Method for treating a petrol containing sulphur compounds

Abstract

A process for treating a gasoline containing sulfur compounds, olefins and diolefins comprises step a) bringing into contact the gasoline, hydrogen and a hydrodesulfurization catalyst, in at least one reactor. In step b) effluent from a), hydrogen, and a hydrodesulfurization catalyst are brought into contact in at least one reactor. In step c) effluent from b) is sent to a separation drum operating at a pressure of between 1.0 and 2.0 MPa to obtain a gaseous fraction containing H2S and hydrogen and a liquid fraction containing desulfurized gasoline and a fraction of dissolved H2S. In step d), the liquid fraction is sent to a stabilization column to obtain at the top a stream comprising residual H2S and C4- hydrocarbon compounds and at the bottom a stabilized gasoline. In step e), the gaseous fraction is recycled at least in part to at least one of steps a) and/or b).

1 . A process for treating a gasoline containing sulfur compounds, olefins and diolefins, the process comprising:
 a) bringing the gasoline, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase comprising a group VIB metal and a group VIII metal into contact in at least one reactor at a temperature of between 21° and 320° C., at a pressure of between 1.5 and 3 MPa, with a space velocity of between 1 and 10 h−1 and a ratio of the hydrogen flow rate, expressed in normal m 3  per hour, to the flow rate of feedstock to be treated, expressed in m 3  per hour at standard conditions, of between 100 and 600 Nm3/m3, so as to convert at least a portion of the sulfur compounds into H 2 S;   b) bringing the effluent resulting from a) without removal of the H 2 S formed, hydrogen and a hydrodesulfurization catalyst comprising an oxide support and an active phase consisting of at least one group VIII metal are brought into contact in at least one reactor at a temperature of between 280 and 400° C., at a pressure of between 1.0 and 3 MPa, with a space velocity of between 1 and 10 h−1 and a ratio of the hydrogen flow rate, expressed in normal m 3  per hour, to the flow rate of feedstock to be treated, expressed in m 3  per hour at standard conditions, of between 100 and 600 Nm3/m3;   c) the effluent resulting from b) is sent to at least one separation drum operating at a pressure of between 1.0 and 2.0 MPa to obtain a gaseous fraction containing H 2 S and hydrogen and a liquid fraction containing desulfurized gasoline and a fraction of residual H 2 S;   d) said liquid fraction obtained in c) is sent to a stabilization column to obtain at the top a stream comprising residual H 2 S and C4- hydrocarbon compounds and at the bottom a stabilized gasoline;   e) the gaseous fraction obtained on completion of c) is recycled at least in part to at least one of a) and/or b).   
     
     
         2 . The process as claimed in  claim 1 , wherein the pressure of the separation drum of c) is between 1.2 and 1.8 MPa. 
     
     
         3 . The process as claimed in  claim 1 , wherein the catalyst of a) comprises a content of group VIII metal of between 0.1% and 10% by weight of oxide of the group VIII metal relative to the total weight of the catalyst, and a content of group VIB metal of between 1% and 20% by weight of oxide of the group VIB metal relative to the total weight of the catalyst. 
     
     
         4 . The process as claimed in  claim 1 , wherein the catalyst of a) comprises a molar ratio of group VIII metal to group VIB metal of the catalyst of between 0.1 and 0.8. 
     
     
         5 . The process as claimed in  claim 1 , wherein the catalyst of a) comprises a specific surface area of between 5 and 400 m 2 /g. 
     
     
         6 . The process as claimed in  claim 1 , wherein the catalyst of a) comprises alumina and an active phase comprising cobalt, molybdenum and optionally phosphorus, said catalyst containing a content by weight, with respect to the total weight of catalyst, of cobalt oxide, in CoO form, of between 0.1% and 10%, a content by weight, with respect to the total weight of catalyst, of molybdenum oxide, in MoO 3  form, of between 1% and 20%, a cobalt/molybdenum molar ratio of between 0.1 and 0.8 and a content by weight, with respect to the total weight of catalyst, of phosphorus oxide in P 2 O 5  form of between 0.3% and 10%, when phosphorus is present, said catalyst having a specific surface area of between 50 and 250 m 2 /g. 
     
     
         7 . The process as claimed in  claim 1 , wherein the catalyst of b) comprises a content of group VIII metal of between 1% and 60% by weight of oxide of the group VIII metal relative to the total weight of the catalyst. 
     
     
         8 . The process as claimed in  claim 1 , wherein the catalyst of b) has a specific surface area of between 5 and 400 m 2 /g. 
     
     
         9 . The process as claimed in  claim 1 , wherein the catalyst of b) consists of alumina and of nickel, said catalyst containing a content by weight, with respect to the total weight of catalyst, of nickel oxide, in NiO form, of between 5% and 20%, said catalyst having a specific surface area of between 30 and 180 m 2 /g. 
     
     
         10 . The process as claimed in  claim 1 , wherein the temperature of b) is higher than the temperature of a). 
     
     
         11 . The process as claimed in  claim 10 , wherein the temperature of b) is at least 5° C. higher than the temperature of a). 
     
     
         12 . The process as claimed in  claim 10 , wherein, before a), a distillation of the gasoline is carried out so as to fractionate said gasoline into at least two, light and heavy, gasoline cuts, and the heavy gasoline cut is treated in a), b), c), d) and e). 
     
     
         13 . The process as claimed in  claim 1 , wherein, before a) and before any optional distillation step, the gasoline is brought into contact with hydrogen and a selective hydrogenation catalyst in order to selectively hydrogenate the diolefins contained in said gasoline to give olefins. 
     
     
         14 . The process as claimed in  claim 1 , wherein the gasoline is a catalytic cracking gasoline.