Sour Gas Sweetening By Adsorption in Zeolites

Natural gas contributes a third of the fossil fuel usage in the United States, and with the discovery of new gas fields, this fraction is on the rise. Hydrogen sulfide removal is a long-standing economic and environmental challenge facing the natural gas industry. Our goal is to develop next-generation solutions that efficiently capture hydrogen sulfide from natural gas mixtures. To this end, we are exploring separation processes using zeolites – nanoporous materials with highly specific pore sizes and shapes. H₂S is a highly toxic gas, and performing a wide experimental screening of all zeolites will not only be a very expensive endeavor, but will also require impeccable safety measures. This is an apt situation for molecular modeling to take the lead and guide real experiments.

We present here the development of a new hydrogen sulfide force field that accurately describes a wide set of physical properties such as the pure-component and binary vapor–liquid equilibria with CH₄ and CO₂, the liquid and solid structures, the relative permittivity, the triple point, and the gas-phase diffusion behavior.^[1] Using this new H₂S model, we have computationally investigated separation using various zeolitic frameworks and have identified promising sorbents for gas sweetening.^[2,3]

[1] M. S. Shah, M. Tsapatsis, and J. I. Siepmann, ‘Development of the transferable potentials for phase equilibria model for hydrogen sulfide,’ J. Phys. Chem. B 2015, 119, 7041–7052.

[2] M. S. Shah, M. Tsapatsis, and J. I. Siepmann, ‘Monte Carlo Simulations Probing the Adsorptive Separation of Hydrogen Sulfide/Methane Mixtures using All-silica Zeolites,’ Langmuir 2015, 31, 12268–12278.

[3] M. S. Shah, M. Tsapatsis, and J. I. Siepmann, ‘Identifying Optimal Zeolitic Sorbents for Sweetening of Highly Sour Natural Gas,’ Angew. Chem. Intl. Ed. 2016, 55, 5938–5942.