Selective Recovery of H₂S from Gas Mixtures Using a Hydroquinone Clathrate

Abstract

The formation and guest enclathration of hydroquinone (HQ) clathrates with gas mixtures were investigated for potential applications to a clathrate-based removal process for sulfides. The HQ clathrate samples were prepared with hydrogen sulfide (H 2 S)−carbonyl sulfide (COS)−nitrogen (N 2 ) gas mixtures at pressures from 2.0 to 8.0 MPa and ambient temperature. Solid-state 13 C NMR and Raman spectroscopy methods were used to identify the crystal structure of the samples and guest enclathration into the clathrate framework. Quantitative information regarding the amount of captured gases was obtained by a combination of the elemental analysis and the numerical integration of the NMR spectra. The results show that H 2 S can be more concentrated in the solid HQ clathrates than in the gas phase, depending on the formation pressure. In particular, COS did not participate in the enclathration under all conditions, indicating that the molecular size of COS is too large to fit into the cages of the HQ clathrate. The recovery efficiency of H 2 S was described in terms of the enhancement of the concentration and selectivity of H 2 S in the HQ clathrates. These results open up the potential for clathrate-based gas separation for sulfur compounds, especially under dilute conditions.

Insights into Host–Guest Binding in Hydroquinone Clathrates: Single-Crystal X-ray and Neutron Diffraction, and Complementary Computational Studies on the Hydroquinone-CO2 Clathrate

“…Much of the research has incorporated CO 2 , − presumably due to its aforementioned industrial relevance. Studies incorporating other molecular species including CH 4 , − ,,,,,, H 2 S, , N 2 , ,− H 2 , ,− O 2 , CO, COS, noble gases Ar, Kr, and Xe, − and gas mixtures including CO 2 /CH 4 , ,,,, CO 2 /N 2 , flue gases, and syngas have been performed probing the structure, kinetics, intermolecular interactions, and thermal behavior of HQ crystals. Determining and understanding the adsorption selectivity of one molecule (often CO 2 ) over another is a fundamental focus of most of these studies involving mixed gases, where the selectivity is commonly rationalized in terms of differences in molecular properties (especially dipole and quadrupole moments and polarizabilities) and the electrostatic nature of the adsorbent. ,, …”