Process for hydrodesulphurizing gasoline employing a catalyst with controlled porosity

Abstract

A novel process is described which allows selective hydrodesulphurizing gasoline cuts containing sulphur-containing compounds and olefins. The process employs a catalyst comprising a support selected, for example, from refractory oxides such as aluminas, silicas, silica-aluminas or magnesia, used alone or as a mixture, a group VI metal, preferably Mo or W which may or may not be promoted by a group VIII metal, Co or Ni. The catalyst is characterized by a mean pore diameter of more than 22 nm. The process may comprise one or more steps.

1 . A process for hydrodesulphurizing a gasoline, comprising employing a catalyst comprising a support and an active phase comprising nickel or cobalt and in which the mean pore diameter of said catalyst is more than 20 nanometres.  
     
     
         2 . A process according to  claim 1 , in which the mean pore diameter is in the range 20 to 100 nm.  
     
     
         3 . A process according to  claim 1  or  claim 2 , in which the catalyst contains at least one group VI metal.  
     
     
         4 . A process according to  claim 3 , in which the surface density of the group VI metal is in the range 2×10 −4  to 40×10 −4  grams of the oxide of said metal per m 2  of support.  
     
     
         5 . A process according to  claim 1 , in which the support is selected from the group constituted by aluminas, silica, silica aluminas or oxides of titanium or magnesium, used alone or as a mixture with alumina or silica alumina.  
     
     
         6 . A process according to  claim 1 , in which the support is at least in part constituted by an alumina.  
     
     
         7 . A process according to  claim 1 , in which the specific surface area of the support is less than 200 m 2 /g.  
     
     
         8 . A hydrodesulphurization process according to  claim 1 , comprising at least two successive hydrodesulphurization steps in which said catalyst is employed in at least one of said steps.  
     
     
         9 . A process according to  claim 8 , in which the reaction temperature of the successive steps is in the range from about 150° C. to about 450° C., the pressure is in the range from about 0.4 to about 3 MPa relative, and the volume ratio of hydrogen to hydrocarbons, H 2 /HC, is in the range from about 50 Nl/l to about 800 Nl/l.  
     
     
         10 . A process according to  claim 9  in which, for each step, the pressure is less than 2 MPa relative and the temperature is more than 250° C.  
     
     
         11 . A process according to  claim 8 , in which the successive steps are carried out without intermediate degassing.  
     
     
         12 . A process according to  claim 8 , comprising a succession of hydrodesulphurization steps, characterized in that the activity of the catalyst of a step n+1 is in the range 1% to 90% of the activity of the catalyst of step n.  
     
     
         13 . A process according to  claim 12 , in which the activity of a step is in the range 1% to 50% of the activity of the catalyst in the preceding step.  
     
     
         14 . A process according to  claim 12 , in which the reaction temperature in step n+1 is higher than that in step n.  
     
     
         15 . A process according to  claim 12 , in which the catalyst of step n+1 is the catalyst of step n which has undergone partial deactivation.  
     
     
         16 . A process according to  claim 15 , in which the catalyst is deactivated by bringing the catalyst into contact with a feed containing a hydrocarbon fraction comprising olefins at a temperature of at least 250° C.  
     
     
         17 . A process according to  claim 16 , in which the catalyst of step n is recycled to step n+1 when its activity has reduced by at least 10%.  
     
     
         18 . A process according to  claim 12 , in which the catalyst of step n+1 has a lower metals content than that of the catalyst of step n.