Structural and Thermodynamic Investigations of Nitroalkane+CH4 Hydrates with Structures II and H

Thermodynamic promoters improve the thermodynamic stabilities of CH4 hydrates by decreasing their equilibrium pressures (P) and increasing their equilibrium temperatures (T), which result in reduced energy consumption during the preparation, storage, and transportation of the hydrates. In this study, CH4 hydrates containing nitroalkane large guest molecules (LGMs), including 2-methyl-2-nitropropane (tert-nitrobutane, tBuNO2), nitrocyclopentane (cPeNO2), and nitrocyclohexane (cHxNO2) as thermodynamic promoters, were investigated. Structural analyses proved that tBuNO2 and cPeNO2/cHxNO2 form sII-and sH-type hydrates, respectively. All nitroalkanes improved the equilibrium temperatures by 3-12 K. In particular, tBuNO2, which is a solid at ambient temperature, exhibited the strongest promotion effect among the nitroalkane LGMs reported thus far. The dissociation enthalpies (Delta Hd) were also determined based on the equilibrium P-T conditions. The Delta Hd values significantly varied with the structural type of the hydrate but were nearly independent of the type of the LGM. The structural and thermodynamic results of this study may provide valuable information for the development of CH4 storage and transport technologies.

Automated summary

In this study, the thermodynamic promotion effect of nitroalkane large guest molecules (LGMs) on CH4 hydrates was investigated. The structural analysis confirmed the formation of different hydrate types with different LGMs. All nitroalkanes improved the equilibrium temperatures, with tBuNO2 showing the strongest promotion effect. The structural and thermodynamic results of this study provide valuable information for the development of CH4 storage and transport technologies.