Experimental rate and equilibrium data of adsorption and desorption of propane-propylene mixtures and determination of the expressions of the binary isotherms

The experimental adsorption and desorption rate and equilibrium data of single-component propylene and propane as well as of binary propylene-propane mixtures on 13X molecular sieves were measured with a differential sorption bed system for temperatures of 25, 50, and 70°C and a total pressure of 1 atm. The single-component adsorption data showed that propylene has a higher affinity than propane; for the propylene-propane binary adsorption, propylene is the preferentially adsorbed component. The Langmuir and Toth equations were examined to test their ability to fit the experimental single-component isotherms, and it was found that the fit with the Toth equation is excellent while that with the Langmuir equation is relatively poor. The feasibility of describing binary equilibrium adsorption behavior with the ideal adsorbed solution (IAS) theory employing the Toth equation as a mixed-gas isotherm was examined. The results indicate that the IAS theory describes the experimental propylene-propane binary adsorption equilibrium data reasonably well at 25°C, but does not give satisfactory results at either 50 or 70°C. The heterogeneous ideal adsorbed solution (HIAS) theory was compared to the IAS theory; the comparison of the results showed only small differences. Correlations using the theory of heterogeneous ideal adsorbed solution with geometric specificity exhibited improvements over the IAS and HIAS theories at 25°C; however, at 50 and 70°C, the results showed little improvement for propylene and were worse for propane. The adsorption rates of propylene and propane in the binary mixtures showed that the nature of the adsorption is competitive, which causes displacement of propane molecules by those of propylene. The adsorption and desorption rate data can be used to obtain fundamental transport properties which are essential to adsorption/desorption process design --Abstract, page iii