On the Gonzalez-Holland model for adsorption of gas mixtures

✍ Scribed by Mieczyslaw Jaroniec; Malgorzata Borowko; Wladyslaw Rudzinski

• Publisher: American Institute of Chemical Engineers
• Year: 1977
• Tongue: English
• Weight: 292 KB
• Volume: 23
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690230432

✦ Synopsis

On the Gonzalez-Holland Model for Adsorption of Gas Mixtures Recently, Gonzalez and Holland (1970, 1971) derived interesting equations for multilayer adsorption isotherm of m-component gas mixtures on homogeneous surfaces: and I n the above equations m ( n -l l n an-1 = nn-2(1 + U ~-' @ ( ~) J + Y 2

for n h 2 (4) a 0 = 1 Equation ( l a ) has been derived on the assumption that the adsorption of all components in the second and higher layers is small relative to the adsorption of the componellts in the first layer. When the above assumption is not made, the more general result given by Equation ( l b ) is obtained. Both Equations ( l a ) and ( I b ) have been obtained on the basis of a Langmuir model with three additional assumptions characterizing the formation of mixed multilayer.

1. The adsorption of a given molecule in a given layer is independent of the identity of the molecule adsorbed beneath it in the previous layer.

The ratio of parameters characterizing the formation of the ( j + l)th and jth layer is constant, and it is independent of the kind of the component.

The adsorption layers are treated as independent; that is, the adsorption potential of the ith component in the jth layer pj,i is equal to the chemical potential of the ith component in the gas phase (pj,i = pi).

However, the BET equation is based on the assumption that formation of the fth layer depends upon formation of the ( jl)th layer; pj,i # p+ (see Hill, 1952).

Assumption 3 makes possible the separation of monolayer and multilayer effects in total adsorption; that is, the multilayer adsorption isotherm may be presented in the form of the product of the monolayer isotherm and a certain function describing the formation of the multilayer.