Formation of Coke on Hydrotreating Catalysts and its Effect on Activity

Zeuthen, P.; Bartholdy, Jesper; Wiwel, Peter; Cooper, Barry H.

doi:10.1016/s0167-2991(08)62741-x

Cited by 28 publications

(20 citation statements)

References 7 publications

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“…Soft coke is thought to form by condensation of components of the feed onto the catalyst surface, whilst hard coke forms by reaction of the coke upon the catalyst. The formation of hard coke indicates the polymerization and breakage of side chains from aromatic compounds because hard coke has been associated with the presence of large polynuclear aromatics (Zeuthen et al 1994). The increased deposit of hard coke at 450°C indicates that the catalyst was more reactive toward coke at this temperature and that the more-severe conditions, led to the possible formation of polynuclear aromatics upon the catalyst surface, rather than the larger quantity of soft coke formed at the lower reaction temperatures.…”

Section: Analysis Of Coke Depositsmentioning

confidence: 99%

Experimental Optimization of Catalytic Process In Situ for Heavy-Oil and Bitumen Upgrading

Shah

Fishwick

Leeke

et al. 2011

Journal of Canadian Petroleum Technology

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Summary The worldwide conventional crude-oil demand is on the rise, and because of the rising prices, unconventional oils are becoming more economically attractive to extract and refine. However, technological innovation is needed if heavier oil supplies are to be exploited further. Toe-to-heel air injection (THAI) and its catalytic add-on processes (CAPRI) combine in-situ combustion with catalytic upgrading using an annular catalyst packed around the horizontal producer well. These techniques offer potentially higher recovery levels and lower environmental impact than alternative technologies (e.g., steam-based techniques). An experimental study is reported concerning the optimization of catalyst type and operating conditions for use in the THAI-CAPRI process. The feed oil was supplied from the Whitesands THAI-pilot trial. Experiments were carried out using microreactors containing 10 g of catalyst, with oil flow of 1 mL/min and gas flow of 0.5 L/min, under different temperatures, pressures, and gas environments. Catalysts tested included alumina-supported CoMo, NiMo, and ZnO/CuO. It was found that there was a trade-off in operation temperature between upgrading performance and catalyst lifetime. At a pressure of 20 bar, operation at 500°C led to an average of 6.1°API upgrading of THAI oil to 18.9°API, but catalyst lifetime was limited to 1.5 hours. Operation at 420°C was found to be a suitable compromise, with upgrading by an average of 1.6°API, and sometimes up to 3°API, with catalyst lifetime extended to 77.5 hours. Coke deposition occurred within the first few hours of the reaction, such that the catalyst pore space became blocked. However, upgrading continued, suggesting that thermal reactions or reactions catalysed by hydrogen transfer from the coke itself play a part in the upgrading reaction mechanism. The CAPRI process was relatively insensitive to changes in reaction-gas medium, gas-flow rate, and pressure, suggesting that the dissolution of hydrogen or methane from the gas phase does not play a key role in the upgrading reactions. By careful control of the temperature and oil-flow rate in the in-situ CAPRI process, additional upgrading compared with the THAI process alone may be effected, resulting in a more-valuable produced oil, which is easier to transport.

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Section: Analysis Of Coke Depositsmentioning

confidence: 99%

Experimental Optimization of Catalytic Process In Situ for Heavy-Oil and Bitumen Upgrading

Shah

Fishwick

Leeke

et al. 2011

Journal of Canadian Petroleum Technology

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“…Thus there are many ways in which catalysts deactivate; nevertheless, these can be grouped basically into five intrinsic mechanisms of catalyst decay: (I) poisoning, (2) fouling, (3) thermal degradation, (4) loss of catalytic phases by vapor-solid and/or solid-solid reactions (including formation of volatile compounds), and (5) attrition. Since ( I ) and (4) are essentially chemical in nature, whereas (2) and (5) are mechanical, the causes of deactivation are basically three types: chemical, mechanical and thermal.…”

Section: Causes and Mechanisms Of Deactivationmentioning

confidence: 99%

“…Two principal mechanisms are involved in mechanical failure of catalyst agglomerates: (1) fracture of agglomerates into smaller agglomerates of approximately 0.2 do -0.8 do and (2) erosion (or abrasion) of small aggregates of primary particles having diameters ranging from 0.1 to 10 pm from the surface of the agglomerate (Pham et al, 1999). While erosion is caused by mechanical stresses, fracture may be due to mechanical, thermal and/or chemical stresses.…”

Section: Mechanical Failure: Attrition and Crushing Of Catalystsmentioning

confidence: 99%

“…Accelerated laboratory experiments involving deactivating catalysts are useful in (1) simulating a process, (2) determining kinetic data to be used in modeling or design of a process, and (3) understanding the mechanisms of decay. Accelerated laboratory experiments involving deactivating catalysts are useful in (1) simulating a process, (2) determining kinetic data to be used in modeling or design of a process, and (3) understanding the mechanisms of decay.…”

Section: Experimental Assessment Of Deactivation Kineticsmentioning

confidence: 99%

See 1 more Smart Citation

Catalyst Deactivation: Causes, Mechanisms, and Treatment

2005

Fundamentals of Industrial Catalytic Processes

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“…For this type of catalysts, coke and metal depositions are the main causes of deactivation. Several studies on deactivation by metals and coke in hydroprocessing catalysts have been reported [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Nonetheless, only few studies on deactivation pattern along residue hydrotreating bench-scale reactor have been published [29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%