Supercritical water
Biomass gasification in supercritical water

In the diagram (pressure, temperature) of a pure substance, the line of coexistence of the gas and liquid phases ends at the critical point of the substance in question. For values above this critical pressure and temperature, a single phase exists, known as the supercritical phase, for which there is no discontinuity when the pressure or temperature changes to the liquid or gaseous state. In general, supercritical fluids have specific, common properties of interest, such as a fairly high density, sometimes close to that of liquids, a low viscosity close to that of gases, and good transfer coefficients. This gives them good solvent properties and justifies their interest in implementing chemical reactions or various unit operations. The two compounds most...