Formulating Noncovalent Interactions for Gas Hydrates with Electrolytes: A New Approach of Stability Analysis

Understandingof gas hydrate stability is crucial for the predictionof hydrate equilibrium pressures in the presence of electrolytes.In this contribution, a new theoretical framework is conceptualizedto describe the hydrate phase precisely. For this, a noncovalent interactionanalysis is proposed to be performed on a unit hydrate lattice composedof pure and mixed guests in the vicinity of salts at the B3LYP-D3+def2-SVPDlevel of theory. It is seen that the guests affect the steric andhydrogen bond interactions, while salts influence the van der Waalsand dispersion interactions. Energies associated with these noncovalentinteractions are quantified using the fundamental molecular propertiesand then consolidated to comprehensively describe the hydrate phase.Finally, the proposed approach is widely tested for hydrate systems(total 30) with pure or mixed guests in the presence of single ormultiple salts. Our model secures better predictions of the phaseequilibria data compared with the existing methodologies.

Automated summary

In this study, a new theoretical framework is proposed to describe the stability of gas hydrates. The framework involves a noncovalent interaction analysis on a unit hydrate lattice composed of pure and mixed guests in the presence of salts. The quantified energies of these interactions are used to accurately describe the hydrate phase. The results show that this proposed approach improves the prediction of phase equilibrium data compared to existing methodologies.