Process for finiishing hydrodesulfurization of gasolines using a chain of catalysts

A process for treating a gasoline containing sulfur compounds and olefins, the process comprising at least the following steps:

• a) the gasoline, hydrogen and a hydrodesulfurization catalyst comprising an active phase comprising a group VIB metal and a group VIII metal at least partly in sulfide form, and an oxide support, are brought into contact in a first reaction section at a temperature of between 200° C. and 350° C., at a pressure of between 0.2 MPa and 5 MPa, with an hourly space velocity of between 1 h−1 and 20 h−1 and a ratio of the hydrogen flow rate, expressed in normal m3 per hour, to the volume flow rate of feedstock to be treated, expressed in m3 per hour under standard conditions, of between 10 Nm3/m3 and 1000 Nm3/m3, in order to obtain a first partially desulfurized effluent;
• b) without separating the H2S formed in step a), the first partially desulfurized effluent obtained on conclusion of step a) and a first polishing hydrodesulfurization catalyst comprising an active phase consisting of a group VIII metal at least partly in sulfide form, and an oxide support, are brought directly into contact in a second reaction section at a temperature of between 250° C. and 400° C., at a pressure of between 0.2 MPa and 5 MPa, with an hourly space velocity of between 1 h−1 and 40 h−1, in order to obtain a second partially desulfurized effluent;
• c) without separating the H2S formed in step b), the second partially desulfurized effluent obtained on conclusion of step b) and a second polishing hydrodesulfurization catalyst comprising an active phase comprising at least one group VIB metal and at least one group VIII metal at least partly in sulfide form, and an oxide support, are brought directly into contact in a third reaction section at a temperature of between 250° C. and 400° C., at a pressure of between 0.2 MPa and 5 MPa, with an hourly space velocity of between 1 h−1 and 40 h−1, in order to obtain a third partially desulfurized effluent.