Heat of adsorption of benzene on synthetic faujasites

Khudiev, A. T.; Klyachko-Gurvich, A. L.; Brueva, T. R.; Isakov, Ya. I.; Rubinshtein, A. M.

doi:10.1007/bf00905733

Cited by 1 publication

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“…In the sodium form the cations in type 11 sites, of which there are 32 per unit cell are positioned such that they can interact specifically with adsorbed molecules (Breck, 1964). Such interaction is evidenced by the substantially higher heat of adsorption of benzene and cumene on SaY than HY (Tuang et al, 1967;Khudiev et al, 1968) and the significantly higher heat of adsorption of benzene over cyclohexane on NaY and CaY (Klaychko et al, 1967).…”

Section: Effect Of Diffusote-zeolite Interactionsmentioning

confidence: 99%

Counterdiffusion of liquid hydrocarbons in type Y zeolite: Effect of molecular size, molecular type, and direction of diffusion

Moore

Katzer

1972

AIChE Journal

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This paper presents experimental results on the counterdiflusion of liquid hydrocarbons in the Y zeolite as determined by an unsteady state technique using the zeolite powder. The critical diameter of aromatic molecules counterdiffusing with respect to cyclohexane into NaY zeolite has a marked effect upon the counterdiffusion rate. For a given molecular type, the s a l e parameter of critical molecular diameter correlates the size effect well. Molecular type, for example, toluene vs. phenol, also has a pronounced effect on the counterdiffusion rate. Those molecules showing stronger interactions with the zeolite have lower counterdiffusion rates. In both NaY and SK-500, the diffusion coefficients for adsorptive counterdiff usion are an order of magnitude greater than the diffusion coefficients for desorptive counterdiffusion indicating that factors other than simple intracrystalline diffusion as such are also important in zeolite counterdiffusion. Simple diffusion models do not account for the differences observed indicating that a more sophisticated approach is necessary. SCOPEZeolites play a very important role in the chemical and petroleum industry as both adsorbents and catalysts (Collins, 1968). Adsorbent applications utilize the strong selective adsorption which zeolites often show toward a compound or a class of compounds or the very fine, uniform pore structure which permits the adsorption of molecules smaller than a given critical diameter. Adsorbent applications involve the diffusion of at least one species and often the counterdiffusion of different species within the pore structure, and thus design of adsorption units requires information on diffusion and/or counterdiffusion rates (Roberts and York, 1967; Gehrhardt and Kyle, 1967; Fukunaga et al., 1968). Such information is not generally available, and thus the design of such units remains mainly an empirical art. In catalytic applications Correspondence concerning this paper should be addressed to J. R. Katzer. R. M. Moore is with the University of Technology, Loughborougb, England.since the locus of catalytic activity for many reactions is within the pore structure, the simultaneous counterdiffusion of reactants and products must occur within the structure. The presence of diffusion limitations in zeolite catalysts would reduce the activity observed and for multiple-step reactions could also alter the selectivity. Thus a quantitative understanding of counterdiff usion in zeolites is important to the engineering design of zeolite catalysts and of processes utilizing them.Very little information is available on counterdiff usion in zeolites. Furthermore, counterdiffusion rates are grossly different from single componcnt unidirectional rates, cannot be estimated from single component rates, and thus must be determined independently (Satterfield and Katzer, 1971). Studies of the counterdiffusion of hydrocarbons in large pore zeolites under practical conditions are necessary to provide an understanding of the important variables affecting it. Such work wi...

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Section: Effect Of Diffusote-zeolite Interactionsmentioning

confidence: 99%