Manganese Nodules as Demetalation Catalysts

Chang, Clarence D.; Silvestri, A.J.

doi:10.1021/i260051a024

Cited by 31 publications

(15 citation statements)

References 3 publications

(3 reference statements)

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“…The hydrodemetallation (especially the the conventional volumetric method and also by atomic abremoval of Ni and V from petroleum crude) activity of sorption spectrometry (Varian Model AA-1475). Acetic Pacific Ocean manganese nodules has been studied in great acid-sodium aceate buffer was used to maintain the pH of detail (14,15). A preliminary study on the removal of toxic the adsorbate.…”

Section: Introductionmentioning

confidence: 99%

Studies on Indian Ocean Manganese Nodules

Parida

Satapathy

Das

1996

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 99%

Studies on Indian Ocean Manganese Nodules

Parida

Satapathy

Das

1996

Journal of Colloid and Interface Science

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“…A model describing demetallation in a spherical, nonuniformactivity HDM catalyst was developed. Several investigators have observed the rate of metal removal to be first order with respect to metal concentration (Larson and Beuther, 1966;Chang and Silvestri, 1974;Spry and Sawyer, 1975;Dautzenberg et al, 1978;Riley, 1978;Pazos et al, 1981;Galiasso and Morales, 1983;Higashi et al, 1985). More complex reaction mechanisms have also been observed which may cause a local deposition maximum just inside the pore mouth.…”

Section: Deactivation Modelmentioning

confidence: 99%

Effect of nonuniform activity on hydrodemetallation catalyst

Limbach

Wei

1988

AIChE Journal

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A model is developed to qualitatively predict the effect of a nonuniform activity distribution on the total quantity of metal deposited in hydrodernetallation catalysts. A fixed catalyst support system is assumed and no restrictions are placed on local or overall catalytic activity in seeking an optimal solution that maximizes the amount of contaminant metal deposition over the useful catalyst life. Results indicate that deposition capacity could be substantially increased by a nonuniform activity profile in which the activity at the catalyst center is higher than that at the outer edge. The shape of the optimum activity profile is presented along with practical design improvements.

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“…Published kinetics studies (Dautzenberg et al, 1978;Beuther and Schmid, 1963;Chang and Silvestri, 1974;Gates et al, 1979;Satterfield and Roberts, 1968;Speight, 1981;Shah and Paraskos, 1975) have correlated experimental data for both hydrodemetallization and hydrodesulfurization by first and second order and Langmuir-Hindshelwood rate equations. In the concentration range where the hydrogen concentration in the liquid is much greater than the contaminant concentration, pseudofirst-order kinetics appears to be applicable.…”

Section: Page 740mentioning

confidence: 99%

Deactivation of hydrodesulfurization catalysts by metals deposition

Ahn¹,

Smith²

1984

AIChE Journal

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Primary causes of deactivation of hydrodesulfurization catalysts are partial poisoning of the interior pore surface and pore-mouth plugging by deposition of metals from organo-metallic compounds in the reactor feed. A model is developed to account for both causes of deactivation. It can be used to predict which occurs first: complete surface poisoning or pore-mouth plugging. Equations are formulated for catalyst activity as a function of time for demetallization and also for desulfurization. The results depend upon particle geometry and geometry of deposited species, Thiele moduli for demetallization and desulfurization, and relative rates of desulfurization on fresh and partially poisoned catalytic surfaces. The treatment is for a single, isothermal catalyst particle. BUM-JONG SCOPEThe irreversible deposition of metals, particularly vanadium and nickel, has been identified as a major cause of deactivation of hydrodesulfurization (HDS) catalysts. Tamm et al. (1981) has presented experimental data suggesting that partial surface poisoning by metals deposition is responsible for the initial rapid deactivation while pore-mouth plugging is predominant at longer times. Deactivation by pore plugging has been carefully analyzed mathematically by Rajagoplan and Luss (1979).They included the effect of restricted diffusivities in the pore when the metal deposit reduces the pore radius to the same magnitude as the size of the organo-metallic molecules.A similar quantitative treatment of the effects of combined partial surface poisoning and pore-mouth plugging on HDS catalyst activity does not appear to have been published. Our objective is to present such a combined model, which, amongst other aspects, will describe the conditions for which pore plugging will occur prior to complete surface poisoning. Since the large organo-metallic molecules have low diffusivities, the shell model of deactivation (Masamune and Smith, 1966) is employed to treat partial surface poisoning. The mathematical development is restricted to isothermal behavior of a single catalyst pellet with uniform pore-size distribution. First-order demetallization and desulfurization kinetics are assumed. CONCLUSIONS AND SIGNIFICANCEThe deactivation by metals deposition on HDS catalysts, due to the combination of partial surface poisoning and pore-mouth plugging, is described quantitatively in terms of two parameters. These are the Thiele modulus cp, for metals deposition and a partial poisoning parameter T which depends, among other quantities, on the porosity of the catalyst and the density of the metal deposits. For large values of cp, and T , it is shown that the pore mouth is physically blocked before the deposited metal reaches the center of the catalyst particle. When this occurs demetallization and HDS activity are reduced to zero even though only partially poisoned and fresh catalyst surface still exist within the particle. For small values of cp, and T all the pore surface becomes partially deactivated before pore plugging occurs.. Then some demetall...

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Manganese Nodules as Demetalation Catalysts

Cited by 31 publications

References 3 publications

Studies on Indian Ocean Manganese Nodules

Studies on Indian Ocean Manganese Nodules

Effect of nonuniform activity on hydrodemetallation catalyst

Deactivation of hydrodesulfurization catalysts by metals deposition

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