Thermodynamic consistency for binary gas adsorption equilibria

An integral and a differential thermodynamic consistency test between pure and binary gas adsorption data and three differential thermodynamic consist ency tests for binary gas adsorption data alone can be formulated using the Gibbsian surface excess model of gas adsorption. These relationships origi nate from the Gibbs adsorption equation. It is necessary to measure the sur face excess of the components of the binary gas mixture as functions of pre ssure at constant gas phase composition and temperature, as functions of ga s phase compositions at constant pressure and temperature, and as functions of temperature at constant gas phase compositions and pressures, to apply these tests practically. The tests are very useful to check the quality of the data before they can be extrapolated for adsorptive process design usin g multicomponent equilibrium adsorption models. A set of pure and binary ga s data for adsorption of CH4 and N-2 on a 5A zeolite was used to demonstrat e the applicability of these consistency tests, and the data were found to be consistent by all tests. Some of these tests could not be applied previo usly because of a lack of sufficient data. A series of published pure and b inary gas adsorption equilibrium data sets on various microporous adsorbent s of practical interest, which passed the integral thermodynamic consistenc y test, is listed. They can be used to validate theoretical models for pred iction or correlation of multicomponent adsorption data. The criteria for o beying the thermodynamic consistency tests by several analytical pure and m ulticomponent gas adsorption models (Langmuir, Nitta et al., Toth, and Mart inet and Basmadjian) are derived. These models are frequently used in descr ibing experimental data on microporous homogeneous and heterogeneous adsorb ents.