Soret coefficient of the n-dodecane-n-hexane binary mixture under high pressure

In the present work, the Soret coefficient has been determined at high pressure for a binary hydrocarbon mixture by combining the thermogravitational column and the dynamic near-field imaging techniques. The analyzed mixture is an iso-massic n-dodecane-n-hexane mixture at 298.15 K. The molecular diffusion coefficient has been measured up to 20 MPa by means of the dynamic analysis of the light scattered by non-equilibrium concentration fluctuations. With a cylindrical thermogravitational column the thermodiffusion coefficient was determined from 0.1 MPa to 10 MPa. Density, as well as, mass expansion and thermal expansion have been measured with a high pressure densimeter. Dynamic viscosity at up to 20 MPa has been determined with a high pressure viscometer. This work shows the decreasing tendency of both the molecular diffusion and the thermodiffusion coefficient with increasing pressure.