NOVELTY - Treating gaseous mixture containing mercaptans, comprises performing adsorption of mercaptans on adsorption molecular sieve (7a, 7b), recovering purified gas stream at output of sieve, performing desorption of mercaptans using preheated desorption gas stream and recovering a mercaptan loaded stream, transferring and heating the mercaptan loaded stream to a conversion reactor (20a, 20b), performing catalytic conversion, recovering stream comprising hydrocarbons and hydrogen sulfide, cooling the stream of hydrocarbons and hydrogen sulfide, and combusting the coke.    USE - The method is useful for treating a gaseous mixture containing mercaptans in the production of a liquefied natural gas (all claimed).    ADVANTAGE - The method is capable effectively treating the gaseous mixture with reduced energy consumption and high conversion rate and without loss of hydrocarbons.    DETAILED DESCRIPTION - Treating a gaseous mixture containing mercaptans comprises performing adsorption of mercaptans on at least one adsorption molecular sieve (7a, 7b), recovering a purified gas stream at an output of the adsorption molecular sieve, performing desorption of mercaptans of adsorption molecular sieve using preheated desorption gas stream and recovering a mercaptan loaded stream, transferring and heating the mercaptan loaded stream to a conversion reactor (20a, 20b), performing catalytic conversion of mercaptan in the conversion reactor to produce hydrocarbons, hydrogen sulfide and coke, recovering a stream comprising hydrocarbons and hydrogen sulfide at the output of the reactor, cooling the stream of hydrocarbons and hydrogen sulfide, and combusting the coke produced in the conversion reactor. The desorption gas stream and/or mercaptan loaded stream are heated by performing heat exchange with the stream of hydrocarbon and hydrogen sulfide and/or cooling. INDEPENDENT CLAIMS are included for:    (1) an installation for treating a gaseous mixture containing mercaptans, comprising a line (1a, 1b) for supplying the gaseous mixture, an adsorption molecular sieve capable of operating in adsorption and desorption, where the adsorption molecular sieve is supplied with the line and supplied with a line (9) for withdrawal of purified gas stream when it is operated in adsorption and is supplied with a desorption stream supplying line (13) and mercaptans loaded stream withdrawal line (when it is operated in desorption), a reactor to convert mercaptans into hydrocarbons and hydrogen sulfide supplied by mercaptans loaded stream withdrawal line, a heating unit on the mercaptans loaded stream withdrawal line, and a heat exchanger between a hydrocarbon recovering line and mercaptans loaded stream withdrawal line and/or another heat exchanger between the hydrocarbon recovering line and the desorption stream withdrawal line; and    (2) producing liquefied natural gas, comprising treating a natural gas comprising mercaptans, and additionally treating, cooling and liquefying the purified gaseous stream.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an installation for treating a gaseous mixture.    Gaseous mixture supplying line (1a, 1b)    Adsorption molecular sieve (7a, 7b)    Purified gaseous stream withdrawal line (9)    Desorption stream supplying line (13)    Conversion reactor. (20a, 20b)