Mass transfer in supercritical fluids related to the solute-solvent interactions

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The following results were obtained for the four research topics studied in this project :(1) Infinite dilution binary diffusion coefficients of acetone and benzene in supercritical carbon dioxide were measured by the Taylor dispersion method in the near critical region. The anomaly of the diffusion coefficients in the near critical point was observed. The diffusion coefficients were expressed with the background diffusivity and the excess diffusivity showing the anomaly.(2) Effective axial dispersion coefficients in packed beds were measured under supercritical conditions of carbon dioxide and at atmospheric pressure of organic solvents : hexane, cyclohexane and dodecane. The dispersion coefficients were correlated with a function of particle Reynolds number, Schmidt number, bed void fraction and molecular diffusivity. The correlation was consistent for all solvents, irrespective of pressure.(3) The possible clustering of molecules due to solute-solvent and/or solute-solute interaction was observed with FTIR spectroscopy for the mixtures of carbon dioxide and acetone under supercritical conditions. The condition showing the clustering was consistent with that appearing the anomaly of the diffusion coefficient.(4) The reaction rate constants of hydrolysis and pyrolysis were determined for the decomposition of dibenzyl ether in supercritical water. The hydrolysis rate constants agreed with the correlation of the rate constant with the dielectric constant of water obtained by Townsend et al. (1998). The pyrolysis rate constants determined were found to be consistent with the literature values, and be irrespective of atmosphere.