Saturation loadings on 13X (Faujasite) zeolite above and below the critical conditions. Part IV: inorganic multi-atomic species, halocarbons and oxygenated hydrocarbons data evaluation and modeling

Abstract

The saturation loadings for subcritical adsorption of multi-atomic inorganic species, halocarbons and oxygenated hydrocarbons on 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. A similar equation is used for supercritical adsorption involving supercritical adsorbate densities and crystallographic data for the 13X zeolite employing a different f(Tr) expression than used by Spencer and Danner. Adsorption data from the literature are 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 \(\left( {\partial \ln q} \right)/\left( {\partial \ln p} \right)\) slope of zero at the maximum pressure point are assumed to be saturated (capillary condensation points are deleted). 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 data that is subcritical except for water and methanol. However, steric factors are required in the model for tetrafluoromethane, sulfur hexafluoride and the aldehydes. The adsorption data for ethyl acetate is questionable. A significant amount of data in the supercritical region (tetrafluouromethane, and hexafluoroethane) revealed a decreasing trend with increasing Tr. For this data a f(Tr) is modeled using TCAR and the slope of the decreasing linear plot against Tr. The physical phenomenom causing this effect is attributed to increasing molecular vibration in the cavity reducing the total molecular loading with temperature rise.