Phenol Decomposition by Pulsed-Discharge Plasma Above a Water Surface in Oxygen and Argon Atmosphere

摘要

By-products from phenol by the exposure of pulsed-discharge plasma above a phenol aqueous solution are investigated by gas chromatography mass spectrometry, and the decomposition process of phenol is deduced. When Ar is used as a background gas, catechol, hydroquinone, and 4-hydroxy-2-cyclohexene-1-one are produced, and no O_3 is detected; therefore, active species such as OH, O, HO_2, H_2O_2, which are produced from H_2O in the discharge, can convert phenol into those by-products. When O_2 is used as a background gas, formic acid, maleic acid, succinic acid, and 4,6-dihydroxy-2,4-hexadienoic acid are produced in addition to catechol and hydroquinone. O_3 is produced in the discharge plasma, so that phenol is probably decomposed into 4,6-dihydroxy-2,4-hexadienoic acid by 1,3- dipolar addition reaction with O_3, and then 4,6-dihydroxy-2,4-hexadienoic acid can be decomposed into formic acid, maleic acid, and succinic acid by a 1,3-dipolar addition reaction with O_3.