Brunauer-Deming-Teller classification, adsorption

Figure 7.2 The Brunauer-Deming-Teller classification of isotherm types I to VI (from top left to bottom right). In each case adsorption uptake is plotted against p/Po, where p is the adsorbate pressure and Po the saturated vapour pressure of the pure liquid adsorbate at the isotherm temperature.

Fig. I.l The five types of adsorption isotherm, I to V, in the classification of Brunauer, Deming, Deming and Teller (BDDT), together with Type VI, the stepped isotherm.

Adsorption isotherms are plots of the amount of gas adsorbed at equilibrium as a function of the partial pressure p/p°, at constant temperature. The quantity of gas adsorbed is mainly expressed as the mass of gas (usually g) or the volume of gas reduced to STP (standard temperature and pressure). The majority of isotherms which result from physical adsorption may conveniently be grouped into five classes — the five types I to V included in the classification originally proposed by Brunauer, Deming, Deming and Teller — sometimes referred to simply as the Brunauer classification [2]. The essential features of these types are indicated in Fig. 12.1. 

The majority of isotherms which result from physical adsorption may conveniently be grouped into five classes, i.e., the five types I to V included in the classification originally proposed by Brunauer, Deming, Deming and Teller [4]. The essential features of these types are indicated in Fig. 13.3. 

Another important contribution by Brunauer, Deming, Deming and Teller [132] deals with the identification of five principal types of adsorption isotherms for gases and vapours. This identification is known as the BDDT classification and is recommended as the basis for a more complete classification introduced by lUPAC [15],... 

The nitrogen adsorption at 77 K of the samples is shown in Figure 1. The adsorption isotherms are of type I+II in the Brunauer, Deming, Deming and Teller (BDDT) classification... 

Experimental adsorption isotherms recorded in the literature, measured on a wide variety of gas-solid systems, have a wide variety of forms. Nevertheless, the majority of these isotherms which result from physical adsorption may conveniently be grouped into six classes in the IUPAC classification (cf. Figure 1.7). The first five types (I to V) of the classification were originally proposed by S. Brunauer, L.S. Deming, W.S. Denting and E. Teller as the BDDT classification (1940), sometimes referred to as the Brunauer classification (1945). 

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