Review and Analysis of Saturation Loadings for Subcritical Alkane Adsorption On 13X Zeolite

Data for the adsorption of various alkanes on 13X zeolite at subcritical temperatures was collected from the literature and screened for consistency. Isotherms from 22 different studies are analyzed thoroughly. Untabulated adsorption data on NaX are extracted by digitizing the appropriate Figures. The focus was on acquiring adsorption data near saturation loadings. The data has been systematically evaluated for consistency; inconsistent data were removed from consideration. The consistent adsorption data of alkane sorbates on 13X zeolite are examined in order to deduce the saturation loading. The isotherms plateaued as P_sat is approached and the corresponding saturation loading (q_max) for 13X was then obtained from the highest data point of the isotherm providing d log(q)/d log(p) is approaching zero. The objective is to deduce an equation for the prediction of the intrinsic saturation loadings using as input the crystallographic parameters of the zeolite and the thermodynamic parameters of the sorbates.  The experimental saturation loadings are compared to the value of the maximum adsorbate loading calculated from the modified Rackett equation. The results indicate that the modified Rackett thermodynamic model provides a satisfactory estimate of the saturation loadings for subcritical alkanes on 13X zeolite when combined with the crystallographic zeolitic data.