ADSORPTION EQUILIBRIA OF HYDROGEN, DEUTERIUM, AND THEIR MIXTURES. PART I

Abstract

Adsorption isotherms of hydrogen and deuterium have been measured at temperatures of 75–90 °K and pressures up to 760 mm Hg on the following six adsorbents: charcoal (2), silica gel, and Linde molecular sieves type 4A, 5A, and 13X.Deuterium was found to be adsorbed to a greater extent than hydrogen in all cases investigated, its isosteric heat of adsorption exceeding that of hydrogen by 50 to 300 cal/mole.Binary adsorption isotherms were determined on the same adsorbents in the range 10–90% D₂ at temperatures of 75 and 90 °K and a total pressure π of 750 and 200 mm Hg. The analyses were performed by the thermal conductivity method using thermistor sensing elements in a static system at atmospheric pressure. The device proved of exceptional stability, requiring no recalibrations and yielding an analytical accuracy of better than 0.02% deuterium content. The binary separation factors α were found to be constant over the concentration range investigated, with values for α varying from about 1.25 on charcoal to 2.54 on type 4A molecular sieves at 75 °K and 750 mm Hg. The results suggest that the variations in α are due mainly to differences in chemical composition of the adsorbents rather than pore size, surface area, or origin of the materials.