Fundamental researches on the novel process for laboratory waste treatment by supercritical water oxidation

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The objective of this project was to obtain the fundamental engineering information on the lab-waste treatment process by supercritical water oxidation (SCWO). The outreaches of this project are summarized as follows.(1)For the degradation of 2-chrolophenol (2-CP), chosen as a model compound of halogenated organic compounds, a consecutive combination of pyrolysis with oxidation was suggested to be effective to obtain high conversion of 2-CP and to avoid the formation of undesired by-products. In the decomposition of chrolobenzoic acid, very high selectivities for dechrolinated products can be achieved, particularly at lower temperatures. It was also found that addition of such alkali species as Na and K promotes dechlorination of 2-CP.(2)In the co-oxidation of such refractory compounds as acetic acid, phenol and methane with alcohol in supercritical water, it was experimentally suggested that the presence of alcohols enhanced the disappearance rate of the co-existing refractory compounds. The calculated results based on detailed chemical kinetics model suggest that the kinetic effect of such mixtures in SCWO is well characterized by the concentration of OH radical.(3)The catalytic oxidation of phenol in the presence of such heterogeneous catalyst as metal oxide or activated carbon was examined. A non-supported MnO, catalyst possessed a strong activity for promoting phenol oxidation, though the overall reaction rate was appreciably influenced by internal mass transfer resistance. From the kinetic analyses, the global rate expression of the surface reaction was determined, and a Langmuir-type mechanism was proposed to explain the reaction orders for phenol, oxygen and water. It was also experimentally demonstrated that phenol can be effectively oxidized with inexpensive carbon catalysts.