Process for the preparation of and composition of a feedstock usable for the preparation of lower olefins

Abstract

The invention provides a process for the preparation of lower olefins by a thermal cracking process, a process for the preparation of a synthetic hydrocarbon feedstock for such a process, and a composition of a high performance feedstock usable in said process.

1 . A process for the preparation of lower olefins from a synthetic hydrocarbon feed including at least a fraction having a boiling point above the boiling point range of the lower olefins, wherein the hydrocarbon feed includes at least a fraction which is unhydrogenated, which process includes the thermal processing of the hydrocarbon feed.  
     
     
         2 . A process as claimed in  claim 1 , wherein the synthetic hydrocarbon feed is a product of a FT reaction.  
     
     
         3 . A process as claimed in  claim 2 , the unhydrogenated fraction of the synthetic hydrocarbon feed is an unhydrogenated fraction of the process products of the FT reaction.  
     
     
         4 . A process as claimed in  claim 1 , wherein the synthetic hydrocarbon feed is prepared by combining at least 
 an unhydrogenated fraction of the process products of a FT reaction; and    a hydroconverted fraction of the process products of a FT reaction.    
     
     
         5 . A hydrocarbon feed to a cracking process for the preparation of lower olefins from a synthetic hydrocarbon feed including at least a fraction having a boiling point above the boiling point range of the lower olefins, said hydrocarbon feed including at least a fraction which is unhydrogenated.  
     
     
         6 . A synthetic hydrocarbon feed as claimed in  claim 5 , which is a product of a FT reaction.  
     
     
         7 . A synthetic hydrocarbon feed as claimed in  claim 5 , which is prepared by combining at least 
 an unhydrogenated fraction of the process products of the FT reaction; and    a hydroconverted fraction of the process products of the FT reaction.    
     
     
         8 . A synthetic hydrocarbon feed as claimed in  claim 7 , wherein the unhydrogenated fraction is a condensate fraction of the FT reaction products.  
     
     
         9 . A synthetic hydrocarbon feed as claimed in  claim 7 , wherein the hydroconverted fraction is a hydrocracked wax fraction of the FT reaction products.  
     
     
         10 . A hydrocarbon feed to a cracking process for the preparation of lower olefins from a synthetic hydrocarbon feed including at least a fraction having a boiling point above the boiling point range of the lower olefins, said hydrocarbon feed comprising at least 15% olefins and whose aromatics content is below 1%.  
     
     
         11 . A hydrocarbon feed as claimed in  claim 10 , wherein the hydrocarbon feed comprises at least about 20% olefins.  
     
     
         12 . A process for the preparation of a synthetic hydrocarbon feed to a process for the preparation of lower olefins, said feed including at least a fraction having a boiling point above the boiling point range of the lower olefins, said process including the steps of: 
 a) fractionating a straight run unhydrogenated condensate fraction of a FT synthesis product of H 2  and CO to obtain a synthetic olefinic naphtha;    b) hydroconverting by a process including hydrocracking at least a wax fraction of the FT synthesis product of H 2  and CO, or a derivative thereof;    c) fractionating the hydroconverted wax product from step b) to obtain a hydroconverted naphtha fraction separated from the other products from the hydroconversion process; and    d) blending said olefinic naphtha from step a) with the hydroconverted naphtha from step c) to obtain a synthetic hydrocarbon feed in a desired ratio having a boiling point above the boiling point range of the lower olefins.    
     
     
         13 . A process as claimed in  claim 12 , wherein the wax fraction of step b) has a true boiling point (TBP) in the range of about 70° C. to 700° C.  
     
     
         14 . A process as claimed in  claim 12 , wherein the condensate fraction of step a) has a true boiling point (TBP) in the range −70° C. to 350° C.  
     
     
         15 . A process as claimed in  claim 12 , wherein the synthetic hydrocarbon feed may be a CS to 160° C. boiling range synthetic naphtha.  
     
     
         16 . A process as claimed in  claim 12 , wherein the synthetic olefinic naphtha of step a) is blended with the hydroconverted naphtha fraction of step c) in a volumetric ratio of from 1:4 to 4:1 to form the synthetic hydrocarbon feed of step d).  
     
     
         17 . A process as claimed in  claim 12 , wherein, the synthetic olefinic naphtha of step a) is blended with the hydroconverted naphtha of step c) in a volumetric ratio of from 1:2 to 2:1 to form the synthetic hydrocarbon feed of step d).  
     
     
         18 . A process for the preparation of a synthetic hydrocarbon feed for a process for the preparation of lower olefins, said feed including at least a fraction having a boiling point above the boiling point range of the lower olefins, said process including the steps of: 
 a) hydroconverting by a process including hydrocracking at least a wax fraction of the FT synthesis product of H 2  and CO, or a derivative thereof;    b) blending said hydroconverted product from step a) with a straight run unhydrogenated condensate fraction in a desired ratio to obtain a blend that includes hydrocarbons boiling over a broad temperature range; and    c) fractionating the hydrocarbons blend from step b) to obtain a synthetic hydrocarbon feed for the thermal cracking process having a boiling point above the boiling point range of the lower olefins.    
     
     
         19 . A process as claimed in  claim 18 , wherein the hydroconverted product of step a) is blended with the condensate fraction in step b) in a volumetric ratio of from 1:10 to 10:1 before being fractionated in a single unit to form the synthetic hydrocarbon feed of step c).  
     
     
         20 . A process as claimed in  claim 18 , wherein the wax fraction of step a) has a true boiling point (TBP) in the range of about 70° C. to 700° C.  
     
     
         21 . A process as claimed in  claim 18 , wherein the condensate fraction of step b) has a true boiling point (TBP) in the range −70° C. to 350° C.  
     
     
         22 . A semi-synthetic feedstock usable for the production of lower olefins via thermal cracking, said feedstock comprising an olefinic synthetic feedstock obtained from a FT synthesis product of H 2  and CO and a highly paraffinic fraction selected from a petroleum liquid fraction and a natural gas liquid fraction, blended to have at least a 15% mass olefins content and an aromatics content below 1%.