Development of a model system to study fuel autoxidation in supercritical media:: decomposition kinetics of 2,2′-azobis(isobutyronitrile) in supercritical carbon dioxide

A high pressure reactor has been constructed and used for in situ spectroscopic measurements of reaction kinetics in supercritical fluids. The thermal decomposition of 2,2'-azobis(isobutyronitrile) (AIBN) in supercritical carbon dioxide (SC-CO2) was studied as part of an effort to characterize free-radical autoxidation of hydrocarbon fuels under supercritical conditions. The findings show that AIBN decomposes both thermally and photochemically in SC-CO2 to form the 2-cyano-2-propyl free radical which dimerizes to form tetramethylsuccinic dinitrile and dimethyl-N-(2-cyano-2-propyl) ketenimine. Examination of the decomposition kinetics of the ketenimine revealed that it was photochemically stable in the kinetic reactor, but decomposed thermally to form the dinitrile. Published by Elsevier Science Ltd. All rights reserved.