DETERMINATION OF BINARY DIFFUSION-COEFFICIENTS OF BENZENE AND SOME ALKYLBENZENES IN SUPERCRITICAL CO2 BETWEEN 308-K AND 328-K IN THE PRESSURE RANGE 80-BAR TO 160-BAR WITH SUPERCRITICAL FLUID CHROMATOGRAPHY (SFC)

Binary diffusion coefficients D//1//2 have been determined for benzene, n-propylbenzene and 1,3,5-trimethylbenzene in supercritical CO//2 at 40 degree C from 80 to 160 bar and additionally between 35 and 55 degree C at 110 and 130 bar with the chromatographic broadening technique (CBT). The effect of secondary flow was investigated. The observed binary diffusion coefficients are of the order of 2 multiplied by 10** minus **4 cm**2 multiplied by s** minus **1. For a pressure rise from 80 to 160 bar, the diffusion coefficients decrease by about 50%. The isobaric temperature dependence of diffusion coefficients at 110 bar is substantially higher than that at 130 bar; for constant densities rho , however, the temperature coefficients seem to be very small. n-Propylbenzene is found to diffuse faster than its structural isomer 1,3,5-trimethylbenzene.