Método de adsorção

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Colloidsand Surfaces
A: Physicochemicaland EngineeringAspects113 (1996) 39-50

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SURFACES

A pplication of the Dubinin-Radushkevich and Dubinin-Astakhov e quations in the characterization of microporous solids
A. Gil*, P. Grange
Unit~ de Catalyse et Chimie des Mat~riaux Divis~s, Universit~ Catholique de Louvain, Place Croix du Sud, 2/17,
1348 Louvain-la-Neuve, Belgium

Received 26 July 1995; accepted 16 January 1996

Abstract

The application of the Dubinin-Radushkevich (DR) and Dubinin-Astakhov (DA) equations to the characterization and comparison of microporous solids has been studied. Nitrogen adsorption isotherms at low relative pressures have been measured for a variety of microporous solids: four pillared clays (A1-PILC, SiA1-PILC, Ti-PILC and Zr-PILC), two zeolites (Y-82 and H-ZSM5), and two activated carbons. Both equations have been used to obtain the adsorption potential distributions for all samples. The pillared clays show bimodal adsorption potential distributions in both formalisms. These bimodal distributions are related to bimodal micropore size distributions, and the presence of two types of surfaces of adsorption in the micropores is also considered. The zeolites and activated carbons show singlepeaked distributions in both formalisms, but modifications of the adsorption potential distributions are observed.
Keywords: Adsorption isotherms; Adsorption potential distributions; Dubinin-Astakhov equation; Dubinin-

Radushkevich equation; Microporosity; Pillared clays

1. Introduction

T he physical adsorption of gases and vapours is a very useful technique for the characterization of p orous solids, and especially, microporous solids.
M any molecules of different sizes and polarities c an be used as adsorptives in order to obtain i nformation about the textural properties of the solids. Usually, the adsorption of nitrogen has been used to characterize microporous solids.
A n