Oxidation reaction of high molecular weight carboxylic acids in supercritical water.
Stearic acid, being a model compound of high molecular weight carboxylic acids, was oxidized in a batch reactor by changing the oxygen supply with an insufficient oxygen supply at a constant reaction time at 420 degrees C. On the basis of the intermediate products identified by GC/MS, NMR, and HPLC analyses and the free-radical reaction mechanism, the oxidation pathways of high molecular weight carboxylic acids in supercritical water are discussed. The reaction of carboxylic acids in supercritical water proceeds with the consecutive oxidation of higher molecular weight carboxylic acids to lower molecular weight carboxylic acids through several major pathways. The attack of the hydroxyl radical occurs not only at the carbons in alpha-, beta-, gamma-positions to a --COOH group but also at the carbons ((omega-1)-carbon and/or omega-carbon) far in the alkyl chain from a --COOH group, which may lead to the formation of dicarboxylic acids.
Jin
Fangming
F
Department of Geoscience and Technology, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. jin@eno4s.earth.tohoku.ac.jp
Moriya
Takehiko
T
Enomoto
Heiji
H
D002851:Chromatography, High Pressure Liquid; D005609:Free Radicals; D008401:Gas Chromatography-Mass Spectrometry; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011312:Pressure; D013229:Stearic Acids / Q000737:chemistry*; D014867:Water; D018508:Water Purification / Q000379:methods*
D005609:Free Radicals; D013229:Stearic Acids; D014867:Water; C031183:stearic acid