Kinetics of coke combustion during temperature-programmed oxidation of deactivated cracking catalysts

Minh, Cam Le; Brown, Thomas J.

doi:10.1016/s0167-2991(97)80178-4

Cited by 11 publications

(8 citation statements)

References 20 publications

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“…High carbon content coke is burnt off afterwards at higher temperatures [98,99]. This is why water is the first molecule observed on a classical TPO spectrum, followed by CO and CO 2 production, which corresponds to the competing mechanisms of carbon oxidation [98,100,101]. Intrinsic mechanisms of coke have not been formally determined yet since coke nature has a great influence over the oxygenated intermediates formed during oxidation, which are considered as precursors for carbon oxide formation [102].…”

Section: Oxidation Mechanismsmentioning

confidence: 99%

“…Intrinsic mechanisms of coke have not been formally determined yet since coke nature has a great influence over the oxygenated intermediates formed during oxidation, which are considered as precursors for carbon oxide formation [102]. The following equations presented in Table 1 are commonly used to describe more precisely the steps of coke combustion, from light coke dehydrogenation to heavy coke oxidation via the formation of oxygenated intermediates [100,101]. Table 1.…”

Section: Oxidation Mechanismsmentioning

confidence: 99%

“…As for every reaction, coke oxidation is influenced by different parameters (as developed in Section 3.1.3. [101,103].…”

Section: Heavy Coke Combustionmentioning

confidence: 99%

“…Thanks to mass loss, determined by microgravimetry, and to the formed products during oxidation, commonly analyzed in-line via GC-MS, it is possible to extract information about coke nature. Some data concerning global oxidation mechanisms are also available from TPO curves, typically showing distinct oxidation peaks for hydrogen (H 2 O firstly observed) and carbon removal (mixed CO/CO 2 ) [101]. Chen et al used TPO experiments to characterize coke formed over Y-zeolite during catalytic pyrolysis of PE and observed, from the deconvolution curves (dash lines) presented in Figure 20, two types of coke: external coke with a peak temperature at 400-433 • C and internal coke oxidized at 464-488 • C [65].…”

Section: Coke Analysismentioning

confidence: 99%

“…These models integrate variable input parameters such as oxygen concentration or heating rate influencing oxidation kinetics. Kinetic parameters are determined using models that best fit experimental data [101,106].…”

Section: Reactivity and Kineticsmentioning

confidence: 99%

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Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

2021

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In catalytic industrial processes, coke deposition remains a major drawback for solid catalysts use as it causes catalyst deactivation. Extensive study of this phenomenon over the last decades has provided a better understanding of coke behavior in a great number of processes. Among them, catalytic pyrolysis of plastics, which has been identified as a promising process for waste revalorization, is given particular attention in this paper. Combined economic and environmental concerns rose the necessity to restore catalytic activity by recovering deactivated catalysts. Consequently, various regeneration processes have been investigated over the years and development of an efficient and sustainable process remains an industrial challenge. Coke removal can be achieved via several chemical processes, such as oxidation, gasification, and hydrogenation. This review focuses on oxidative treatments for catalyst regeneration, covering the current progress of oxidation treatments and presenting advantages and drawbacks for each method. Molecular oxidation with oxygen and ozone, as well as advanced oxidation processes with the formation of OH radicals, are detailed to provide a deep understanding of the mechanisms and kinetics involved (direct and indirect oxidation, reaction rates and selectivity, diffusion, and mass transfer). Finally, this paper summarizes all relevant analytical techniques that can be used to characterize deactivated and regenerated solid catalysts: XRD, N2 adsorption-desorption, SEM, NH3-TPD, elemental analysis, IR. Analytical techniques are classified according to the type of information they provide, such as structural characteristics, elemental composition, or chemical properties. In function of the investigated property, this overall tool is useful and easy-to-use to determine the adequate analysis.

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Section: Oxidation Mechanismsmentioning

confidence: 99%

Section: Oxidation Mechanismsmentioning

confidence: 99%

“…As for every reaction, coke oxidation is influenced by different parameters (as developed in Section 3.1.3. [101,103].…”

Section: Heavy Coke Combustionmentioning

confidence: 99%

Section: Coke Analysismentioning

confidence: 99%

Section: Reactivity and Kineticsmentioning

confidence: 99%

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Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

2021

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The structure of deposited coke on hydrocracking and reforming catalysts: Coke deactivation and kinetics

Shakor,

Alasseel,

Al‐Shafei

2024

Can J Chem Eng

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This comprehensive study investigates the structural deposition of coke, particularly its association with sulphides, in spent hydrocracking and reforming catalysts, leveraging advanced kinetic modelling and characterization techniques. Its objective is to elucidate coke removal kinetics, offering insights into optimizing catalyst regeneration. Utilizing thermogravimetric analysis, spectroscopic methods, and modelling, the research outlines the characteristics and kinetic behaviour of coke during regeneration. The novelty aspect of this study is the use of a reaction‐based model for accurate kinetic analysis and identifying optimal conditions for coke removal. The study recognized both hydrogen‐deficient and hydrogen‐rich amorphous coke, alongside graphitic coke spent catalysts. Thermogravimetric analysis revealed that coke constitutes ~23.8% and 4.6% of the total weight in hydrocracking and reforming catalysts, respectively. The traditional model‐free method for deactivation was found inadequate in predicting coke in the spent reforming catalyst, likely due to the presence of low‐temperature hydrocarbons of soft coke within the catalyst pores. In contrast, a reaction model‐based deactivation approach yielded more consistent evaluations for soft and hard coke of spent catalyst. For the spent hydrocracking catalyst, the estimated activation energies for coke decomposition were 41.56 and 128.97 kJ/mol for soft and hard coke, respectively, during regeneration. Although the coke in the spent reforming catalyst displayed similar temperature trends for decomposition, the average activation energies were 52.61 and 128.62 kJ/mol for soft and hard coke, respectively. The theoretical results from the multi‐reaction model for coke decomposition are consistent with the experimental results for both catalysts.

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Influence of hydrocarbon species on its adsorption on a VSCR catalyst under simulated diesel engine operating conditions

Ottinger

Liu

2017

Applied Catalysis B: Environmental

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Kinetics of coke combustion during temperature-programmed oxidation of deactivated cracking catalysts

Cited by 11 publications

References 20 publications

Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

Deactivation and Regeneration of Zeolite Catalysts Used in Pyrolysis of Plastic Wastes—A Process and Analytical Review

The structure of deposited coke on hydrocracking and reforming catalysts: Coke deactivation and kinetics

Influence of hydrocarbon species on its adsorption on a VSCR catalyst under simulated diesel engine operating conditions

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