The Reaction Network in the Conversion of 1,2,4-Trimethylbenzene over HZSM-5

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

doi:10.1006/jcat.1998.1987

Cited by 42 publications

(35 citation statements)

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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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confidence: 99%

“…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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confidence: 99%

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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%

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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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“…Specific details on the modification procedures have been described previously [8][9][10][11][12] . Cr ystal sizes were approximately log-normally distributed around the mean values indicated in Tables 1 and 2.…”

Section: Methodsmentioning

confidence: 99%

“…200 m diameter. The catalytic activity of the external surface was determined using the cracking of 1,3,5, -triisopropyl benzene (TiPB) as a probe reaction 11) . TiPB has a kinetic diameter of 0.85 nm and is not expected to enter the channels of the zeolites.…”

Section: Methodsmentioning

confidence: 99%

“…In this respect, the reactions most widely studied to date have been the disproportionation of alkyl aromatics (e.g. 6,7,[10][11][12] ) since these reactions lead to the formation, respectively, of a variety of alkyl isomers with different diffusional coefficients and can thus be used to observe the effect of changes in diffusional properties.…”

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confidence: 99%

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The Effect of Silanisation on the Catalytic and Sorption Properties of Zeolites

O’Connor

Möller

Manstein

2007

KONA

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Tracking the Impact of Koch‐Carbonylated Organics During the Zeolite ZSM‐5 Catalyzed Methanol‐to‐Hydrocarbons Process

Zhou,

Gong,

Abou‐Hamad

et al. 2024

Angewandte Chemie

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A methanol‐based economy offers an efficient solution to current energy transition challenges, where the zeolite‐catalyzed methanol‐to‐hydrocarbons (MTH) process would be a key enabler in yielding synthetic fuels/chemicals from renewable sources. Despite its original discovery over half a century ago over the zeolite ZSM‐5, the practical application of this process in a CO2‐neutral scenario has faced several obstacles. One prominent challenge has been the intricate mechanistic complexities inherent in the MTH process over the zeolite ZSM‐5, impeding its widespread adoption. This work takes a significant step forward by providing critical insights that bridge the gap in our understanding of the MTH process. It accomplishes this by connecting the (Koch‐carbonylation‐led) direct and dual cycle mechanisms, which operate during the early and steady‐state phases of MTH catalysis, respectively. To unravel these mechanistic intricacies, we have performed catalytic and operando (i.e., UV‐Vis coupled with an online mass spectrometer) and solid‐state NMR spectroscopic‐based investigations on the MTH process, involving co‐feeding methanol and acetone (cf. a key Koch‐carbonylated species), including selective isotope‐labeling studies. Our iterative research approach revealed that (Koch‐)carbonyl group selectively promotes the side‐chain mechanism within the arene cycle of the dual cycle mechanism, impacting the preferential formation of BTX fraction (i.e., benzene‐toluene‐xylene) primarily.

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The Reaction Network in the Conversion of 1,2,4-Trimethylbenzene over HZSM-5

Cited by 42 publications

References 16 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

The Effect of Silanisation on the Catalytic and Sorption Properties of Zeolites

Tracking the Impact of Koch‐Carbonylated Organics During the Zeolite ZSM‐5 Catalyzed Methanol‐to‐Hydrocarbons Process

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