Thermophysical Properties of <i>n</i> -Hexane under the Influence of Dissolved Hydrogen by Experiments and Equilibrium Molecular Dynamics Simulations

This study demonstrates the applicability of different experimental techniques in combination with equilibrium molecular dynamics (EMD) simulations for investigating the influence of hydrogen (H2) on various thermophysical properties of n-hexane at temperatures T from (298 to 473) K and pressures p from (0.1 to 20) MPa at or close to vapor-liquid equilibrium. The amount fraction of H2 in the liquid phase, xH2, and the liquid density ρ are determined via the isochoric saturation method and vibrating-tube densimetry. Polarization-difference Raman spectroscopy (PDRS) serves to characterize xH2 during dynamic light scattering (DLS) experiments allowing access to the thermal diffusivity a and the Fick diffusion coefficient D11 in the liquid phase as well as surface light scattering (SLS) experiments used to determine the liquid dynamic viscosity η and the vapor-liquid interfacial tension σ. With increasing p and xH2, the measurement results for a and D11 are not significantly affected, except for states approaching the critical point. The experimental data for ρ, η, and σ show decreasing values with increasing xH2. The EMD simulations predict the influence of H2 on D11, η, σ, and ρ well, and allow to discuss the behavior of D11 and σ in connection with the fluid structure.