Concentration profiles in impregnation of porous catalysts: Nickel on alumina

Komiyama, Masaharu; Merrill, Robert P.; Harnsberger, H.F.

doi:10.1016/0021-9517(80)90058-5

Cited by 76 publications

(27 citation statements)

References 13 publications

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“…In the slow drying regime, where capillary flow is faster than evaporation, the migration of the metal component is determined by the competition of the capillary flow and diffusion. This is in agreement with the experimental results of Komiyama et al (1980) who reported that a uniform profile could be obtained at a very high drying rate and an egg-shell profile could be observed at a relatively low drying rate.…”

Section: Introductionsupporting

confidence: 94%

“…However, experimental work has shown that drying may also significantly impact the metal distribution within the support (Komiyama et al, 1980;Kotter and Riekert, 1983;Lee and Aris, 1985;Li et al, 1994;Maatman and Prater, 1957;Neimark et al, 1981). Therefore, to achieve a desired metal profile we need to have a fundamental understanding of both impregnation and drying.…”

Section: Introductionmentioning

confidence: 97%

“…The impact of impregnation on the distribution of active components in the support has been studied in a number of papers (Komiyama et al, 1980;Lee, 1984;Melo et al, 1980a,b;Vincent and Merrill, 1974). Theoretical models describing both wet and dry support impregnation have been also proposed.…”

Section: Introductionmentioning

confidence: 98%

“…They proposed a classification scheme used to differentiate the effect of processing variables and solvent ingredients on the distribution of Pt in alumina supports. A three-dimensional model was developed by Komiyama et al (1980) for impregnation of Nickel in alumina spheres. They found that the Nickel distribution profile strongly depends on the initial NiCl 2 concentrations.…”

Section: Introductionmentioning

confidence: 99%

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A parametric investigation of impregnation and drying of supported catalysts

Khinast

Glasser

2008

Chemical Engineering Science

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Section: Introductionsupporting

confidence: 94%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A parametric investigation of impregnation and drying of supported catalysts

Khinast

Glasser

2008

Chemical Engineering Science

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“…Guidelines for good judgments are of great value in such an environment. In view of the importance of the above separation processes, as well as the significant role that adsorption plays in catalyst preparation (such as, Komiyama et al, 1980), an investigation of the conditions, under which such an assumption can be justified, is long overdue. …”

mentioning

confidence: 99%

Assumption of local equilibrium in adsorption processes

Koopman¹,

Cole²,

Lee³

1992

AIChE Journal

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A local equilibrium between the concentration of adsorbate in the bulk fluid and surface phases is often assumed in the description of adsorption processes. This assumption leads to a considerable simplification in the problem by allowing an equilibrium treatment of the relationship between adsorbate concentration and surface coverage. The assumption indicates that the fractional coverage of the adsorbent by an adsorbate at any point in the process is in dynamic equilibrium with the adsorbate concentration in solution. Simple criteria developed here determine conditions under which such an assumption is justified.The local equilibrium assumption has been used in an equilibrium theory of parametric pumping (Pigford et al., 1969) to develop a theory for multicomponent chromatography (Rhee et al., 1970), to analyze multicomponent ion exchange adsorption separations in packed beds (Helfferich, 1967), and to model the concentration profiles during impregnation of porous catalysts (Vincent and Merrill, 1974). The assumption is almost invariably invoked in temperature-and pressure-swing adsorption separation modeling (Yang, 1987). Often this takes the form of a Langmuir isotherm or a linear version of the isotherm.Many of the empirical guidelines used in adsorption process engineering, such as that mass transfer is the rate-limiting step rather than adsorption kinetics, were developed from experience with processes involving adsorption of simple gas-phase molecules, strong adsorbents, and so on. Adsorption processing's scope has expanded considerably over the years, and adsorption separations have a significant foothold in the environmental and biochemical fields today. Engineers must deal with novel systems more often than in the past. Guidelines for good judgments are of great value in such an environment. In view of the importance of the above separation processes, as well as the significant role that adsorption plays in catalyst preparation (such as, Komiyama et al., 1980), an investigation of the conditions, under which such an assumption can be justified, is long overdue. Adsorption ProblemConsider the competitive adsorption of n species from a Correspondence concerning this work should be addressed to H. H. Lee fluid onto a solid adsorbent in a packed bed. Species' concentrations evolve based on the response times associated with various resistances, such as dispersion in the bulk fluid, mass transfer to the surface, convection, diffusion in porous adsorbents, and kinetics. To establish a direct absolute criteria between adsorption kinetic rate effects and bulk fluid convection effects, assume that all effects of mass transfer are negligible. The ultimately derived criteria will consequently state only when adsorption kinetics cannot be considered in equilibrium relative to bulk fluid change rates. The relative importance of mass transfer rate effects to either bulk convection or adsorption kinetic rate effects will not be established by what follows. These assumptions yield the following solute mass balances: wh...

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