Cryogenic process for desulphurization and gasoline removal of a gaseous mixture comprising methane containing H.sub.2 S and hydrocarbons having 2 carbon atoms and higher

A process for removing sulphur containing compounds and recovering hydrocarbons having at least three carbon atoms from a gaseous mixture comprising methane, hydrocarbons having at least two carbon atoms and acid gas compounds comprising H.sub.2 S which comprises:

• (a) contacting the gaseous mixture, at an absolute pressure above about 0.5 MPa and a sufficiently low temperature, with an amount of a solvent, to provide a treated gas containing methane and a partial pressure of H.sub.2 S not higher than 65 Pa, and a rich solvent comprising H.sub.2 S and at least 80 molar percent of the hydrocarbons having at least three carbon atoms in the gaseous mixture, the solvent being a solvent for H.sub.2 S, having a boiling point at atmospheric pressure above 40.degree. C. and a viscosity at -40.degree. C. less than 0.1 Pa.s;
• (b) demethanizing the rich solvent to provide a demethanized rich solvent and a gas rich in methane;
• (c) cooling the demethanized rich solvent to a temperature at which the demethanized rich solvent separates into a purified rich solvent containing acid gas compounds and an amount of hydrocarbon, expressed as methane equivalent, less than about 5 molar % of the acid gas compounds and a primary fraction comprising the hyrocarbons which were present in the demethanized rich solvent and not present in the purified rich solvent;
• (d) separating the purified rich solvent from the primary fraction;
• (e) regenerating the purified rich solvent to produce an acid gas comprising H.sub.2 S and, expressed on a methane equivalent basis, less than about 5 molar % of hydrocarbon based on the acid gas and a regenerated solvent;
• and
• (f) recycling the regenerated solvent as the solvent for contacting the gaseous mixture.