Xylene Isomerization over USY Zeolite in a Riser Simulator:  A Comprehensive Kinetic Model

Iliyas, Abduljelil; Al-Khattaf, S.

doi:10.1021/ie034133f

Cited by 29 publications

(23 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The decrease of I/D with temperature indicates that disproportionation reaction is more sensitive to temperature than isomerization. This observation is in line with the fact that disproportionation requires a higher energy of activation as compared to isomerization reaction [31][32][33]. conversion, this ratio decreases from 7.5 to 1.8 by increasing the temperature from 400 to 500°C.…”

Section: Isomerization To Disproportionation (I/d) Ratiosupporting

confidence: 77%

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

Al-Khattaf

2007

Chemical Engineering and Processing - Process Intensification

Self Cite

View full text Add to dashboard Cite

In the present work, the transformation of m-xylene was studied over fresh and pre-coked H-ZSM-5 catalyst in a riser simulator over the temperature range of 350-500 o C.Significant differences were observed in both the activity and product selectivity pattern for the two forms of the catalyst.While, the fresh catalyst generally gave higher m-xylene conversion, the pre-coked catalyst produced higher Isomerization/Disproportionation (I/D) and Para/ Ortho xylene (P/O) ratios .For both forms of the catalyst, m-xylene conversion was found to increase with both reaction temperature and reaction time (0-15 s). A maximum conversion of 30.8% was achieved at 500 o C for a reaction time of 15 s using the fresh catalyst. The corresponding value for the pre-coked catalyst was 24.6%. P/O and I/D ratios as high as 2.5 and 10 respectively were observed with the pre-coked catalyst. It was also observed that the P/O and I/D ratios decreased with increasing temperature for both catalyst and that the difference between these ratios for the two catalysts is more pronounced between 400 and 450 o C than at higher temperatures. Kinetic modeling of the m-xylene transformation over the pre-coked catalyst yielded a lower activation energy for p-xylene formation compared to the fresh catalyst. And an activation energy of 17.5 kcal/mol for the of m-xylene dispropotionation was obtained for the precoked catalyst compared to 7.82 kcal/mol for the fresh catalyst. These values are indicative of the restriction posed on disproportionation by the pre-coked catalyst as reflected by higher I/D ratios.

show abstract

Section: Isomerization To Disproportionation (I/d) Ratiosupporting

confidence: 77%

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

Al-Khattaf

2007

Chemical Engineering and Processing - Process Intensification

Self Cite

View full text Add to dashboard Cite

show abstract

“…fusion of molecules with higher dipole moment is more hindered due to stronger adsorption on highly acidic catalysts [28,43,45]. The dipole moments for OX, MX, and PX are 0.62, 0.36, and 0.00 D, respectively [46]; this might explain the lower diffusivity of OX in large-pore zeolites.…”

Section: )mentioning

confidence: 99%

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Gonçalves

Rodrigues

2015

Chem Eng & Technol

View full text Add to dashboard Cite

Three large-pore zeolites, Beta with Si/Al ratios of 25 and 35 and Mordenite with an Si/Al ratio of 30, were studied in the conversion of o-xylene at 493 K. Maximum conversion was achieved by the catalyst with the highest Si/Al ratio due to faster diffusion of the isomer inside the zeolite channels because of the lower acidity of the solid even with larger crystal size. A kinetic study was then carried out over this catalyst between 473 and 513 K in a batch reactor in the liquid phase. The activation energies obtained do not indicate the presence of diffusional constraints towards any isomer. Finally, the kinetic model obtained was simulated in a fixed-bed reactor and compared to ZSM-5 in the temperature range from 493 to 533 K. An increment in p-xylene production of 20 % on average was obtained.

show abstract

“…The advantage of utilizing rigorous models as compared to empirical approaches is that the prediction accuracy of rigorous models is significantly superior over a wide operating range, hence researchers pursue the kinetic model of process industries. As to C 8 -aromatics isomerization, many kinetic models have been developed over several zeolites [2][3][4][5][6]. Normally, hydrogen is added to promote the isomerization and to prevent the coking on catalyst in the hydroisomerization process.…”

Section: Introductionmentioning

confidence: 99%

“…As to the developed kinetic models, only a few models [4][5][6] consider the catalyst deactivation function. The ''reactant converted'' decay model has successfully accounted for the catalyst deactivation in low reactant yield.…”

Section: Introductionmentioning

confidence: 99%

Kinetic model for hydroisomerization reaction of C8-aromatics

Jin

et al. 2008

Front. Chem. Eng. China

View full text Add to dashboard Cite

Based on the reported reaction networks, a novel six-component hydroisomerization reaction network with a new lumped species including C 8 -naphthenes and C 8 -paraffins is proposed and a kinetic model for a commercial unit is also developed. An empirical catalyst deactivation function is incorporated into the model accounting for the loss in activity because of coke formation on the catalyst surface during the long-term operation. The Runge-Kutta method is used to solve the ordinary differential equations of the model. The reaction kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimization method (BFGS). The kinetic model is validated by an industrial unit with sets of plant data under different operating conditions and simulation results show a good agreement between the model predictions and the plant observations.

show abstract

Xylene Isomerization over USY Zeolite in a Riser Simulator: A Comprehensive Kinetic Model

Cited by 29 publications

References 29 publications

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

Enhancing p -xylene selectivity during m -xylene transformation using mildly pre-coked ZSM-5 catalyst

Xylene Isomerization in the Liquid Phase Using Large‐Pore Zeolites

Kinetic model for hydroisomerization reaction of C8-aromatics

Contact Info

Product

Resources

About