Coke formation on catalysts during the hydroprocessing of heavy oils

Absi‐Halabi, M.; Stanislaus, A.; Trimm, D.L.

doi:10.1016/0166-9834(91)85053-x

Cited by 221 publications

(96 citation statements)

References 24 publications

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“…3) and this effect may be of importance for the catalytic activity. A partial blocking of the pore entrance may lead to a decrease in accessibility of the reactants to the active sites [30,31]. Moreover, the unsupported CoMo catalyst derived from ATM presents a higher HDS activity than the material prepared from TMATM (Figs.…”

Section: Discussionmentioning

confidence: 99%

Preparation and Characterization of SBA-15 Supported Cobalt–Molybdenum Sulfide Catalysts for HDS Reaction: An All Sulfide Route to Hydrodesulfurization Catalysts

et al. 2008

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MoS 2 hydrodesulfurization (HDS) catalysts promoted with Co supported on SBA-15 were synthesized from sulfur-containing Mo sources [ammonium thiomolybdate (ATM), and tetramethylammonium thiomolybdate (TMATM)] and Co complexes cobalt dimethylthiocarbamate by using different synthesis strategies in order to achieve active catalysts. The (Co)-MoS 2 /SBA-15 catalysts were characterized with X-ray diffraction, N 2 -physisorption and High-Resolution Transmission Electron Microscopy. The catalytic performance in the HDS reaction of dibenzothiophene was examined at T = 623 K and P H2 = 3.4 MPa. The results of the experiments suggest that the sequence of impregnation steps has no significant influence on the HDS activity. On the other hand, the use of different thiomolybdate precursors significantly affects the catalytic activity. The catalysts derived from TMATM show lower HDS activities compared to the catalysts synthesized from ATM which is probably due to the presence of pronounced pore blocking as well as the generation of big needle-like aggregates of the Co-MoS 2 phase. It seems that the formation of intermediate MoS 3 is not a prerequisite for the generation of catalytic active CoMoS phases. The high activity and high selectivity for the direct desulfurization pathway of catalysts prepared with ATM despite the large MoS 2 stacking could be due to the generation of a large number of coordinately unsaturated sites.

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Section: Discussionmentioning

confidence: 99%

Preparation and Characterization of SBA-15 Supported Cobalt–Molybdenum Sulfide Catalysts for HDS Reaction: An All Sulfide Route to Hydrodesulfurization Catalysts

et al. 2008

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“…However, HDM and HDS conversions obtained with NiMo/Al 2 O 3 were higher than the CNF-supported catalysts. It is known that the tendency to form coke is highly related to the HDS and HDM activity [50]. The higher coke deposits obtained with NiMo/Al 2 O 3 would allow for the removal of a larger fraction of heteroatoms present in coke precursor molecules in the VR.…”

Section: Heteroatom Removalmentioning

confidence: 99%

Carbon nanofibres coated with Ni decorated MoS2 nanosheets as catalyst for vacuum residue hydroprocessing

Pinilla

Purón

Torres

et al. 2014

Applied Catalysis B: Environmental

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Catalysts based on functionalised carbon nanofibers (FCNF) coated with Ni-decorated MoS 2 nanosheets were obtained by direct decomposition of ammonium thiomolybdate and nickel nitrate impregnated on the FCNF under controlled temperature conditions in inert atmosphere. The catalysts were characterised by X-ray Diffraction (XRD), N 2 adsorption, Raman spectroscopy, temperature programmed reduction of sulfur species (TPR-S), NH 3 temperature programmed desorption (NH 3 -TPD) and transmission electron microscopy (TEM). Decomposition temperature was found to have a paramount importance in the formation of uniform MoS 2 slabs, as revealed by the TEM study: at 600 °C, non-uniform covering of the carbon nanofiber (CNF) was observed Higher asphaltene conversions were obtained for the CNF-supported catalysts prepared at 450 °C, which overperformed the Al 2 O 3 -supported benchmark catalyst. However, the catalytic performance in hydrodesulfurisation and hydrodemetallisation of the CNFbased catalysts was slightly lower than that of the benchmark catalyst.

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“…Three main mechanisms leading to catalyst deactivation have been identified: deactivation by coke deposition or "fouling", by metals and by pore mouth constriction and blockage [1,2]. Coke deposition occurs in the early stages of hydroprocessing and it reaches a pseudo steady state, whereas deactivation by metal deposits continues over a longer time scale [2][3][4].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms of Catalytic Activity in Heavily Coated Hydrocracking Catalysts

Millán

Adell

Hinojosa

et al. 2008

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Étude de mécanismes de l'activité des catalyseurs d'hydrocraquage avec fort cokageLa désactivation des catalyseurs par cokage a un impact direct sur la viabilité économique des procédés de raffinage d'hydrocarbures lourds, tels que la liquéfaction du charbon et l'hydrotraitement des résidus pétroliers. Le cokage est responsable de la perte rapide de l'activité du catalyseur qui a lieu principalement au début de l'hydrocraquage. Dans ce travail, les effets sur l'activité catalytique liés aux dépôts de carbone ont été étudiés sur un catalyseur à base d'argile de type chrome-montmorillonite. L'activité catalytique lors de l'hydrocraquage d'un extrait de charbon a été évaluée par la méthode de distribution des points d'ébullition des produits et réactifs. Ces derniers furent analysés par thermogravimétrie (TGA), puis caractérisés par chromatographie d'exclusion stérique (SEC) et spectroscopie de fluorescence. Lors de deux expériences successives de 2 heures chacune et pour lesquelles le catalyseur fût réutilisé, il a été constaté que la Cr-montmorillonite conservait toute son activité. Ceci en dépit d'un dépôt important de carbone, d'une diminution de sa surface d'échange et d'une obstruction apparente de ses pores. Certaines observations peuvent contribuer à l'explication de cette persistance de l'activité catalytique. Tout d'abord, des indications suggèrent l'aspect dynamique des dépôts de carbone, qui échangeraient continuellement de la matière avec la phase liquide, permettant ainsi à l'activité catalytique de perdurer. Ensuite, une analyse par microscopie électronique à balayage (MEB) de la Cr-montmorillonite, exposée lors des expériences, montre un dépôt localisé sur certaines zones du catalyseur, laissant ainsi une partie de la surface relativement libre. Enfin, les résultats de MEB couplé à un spectromètre X, suggèrent aussi que les dépôts sont plus clairsemés sur les zones où la phase active du catalyseur est en forte concentration. L'hydrogénation au niveau des sites actifs rendrait les dépôts plus solubles dans la phase liquide, libérant ainsi les zones adjacentes aux sites actifs. Abstract -Mechanisms of Catalytic Activity in Heavily Coated

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Coke formation on catalysts during the hydroprocessing of heavy oils

Cited by 221 publications

References 24 publications

Preparation and Characterization of SBA-15 Supported Cobalt–Molybdenum Sulfide Catalysts for HDS Reaction: An All Sulfide Route to Hydrodesulfurization Catalysts

Preparation and Characterization of SBA-15 Supported Cobalt–Molybdenum Sulfide Catalysts for HDS Reaction: An All Sulfide Route to Hydrodesulfurization Catalysts

Carbon nanofibres coated with Ni decorated MoS2 nanosheets as catalyst for vacuum residue hydroprocessing

Mechanisms of Catalytic Activity in Heavily Coated Hydrocracking Catalysts

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