Coke Formation in the Thermal Cracking of Hydrocarbons. 4. Modeling of Coke Formation in Naphtha Cracking

Reyniers, Geert C.; Froment, Gilbert F.; Kopinke, Frank‐Dieter; Zimmermann, G.

doi:10.1021/ie00035a009

Cited by 113 publications

(112 citation statements)

References 5 publications

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“…The coke macroradical then reacts by addition to unsaturated molecules and also to radicals from the gas phase. After dehydrogenation, graphitic layers with sp 2 hybridization for C are formed [20]. Ð A homogeneous non catalytic mechanism: The homogeneous non catalytic mechanism, or gas phase coking, results from a sequence of molecular and/or radical reactions in the gas phase leading to high molecular weight polynuclear aromatic compounds which can be solid even at the high temperatures prevailing in the cracker coil.…”

Section: Proposed Mechanism Of Coke Formationmentioning

confidence: 99%

Anticoking Coatings for High Temperature Petrochemical Reactors

Ropital

Broutin

Reyniers

et al. 1999

Oil & Gas Science and Technology - Rev. IFP

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RŽsumŽ Ñ Rev•tements pour rŽacteurs pŽtrochimiques ˆ cokage rŽduit Ñ La formation de coke est un probl•me crucial pour de nombreux procŽdŽs pŽtrochimiques. Ralentir le cokage permet de rŽduire la frŽquence des dŽcokages et de limiter la dŽgradation du transfert thermique. Un des moyens envisageables pour rŽduire le cokage est le dŽp™t dÕun rev•tement ˆ la paroi de ces rŽacteurs. La mise au point de tels rev•tements a fait lÕobjet dÕun projet de recherche europŽen Brite-Euram, pour lequel le vapocraquage a ŽtŽ la principale application considŽrŽe.

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Section: Proposed Mechanism Of Coke Formationmentioning

confidence: 99%

Anticoking Coatings for High Temperature Petrochemical Reactors

Ropital

Broutin

Reyniers

et al. 1999

Oil & Gas Science and Technology - Rev. IFP

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“…[17,18] The latter is formed during thermal cracking of hydrocarbons and is highly undesirable for the efficient operation of a cracking unit for the production of light alkenes. [19][20][21] Goddard et al [22] studied several elementary reactions involved in the thermal decomposition of larger polyaromatics. Vereecken et al [23] also studied the growth of PAHs incorporating five-membered rings, which can also act as possi-Hydrocarbon-bond dissociation enthalpies (BDE) at 298 K are calculated for a set of hydrocarbons.…”

Section: Introductionmentioning

confidence: 99%

Hydrocarbon Bond Dissociation Enthalpies: From Substituted Aromatics to Large Polyaromatics

2006

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Hydrocarbon-bond dissociation enthalpies (BDE) at 298 K are calculated for a set of hydrocarbons. An efficient method for calculating the BDE values is derived on the basis of a comparative study with experimental data. The methods considered are based on density functional theory (DFT) including the B3LYP, MPW1PW91, B3P86, B3PW91, MPW1P86, KMLYP, MPW1K and BMK functionals. The commonly known sequence for radical stability is quantified on the basis of BDE values. The recommended procedure is extrapolated to substituted aromatics and large polyaromatic hydrocarbons (PAHs) to obtain insight into the factors that govern the stability of the radicals. Furthermore it is shown that BDEs are also good reactivity descriptors for subsequent additions involving the formed radicals. Linear correlations, similar to classical Evans-Polanyi-Semenov plots, between the BDE and the reaction barriers for addition reactions with ethene, ethyne, propene, propyne and butadiene are found, as the exothermicity is primarily determined by the stability of the originating reactant radical.

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“…Calculated rate constants, activation energies, and pre-exponential factors for hydrogen abstraction at various sites in nonlinear methylated PAHs. The BMK/6-311 [12][13][14]. Analogous to the series of linear PAHs, the abstraction from methylated species occurs faster in comparison with the abstraction from non-methylated species.…”

Section: Rate Constants For the Nonlinear Methylated Pahsmentioning

confidence: 99%

“…Initially, semiempirical models were used to predict coke formation during thermal cracking for a limited range of feedstocks. [14,15] A model based on elementary reactions was, however, proposed by Wauters and Marin and this should have a much wider applicability. [2,3] It is in any case essential to have reliable estimates of the reaction rates in the mechanism, as pointed out by Zador et al in a recent sensitivity analysis study.…”

Section: Introductionmentioning

confidence: 99%

A DFT‐Based Investigation of Hydrogen Abstraction Reactions from Methylated Polycyclic Aromatic Hydrocarbons

2008

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The growth of polycyclic aromatic hydrocarbons (PAHs) is in many areas of combustion and pyrolysis of hydrocarbons an inconvenient side effect that warrants an extensive investigation of the underlying reaction mechanism, which is known to be a cascade of radical reactions. Herein, the focus lies on one of the key reaction classes within the coke formation process: hydrogen abstraction reactions induced by a methyl radical from methylated benzenoid species. It has been shown previously that hydrogen abstractions determine the global PAH formation rate. In particular, the influence of the polyaromatic environment on the thermodynamic and kinetic properties is the subject of a thorough exploration. Reaction enthalpies at 298 K, reaction barriers at 0 K, rate constants, and kinetic parameters (within the temperature interval 700-1100 K) are calculated by using B3LYP/6-31+G(d,p) geometries and BMK/6-311+G(3df,2p) single-point energies. This level of theory has been validated with available experimental data for the abstraction at toluene. The enhanced stability of the product benzylic radicals and its influence on the reaction enthalpies is highlighted. Corrections for tunneling effects and hindered (or free) rotations of the methyl group are taken into account. The largest spreading in thermochemical and kinetic data is observed in the series of linear acenes, and a normal reactivity-enthalpy relationship is obtained. The abstraction of a methyl hydrogen atom at one of the center rings of large methylated acenes is largely preferred. Geometrical and electronic aspects lie at the basis of this striking feature. Comparison with hydrogen abstractions leading to arylic radicals is also made.

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Coke Formation in the Thermal Cracking of Hydrocarbons. 4. Modeling of Coke Formation in Naphtha Cracking

Cited by 113 publications

References 5 publications

Anticoking Coatings for High Temperature Petrochemical Reactors

Anticoking Coatings for High Temperature Petrochemical Reactors

Hydrocarbon Bond Dissociation Enthalpies: From Substituted Aromatics to Large Polyaromatics

A DFT‐Based Investigation of Hydrogen Abstraction Reactions from Methylated Polycyclic Aromatic Hydrocarbons

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