Process for the obtention of purified heptafluoropropane

Abstract

Process for the obtention of HFC-227ea having a reduced content of organic impurities, comprising at least subjecting a crude HFC-227ea to two distillation steps at different pressures.

1 . A process for the obtention of 1,1,1,2,3,3,3,-heptafluoropropane (HFC-227ea) having a reduced content of organic impurities, which comprises 
 (a) subjecting a crude HFC-227ea containing organic impurities to at least two distillations steps, consisting of a high pressure distillation step and a low pressure distillation step carried out at a pressure of at least 1 bar lower than the high pressure distillation step and    (b) recovering HFC-227ea having a reduced content of organic impurities.    
     
     
         2 . The process according to  claim 1  wherein the pressure difference between the high pressure distillation step and the low pressure distillation step is from 2 to 5 bar.  
     
     
         3 . The process according to  claim 1  wherein the pressure in the low pressure distillation step is from 1 to 12 bar and the pressure in the high pressure distillation step is from 6 to 30 bar.  
     
     
         4 . The process according to  claim 1  wherein the low pressure distillation step is carried out before the high pressure distillation step.  
     
     
         5 . The process according to  claim 1  wherein the low pressure distillation step is carried out after the high pressure distillation step.  
     
     
         6 . The process according to  claim 5  wherein HFC-227ea having a reduced content of organic impurities is recovered from the top of the low pressure distillation.  
     
     
         7 . The process according to  claim 1 , wherein a fraction comprising low-boiling organic impurities is drawn off from the high pressure distillation step.  
     
     
         8 . The process according to  claim 7 , wherein the crude HFC-227ea comprises water and the fraction comprising said low-boiling organic impurities also comprises water which is thereby removed from the crude HFC-227ea.  
     
     
         9 . The process according to  claim 6 , wherein the fraction comprising said low-boiling organic impurities is continuously drawn off from the high pressure distillation step.  
     
     
         10 . The process according to  claim 7 , wherein in the high pressure distillation the mass ratio of the feed of crude HFC-227ea to the fraction comprising said low-boiling organic impurities withdrawn from said high pressure distillation is kept in a range from 1 to 100.  
     
     
         11 . The process according to  claim 1 , wherein the crude HFC-227ea has a purity of at least 95%.  
     
     
         12 . The process according to  claim 1 , wherein the crude HFC-227ea has been obtained by a reaction comprising use of hexafluoropropylene as a starting material.  
     
     
         13 . The azeotropic or pseudo-azeotropic mixture according to  claim 13 , comprising in addition organic impurities which are low-boiling with respect to HFC-227ea at a pressure of from more than 9 to 16 bar.  
     
     
         14 . A process for the obtaining a 1,1,1,2,3,3,3,-heptafluoropropane (HFC-227ea) having a reduced content of organic impurities, which comprises 
 (a) subjecting a crude HFC-227ea containing organic impurities to at least two distillations steps, consisting of a high pressure distillation step and a low pressure distillation step carried out at a pressure of at least 1 bar lower than the high pressure distillation step and    (b) recovering HFC-227ea having a reduced content of organic impurities.