CALORIMETRIC HEATS OF ADSORPTION AND ADSORPTION-ISOTHERMS .1. O-2, N-2, AR, CO2, CH4, C2H6 AND SF6 ON SILICALITE

A Tian-Calvet type calorimeter is applied to the simultaneous determin ation of adsorption isotherms and heats of adsorption. This is the fir st of a series of studies of the effect of adsorbate size and polarity on the energetics of adsorption in zeolites. The adsorbate gases used is this study are quadrupolar (N-2 and CO2) and nonpolar (Ar, O-2, CH 4, C2H6, and SF6). The heats of adsorption of both polar and nonpolar gases are either constant or increase with coverage, so silicalite may be classified as a relativity homogeneous adsorbent compared to X typ e zeolite, Reversibility was established by comparing adsorption and d esorption isotherms. Reproducibility was studied by comparing runs for different samples of the same adsorbent, The average experimental err or in loading is +/-0.6%. The error in the isosteric heat of adsorptio n is +/-2% for heats lar ger than 20 kJ/mol and +/-5% for heats smalle r than 20 kJ/mol.