Isotherm Model Development from Liquid Excess Adsorption Measurements and Ideal Adsorbed Solution Theory

A liquid/vapor isotherm model is developed by application of the ideal adsorbed solution theory (IAST) to liquid-phase excess adsorption data. The surface adsorption of mixtures is treated with IAST based on Langmuir isotherms on a fugacity basis. The mixture surface adsorption predictions are then directly related to experimental liquid excess adsorption measurements through mass balance. Excess adsorption measurements of several hydrocarbons on silica gel are performed, which allow for the extraction of the unary Langmuir isotherm parameters. The unary basis of the parameters allows for predictability in a wide range of mixtures. This methodology provides a novel and unified description of complex mixture adsorption from both vapors and liquids. The approach is then extended to petroleum pseudocomponents. From this petroleum representation, we demonstrate the accurate prediction of vapor and liquid adsorption data for species that were not included in the model development.