Jointly published by React.Kinet.Catal.Lett. Akadémiai Kiadó, Budapest Vol. 77, No. 1, 35-42 and Kluwer Academic Publishers, Dordrecht (2002) 0133-1736/2002/US$ 12.00. © Akadémiai Kiadó, Budapest. All rights reserved. RKCL3949 UNCATALYZED PARTIAL OXIDATION OF p-XYLENE IN SUB- AND SUPERCRITICAL WATER Young-Lae Kim, Seung Joon Chung, Jae-Duck Kim, Jong Sung Lim, Youn-Woo Lee and Sung-Chul Yi* Supercritical Fluids Research Lab, Korea Institute of Science and Technology, P.O.Box 131, Cheongryang, Seoul 130-650, Korea. e-mail: ylkim@kist.re.kr, Fax: +82-2-958-5879 Department of Chemical Engineering, Hanyang University, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791, Korea* Received July 31, 2001 In revised form April 12, 2002 Accepted April 15, 2002 Abstract In sub- and supercritical water, partial oxidation of p-xylene was performed in a batch reactor without a catalyst at 240-500 o C, 220-300 bar. The loaded amount of hydrogen peroxide was set to 0-100% of the theoretically required oxygen amount. Conversion of p-xylene was reached over 99% within 15-20 min. In sub- and supercritical water, we propose two parallel pathways and major products that consist of p-tolualdehyde, p-toluic acid, terephthalic acid, toluene and benzaldehyde. Yields of major products in subcritical conditions were higher than in a supercritical conditions. Keywords: p-Xylene, partial oxidation, sub- and supercritical water INTRODUCTION The most common processes used worldwide for the production of terephthalic acid (TPA), an oxidized p-xylene derivative, have been used to make useful products such as polyester fiber and polyethylene terephthalate. TPA has recently become an important, fast-growing chemical as raw material for polyethylene terephthalate (PET). In 1999, ca. 26 million tons of PET were manufactured worldwide and its growth is estimated at a minimum of 5% annually to the year 2002. Nowadays, about 70% of the TPA used worldwide is