Diffusivities in Binary Mixtures of n-Decane, n-Hexadecane, n-Octacosane, 2-Methylpentane, 2,2-Dimethylbutane, Cyclohexane, Benzene, Ethanol, 1-Decanol, Ethyl Butanoate, or n-Hexanoic Acid with Dissolved He or Kr Close to Infinite Dilution

Diffusive mass transport in binary mixtures of a liquid solvent and dissolved helium (He) or krypton (Kr) close to infinite dilution is investigated by determining the Fick diffusion coefficient D-11 experimentally with dynamic light scattering (DLS). Equilibrium molecular dynamics (EMD) simulations are used to access the solute self-diffusion coefficient D-1, which is equal to D-11 at the limit of infinite dilution. To address how the molecular characteristics of the solvent influence molecular diffusion, a wide range of different solvents is considered, including n-decane, n-hexadecane, n-octacosane, ethanol, 1-decanol, cyclohexane, benzene, 2-methylpentane, 2,2-dimethylbutane, ethyl butanoate, and n-hexanoic acid. Mixtures are investigated between (303 and 448) K and up to 6.5 MPa. The average expanded experimental uncertainty (k = 2) of D-11 from DLS experiments is 8.6%, and the average expanded statistical uncertainty (k = 2) of D-1 from EMD simulations is 5.8%. Solvent force fields (FF) used in EMD simulations to describe interactions within and between molecules are primarily based on the all-atom optimized potentials for liquid simulation (OPLS) FF, and a temperature-dependent modification developed within our research group is applied. The average absolute relative deviation of the simulated D-1 with respect to the experimental D-11 is 14%. Results from DLS and EMD show that diffusive mass transport in mixtures containing dissolved He for a given solvent is (20-50)% greater than in those with Kr. In comparison to mixtures based on linear alkanes, those based on branched alkanes have larger D-11, while mixtures based on oxygenated and cyclic components have smaller D-11.