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The oxidation rate of methanol and the subsequent production and destruction of the primary intermediate, formaldehyde, were investigated using Raman spectroscopy as an in situ analytical method. Experiments were conducted in supercritical water over temperatures ranging from 440 to 500 °C at 24.1 MPa and at a nominal feed concentration of 0.05 mol/L (1.5 wt %). Effluent samples were also examined using gas chromatography. In these experiments, feed concentrations ranging from 0.011 to 1.2 wt % and temperatures from 430 to 500 °C were examined and showed that the effective first-order reaction rate for the oxidation of methanol is dependent on the initial feed concentration. Raman measurements reveal a temperature-dependent induction period of less than 1 s over the range of conditions investigated. In addition, quantitative measurements of the production of formaldehyde indicate it is a key metastable intermediate. An elementary reaction mechanism, which reproduces accurately the quantitative features of methanol oxidation and formaldehyde production, is used to identify key rate controlling reactions during the induction period and the transition to the primary oxidation path.

The oxidation of isopropyl alcohol in supercritical water has been investigated using Raman spectroscopy. Results for species concentration as a function of residence-time are presented for temperatures ranging from 400 to 480 °C at constant pressure, 24.4 ± 0.3 MPa, and constant equivalence ratio, 0.88 ± 0.02. Acetone has been identified as the principal intermediate formed and subsequently destroyed, during the oxidation process. By assuming first-order kinetics for the destruction of both isopropyl alcohol and acetone, effective first-order rate constants have been determined from fits of the experimental data. Assuming Arrhenius behavior, the fits yield rate constants for isopropyl alcohol, k eff,ipa = 3.255 × 1022(s-1) exp[−301.1(kJ·mol-1)/RT], and for acetone, k eff,ace = 1.948 × 1010(s-1) exp[−137.7(kJ·mol-1)/RT]. These results indicate that for temperatures greater than 425 °C, the destruction of isopropyl alcohol proceeds faster than that of acetone.

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The U.S. military stockpile has large quantities of obsolete munitions awaiting disposal. Although suitable means for the safe dismantlement of much of this stockpile have been. identified, there are still considerable quantities of specialty materials for which existing methods have been deemed inappropriate from an environmental standpoint. Among these munitions are colored spotting dyes and a wide assortment of pyrotechnics, including • colored smokes and flares. In open burn or incineration treatment processes these materials produce large quantities of toxic, and possibly carcinogenic, gases and particulate matter. The U.S Army Armament Research, Development and Engineering Center at Picatinny Arsenal, NJ is interested in developing a method of treatment that will dispose of these munitions without the difficulties identified above. This report examines the feasibility of supercritical water oxidation, an emerging waste treatment technology, to process these materials. Four colored dyes and one pyrotechnic smoke composition were processed in a flow reactor, and the effluent was analyzed to determine the effectiveness of the processing. The tests showed that all of these materials could by oxidized to much less hazardous compounds in less than 10 seconds with a destruction and removal efficiency (DRE) typically > 99.5%. Two technical issues were identified as needing more attention in Phase II of this project: formation of sulfate and chloride salt deposits within the flow reactor and corrosion of the materials of construction. Based on the tests reported here this technology shows much promise, and its implementation for the treatment of military dyes, and at least some pyrotechnic compositions, is feasible. Recommendations for further testing and system development for Phase II of this project are included.