MEASUREMENT AND CORRELATION OF BINARY DIFFUSION-COEFFICIENTS IN NEAR-CRITICAL FLUIDS

The binary diffusion coefficients of benzoic acid, oleic acid, alpha-tocopherol, and glycerol trioleate were measured in near critical carbon dioxide over the temperature range 298-318 K and pressure range 71-251 bar. A correlation based on an extensive literature database was developed which can be used to estimate both self and binary diffusion coefficients in a range of near critical solvents over the solvent reduced density range 1-2.5, with an average error of +/- 10%. The correlation is not suitable for estimating binary diffusion coefficients at the binary mixture critical point. The only input data required for the correlation are the solvent molecular weight, reduced temperature, and density, the solute molecular weight, and an estimate of the solute critical volume.