US Patent 7175716 Critical and supercritical cleaning of hydrocarbon-containing materials

A method for cleaning materials containing solids and/or liquids is disclosed which involves contacting the materials with an extracting fluid including Xe, NH3, lower aromatics, nitrous oxide, water, CO, CO2, H2O, lower alcohols, lower alkanes, lower alkenes, or mixtures or combinations thereof under conditions of temperature and pressure sufficient to maintain the fluid at, near or above its critical point and to products derived therefrom.