(426b) Carrying out Volumetric Experiments without the Use of Helium

Equilibrium measurements require the determination of the volume of the solid to be then used in the conversion of the data to equilibrium isotherm. In volumetric systems, the standard procedure consists on a He expansion carried out on the regenerated sample immediately before the isotherm measurement. While this method is very simple to apply, the use of He requires an often time- and gas-consuming procedure to ensure that no residual He is left inside the pores of the sample as well as in the volumes of the instrument. This ensures that potential contaminations from He do not become a source of inaccuracy in the measurements. With the progressive reduction of fossil fuel extraction, He is becoming a scarce resource with direct effects on its costs and availability. Therefore, an effort should be made to develop approaches that minimize and potentially eliminate the use of He.

With this contribution we present a new methodology that allows the measurement of the sample volume without the use of He. The approach is designed to simplify the current procedure and can be applied to all volumetric systems, including commercial and custom-built apparatuses. In addition, it allows to measure directly the volume of the solid needed for the absolute adsorbed amount with no need to convert from the excess volume. The methodology is demonstrated on the measurement of equilibrium isotherms on our Adsorption Differential Volumetric Apparatus (ADVA) and on a commercial Autosorb iQ. Equilibrium isotherms obtained using the standard and the novel procedure are compared on both instruments to validate the approach.