Surface diffusion on modified surface of porous glass.

Abstract

Surface silanol groups of porous glass were esterified completely with three alcohols -methanol, ethanol and 1-propanolor partially with 1-propanol. Through these glasses, single-gas permeation experiments using carbon dioxide, propane, R-22, and R-114 were carried out at 308, 318 and 328 K. The possibility was indicated that selectivity is improved by suitable modifications. From these experiments, surface diffusivities and Henry constants of adsorption were determined. Their values also changed with surface modifications. Surface diffusivity Ds was studied in terms of molecular hopping on the assumption that the group-group distance is equal to the hopping distance λ.Ds/λ2, which is expected to be proportional to the average number of hopping molecules on one site, was successfully correlated with the dimensionless heat of adsorption Q/RT for original surfaces and partially and completely modified surfaces.