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

本计画的目的是获得超临界水氧化法处理实验室废弃物的基本工程资讯。该项目的影响概述如下。（1）对于卤代有机物的模型化合物2-氯苯酚（2-CP）的降解，提出了热解与氧化的连续组合，以获得高转化率的2-CP，并避免不希望的副产物的形成。在氯代苯甲酸的分解中，可以实现脱铬产物的非常高的选择性，特别是在较低温度下。实验还发现，加入Na和K等碱物质可促进2-CP的脱氯。(2)In乙酸、苯酚和甲烷等难降解化合物与醇在超临界水中的共氧化，实验表明醇的存在提高了共存难降解化合物的消失速率。基于详细化学动力学模型的计算结果表明，在超临界水氧化反应中，OH自由基的浓度很好地表征了这类混合物的动力学效应。（3）研究了在金属氧化物或活性炭等非均相催化剂存在下苯酚的催化氧化。非负载型MnO_2催化剂具有较强的促进苯酚氧化的活性，但总反应速率受内传质阻力的影响较大。从动力学分析，全球的表面反应的速率表达式被确定，并提出了一个Langmuir型机制来解释苯酚，氧气和水的反应级数。实验还表明，廉价的碳催化剂可以有效地氧化苯酚。

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.