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

Prasher, Brahm D.; Gabriel, G.A.; Hua, Yi

doi:10.1021/i260067a010

Cited by 43 publications

(26 citation statements)

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“…The catalyst fouling rate of HY zeolite in vapor phase was greater than that of silica alumina (Marczewski and Wojciechowski, 1982;Hano et al, 1975). The difference in the catalyst fouling rate between HY zeolite and silica alumina are caused by differences in concentration of strong acid sites and in diffusional limitation of reactant or product by coke deposition (Prasher et al, 1978;Rajagopalan and Luss, 1979). However, the observed deactivation coefficients for HY zeolite are smaller than those of silica alumina, and they tend to be proportional to the reaction rates.…”

Section: Discussionmentioning

confidence: 99%

Liquid phase decomposition of t‐butyl derivatives over solid acidic catalyst

Takahashi

Hong

Tashiro³

1985

Can J Chem Eng

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The de-r-butylation of some r-butyl-derivatives has been carried out in the liquid phase using amorphous silica alumina and HY type zeolite. The deactivation coefficients obtained in liquid phase were about 10 to 100 times as large as those in the vapor phase de-r-butylation of r-butylbenzene. The activation energies for the reaction of the phenolic derivatives were nearly the same as that for the vapor phase de-r-butylation. However, the activation energies for the di-t-butyl derivatives were almost doubled. The activity of HY type zeolite was lower than that of the silica alumina, but the shape selectivity of the former was observed in the reaction of p-t-butyl-o-phenol.On a procCdC 1 la d6-r-butylation de quelques dCrivCs r-butyliques, en phase liquide, en employant une silice-alumine amorphe et une zBolithe du type HY. Les coefficients de dksactivation obtenus en phase liquide ont 6tC a peu pres 10 a 100 fois plus grands que ceux de la db-t-butylation, en phase gazeuse du r-butyl-benzene. Les energies d'activation pour la rkaction des dBrivCs phCnoliques ont Ct6 presque les m&mes que pour la dC-t-butylation en phase gazeuse; toutefois, les Bnergies d'activation pour les dBrivCs di-r-butyliques ont presque doublC. L'activit6 de la zColithe de type HY a 6t6 plus faible que celle de la silice-alumine amorphe, mais on a observ6 une sClectivitC de forme de la premiere dans la &action du p-r-butyl-ortho-phCnol.

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Section: Discussionmentioning

confidence: 99%

Liquid phase decomposition of t‐butyl derivatives over solid acidic catalyst

Takahashi

Hong

Tashiro³

1985

Can J Chem Eng

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“…There have been a number of studies (Beck and Schultz, 1970;Prasher and Ma, 1977;Prasher et al, 1978;Thrash and Pildes, 1981;Deen et al, 1981;Galiasso and Morales, 1983) which have reported effective diffusivities of liquids within the pore structure of catalysts and other solids. The data in some studies (Sanerfield et al, 1973;Chantong and Massoth, 1983;Baltus and Anderson, 1983;Seo and Massoth, 1985) have generally been correlated by empirical equations of the type * *…”

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confidence: 99%

The diffusion of liquids in pores

Ternan¹

1986

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An equation for the diffusion of solute molecules in pores filled with liquids has been developed. It has been found to represent the diffusion of a variety of materials, from simple molecules to fractions of petroleum asphaltenes.On a Btabli une Bquation pour la diffusion de molkcules de solutB dans des pores remplies de liquides. On a montrB qu'elle peut reprksenter la diffusion de matBriaux aussi divers que des moltkules simples ou des fractions d'asphaltknes de p6trole.

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“…Both factors can account for the low diffusivity values obtained for the aged crushed catalysts. Prasher et al (1978) report diffusivities at 298 K for a number of aromatic compounds to be lowered by a factor of four to five for a catalyst exposed to resid for several days (probably containing mostly coke and little metals).…”

Section: Discussionmentioning

confidence: 98%

Diffusion and catalytic activity studies on resid‐deactivated HDS catalysts

1986

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Three different pore size CoMo/AI,O, catalysts, which had been deactivated to the same extent during bench-scale tests with an atmospheric resid, were examined for coke and metal deposits, diffusivity, and intrinsic activity for hydrodesulfurization, hydrogenation, and hydrodenitrogenation using model compounds. The aged catalysts had very low effective diffusivities and lower intrinsic activities than the fresh catalysts. Both metals and coke deposits were responsible for lowering diffusivity, but activity reduction appears to be predominantly due to metal deposits. B. G. Johnson, F. E. Massoth Department of Fuels EngineeringUniversity of Utah Salt Lake City, UT 841 12 J. BartholdyHaldor Topsoe Research Laboratories Lyngby, Denmark SCOPESupported CoMo /AI,O, catalysts have been used for many years to hydroprocess light to moderate molecular weight refinery feedstocks. Application of these catalysts to heavier feedstocks has been less successful because of catalyst deactivation. Residuum hydroprocessing catalysts must be replaced every six months to one year depending on the feedstock properties. The economic feasibility of such hydroprocessing is markedly affected by catalyst costs.The catalysts deactivate due to deposition of coke and metals from the feedstock onto the catalyst surface. These deposits cause lower intrinsic surface activity by covering active catalyst sites and cause lower catalyst effectiveness factors by pore constriction or blockage.It has been shown that the effective catalyst lifetime is a function of the catalyst support pore structure. Nielsen et al. (1981) and Hannerup and Jacobsen (1983) have shown that there is an optimum catalyst pore size giving a maximum lifetime for any particular feedstock and processing condition. Understanding the principles behind catalyst deactivation can lead to better designed catalysts with longer lifetimes.The objective of this study was to assess the role of the structural properties of the support on hydroprocessing catalyst deactivation. The physical properties of the fresh and aged forms of three different pore size CoMo/Al,O, catalysts were measured and compared. The catalysts were tested for room temperature effective diffusivity of a polyaromatic model compound using a method developed by this laboratory (Chantong and Massoth, 1983). High-pressure activity testing was used to determine the residual activity of the deactivated catalysts. CONCLUSIONS AND SIGNIFICANCECatalyst deactivation lowered the effective diffusivity of coronene at room temperature by a factor of over 500. This was a result of the buildup of an outer edge diffusion barrier, which was high in metals deposits. This diffusion barrier may significantly affect the catalyst effectiveness near the end of a hydroprocessing run.Metals and coke deposits lowered catalyst diffusivities by forming wedge-type deposits at pore mouths throughout the catalyst particles. Complete blockage of pore mouths by deposits did not occur in these cataCorrespondence concerning this papa should be address...

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

Cited by 43 publications

References 13 publications

Liquid phase decomposition of t‐butyl derivatives over solid acidic catalyst

Liquid phase decomposition of t‐butyl derivatives over solid acidic catalyst

The diffusion of liquids in pores

Diffusion and catalytic activity studies on resid‐deactivated HDS catalysts

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