Zeolites are capable of selectively adsorbing molecules and therefore are applicable to chemical separation challenges. In this work, two probe molecules, ethylene (C 2 H 4 ) and water (H 2 O) are modeled for their adsorption behavior in silver (Ag) ion-exchanged SSZ-13 zeolite (Si/Al = 11). A microkinetic model was constructed to include adsorbate−adsorbate effects due to multiple adsorption on individual active sites. As a basis for comparison, adsorption fractions were also predicted with the classical Langmuir competitive adsorption. Density functional theory (DFT) calculations were conducted, with 3 functionals to explore uncertainties, and up to three adsorbed molecules per Ag active site were investigated. When the DFT energies were passed to the adsorption models, the highest probability adsorption fraction prediction was for ethylene adsorption dominating water adsorption. An exception was that the Heyd-Scuseria-Ernzerhof functional energies passed to the Langmuir model predicted greater water adsorption than ethylene adsorption. The change in adsorption fractions as a function of shifting C 2 H 4 feed gas concentration are reported.

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Three potential adsorption sites within the Ag/SSZ-13 zeolite are compared for their ethylene and water adsorption capacity. Ethylene acts as a model hydrocarbon molecule in this work to stand in for vehicle exhaust, as Ag/SSZ-13 is a candidate material for trapping vehicle emissions during cold-start. Water is also present in vehicle exhaust and competes for adsorption sites with ethylene. The three active sites studied are the intended Ag ion-exchanged with an H in the zeolite framework, an H site (known as a Brønsted acid site) and Ag2O which may form as a nonzeolite adsorption site during the Ag ion-exchange synthesis. Density functional theory (DFT) calculations are conducted using the BEEF-vdw functional for up to two molecules of ethylene and/or water adsorbed per site. A microkinetic model parametrized by the DFT predicts the ethylene adsorption capacity for shifting ethylene feed gas concentrations at 100 °C in the presence of 6% water. Experimental observations are taken at matching conditions as microkinetic model simulations. The DFT energies and their uncertainties for each adsorption site are updated from experiments using a Bayesian statistical framework. The Ag ion and Ag2O sites adsorb more ethylene relative to the Brønsted acid site. The Ag ion and Brønsted acid sites adsorb more water relative to Ag2O.