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.