Summary: | 碩士 === 中原大學 === 化學研究所 === 105 === According to the Stockholm Convention, dioxins is a class of substances which is hard to break down in the natural environment, with high toxicity. It will accumulate in the environment and the body, thus is listed as one of the persistent organic pollutants. Question on how to reduce persistent organic pollutants''s concentration and toxicity, or how to degrade it into small molecules is still a key topic of scientists who have been concerned about environmental issues.
In recent years, related research of dioxins, such as ball milling, photodegradation or pyrolysis and other methods, can successfully reduce the toxicity of dioxins, but they are limited by time or temperature. Researchers continue to strive discover simpler and more efficient methods to remediate dioxins.
In this study, we use palladium/ graphene (Pd/G) catalyst to degrade 2-chloro-dibenzo-p-dioxin in supercritical carbon dioxide. When the ratio of metal Pd in catalyst increases, degradation into small molecules is enhanced. After varying the temperature, the amount of hydrogen gas, and the reaction time, it was found that 115°C, 1 hour reaction time, and 20 atm hydrogen gas mix with 75 atm carbon dioxide, produce the best results. The hydrodechlorination of 2-chloro-dibenzo-p-dioxin is achieved and C-O bond is broken. The end products are mainly dodecahydrodibenzo [b,e][1,4]dioxin, 2-(cyclohexenyloxy)cyclohexanol and cyclohexane.
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