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

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.