OXIDATION AND HYDROTHERMOLYSIS OF HYDROCARBONS IN SUPERCRITICAL WATERAT HIGH-PRESSURES

Oxidation, pyrolysis and hydrolysis of methane, ethane, methanol and t o some extent heptane and toluene, in supercritical water or nitrogen, at temperatures to 600-degrees-C and pressures to 1000 bar were studi ed. Temperatures of the reactive mixtures were always above the respec tive critical curves. Oxidation was performed with oxygen or air injec tion, flameless or with diffusion flames. High pressure, non-corrosive reaction vessels of different types and the complementary apparatus f or high pressure injection and analysis are described. Flameless oxida tion of methane in homogeneous supercritical aqueous mixtures produces CO, CO2, H-2 and CH3OH. Methanol formation can reach 30% of reacted m ethane, ''selectivity'', at 600 bar. High pressure increases the metha nol selectivity, flame reaction decreases it. Overall rate constants a re given. Similar studies were made with supercritical aqueous ethane mixtures. Hydrothermal pyrolysis, ''hydrothermolysis'', was investigat ed. Even at 600-degrees-C and 600 bar less than 3% methane decomposed after 120 minutes. Pyrolysis of methanol at 500-degrees-C and 600 bar is much slower in an aqueous environment than in nitrogen. Hydrotherma l soot formation was studied with several hydrocarbons in supercritica l fluids. Water, as compared with argon, as a mixture component appear s to suppress soot formation. CO conversion with supercritical water w as also quantitatively pursued.