COMPARATIVE STUDY ON PHYSICAL ADSORPTION OF VAPOR AND SUPERCRITICAL H 2 AND CH 4 ON SWNH AND ACF.

Adsorption isotherms of H 2 and CH 4 on activated carbon fibers (ACF) and single-walled carbon nanohorns (SWNH) were measured at vapor and supercritical conditions. H 2 and CH 4 are adsorbed sufficiently on micropores of ACF and SWNH at the vapor conditions and their adsorption isotherms were described by the Dubinin-Radushkevich equation. This shows clearly that even adsorption of H 2 and CH 4 vapors can be described by micropore filling mechanism. However, the adsorption isotherms of supercritical H 2 and CH 4 sensitively depend on the measuring temperature; the higher the measuring temperature, the smaller the amount of adsorption. Although H 2 adsorption isotherm of SWNH at 77 K is of type I and the maximum surface excess adsorption is 0.7 wt.% at 5 MPa, the adsorption isotherm was of Henry type at 300 K and the adsorption amount is less than 0.1 wt.% at 5 MPa. [ABSTRACT FROM AUTHOR]