CORRELATIONS OF ADSORPTION ENERGIES WITH PHYSICAL AND STRUCTURAL-PROPERTIES OF ADSORBATE MOLECULES

The purpose of this work is to find a suitable method to correlate Hen ry's law adsorption energies such as the isosteric heat or the gas-sol id interaction energy. Available adsorption energies for a total of 63 gases distributed among five adsorbents-a zeolite, a silica gel, a ca rbon black, and two microporous carbons adsorbents were correlated wit h the boiling point, a critical constant ratio involving critical temp erature and critical pressure, the log of the octanol-water partition coefficient, and molecular structural energy. In the structural approa ch each gas molecule is considered to be composed of a series of struc tural units that each make a fixed contribution to the total molecular adsorption energy. Multiple regression analyses were done for each of the five adsorbent systems using the four main correlation methods. T he method based on the structural units of a molecule and its dipole m oment was found to give a 0.99 correlation coefficient for all five ga s-solid systems. This structural method was superior to correlations b ased on boiling points, critical constants, partition coefficients, an d various combinations of other physical properties that were also exa mined, Since there has been a variety of interest in either predicting the energy of adsorption or extent of adsorption for specific adsorba te-adsorbent pairs, our correlation results could be useful in future quantitative structure-activity relationship (QSAR) correlations of ad sorption. (C) 1997 Academic Press.