Saturation loadings on 13X (faujasite) zeolite above and below the critical conditions. Part II: unsaturated and cyclic hydrocarbons data evaluation and modeling

Abstract

The saturation loadings for subcritical adsorption of alkenes, aromatics and cyclic alkanes 13X zeolite are modeled using the modified Rackett model of Spencer and Danner (J Chem Eng Data 17(2):236–240, 1972) for the saturated liquid densities combined with crystallographic data for the 13X zeolite. Adsorption data from the literature is first critically evaluated and then compared to the model. Log–log plots are used to determine whether each isotherm is near saturation; isotherms that exhibit a (∂ ln q)/(∂ ln p) slope of zero at their maximum pressure point are assumed to be saturated. For subcritical isotherms, the reduced pressure at which all isotherms became saturated is found to be relatively constant below a molecular weight of 60 g/mol, and then to decrease exponentially with molecular weight above 60 g/mol. The highest loading is used from each isotherm that approaches saturation. Unsaturated isotherms are not considered further. The theoretical equation satisfactorily models the available experimental data for the alkenes and cyclic alkanes. However, steric factors are required in the model for the aromatics. For supercritical temperatures, no model presently exists to explain the data. However, the supercritical alkene data are satisfactorily modeled with an equation of the form qmax = 10 ± 2.0 g/100 g. There are no supercritical data for aromatic species or for cyclic alkanes.