SUPERCRITICAL WATER OXIDATION OF UREA

摘要

Urea in an aqueous solution was decomposed under sub- and supercritical conditions of water in the presence and the absence of hydrogen peroxide at temperatures from 553 to 693 K. at 23 MPa in a continuous flow reactor, The major products with and without H_2O_2 were carbon dioxide and ammonia, A small amount of OCN~- was also detected without H_2O_2, and NO_3~- and NO_2~- were produced with H_2O_2. The decomposition reactions of urea with and without H_2O_1 were represented by the first order reaction kinetics, and the pre-exponential factors and the activation energies were 17 s~(-1) and 73 kJ mol~(-1) with H_2O_2, and 20 s~(-1) and 93 kJ mol~(-1) without H_2O_2, respectively, at temperatures from 573 to 643 K. The presence of NaCl did not affect the product distribution significantly, but enhanced the rates at temperatures higher than 653 K.