity could be increased by blending toluene into feedstocks during the TMB disproportionation reaction.Over medium pore zeolites, TMB transformations revealed much lower yield of xylenes compared to that under large pore and high acidity zeolites [5][6][7][8] . Roger et al. 7 studied the conversion of 1,2,4-TMB over HZSM5. They observed that isomerization of 1,2,4-TMB t...

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Chemical Imaging of the Binder‐Dependent Coke Formation in Zeolite‐Based Catalyst Bodies During the Transalkylation of Aromatics

et al. 2019

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The choice of binder material, added to a zeolite-based catalyst body, can significantly influence the catalyst performance during a reaction, i. e. its deactivation and selectivity. In this work the influence of the binder in catalyst extrudates on the formation of hydrocarbon deposits was explored during the transalkylation of toluene with 1,2,4-trimethylbenzene (1,2,4-TMB). Using in situ UV-vis micro-spectroscopy and ex situ confocal fluorescence microscopy approach, coke species were revealed to predominantly form on the rim of zeolite crystals within Al 2 O 3 -bound extrudates. It was found that this was due to Al migration between the zeolite crystals and the Al 2 O 3binder creating additional acid sites near the zeolite external surface. In contrast, minimal isomerization of 1,2,4-TMB in the SiO 2 -bound extrudate allowed greater access to the zeolite internal pore network, creating a more homogeneous coke distribution throughout the zeolite crystals.

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The transformation of 1,2,4-trimethylbenzene A probe reaction to monitor external surface modifications of HZSM-5?

Cited by 38 publications

References 20 publications

1,2,4-Trimethylbenzene Transformation Reaction Compared with its Transalkylation Reaction with Toluene over USY Zeolite Catalyst

1,2,4-Trimethylbenzene Transformation Reaction Compared with its Transalkylation Reaction with Toluene over USY Zeolite Catalyst

Catalytic Transformation of 1,3,5-Trimethylbenzene over a USY Zeolite Catalyst

Chemical Imaging of the Binder‐Dependent Coke Formation in Zeolite‐Based Catalyst Bodies During the Transalkylation of Aromatics

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