TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The installation further comprises a deacidification unit located on the gaseous mixture supplying line, and preferably is a washing line, and a dehydration unit located on the gaseous mixture supplying line, the mercaptan loaded stream withdrawal line and the hydrocarbon recovering line. The hydrocarbon recovering line supplies the gaseous mixture supplying line. The desorption stream supplying line is fed by purified gaseous stream withdrawal line. The conversion reactor is adapted to be regenerated being fed by gaseous oxidizer stream supplying line.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The method further comprises performing a deacidification step of the gaseous mixture before the adsorption of mercaptan, preferably by washing with an absorbent solution comprising an amine compound. The stream comprising hydrocarbon and hydrogen sulfide is added to the gaseous mixture upstream of the mercaptan adsorption step and optionally upstream of the deacidification step. The desorption gas stream is obtained from at least one part of purified gaseous stream and comprises hydrocarbon, preferably methane. The hydrocarbon stream is conveyed in a separation unit for recovering a part of treated gas, preferably methane and other part of liquid petroleum gas. The coke product is accumulated in the conversion reactor. The step of combusting coke comprises supplying a gaseous oxidant stream to conversion reactor and recovering a gaseous stream of combustion. The catalytic conversion step is carried out at 400-700 degrees C, preferably 500-575 degrees C. The method comprises performing dehydration of the gaseous mixture upstream of the adsorption step, the stream comprising hydrocarbon and hydrogen sulfide at output of reactor and/or the mercaptans loaded stream. Preferred Components: The gaseous mixture containing mercaptan additionally contains hydrocarbons, preferably natural gas. The purified gas stream is a hydrocarbon stream. The conversion reactor comprises a zeolite, preferably Zeolite Socony Mobil-5 in the form of acid and ferrierite.