Intrapore field-dependent micropore filling of supercritical N2 in slit-shaped micropores

Abstract

The micropore filling of supercritical N2 on micrographitic carbon fibers having slit-shaped micropores of different micropore widths from 0.7 to 1.4 nm was examined at 303 K under the high pressure of N2 up to 10 MPa. Supercritical N2 in the micropore was presumed to be transformed into quasivapor by strong micropore field; the Dubinin–Radushkevich equation for a vapor was extended to the quasivapor in the micropore. The determination method of the saturated vapor pressure Psq of the quasi-N2 vapor in the micropore was proposed and was applied to the experimental results on N2/micrographitic carbon fiber systems; the determined Psq increases with the micropore width. The relationship between the extent of micropore filling of a supercritical gas through the quasivapor state and the interaction energy between a molecule and two parallel micrographites from the Lennard-Jones potential was theoretically derived, which was evidenced by the simple experimental relationship between the amount of high pressure N2 adsorption at 303 K and the micropore width.