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INFLUENCE OF H 2 S ON THE THERMAL CRACKING OF ALKYLBENZENES AT HIGH PRESSURE (70 MPA) AND MODERATE TEMPERATURE (583-623 K)

Abstract : Highlights  Pyrolysis of n-butylbenzene/H 2 S mixture (80 % : 20% mol) at 70 MPa and from 583 K to 623 K was performed in sealed gold tubes.  The main products are toluene, ethylbenzene, iso-butylbenzene and hydrocarbon gases (C 1 , C 2 and C 3).  Several organosulfur compounds are produced: mainly short thiols, phenylbutanethiols, and phenylthiophenes.  H 2 S accelerates the pyrolysis of n-butylbenzene by a factor up to almost 4 depending on the experimental conditions.  The molecular composition of the products is highly modified in the presence of H 2 S. Abstract The thermal cracking of n-butylbenzene was experimentally studied in the presence of H 2 S (80% : 20% mol) at high pressure (70 MPa), moderate temperature (583, 603 and 623 K) and for durations of 3, 7 and 15 days. The pyrolysis was performed in sealed gold tubes under isobaric conditions. Under these conditions, the conversion of n-butylbenzene varied between 2.5% and 73.2%. The pyrolysis of n-butylbenzene is accelerated by H 2 S by a factor of up to 3.6 depending on the operating conditions. This acceleration factor seems to decrease with increasing time and temperature. The apparent activation energy of the pyrolysis of n-butylbenzene decreases from 66.6 kcal/mol (pure n-butylbenzene) to 55.9 kcal/mol (n-butylbenzene in mixture with H 2 S). The main hydrocarbons produced are alkylbenzenes (mostly toluene and ethylbenzene), branched alkylbenzenes (mostly isomers of iso-butylbenzene and iso-heptylbenzene to a lesser extent) and short alkanes (from CH 4 to C 3). Several sulfur compounds are also produced and their relative abundances are in the range 4-16% depending on the operating conditions. These sulfur compounds are mostly short thiols (methanethiol, ethanethiol and propanethiols), phenylbutanethiols and phenylthiophenes. Additional experiments were also conducted with alkylbenzenes bearing shorter substituents than n-butylbenzene (toluene, ethylbenzene and n-propylbenzene) in order to hightlight the influence of the length of the side chain. Finally, the kinetic effect of H 2 S on the pyrolysis of n-butylbenzene was compared to its effect on n-octane pyrolysis: the effect seems antagonistic under the studied experimental conditions but some similarities can be highlighted.
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Contributor : Valerie Burkle-Vitzthum <>
Submitted on : Tuesday, November 19, 2019 - 4:08:15 PM
Last modification on : Tuesday, November 26, 2019 - 1:01:57 AM

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V. Burklé-Vitzthum, N.C. Leguizamon Guerra, C. Lorgeoux, D. Faure-Catteloin, R. Bounaceur, et al.. INFLUENCE OF H 2 S ON THE THERMAL CRACKING OF ALKYLBENZENES AT HIGH PRESSURE (70 MPA) AND MODERATE TEMPERATURE (583-623 K). Journal of Analytical and Applied Pyrolysis, Elsevier, 2019, 140, pp.423-433. ⟨10.1016/j.jaap.2019.04.025⟩. ⟨hal-02370894⟩

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