Porous texture standard isotherm

The importance of Standard Isotherms in the Analysis of Adsorption Isotherms for Determining the Porous Texture of Solids, pp 265-281. 

The characterization of the porous texture of the inhia] and oxidized activated carbon and the catalysts was achieved using nitrogen adsorption at 77.4 K in a standard volumetric apparatus. The nitrogen adsorption isotherms were used for detomining the follovnng texture parameters specific surface area (Sb t), by the BET method nucropore volume (Vj and specific surface area of the mesopores the t/F method mesopore vdume... 

Conunonly, textural characterization of porous solids is carried out by physical adsorption of gases, which can be analyzed using several theories, to provide detailed information about the carbon micropore structure. A number of attempts have been made to establish standard procedures for the interpretation of the adsorption data in the characterization of porous solids [11-13]. However, there is still a lack of agreement on the assessment and interpretation of the adsorption data [14], and the results found in the literature depend upon the theory used to interpret the isotherms [15-18]. Usually, the PSD of porous solids is evaluated firom N2 adsorption at 77 K, and the structural heterogeneity of the microporosity is determined from the Dubinin-Radushkevich method (DR) and its modifications (Dubinin-Asthakov, DA,... 

Gas adsorption is the standard technique to study the textural properties of porous solids (ref. 1). The classical technique is based on incremental additions of gas providing a discret set of points along the isotherm. This technique can be referred as a "discret technique. It appears to be limited and time consumming when high accuracy is required. This is especially true in the case of microporous solids. To overcome this intrinsec limitation, "continuous" adsorption techniques have been developed. In these techniques the adsorbate is admitted to the sample tube at a slow flow rate. As it is critical to maintain, at any given time, the adsorption equilibrium, very low adsorbate flow rates must be used. 

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