Concentration dependent refractive index of CO2/CH4 mixture in gaseous and supercritical phase

C. Giraudet , L. Marlin , Didier Bégué (1) , Fabrizio Croccolo (2, 3) , Henri Bataller (2)

1 IPREM - Institut des sciences analytiques et de physico-chimie pour l'environnement et les materiaux
2 LFCR - Laboratoire des Fluides Complexes et leurs Réservoirs
3 Physics Department

Carbon dioxide (CO2)/methane (CH4) binary mixtures are investigated at pressure values up to 20 MPa at 303 K in order to investigate the pressure dependence of the optical concentration contrast factor, ∂ n / ∂ c P, T, through gaseous and supercritical phase. Refractive index is measured by means of a Michelson interferometer. Refractivities of the mixtures are found in good agreement with Lorentz-Lorenz predictions after density calculations by means of the AGA8-DC92 equation of state. Experimental polarizabilities of pure fluids are compared to quantum calculations of monomers and dimers for each pressure; it results that the quantity of dimers is small in the investigated thermodynamic conditions. Finally, by extending our experimental database with numerical simulations, we evidence that ∂ n / ∂ c P, T presents a critical enhancement similar to heat capacity.

Mots clés: Refractive index; Carbon dioxide; Polarizability; High pressure; Polymers

Domaines: Chimie

C. Giraudet, L. Marlin, Didier Bégué, Fabrizio Croccolo, Henri Bataller. Concentration dependent refractive index of CO2/CH4 mixture in gaseous and supercritical phase. Journal of Chemical Physics, 2016, 144 (13), ⟨10.1063/1.4944984⟩. ⟨hal-01500051⟩