Reaction induced by pulsed-discharge micro-plasma in supercritical fluids

Micro-plasmas generated by pulsed discharge in sub- and supercritical fluids have possibilities as a novel reaction field. We have studied generation of pulsed discharge plasma in subcritical or supercritical fluids, such as carbon dioxide, water, or argon. Two-phase system, where liquid and supercritical fluid coexist, was also used as a media to generate discharge plasma. The discharge behavior was investigated in terms of breakdown phenomena. Plasma generated in supercritical carbon dioxide was used for the reaction of fatty acid. By treating in discharged plasma, reaction containing C-C bond cleavage and C-C bond formation proceeded. We applied plasma generated in subcritical water to chemical reactions of phenol and aniline. Phenol was decomposed in discharged plasma at 523 K and 25 MPa. The analysis of oily product found that phenol was converted into its oligomers and polymers, where hydroxyl radical of phenoxy radical was bonded at meta position in phenol. When aniline was used as a reactant, the polymerization of aniline was also observed. Discharge plasma was generated at the interface between supercritical fluid and water. The phenomena of plasma was observed and analyzed.