Time-resolved determination of surface diffusion coefficients for physically adsorbed or chemisorbed species on heterogeneous surfaces, by inverse gas chromatography

A new simple method is developed for measuring surface diffusion coefficients D-s of gases adsorbed on heterogeneous surfaces, using the reversed-flow version of inverse gas chromatography. The D-s values are found in a time-resolved way, together with the corresponding adsorption energy values, the local adsorbed concentrations, and the local adsorption isotherm values. A relative dynamic adsorption rate constant, an adsorption/desorption rate constant, and a surface reaction rate constant are also found in the same experiment, together with the total diffusion coefficient of the gas in the solid bed. The method has been applied for carbon monoxide, oxygen gas, and carbon dioxide as adsorbates on 75% Pt+25% Rh catalyst supported on SiO2, at 593.8 K. (C) 2002 Elsevier Science B.V. All rights reserved.