Chromatographic separation of hydrocarbon gases on zeolites with the use of carbon dioxide as carrier gas

Abstract

In gas chromatography on zeolites “active” carrier gases such as water vapour and carbon dioxide are rarely used because they are adsorbed on zeolites selectively and strongly. It is shown here that the use of carbon dioxide as the carrier gas allows the complete separation of model mixtures of hydrocarbon gases on zeolites at a lower column temperature and faster than with the use of conventional inert carrier gases such as nitrogen or helium. It was found that mixtures of C 1–C 4 hydrocarbon gases can be separated on zeolites of type Y in the sodium, cadmium and silver forms at column temperatures of 25–100°C. The specificity of the effect of silver and cadmium cations in zeolites on the separation of these mixtures is different to that with the use of helium or nitrogen as the carrier gas. Calculation of the heats of adsorption and the change in the entropy of adsorption ( ΔS) of hydrocarbon gases in their chromatography on zeolites showed that they are considerably dependent on the nature of the carrier gas used.