Deactivation kinetics and modelling of coke removal under supercritical conditions for the example of ethylbenzene disproportionation

Niu, Fenghui; Kolb, Gunther; Hofmann, H.

doi:10.1002/ceat.270180409

Cited by 12 publications

(4 citation statements)

References 6 publications

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Section: Introductionmentioning

confidence: 99%

“…Niu et al demonstrated the significant power of supercritical fluids for the in situ regeneration of coked Y-zeolite catalyst in the disproportionation of ethylbenzene. Deactivation and coke removal kinetics were derived from experimental data for the same reaction over a Y-faujasite catalyst . Niu and Hofmann demonstrated that the coke deposition profiles were dependent upon the physicochemical properties of the catalysts used and made comparisons between the behavior of USY-zeolite, H-ZSM-5, and H-mordenite.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Wang

Chigada

Al‐Duri

et al. 2011

Ind. Eng. Chem. Res.

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Catalytic deactivation caused by coking was studied in zeolite Y and ZSM5 during 1-hexene isomerization under subcritical and supercritical conditions. The effects of varying temperature and pressure, from 220 to 250 °C and from 10 to 70 bar, respectively, on conversion and coke deposition were studied in both zeolites. Thermogravimetric analysis (TGA) data, diffuse reflectance infrared Fourier transform spectra (DRIFTS), and nitrogen sorption isotherms for fresh and coked catalysts were compared. In zeolite Y an exponential decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 °C and 40 bar than subcritical conditions at 235 °C and 10 bar. It is thought that in zeolite Y the micropores with diameter 7.4 Å could accommodate coke molecules leading to the observed deactivation; however, in ZSM5 the micropores of 5.3À5.6 Å diameter were too small to accommodate coke molecules, and thus coke was deposited outside the zeolite crystals within the mesopores of the alumina binder. Although zeolite Y deactivated, while ZSM5 did not, the use of a supercritical fluid reaction environment enabled the conversion at 235 °C, 40 bar to be maintained at 42% over zeolite Y, which was higher than the conversion of 34% over ZSM5 catalyst under the same conditions. Operating with supercritical fluid led to the partial alleviation of the significant coking effects observed with zeolite Y and improved its viability for use in this reaction compared with the performance of ZSM5.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Wang

Chigada

Al‐Duri

et al. 2011

Ind. Eng. Chem. Res.

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“…As to the application of supercritical fluid to the regeneration of deactivated catalysts, while most works have been focused on the removal of oligomers on solid acid catalysts,12–16 less attention has been received by the reactivation of metal catalysts for hydrogenation reactions by this technique. Available examples include scCO 2 reactivation of a Pd/Al 2 O 3 catalyst for cyclododecatriene hydrogenation,17 and scCO 2 regeneration of a spent Pd/AC catalyst used in the hydrogenation of a variety of organic compounds 18, 19.…”

Section: Introductionmentioning

confidence: 99%

Reactivation of spent Pd/AC catalyst by supercritical CO₂ fluid extraction

2009

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In this article, we reported a nondestructive and environmentally friendly method for the reactivation of a spent Pd/AC catalyst for the hydrogenation of benzoic acid by using supercritical CO 2 (scCO 2 ) fluid extraction. The effects of reactivation conditions, such as extraction temperature, pressure, CO 2 flow rate, and time, on the activity of the reactivated Pd/AC catalyst, were presented. The catalyst was characterized by N 2 physisorption, laser particle size analysis, and transmission electron spectroscopy, and the liquid extract was analyzed by GC-MS. It is found that scCO 2 fluid extraction was very efficient in eliminating organic substances blocking the pores of the catalyst, while did not affect noticeably the granule size of the catalyst and the particle size of Pd. The reactivated Pd/AC catalyst regained more than 70% of the activity of the fresh 5.0 wt % Pd/AC catalyst, and has been successfully used in an industrial unit for the hydrogenation of benzoic acid. V

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“…Modeling of coke formation (Subramaniam and McCoy, 1994) and studies of supercritical (sc) adsorption-desorption (Ginosar and Subramaniam, 1995) were also studied. The optimum catalyst activity (Baptist-Nguyen and Subramaniam, 1992), the in situ extraction of coke precursors by supercritical fluids (Clark and Subramaniam, 1998) and the deactivation kinetics and modeling of coke removal under sc conditions (Niu and Hofmann, 1997;Niu et al, 1995) were also examined.…”

Section: Introductionmentioning

confidence: 99%

Coking and Ex Situ Catalyst Reactivation Using Supercritical CO₂: A Preliminary Study

Trabelsi

Abaroudi

Larrayoz

et al. 2000

Ind. Eng. Chem. Res.

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High initial conversions for the cyclododecatriene (CDT) hydrogenation in a slurry reactor at 433 K and 1.2 MPa were obtained from a supercritical (sc) CO 2 -cleaned 0.5% Pd/Al 2 O 3 catalyst. A recovered intermediate selectivity was achieved by the sc CO 2 -cleaned catalyst at the higher CDT conversion values, suggesting an effective cleaning of Pd sites and a possible reconstruction of the residual coke layers onto the surface caused by the solvent nature of sc CO 2 . SEM pictures show that the cleanup of the used catalyst with sc CO 2 removes most of the coke and oily materials from the surface. Pd SEM X-ray microanalysis evidenced a decrease of the Pd dispersion on the surface of the used-activated catalyst. Coke was also characterized using elemental analysis and TGA in air, indicating that about 80 wt % of the deactivating materials were efficiently removed from the surface by sc CO 2 . The formation of the oligomerized and stabilized residual coke (remaining 20%) should be presumably avoided if the catalytic hydrogenation had taken place at sc (in situ) conditions where oligomerization times are minimized. The SCF conditions are then highly challenging at the catalytic hydrogenation of polyunsaturated hydrocarbons.

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Deactivation kinetics and modelling of coke removal under supercritical conditions for the example of ethylbenzene disproportionation

Cited by 12 publications

References 6 publications

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Reactivation of spent Pd/AC catalyst by supercritical CO₂ fluid extraction

Coking and Ex Situ Catalyst Reactivation Using Supercritical CO₂: A Preliminary Study

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Deactivation kinetics and modelling of coke removal under supercritical conditions for the example of ethylbenzene disproportionation

Cited by 12 publications

References 6 publications

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Deactivation during 1-Hexene Isomerization over Zeolite Y and ZSM5 Catalysts under Supercritical Conditions

Reactivation of spent Pd/AC catalyst by supercritical CO2 fluid extraction

Coking and Ex Situ Catalyst Reactivation Using Supercritical CO2: A Preliminary Study

Contact Info

Product

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Reactivation of spent Pd/AC catalyst by supercritical CO₂ fluid extraction

Coking and Ex Situ Catalyst Reactivation Using Supercritical CO₂: A Preliminary Study