Process for desulfurizing a catalytic cracking or steam cracking effluent

A process for lowering the sulfur or sulfur compounds content of a catalytic cracking or steam cracking gasoline boiling between 30.degree. C. and 220.degree. C., without substantially decreasing its octane number, comprising

• (1) fractionating said gasoline into (a) a light gasoline fraction boiling between the initial boiling point of said gasoline and a final boiling temperature T.degree. C. comprised between 75.degree. and 185.degree. C., and (b) a heavy gasoline fraction boiling above T-20.degree. C. and, in major part above T.degree. C.;
• (2) admixing said heavy gasoline fraction with a hydrogen-containing gas;
• (3) subjecting the resultant mixture to complete vaporization;
• (4) feeding the resultant vaporized mixture to a hydrodesulfurization zone, said hydrodesulfurization zone containing (a) at least one bed of at least one selective catalyst containing (i) a non-acidic carrier and (ii) at least one pair of metals selected from the group consisting of cobalt and molybdenum, cobalt and tungsten, nickel and molybdenum, and nickel and tungsten, the total metal content of said selective catalyst, expressed as oxides, being from 2 to 30% with respect to the total weight of the selective catalyst, the atomic ratio ##EQU6## from 0.55 to 0.90, and (b) at least one bed of a second hydrodesulfurization catalyst, said second catalyst containing cobalt and at least one additional metal, being a Group VIII, VII or VI metal, wherein the atomic ratio ##EQU7## is lower than 0.55, the proportion by volume of the selective catalyst being from 5 to 90% with respect to the combined volumes of said selective catalyst and said second catalyst, said vaporized mixture being fed sequentially through the selective catalyst bed and then through the second catalyst bed;
• (5) fractionating the hydrodesulfurization effluent and separately recovering a hydrogen-containing gas, and a hydrocarbon fraction distilling in the gasoline range;
• and
• (6) recombining the resultant hydrocarbon fraction boiling in the gasoline range with the light fraction from step (1), thereby producing a desulfurized gasoline having substantially the same octane number as said catalytic cracking or steam cracking gasoline.