Structures and Energetics of Elemental Sulfur in Hydrogen Sulfide

Abstract

Severe safety concerns arise from sulfur deposition that occurs frequently in the development of high sulfur-content natural gas formation. Solubility reduction of elemental sulfur in H2S is the main reason of sulfur deposition. To understand how elemental sulfur, which exists in the form of sulfur clusters (Sn), interacts with H2S, quantum chemistry calculations are performed to study the structures and thermodynamic properties of Sn–H2S complexes. Weak interaction resulting mainly from intermolecular sulfur–sulfur interaction is revealed for these complexes. The complexes formed by S4, S6 and S8 have similar binding energies that are relatively higher than that of S2–H2S. Because of their small binding energies and Gibbs free energies, these complexes may coexist in formation, but are however easily decomposed or formed depending on stratigraphic or pipeline conditions. Our calculations reveal the status of elemental sulfur in H2S, which is useful for subsequent predictions on sulfur solubility and sulfur deposition in high sulfur-content natural gas formation.