Process for producing middle distillates by hydroisomerization and hydrocracking of a heavy fraction derived from a fischer-tropsch effluent

Abstract

The present invention describes a process for producing middle distillates from a C5+ liquid paraffinic fraction, termed a heavy fraction, with an initial boiling point in the range 15° C. to 40° C. produced by Fischer-Tropsch synthesis, comprising the following steps in succession: passing said C5+ liquid paraffinic fraction, termed a heavy fraction, over at least one ion exchange resin at a temperature in the range 80° C. to 150° C., at a total pressure in the range 0.7 to 2.5 MPa, at an hourly space velocity in the range 0.2 to 2.5 h −1 ; eliminating at least a portion of the water formed in step a); hydrogenating the unsaturated olefinic type compounds of at least a portion of the effluent derived from step b) in the presence of hydrogen and a hydrogenation catalyst; and hydroisomerization/hydrocracking of at least a portion of the hydrotreated effluent derived from step c) in the presence of hydrogen and a hydroisomerization/hydrocracking catalyst.

1 . A process for producing middle distillates from a C5+ liquid paraffinic fraction, termed a heavy fraction, with an initial boiling point in the range 15° C. to 40° C., produced by Fischer-Tropsch synthesis, comprising the following steps in succession:
 a) passing said C5+ liquid paraffinic fraction, termed a heavy fraction, over at least one ion exchange resin to allow esterification of alcohols and carboxylic acids into esters and/or to retain metals dissolved in the feed, at a temperature in the range 80° C. to 150° C., at a total pressure in the range 0.7 to 2.5 MPa, at an hourly space velocity in the range 0.2 to 2.5 h −1 ; 
 b) eliminating at least a portion of the water formed in step a); 
 c) hydrogenating the unsaturated olefinic type compounds of at least a portion of the effluent derived from step b) in the presence of hydrogen and a hydrogenation catalyst; 
 d) hydroisomerization/hydrocracking of at least a portion of the hydrotreated effluent derived from step c) in the presence of hydrogen and a hydroisomerization/hydrocracking catalyst; 
 e) separating and recycling unreacted hydrogen and light gases to the hydroisomerization/hydrocracking step d); 
 f) distilling the effluent derived from step e). 
 
     
     
         2 . A process according to  claim 1 , in which said C5+ liquid fraction undergoes a step for decontamination by passage over a guard bed containing at least one guard bed catalyst, before passage over an ion exchange resin in accordance with step a). 
     
     
         3 . A process according to  claim 2 , in which said guard bed catalyst comprises a macroporous mercury volume for a mean diameter at 50 nm of more than 0.1 cm 3 /g, and a total volume of more than 0.60 cm 3 /g. 
     
     
         4 . A process according to  claim 1 , in which said C5+ liquid paraffinic fraction passes over a single ion exchange resin in order to carry out the simultaneous esterification of alcohols and carboxylic acids into esters and capture of metals dissolved in the feed. 
     
     
         5 . A process according to  claim 4 , in which said resin is used at a temperature in the range 100° C. to 150° C., at a pressure in the range 1 to 2 MPa and at an hourly space velocity in the range 0.5 to 1.5 h −1 . 
     
     
         6 . A process according to  claim 4 , in which said resin is constituted by copolymers of divinyl benzene and polystyrene with a degree of cross-linking in the range 20% to 35%, and an acid strength, assayed by potentiometry during neutralization with a KOH solution, in the range 0.2 to 6 mmol H+ equivalent/g. 
     
     
         7 . A process according to  claim 4 , in which said resin is a polysiloxane grafted with alkylsulphonic type acid groups (of the —CH 2 —CH 2 —CH 2 —SO 3 H type), with a size in the range 0.5 to 1 2 mm and with an acid strength, assayed by potentiometry during neutralization with a KOH solution, of 0.4 to 1.5 mmol H+ equivalent/g. 
     
     
         8 . A process according to  claim 1 , in which said C5+ liquid paraffinic fraction passes over two distinct ion exchange resins with different natures, in two different reactors. 
     
     
         9 . A process according to  claim 8 , in which the reactor containing the ion exchange resin allowing the capture of metals is used upstream of the reactor containing the ion exchange resin allowing the esterification of alcohols and carboxylic acids. 
     
     
         10 . A process according to  claim 8 , in which said first resin is a resin constituted by copolymers of divinyl benzene and polystyrene with a degree of cross-linking in the range 1% to 20% and an acid strength, assayed by potentiometry during neutralization with a KOH solution, in the range 1 to 15 mmol H+ equivalent/g. 
     
     
         11 . A process according to  claim 8 , in which said first resin is used at a temperature in the range 80° C. to 110° C., at a pressure in the range 1 to 2 MPa and at an hourly space velocity in the range 0.2 to 1.5  −1 . 
     
     
         12 . A process according to  claim 8 , in which the hydroisomerization/hydrocracking catalyst contains at least one hydrodehydrogenating element selected from noble metals from group VIII, preferably platinum and/or palladium, and at least one amorphous refractory support, preferably silica-alumina. 
     
     
         13 . A process according to  claim 1 , in which the paraffinic feed produced by Fischer-Tropsch synthesis is produced from a synthesis gas produced from a natural gas using the gas-to-liquid, GTL, route. 
     
     
         14 . A process according to  claim 1 , in which the paraffinic feed produced by Fischer-Tropsch synthesis is produced from a synthesis gas produced from coal using the coal-to-liquid, CTL, route. 
     
     
         15 . A process according to  claim 1 , in which the paraffinic feed produced by Fischer-Tropsch synthesis is produced from a synthesis gas produced from biomass using the biomass-to-liquid route.