Realisation of measuring temperatures for sorption experiments from 82 K – 323 K
The cryoTune series opens new horizons for gas sorption measurements. It offers the possibility for almost all volumetric sorption instruments, no matter if newer or older production dates, to follow the ISO 9277 /1/ for BET measurements as well as the IUPAC recommendation for micropore characterization /2/.
Both publications explain that noble gases, unlike the nitrogen molecule, have no quadrupole moment and spherical symmetry. Therefore, the adsorption of noble gas atoms results from a pure van-der-Waals interaction and the atoms do not have different orientations on the adsorbent surface.
The cryoTune series requires only liquid nitrogen for cooling and allows a temperature range of 82 – 323 K. With the cryoTune 87, e.g. measurements for the determination of specific surfaces at Ar 87 K or Kr 120 K can be performed to obtain scientifically correct results. The cryoTune also allows the sorption of various other measuring gases at their boiling point or other arbitrary temperatures. Due to this unique flexibility, pure gas isotherms of methane, ethane, propane, n-butane, oxygen, carbon dioxide, SF6, etc. can be measured and thermodynamic calculations can be performed at different temperatures. The following table shows the different adsorptives, their boiling termperatures, the density of the liquid adsorptive ρLiquid, the critical diameter of the atom/molecule, the space requirement for one adsorbate atom or molecule am, the saturation pressure p0 and the non-ideality factor of the real gases Fni.