The conversions of 1,3,5-trimethylbenzene over beta zeolite: effect of SiO2/Al2O3 ratio

Chu, S.J.; Chen, Yu Wen

doi:10.1002/(sici)1097-4660(199805)72:1<1::aid-jctb861>3.0.co;2-h

Cited by 6 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the plots, it is observed that 1,2,4-TMB consistently gave higher xylene yield than 1,3,5-TMB at all temperatures studied when compared at similar conversions. It is important to note that the xylene yields in this study are smaller than those reported over zeolite beta 4,9 where higher levels of conversions were reported.…”

Section: Xylene Yieldcontrasting

confidence: 75%

See 1 more Smart Citation

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

Tukur

Al-Khattaf

2007

Energy Fuels

View full text Add to dashboard Cite

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...

show abstract

Section: Xylene Yieldcontrasting

confidence: 75%

“…Almost all of the research on the TMB transformations has been carried out in fixed bed reactors [2][3][4][5][6][7][8][9][10][11] . Fluidized bed on the other hand reveals the importance of diffusional effects in these reactions.…”

Section: Introductionmentioning

confidence: 99%

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

Tukur

Al-Khattaf

2007

Energy Fuels

View full text Add to dashboard Cite

show abstract

“…Highest yield of xylenes was obtained at a temperature of 400 °C and toluene/TMB molar ratio of about 1:1. Chu and Chen used zeolite beta to investigate the effect of Si/Al ratios on TMB transformation. At low Si/Al ratios TMB disproportionation was favored in contrast to high Si/Al ratios, which favored the isomerization reaction.…”

Section: Introductionmentioning

confidence: 99%

Transformation of Toluene and 1,2,4-Trimethylbenzene over ZSM-5 and Mordenite Catalysts: A Comprehensive Kinetic Model with Reversibility

Waziri

Aitani

2010

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

The catalytic transformations of toluene, 1,2,4-trimethylbenzene (TMB), and an equimolar mixture of the two compounds were investigated over H-mordenite and H-ZSM-5 catalysts. A series of experiments were conducted in a riser simulator over a temperature range of 300−400 °C and reaction times of 5−20 s. The influence of reaction conditions on variation of 1,2,4-TMB conversion, toluene conversion, para- to ortho-xylene ratio, xylenes to TMB isomers ratio, 1,3,5-TMB to 1,2,3-TMB ratio, and xylenes to benzene ratio were discussed. The study also includes the development of comprehensive kinetic models for isomerization, disproportionation, and transalkylation reactions of 1,2,4-TMB and toluene. The models account for reversibility of the isomerization reaction based on values of temperature dependent thermodynamic equilibrium constants. Catalysts deactivation was modeled using an activity decay function based on time-on-stream (TOS). The developed models gave a good match with experimental data based on a statistically significant estimate of the kinetic parameters in the models. For the 1,2,4-TMB reaction and transalkylation of 1,2,4-TMB with toluene, the apparent activation energy over H-ZSM-5 was higher than that over H-mordenite (i.e., E app,(H-ZSM-5) > E app,(H-Mordenite)) while the reverse order was observed for the toluene reaction over the two catalysts. A simple correlation that gives accurate representation of the temperature dependency of thermodynamic equilibrium compositions of TMB isomers was also reported.

show abstract