Plasma Chemistry and Plasma Processing, Vol. 23, No. 3, September 2003 ( 2003) The Characteristics of Direct Hydroxylation of Benzene to Phenol with Molecular Oxygen Enhanced by Pulse DC Corona at Atmospheric Pressure Dae-Won Lee, 1 Jung-Hyun Lee, 1 Bae-Hyeock Chun, 2 and Kwan-Young Lee 1,3 Receiûed April 12, 2002; reûised December 12, 2002 The direct hydroxylation of benzene using molecular oxygen by atmospheric pulse DC corona discharge was inûestigated. The conûersion of benzene increased with the increase of oxygen content and input ûoltage but the selectiûity of phenol decreased due to the formation of polymerized products. The reactiûity was also influenced by the kind and content of background inert gas. By using argon as background gas, we could get 2.2% of phenol yield at 60°C and 1 atm with energy consumption of 50 W. The strategy of reductiûe oxidation, which added hydrogen to the reactant, was not faûorable to the phenol formation in this reaction system. The polymerized product showed the oligomeric character and the analysis of its chemical structure with FT–IR was presented. KEY WORDS: hydroxylation of benzene; direct phenol synthesis; non-thermal plasma; pulse DC corona; atmospheric discharge; metastable atom; Penning activation; reductive oxidation. 1. INTRODUCTION Phenol has been regarded as an important material in the chemical industry for its wide uses in the manufactures of resins, caprolactam, bisphenol A, anesthetics and disinfectants. The consumption of phenol in the U.S. has exceeded the production by 200 million metric tons per year and the demand is expected to grow further. (1) Phenol has been produced by the cumene process which consists of three reaction steps starting from benzene and propylene. Drawbacks of this multi-stage process are the inevi- tability of high operation cost because of its complexity and the use of a 1 Department of Chemical and Biological Engineering, Applied Rheology Center, Korea Uni- versity, 1–5, Anam-dong, Sungbuk-ku, Seoul 136–701, Korea. 2 Institute of Automotive Technology, Younsei University, 134, Shinchon-dong, Seodaemun- ku, Seoul 120–749, Korea. 3 To whom all correspondence should be addressed. E-mail: kylee@korea.ac.kr 519 0272-4324030900-05190  2003 Plenum Publishing Corporation