HYDROGEN-PEROXIDE DECOMPOSITION IN SUPERCRITICAL WATER

This work determines the rate constant of hydrogen peroxide decomposit ion in supercritical water. Experiments were conducted at pressures ra nging from 5.0 to 34.0 MPa and for temperatures up to 450 degrees C. T he rate of the homogeneous decomposition reaction is distinguished fro m the rate of the catalytic decomposition on the reactor surface by co nducting experiments at different surface-to-volume ratios. The rate c onstant of H2O2 decomposition follows the expression k(s(-1)) = 10(13. 4+/-1.2) exp[(-180 +/- 16 kJ/mol)/RT], providing a higher value than t hat derived from RRKM calculations. Comparison between experiments at supercritical conditions (P = 24.5 and 34.0 MPa) and experiments in hi gh-pressure steam (P = 5.0 and 10.0 MPa) show that the efficiency of t he catalytic surface reactions decreases significantly under supercrit ical conditions. The rate constant just mentioned was incorporated int o a methanol oxidation model and the new prediction is compared with t he experimental data of Rice et al. (1996), showing a distinct improve ment compared to the original prediction.