Binary Diffusion Coefficients for Gas Mixtures of Propane with Methane and Carbon Dioxide Measured in a Loschmidt Cell Combined with Holographic Interferometry

Abstract

Binary diffusion coefficients D12 for the molecular gas systems propane–methane (C3H8–CH4) and propane–carbon dioxide (C3H8–CO2) have been measured with a Loschmidt cell combined with holographic interferometry at (293 and 313) K, between (0.05 and 0.5) MPa, and for different mixture compositions. Improved experimental and evaluation procedures already validated for the noble-gas system helium–krypton have been successfully adapted for the molecular gas systems. For the investigated mixtures, adsorption–desorption processes are superimposed on the diffusion process and increase the achievable uncertainties. This hinders reliable conclusions regarding a concentration dependency of the diffusion coefficient. D12 clearly increases with increasing temperature and decreasing pressure. At the same pressure, temperature, and C3H8 mole fraction, the diffusion coefficient is larger for C3H8–CH4 than for C3H8–CO2. For both systems, the presented diffusion coefficients are in reasonable agreement with available literature data. In particular, the pressure-dependent trend and the absolute values of D12 at a given temperature match with recent theoretical data based on ab initio calculations in the zero-density limit for both systems.