(692g) Computer Simulations of Phase Equilibria and Transport Properties in Carbon-Dioxide Expanded Acetonitrile

Carbon dioxide expanded liquids (CXL's), which are mixed solvents composed of carbon dioxide condensed into an organic solvent, are benign media for performing catalytic reactions. We present molecular simulation studies of the phase equilibrium and transport properties of the binary mixtures of carbon dioxide with acetonitrile, in which the carbon dioxide mole fraction is adjusted by changing the pressure at a constant temperature of 298 K. We report Gibbs ensemble Monte Carlo (GEMC) and molecular dynamics simulations results of the structure, volume expansion, translational diffusion coefficients, rotational correlation times and shear viscosities for the mixtures. The Gibbs ensemble Monte Carlo simulation results for the volume expansion were found to be superior to the predictions based on the Peng-Robinson equation of state. The molecular dynamics simulations results for the transport properties are in good agreement with the available experimental data for the pure components and provide interesting insights into the largely unknown properties for the mixtures. The translational and rotational diffusion rates increase with carbon dioxide mole fraction for both the acetonitrile and carbon dioxide components. The shear viscosity decreases with increasing amount of carbon dioxide, varying smoothly between the values of pure acetonitrile and pure carbon dioxide.