Physical Adsorption of Mixed Gases at Very Low Pressures

Adsorption of mixed gases, N2-CO, CO-CO2 and Kr-CO, on a Pyrex glass surface were observed at the pressure range of 10-6 to 10-8Torr and at the temperature of 77.4°K. The amounts of adsorption for component gases were measured by using the thermal desorption method for various adsorption times (i.e. cooling times of the adsorbent). The results show that the gas components with higher activation energy of desorption replace the components with lower activation energy of desorption. The replacement of gases physisorbed at low temperature and at low coverage suggests the heterogeneous nature of the Pyrex glass surface which was so far deduced from the analysis of adsorption isotherms.