Spontaneous liquid-gas imbibition for characterization of carbon molecular sieves

Spontaneous liquid-gas imbibition at 293.2K and 0.1 MPa was conducted to assess the micropore size and size-exclusion property of carbon molecular sieves (CMS). The CMS were firstly saturated with N(2) and then immersed into water. The volume of gas recovered by the water imbibition was measured and applied to evaluate the density of the N(2) adsorbed in the CMS. The micropore size of the CMS was determined by comparing the N(2) density from the water-N(2) imbibition with that calculated by grand canonical simulation. The micropore size evaluated by the liquid-gas imbibition coincides with that obtained by N(2) adsorption at ambient temperature. The size-exclusion property of the CMS was estimated through comparing the N(2) recovery by imbibition of liquids with increasing molecular dimensions, that is, water, benzene, and cyclohexane. The amount of N(2) recovered from benzene imbibition is dramatically less than that from the water imbibition, showing that the dominated micropore size of the CMS is smaller than 0.37 nm. Furthermore, the effect of chemical vapor deposition treatment on the porous texture of the CMS was revealed by the liquid-gas imbibition.