(30f) Natural Gas Adsorption in SSZ-13: Equilibrium and Dynamic Properties

In developing new adsorption separation processes, it is necessary to study both the equilibrium and dynamic adsorption properties of potential materials. In particular, experimental determination of isotherms and dynamic breakthrough properties aid in the development of modeling new adsorption systems toward process development. Here, the equilibrium adsorption properties of a small-pore zeolite, SSZ-13, is studied for its natural gas separation potential. In particular, using volumetric and gravimetric adsorption techniques, the equilibrium properties of CO₂, CH₄, C₂H₆, and H₂O are determined, including adsorption isotherms and heats of adsorption. In addition, using a dynamic breakthrough adsorption apparatus, high pressure breakthrough experiments demonstrate the mixed gas separation performance of SSZ-13 in mixtures containing CO₂, CH₄, C₂H₆ and H₂S. Simulation of these breakthrough experiments shows that ideal adsorbed solution theory adequately describes the mixed gas adsorption modeling for this zeolite, and other mixed gas adsorption models fail to account for roll-up effects of C₂H₆ observed during experiments. In gas mixtures containing both CO₂ and H₂S, there is mutual transformation of these gases to COS and H₂O, likely driven by the affinity of H₂O in the zeolite. Comparison with a benchmark zeolite, Na-13X, reveals superior performance for SSZ-13 due to a lower affinity toward H₂O, resulting in less conversion of gases and no early breakthrough of sulfur species.