Systematic study of the excess and the absolute adsorption of N2/H2 and CO2/H2 mixtures on Cu-BTC

In this work, we report thermodynamically consistent adsorption data of H-2/N-2 and H-2/CO2 mixtures on Cu-BTC at 297K and pressures up to 1000kPa. The measurements were performed on a recirculation volumetric set-up. The experimental (excess) data was converted into absolute adsorption by using the pore volume of the material, measured by Nitrogen at 77K. From these data, the absolute and the excess surface phase properties (uptake, selectivity, surface potential) were compared. The results show that the absolute selectivity is lower than the excess selectivity in the two mixtures. Furthermore, an analysis of models' performances in the two mixtures adsorption shows that the extended Langmuir and Toth models predict fairly the excess selectivity whereas IAST is suitable to describe the absolute selectivity.