Patent ID: 7947166

Claim:
A method for treating a hydrocarbon steam cracking effluent corresponding to a cut having a boiling point temperature ranging between 0° C. and 250° C., comprising: a) at least one stage of selective hydrogenation of the feed, referred to as HD1, so as to hydrogenate diolefins, acetylenes, and alkenyl aromatics, b) fractionating in one or more distillation columns the effluent from stage a) in order to produce at least one light C5 cut containing mono-olefins, an intermediate C6 or C6-C7 or C6-C8 cut intended for aromatics production, and a heavy C7+ or C8+ or C9+ cut intended for gasoline production and containing alkylthiophenes, c) at least one stage of hydrodesulfurization and deep hydrogenation of the intermediate cut, referred to as HD2, d) at least one stage of alkylation of the heavy C7+, C8+ or C9+ cut with mono-olefins so as to further alkylate the alkyl thiophenes, thereby increasing molecular weight and facilitating separation thereof, and wherein a fraction of the light C5 cut containing mono-olefins is injected into the heavy C7+, C8+ or C9+ cut for said alkylation stage, said stage being operated at a temperature that ranges between 30° C. and 300° C., a hourly space velocity that ranges between 0.05 h −1 and 5 h −1 , and a pressure that ranges between 1.0 MPa and 4.0 MPa, wherein the stage of alkylation consists essentially of a treatment on a solid acid catalyst selected from the group consisting of acid ion-exchanging resins, zeolites, clays, functionalized silicas, silico-aluminates with an acidity and grafted supports of acid functional groups, e) at least one stage of distillation of the effluent from stage d), intended to produce a light fraction that can be directly used as a low-sulfur gasoline base, and a heavy C11+ or C12+ fraction rich in sulfur compounds, used as middle distillate or fuel oil.