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

Abstract

The present invention describes a process for producing middle distillates from a paraffinic feed produced by Fischer-Tropsch synthesis and divided into two fractions, a light fraction, termed the cold condensate, and a heavy fraction, termed the waxes, comprising a) fractionating said cold condensate fraction into a gaseous C4− fraction and an intermediate fraction with an initial boiling point in the range 15° C. to 40° C. and an end point in the range 300° C. to 450° C.; b) passing the intermediate fraction over at least one ion exchange resin; eliminating at least a portion of the water from the effluent derived from step b); decontaminating said heavy fraction termed the waxes by passage over a guard bed; recombining the purified intermediate fraction and the effluent derived from step d) to obtain a purified C5+ fraction; f) hydrogenating the unsaturated compounds of the purified C5+ fraction; g) hydroisomerization/hydrocracking of the effluent derived from step f); h) separating and recycling unreacted hydrogen and light gases to the hydroisomerization/hydrocracking step; and distilling the effluent derived from step h).

1 . A process for producing middle distillates from a paraffinic feed produced by Fischer-Tropsch synthesis and divided into two fractions, a light fraction, termed the cold condensate, and a heavy fraction, termed the waxes, comprising the following steps:
 a) fractionating said light fraction, termed the cold condensate fraction, into two fractions, a gaseous C4− fraction boiling at a temperature below 15° C. and an intermediate fraction with an initial boiling point in the range 15° C. to 40° C. and an end point in the range 300° C. to 450° C.;   b) passing said intermediate fraction over at least one ion exchange resin at a temperature in the range 50° 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 ;   c) eliminating at least a portion of the water from the effluent derived from step b);   d) decontaminating said heavy fraction, termed the waxes, by passage over a first guard bed containing at least one guard bed catalyst;   e) recombining the purified intermediate fraction derived from step c) and the effluent derived from step d) to obtain a purified C5+ fraction;   f) hydrogenating the unsaturated olefinic type compounds of at least a portion of the purified C5+ fraction derived from step e) in the presence of hydrogen and a hydrogenation catalyst;   g) hydroisomerization/hydrocracking of at least a portion of the effluent derived from step f) in the presence of hydrogen and a hydroisomerization/hydrocracking catalyst;   h) separating and recycling unreacted hydrogen and light gases to the hydroisomerization/hydrocracking step g);   i) distilling the effluent derived from step h).   
     
     
         2 . A process according to  claim 1 , in which prior to step b), said intermediate fraction undergoes a step for decontamination by passage over a guard bed containing at least one guard bed catalyst. 
     
     
         3 . A process according to  claim 1 , in which said C5+ liquid paraffinic fraction derived from step b) 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. 
     
     
         4 . A process according to  claim 3 , in which said resin is used at a temperature in the range 80° 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 . 
     
     
         5 . A process according to  claim 3 , 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. 
     
     
         6 . A process according to  claim 3 , 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. 
     
     
         7 . A process according to  claim 1 , in which said C5+ liquid paraffinic fraction derived from step b) passes over two distinct ion exchange resins with different natures, in two different reactors. 
     
     
         8 . A process according to  claim 7 , 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. 
     
     
         9 . A process according to  claim 7 , 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. 
     
     
         10 . A process according to  claim 7 , in which said first resin is used at a temperature in the range 50° 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 h −1 . 
     
     
         11 . A process according to  claim 1 , in which said guard bed catalyst used in step d) and in the optional decontamination step prior to step b) comprises a macroporous mercury volume for a mean diameter of 50 nm of more than 0.1 cm 3 /g, and a total volume of more than 0.60 cm 3 /g. 
     
     
         12 . A process according to  claim 1 , in which prior to recombination step e), the effluent from step d) passes 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 . 
     
     
         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, BTL, route.