(305b) Multi-Component Gas Separation of Sour Natural Gas Mixtures Using All-Silica Zeolites

Authors: 
Shah, M. S., University of Minnesota
Tsapatsis, M., University of Minnesota
Siepmann, J. I., University of Minnesota

Raw natural gas is a complex mixture comprising of mainly methane but also other impurities

such as ethane, propane, butane, C4+, hydrogen sulfide, carbon dioxide, nitrogen, and water

vapor. For sour gas fields, selective and energy-efficient removal of H2S and CO2 is one of

the key challenges facing the natural gas industry. Separation using nanoporous materials,

such as zeolites, can be an alternative to using highly energy-intensive amine-based absorption

processes. In this work, adsorption of binary mixtures of H2S/CH4 and H2S/C2H6 in the all-

silica forms of the zeolite frameworks contained in the IZASC database is investigated using

Gibbs ensemble Monte Carlo simulations. The recently developed 4-site TraPPE model for

H2S, that yields high accuracy for the H2S/CH4 and H2S/CO2 binary vapor−liquid equilibria,

is used for the purpose of this study. The top-performing zeolites from this initial screening are

further used to simulate multi-component gas mixtures that are more representative of actual

natural gas compositions. All-silica zeolites are well-known for their hydrophobic character;

adsorption selectivity of hydrogen sulfide over water in select frameworks is also computed as

a means to quantify this hydrophobicity in presence of H2S.