Solubilities and Self-Diffusion Coefficients of Light n-Alkanes in NaCl Solutions at the Temperature Range (278.15-308.15) K and Pressure Range (1-300) bar and Thermodynamics Properties of Their Corresponding Hydrates at (150-290) K and (1-7000) bar

Continuous FractionalComponent Monte Carlo (CFCMC) and moleculardynamics (MD) simulations are performed to calculate the solubilitiesand self-diffusion coefficients of four light n-alkanes(methane, ethane, propane, and n-butane) in aqueousNaCl solutions as well as the thermodynamic properties of their correspondinghydrate crystals. Correction factors k (ij) to the Lorentz-Berthelot combining rulesfor alkane groups (CH3) and water are optimized (k (ij) = 1.04) by fitting excesschemical potentials to experimental data at 1 bar and 298.15 K. Usingthese values of k (ij) ,we calculate the solubilities of the four alkanes in aqueous NaClsolutions with different molalities (0-6) mol/kg at differenttemperatures (278.15-308.15) K and pressures (1, 100, 200,300) bar. The diffusion coefficients of the four alkanes in NaCl solutions(0-6) mol/kg are calculated at different temperatures (278.15-308.15)K and 1 bar and corrected for the finite-size effects. The latticeparameters of the corresponding hydrates with different guest moleculesare computed using MD simulations at different temperatures (150-290)K and pressures (5-700) MPa. Isothermal compressibilities at287.15 K and thermal expansion coefficients at 14.5 MPa for the correspondinghydrates are calculated. We present an extensive collection of thermodynamicdata related to gas hydrates that contribute to a fundamental understandingof natural gas hydrate science.

Automated summary

Continuous Fractional Component Monte Carlo (CFCMC) and molecular dynamics (MD) simulations were used to calculate the solubilities and self-diffusion coefficients of four light n-alkanes in aqueous NaCl solutions, as well as the thermodynamic properties of their corresponding hydrate crystals. Correction factors for alkane groups (CH3) and water were optimized by fitting excess chemical potentials to experimental data. Using these values, the solubilities of the four alkanes in NaCl solutions with different molalities and temperatures, and the diffusion coefficients in NaCl solutions were calculated. The lattice parameters and thermodynamic properties of the hydrates with different guest molecules were also computed. This research provides valuable thermodynamic data for understanding natural gas hydrate science.