Diffusion studies of CO2, NO, NO2, and SO2 on molecular sieve zeolites by gas chromatography

Gas chromatographic techniques were used to measure the diffusion coefficients and the isosteric heats of adsorption of CO2, NO, NO2, and SO2 on 5A and 13X molecular sieves, natural mordenites, and synthetic Na‐ and H‐mordenites in the temperature range of 133 to 325°C. Diffusional resistances for all gases studied decrease in the following order: natural mordenites > Na‐mordenites > H‐mordenites > (13X, 5A) indicating the increased ease of flow in the 3‐dimensional network. Isosteric heats of adsorption (range from 3 kcal/mole to 12 kcal/mole) and activation energies (range from 3 kcal/mole to 19 kcal/mole) decrease in the same order. The variations of diffusion coefficients, heats of adsorption, and activation energies are discussed in terms of the interaction between the surface and gas molecules as well as the openings of the pores relative to the size of the diffusing molecules.