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

摘要

Binary diffusion coefficients D-12 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. D-12 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 D-12 at a given temperature match with recent theoretical data based on ab initio calculations in the zero-density limit for both systems.