The near-critical water oxidations (NCWO) of phenol, methanol, ethanol, n-propanol and n-butanol were evaluated at temperatures between 200 and 374 degreesC and pressures between 2 and 220 bar. Reactions were conducted in packed-bed flow reactors with ZrO2 and CaCO3 packings with a stoichiometric amount of HOOH. The effectiveness of CaCO3 as an oxidation catalyst increased markedly, between 200 and 374 degreesC enhancing oxidation rates > 100 X at 374 degreesC for phenol. Hydrolysis was observed for phenol, ethanol, and methanol over CaCO3 at 374 degreesC and was largely, nondetectable ill the absence of CaCO3. Despite being inexpensive and environmentally benign, CaCO3 exhibited catalytic abilities equal to or better than many of the best published performance of NCWO catalysts containing noble or transition metals.