TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Process: Catalyst used in vapor formation stage is a supported catalyst containing at least a metal group VIII, or a catalyst made up: (a) of a support of the solid solution containing an aluminate with structure simple or mixed spinel (x=1; or x=0) of formula MX M1 (1-X) Al2O4, in which M is a metal (magnesium, manganese, copper or zinc), and M1 is at least a non noble metal of group VIII (nickel, iron or cobalt) deposited on a second element (alumina, ceria and/or zircon, where the proportions of the elements M and M1, respectively X and 1-x, is able to vary from 0 to 1, and the content of metals M and/or M1 ( 0-15 wt.%) and (b) of an active phase deposited on the support, which contains one or more metals group VIII. Vapor formation stage is carried out before selective dehydrogenation at 300-500degreesC, where the catalyst (specific catalyst) used in selective dehydrogenation is either identical to that used in vapor formation stage. The stage of conversion of carbon monoxide is carried out at high temperature (350-550degreesC), where the catalyst is based on iron oxide and/or chromium oxide or any supported catalyst containing at least a metal group VIII. The stage of conversion of carbon monoxide is carried out at low temperature (180-260degreesC), where the catalyst is preferably copper containing catalyst or any supported catalyst containing at least a metal group VIII. The purification of the hydrogen is carried out by a separation stage by membrane working in 300-600degreesC and the pressure of the gas to be purified is 0.6-2 MPa. The fuel which is fed to the burner is methane (5-30 % volume), which is expressed on dry gas. Vapor formation is carried out in a tubular reactor, which is laid out in interior of an enclosure, in which one of the ends is occupied by the burner. During certain phases of the process, particularly during starting, a fuel used to generate necessary heat to the vapor formation stage is ethanol, which is used like charges of vapor formation. The molar ratio of the hydrocarbon charge on the water vapor at the entry stage of vapor formation is higher than 3, preferably 4-12.