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

Authors: 
Thompson, J. A. - Presenter, Chevron Energy Technology Company
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.