Thermodynamic Analysis for Rapid Measurements of Equilibrium Adsorption from Binary Gas Mixtures

Simple numerical and graphical procedures, based on an exact thermodynamic analysis (ETA), were developed to determine the experimental adsorbed-phase mole fractions of binary gas systems adsorbed at elevated pressures. Well-defined pure-gas isotherms were required along with the total amount adsorbed of a few data points from mixed-gas constant gas-phase composition isotherms. The procedures were tested with binary data consisting of only two or three mixed-gas isotherms containing between three and five data points each. The results from the numerical ETA compared very well with the binary data. The average absolute difference in the adsorbed-phase mole fractions for 69 mixed-gas data points was 0.02. Features of these ETA procedures are as follows: (1) Low-pressure mixed-gas data are not required. (2) The effects of gas-phase fugacity can be determined a priori with little effort. (3) For ideal gas and also for real gas, an iterative procedure is not necessary; a rapid graphical procedure can be used. (4) The binary data can be checked for thermodynamic consistency in three ways.