Process to prepare middle distillates and base oils

Abstract

A process to prepare a first middle distillates fraction, a second middle distillates fraction, a distillate base oil and a residual base oil by providing a Fischer-Tropsch product stream; separating the Fischer-Tropsch product stream to obtain at least a low boiling fraction, boiling below a temperature ranging from 300 to 450° C., and a high boiling fraction, boiling above a temperature ranging from 300 to 450° C.; subjecting the high boiling fraction to a hydrocracking/hydroisomerization step to obtain a partially isomerised product stream; separating the partially isomerised product stream to obtain a first middle distillates fraction, a heavy distillates fraction and a residual fraction, the residual fraction having a T5 wt. % boiling point between 400 and 650° C.; dewaxing the low boiling fraction to obtain a second middle distillates fraction; dewaxing the heavy distillates fraction to obtain a distillate base oil; and dewaxing the residual fraction to obtain a residual base oil.

1 . A process to prepare a first middle distillates fraction, a second middle distillates fraction, a distillate base oil and a residual base oil, the process comprising the steps:
 (a) providing a Fischer-Tropsch product stream;   (b) separating the Fischer-Tropsch product stream of step (a), thereby obtaining at least a low boiling fraction, boiling below a temperature in the range of from 300 to 450° C., and a high boiling fraction, boiling above a temperature in the range of from 300 to 450° C.;   (c) subjecting the high boiling fraction of step (b) to a hydrocracking/hydroisomerization step to obtain an at least partially isomerised product stream;   (d) separating the product stream of step (c), thereby obtaining a first middle distillates fraction, a heavy distillates fraction and a residual fraction, wherein the residual fraction has a T5 wt. % boiling point of between 400 and 650° C.;   (e) dewaxing the low boiling fraction of step (b) to obtain a second middle distillates fraction;   f) dewaxing the heavy distillates fraction of step (d) to obtain a distillate base oil; and   g) dewaxing the residual fraction of step (d) to obtain a residual base oil.   
     
     
         2 . A process according to  claim 1 , wherein the first middle distillates fraction of step (d) has a T10 wt. % boiling point from 150 to 250° C. and a T90 wt. % boiling point from 300 to 400° C. 
     
     
         3 . A process according to  claim 1 , wherein dewaxing is performed by means of a catalytic dewaxing process in the presence of a catalyst comprising a molecular sieve and a group VIII metal. 
     
     
         4 . A process according to  claim 3 , wherein the molecular sieve is selected from a group consisting of a MTW, MTT, TON type molecular sieve, ZSM-48 and EU-2. 
     
     
         5 . A process according to  claim 3 , wherein the Group VIII metal is platinum or palladium. 
     
     
         6 . A process according  claim 3 , wherein the catalyst comprises a silica or titania binder. 
     
     
         7 . A process according to  claim 1 , wherein the second middle distillates fraction of step (e) has a T10 wt. % boiling point from 150 to 250° C. and a T90 wt. % boiling point from 300 to 400° C. 
     
     
         8 . A process according to  claim 1 , further comprising step (h), wherein prior to performing step (e) the first middle distillates fraction of step (d) or part of it is combined with the low boiling fraction of step (b) to obtain a mixture and wherein this mixture is dewaxed to obtain a third middle distillates fraction. 
     
     
         9 . A process according to  claim 1 , further comprising step (i) wherein the first middle distillates fraction of step (d) or part of it is combined with the second middle distillates fraction of step (e) to obtain a combined middle distillates product. 
     
     
         10 . A process according to  claim 1 , further comprising step (j) wherein before step (c) at least part of the residual fraction obtained in step (d) is combined with the high boiling fraction obtained in step (b).