Brunauer-Emmett Technique theory

Conventional bulk measurements of adsorption are performed by determining the amount of gas adsorbed at equilibrium as a function of pressure, at a constant temperature [23-25], These bulk adsorption isotherms are commonly analyzed using a kinetic theory for multilayer adsorption developed in 1938 by Brunauer, Emmett and Teller (the BET Theory) [23]. BET adsorption isotherms are a common material science technique for surface area analysis of porous solids, and also permit calculation of adsorption energy and fractional surface coverage. While more advanced analysis methods, such as Density Functional Theory, have been developed in recent years, BET remains a mainstay of material science, and is the recommended method for the experimental measurement of pore surface area. This is largely due to the clear physical meaning of its principal assumptions, and its ability to handle the primary effects of adsorbate-adsorbate and adsorbate-substrate interactions. 

The theory of physical adsorption of gas molecules on solid surfaces was derived by Brunauer, Emmett, and Teller (BET). The theory serves as the basis for the most widely used technique to assess specific surface area of powders and solids. It extends the Langmuir isotherm concept. 

A solid particle exposed to a gas will adsorb gas molecules on to its exposed surfaces. The derivation of a multilayer adsorption theory for gases on solid surfaces by Brunauer, Emmett and Teller in 1938 led to the development of the so-called BET adsorption methods for measuring the specific surface area of particulate solids. Several techniques are available (BS 4359/1, 1982 Lowell and Shields, 1984 Allen, 1990). 

Paul Emmett is best known for the leading role he played in developing, along with Steven Brunauer and Edward Teller, the BET theory for measuring the surface area of porous materials. This fundamental technique laid the foundation which ushered in the modem era of catalysis in the mid-1930s. 

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