Processes for production and purification of hydrofluoroolefins

Abstract

Disclosed herein are processes for the production of hydrofluoroolefins including 2,3,3,4,4,4-hexafluoro-1-butene by dehydrofluorination. Also disclosed herein are processes for separation of hydrofluoroolefins from hydrofluorocarbons and from hydrogen fluoride.

1 . A process to produce 2,3,3,4,4,4-hexafluoro-1-butene comprising a) feeding 1,1,1,2,2,3,3-heptafluorobutane to a reaction zone containing a dehydrofluorination catalyst, thereby forming a product mixture comprising said 2,3,3,4,4,4-hexafluoro-1-butene, unreacted 1,1,1,2,2,3,3-heptafluorobutane and hydrogen fluoride, and b) recovering said 2,3,3,4,4,4-hexafluoro-1-butene from the product mixture produced in a). 
     
     
         2 . The process of  claim 1 , wherein said dehydrofluorination catalyst is chromium oxide, fluorided chromium oxide, cubic chromium trifluoride, fluorided alumina or aluminum fluoride. 
     
     
         3 . The process of  claim 2 , wherein said dehydrofluorination catalyst is chromium oxide, fluorided chromium oxide or cubic chromium trifluoride. 
     
     
         4 . The process of  claim 1 , wherein the dehydrofluorination is carried out at a temperature of from about 200° C. to about 500° C. 
     
     
         5 . The process of  claim 1 , wherein the dehydrofluorination is carried out at a temperature of from about 300° C. to about 450° C. 
     
     
         6 . The process of  claim 1 , wherein said 1,1,1,2,2,3,3-heptafluorobutane further comprised an inert diluent. 
     
     
         7 . The process of  claim 6 , wherein said inert diluent is nitrogen, helium or argon. 
     
     
         8 . The process of  claim 7 , wherein said inert diluent in nitrogen. 
     
     
         9 . The process of  claim 8 , wherein the mole ratio of 1,1,1,2,2,3,3-heptafluorobutane to nitrogen is from about 5:1 to about 1:1. 
     
     
         10 . The process of  claim 1 , wherein said product mixture is subjected to a first distillation step to form a first distillate composition comprising an azeotrope or near-azeotrope composition containing, 2,3,3,4,4,4-hexafluoro-1-butene and hydrogen fluoride and a first bottoms composition comprising 1,1,1,2,2,3,3-heptafluorobutane; Subjecting said first distillate composition to a second distillation step from which a composition enriched in either (i) hydrogen fluoride, or (ii) 2,3,3,4,4,4-hexafluoro-1-butene is removed as a second distillate composition with a second bottoms composition being enriched in the other of said components (i) or (ii); and Subjecting said second distillate composition to a third distillation step conducted at a different pressure than the second distillation step in which the component enriched in the second bottoms composition is removed as a third distillate composition with the third bottoms composition of the third distillation step enriched in the same component that was enriched in the second distillate composition. 
     
     
         11 . The process of  claim 10 , further comprising recycling at least some portion of said first bottoms composition to said reaction zone.