Process for preparing a high purity fischer-tropsch gasoil fraction

Abstract

The present invention provides a process for preparing a high purity Fischer-Tropsch gasoil fraction, comprising: a)fractionating a Fischer-Tropsch-derived gasoil feedstock into two or more Fischer-Tropsch gasoil fractions having a different boiling point range, wherein at least one Fischer-Tropsch gasoil fraction is a contaminant-enriched Fischer-Tropsch gasoil fraction, which is enriched in one or more contaminants with respect to the feedstock; b) providing the contaminant-enriched Fischer-Tropsch gasoil fraction to an absorption zone comprising at least one absorbent material and contacting the contaminant-enriched Fischer-Tropsch gasoil fraction with the absorbent material to absorb at least part of contaminant; and c) retrieving from the absorption zone a purified Fischer-Tropsch gasoil fraction as high purity Fischer-Tropsch gasoil fraction, which purified Fischer-Tropsch gasoil fraction is contaminant-depleted with respect to the Fischer-Tropsch-derived gasoil feedstock, and wherein at least part of the contaminants in the contaminant-enriched Fischer Tropsch fraction are formed during the fractionation of step (a).

1 . A process for preparing a purified Fischer-Tropsch gasoil fraction, comprising:
 a) fractionating a Fischer-Tropsch-derived gasoil feedstock, wherein said Fischer-Tropsch-derived gasoil is a fluid comprising paraffins, including isoparaffins and normal paraffins, with alkyl chain lengths in the range of from 7 to 30 carbon atoms, comprising at least 70 wt % of Fischer-Tropsch-derived paraffins having 9 to 25 carbon atoms based on the total amount of Fischer-Tropsch-derived paraffins,   into two or more Fischer-Tropsch gasoil fractions having a different boiling point range, wherein at least one Fischer-Tropsch gasoil fraction is a contaminant-enriched Fischer-Tropsch gasoil fraction, which is enriched in one or more contaminants with respect to the feedstock;   b) providing the contaminant-enriched Fischer-Tropsch gasoil fraction to an absorption zone comprising at least one absorbent material and contacting the contaminant-enriched Fischer-Tropsch gasoil fraction with the absorbent material to absorb at least part of contaminant; and   c) retrieving from the absorption zone a purified Fischer-Tropsch gasoil fraction, which purified Fischer-Tropsch gasoil fraction is contaminant-depleted with respect to the contaminant-enriched Fischer-Tropsch gasoil fraction, and   wherein at least part of the contaminants in the contaminant-enriched Fischer Tropsch fraction are formed during the fractionation of step (a).   
     
     
         2 . The process according to  claim 1 , wherein at least part of the contaminants formed during the fractionation of step (a) are the product of a thermal oxidation of one or more hydrocarbon compounds in the Fischer-Tropsch-derived gasoil feedstock. 
     
     
         3 . The process according  claim 1 , wherein at least part of the contaminants formed during the fractionation of step (a) are oxygenates that are the product of a thermal oxidation of one or more hydrocarbon compounds in the in the Fischer-Tropsch-derived gasoil feedstock. 
     
     
         4 . The process according to  claim 3 , wherein the Fischer-Tropsch-derived gasoil feedstock contains one or more unsaturated aliphatic hydrocarbon compounds and at least part of the oxygenates are the product of a thermal oxidation of one or more of the unsaturated aliphatic hydrocarbon compounds. 
     
     
         5 . The process according to  claim 1 , wherein at least part of the contaminants formed during the fractionation of step (a) are unsaturated hydrocarbon compounds that are the product of a thermal dehydrogenation of one or more hydrocarbon compounds in the in the Fischer-Tropsch-derived gasoil feedstock. 
     
     
         6 . The process according to  claim 1 , wherein the one or more contaminants are selected from the group consisting of oxygenate compounds and aromatics. 
     
     
         7 . The process according to  claim 1 , wherein the absorbent material is a molecular sieve material. 
     
     
         8 . The process according to  claim 1 , the absorption zone comprises two or more absorbent materials. 
     
     
         9 . The process according to  claim 1 , wherein the contaminant-enriched Fischer-Tropsch gasoil fraction is contacted with the absorbent material at a temperature in the range of from 0 to 150° C. 
     
     
         10 . The process according to  claim 1 , wherein the contaminant-enriched Fischer-Tropsch gasoil fraction is contacted with the absorbent material in a fixed bed reactor comprising at least one fixed bed of absorbent material. 
     
     
         11 . The process according to  claim 1 , wherein the contaminant-enriched Fischer-Tropsch gasoil fraction has a final boiling point of no more than 260° C. 
     
     
         12 . The process according to  claim 1  wherein the contaminant-enriched Fischer-Tropsch gasoil fraction has an initial boiling point of more than 260° C. 
     
     
         13 . The process according to  claim 1 , wherein at least one contaminant-enriched Fischer-Tropsch gasoil fraction has a Saybolt number below 30. 
     
     
         14 . The process according to  claim 1 , wherein the Fischer-Tropsch-derived gasoil has a final boiling point of no more than 450° C. 
     
     
         15 . A method of using a purified Fischer-Tropsch gasoil fraction obtained in the process of  claim 1  as a solvent, diluent or functional fluid.