The diffusion factor in coke formation on an aluminosilicate catalyst

Levinter, M. E.; Panchenkov, G. M.; Tanatarov, M. A.

doi:10.1007/bf00729189

Cited by 5 publications

(4 citation statements)

References 2 publications

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“…A density of 1800 kg/m 3 was assigned to the deposited coke . The number of parameters to be optimized is four in this model: , r P , C t , and M C .…”

Section: Resultsmentioning

confidence: 99%

Catalytic Combustion of n-Hexane on TiO₂−Anatase

Averlant

Perrier-Camby

Mollekopf

2005

Ind. Eng. Chem. Res.

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Deactivation of catalytic processes such as direct oxidation of hydrogen sulfide by coking through hydrocarbon combustion has always been a topic of concern. Using n-hexane as a model compound, we develop a kinetic model that predicts its coking rate on the basis of data obtained from a thermobalance. Considering two different processes in the coke reaction, active site coverage and coke growth, and applying a probabilistic model, we obtain an apparent activation energy of 34 and 126 kJ/mol, respectively. Thus, we estimate pore-plugging effects using two network models: a bundle of parallel cylindrical pores using a probabilistic model and a microporous network distributed in a Bethe lattice. Both models describe experimental data. Moreover, they confirm that the TiO 2 catalyst used first deactivates through active sites coverage and second through pore obstruction. As such, the model may be used for estimating deactivation of reactions taking place simultaneously on the catalyst.

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“…A density of 1800 kg/m 3 was assigned to the deposited coke . The number of parameters to be optimized is four in this model: , r P , C t , and M C .…”

Section: Resultsmentioning

confidence: 99%

Catalytic Combustion of n-Hexane on TiO₂−Anatase

Averlant

Perrier-Camby

Mollekopf

2005

Ind. Eng. Chem. Res.

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“…They noticed that the decrease in pore volume during coking was twice the volume of coke deposited. In a similar study, Levinter et al (1967) demonstrated that pore plugging was responsible for significant decreases in pore volume during cracking reactions of hydrocarbons. Suga et al (1967) reported a gradual decrease in effective diffusivity with coke content on catalyst.…”

Section: Nature and Role Of Coke Depositsmentioning

confidence: 90%

Analysis of zeolite catalyst deactivation during catalytic cracking reactions

Reyes¹,

Scriven²

1991

Ind. Eng. Chem. Res.

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Herman, R. G.; Klier, K. Reaction Kinetics of the Higher Alcohol and Oxygenate Synthesis over Cesium Doped Cu/ZnO Catalysta. Znd. Eng. Chem. Res. 1990, to be submitted. Tronconi, E.; Ferlazzo, N.; Forzatti, P.; Pasquon, I. Synthesis ofCatalyst deactivation during cracking reactions is analyzed in terms of the physical, chemical, and transport processes taking place within zeolite crystals. Special attention is given to the interactions of zeolite morphology and the wide range of components present in a typical cracking feed. By analyzing the functional form of activity decays, obtained via a detailed model of adsorption, diffusion, and reaction, it is possible to identify three regimes of deactivation. These can be classified as dynamical, chemical, and structural. They dominate the shape of the activity decay curves at short, intermediate, and longer times, and are related to competitive adsorption, site coverage, and pore blockage phenomena, respectively. The model predicts the correct activity patterns under a wide variety of reaction conditions, closely mimics those observed experimentally, and spans those obtained from available empirical correlations.0888.58851 91 / 2630-0071$02.50/0 -0 1991 American Chemical Societv

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“…Ozawa and Bischoff (1968) conclude that intraparticle diffusivities do not change significantly in the case of ethylene cracking on silica-alumina pellets, but this represents only experiments where coke deposition on catalyst is generally below 1%. Levinter et al (1967), however, reported losing up to 50% of the surface area through coke deposition, which indicates severe pore blockage and size reduction phenomenon. Stoll and Brown (1974), studying the rate of diffusion of gases in reacting and nonreacting systems, found that the effective diffusivities were generally lower when strongly adsorptive impurities were introduced.…”

Section: Introductionmentioning

confidence: 99%

Catalyst Deactivation by Pore Structure Changes. The Effect of Coke and Metal Depositions on Diffusion Parameters

Prasher¹,

Gabriel²,

Hua³

1978

Ind. Eng. Chem. Proc. Des. Dev.

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Diffusion data involving different sized hydrocarbon molecules in three different alumina based pellets are presented. One of the samples has not been used in any reactions, while the two other samples are the same pellets as the unused ones, except that they have been used for the hydrocracking of residuum under varying conditions of high temperature and pressure for several days. The results of the diffusion studies show that the used pellets exhibited severe reduction in intraparticle diffusion characteristics. If intraparticle diffusion influences rate of reaction for hydrocracking, then deactivation can at least partially be explained through the reduction of intraparticle diffusion characteristics, which can be accomplished through severe coke and metal depositions during reaction.

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The diffusion factor in coke formation on an aluminosilicate catalyst

Cited by 5 publications

References 2 publications

Catalytic Combustion of n-Hexane on TiO₂−Anatase

Catalytic Combustion of n-Hexane on TiO₂−Anatase

Analysis of zeolite catalyst deactivation during catalytic cracking reactions

Catalyst Deactivation by Pore Structure Changes. The Effect of Coke and Metal Depositions on Diffusion Parameters

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The diffusion factor in coke formation on an aluminosilicate catalyst

Cited by 5 publications

References 2 publications

Catalytic Combustion of n-Hexane on TiO2−Anatase

Catalytic Combustion of n-Hexane on TiO2−Anatase

Analysis of zeolite catalyst deactivation during catalytic cracking reactions

Catalyst Deactivation by Pore Structure Changes. The Effect of Coke and Metal Depositions on Diffusion Parameters

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Catalytic Combustion of n-Hexane on TiO₂−Anatase

Catalytic Combustion of n-Hexane on TiO₂−Anatase