ISSN:
0001-1541
Schlagwort(e):
Chemistry
;
Chemical Engineering
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
Notizen:
A one-dimensional model is developed to describe reaction between a nonvolatile liquid reactant and a dissolved gas reactant in an isothermal catalytic pellet partially wetted by a flowing liquid film. The kinetics are assumed to be first order and zero order with respect to the dissolved gas and liquid reactant, respectively. The model applies to cases in which there are negligible intraparticle gradients in the direction normal to the wetted surface. A modification of the overall transport coefficients enables the model to approximate cases in which these gradients are important, for both washcoated and uniformly impregnated catalysts. The analytical solutions enable an efficient examination of the interplay between the reaction and several mass transport processes. Conditions are determined for which the catalyst effectiveness is maximized at an intermediate wetting efficiency. It is shown that the maximum is a result of two counteracting processes. As the wetting efficiency is decreased from unity the effectiveness increases if the supply of the gas reactant is more effective on the nonwetted than the wetted part; i.e., effectiveness enhancement. However, if the wetting efficiency is sufficiently reduced, the excess liquid reactant depletes within the pellet, resulting in a decreased effectiveness. A criterion is derived that predicts the minimal activity necessary to initiate depletion of the liquid reactant for a given wetting efficiency. This is useful for determining the conditions for which the common literature assumption of an excess liquid reactant is violated. The model shows good agreement with published data in which the overall rate exhibits a maximum for an intermediate liquid flow rate.
Zusätzliches Material:
13 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/aic.690330905
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