High-Temperature Water as a Medium for Industrial Chemistry (TSE99-F)

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Water near its critical point is an environmentally benign medium for organic chemical reactions. Additionally the properties of water (dielectric constant, density, viscosity, etc.) near its critical point (called high temperature water - HTW) are strong functions of temperature and pressure, which offers the possibility of manipulating these variables to optimize the properties of this reaction medium for a given chemical transformation. The use of HTW as a medium for organic chemical synthesis, rather than organic solvents, is thus one approach to pollution prevention. The PI's long-range goal is to determine reaction mechanisms and quantitative kinetics in HTW to assess the economic feasibility of doing chemical synthesis is HTW.The key objectives of this project are to determine the reaction networks for two different organic chemical reaction systems in HTW, to obtain quantitative reaction rate laws for each reaction network, and to identify reaction mechanisms consistent with the kinetics. The systems chosen for investigation are the reactions of cyclohexanol and the partial oxidation of xylenes. Cyclohaxonol and its reaction products can undergo different reactions (dehydration, dehydrogenation, rearrangement and oxidation) in HTW, so the results would be generally relevant to a broad range of potential chemistries in HTW. The catalytic partial oxidation of xylenes to the corresponding carboxylic acids is done on a very large scale (billions of pounds annually) commercially to produce terephthalic acid and phthalic anhydride, which are important intermediates in the plastics industry. Commercial processes for terephthalic acid production currently use high-pressure, high-temperature acetic acid, which is corrosive, as the reaction medium. The kinetics in HTW are needed to assess economic feasibility of this alternative solvent.