Process to prepare a haze free base oil

Abstract

Process for reducing the cloud point of a base oil having a kinematic viscosity at 100° C. of greater than 10 cSt by separating the molecules inferring the high cloud point from the base oil by subjecting the base oil to a centrifugal force such to obtain a base oil having the reduced cloud point and a fraction rich in haze precursor compounds.

1 . A process for reducing the cloud point of a base oil having a difference between the cloud point and the pour point greater than 10° C. and a kinematic viscosity at 100° C. of greater than 10 cSt by subjecting the base oil to a centrifugal force such to obtain a base oil having the reduced cloud point and a fraction rich in haze precursor compounds. 
   
   
       2 . A process according to  claim 1 , wherein the centrifugal force is obtained in a centrifuge gravitation separator. 
   
   
       3 . A process according to  claim 1 , wherein the centrifugal force is obtained in a liquid cyclone separator. 
   
   
       4 . A process according to  claim 1 , wherein the base oil has a cloud point greater than 20° C., a saturates content of greater than 97 wt %, a kinematic viscosity at 100° C. of greater than 15 cSt, a sulphur content of less than 50 ppm and a viscosity index of greater than 140. 
   
   
       5 . A process to prepare a heavy lubricating base oil from a Fischer-Tropsch derived feedstock by
 (a) subjecting a Fischer-Tropsch derived waxy feedstock to a hydroisomerization process;   (b) isolating, by means of distillation, a heavy base oil precursor fraction from the effluent of step (a), wherein the heavy base oil precursor fraction is the residual fraction of the distillation;   (c) reducing the pour point of the heavy base oil precursor fraction by means of catalytic dewaxing; and   (d) reducing the cloud point of product of step (c) by subjecting the product to a centrifugal force such to obtain a base oil having a reduced cloud point and a fraction rich in haze precursor compounds.   
   
   
       6 . A process according to  claim 5 , wherein the retentate obtained in step (d) is recycled to step (a) or (c). 
   
   
       7 . A process according to  claim 6 , wherein the retentate is recycled to step (a).