Improved method for determining binary adsorption isotherms by using concentration pulse chromatography: adsorption of CO2 and N2 by silicalite at different pressures

Abstract

Adsorption separation of carbon dioxide from nitrogen at different system total pressures with silicalite as the adsorbent was studied by using concentration pulse chromatography. Improving the methodology for determining binary adsorption isotherms by concentration pulse method (CPM) was also the goal of this study. Binary adsorption isotherms, x–y phase diagrams and separation factor plots have been determined at 26 °C to look at the influence of pressure on the separation using concentration pulse chromatography. Available methods for determining binary adsorption isotherms using CPM have been reviewed and shown to be incapable of interpreting this particular binary system. An improved novel model has been proposed to interpret the data in this study. It has been referred to as the Kennedy-Tezel concentration pulse method (KT-CPM) and has been shown to be superior to other methods used in the literature. Results using this data were found to be consistent with the previous results in the literature. The binary isotherms for the CO2–N2 system show a decrease in CO2 selectivity as total system pressure increases. The optimal separation factor for silicalite was found to increase with decreasing system pressure and decreasing mole fraction of CO2 in the feed mixture.