Process for producing and purifying 1,1-difluoroethane, and product thus obtained

Abstract

1,1-Difluoroethane containing less than 10 mg/kg of vinyl chloride is obtained by treatment, with hydrogen fluoride, of a crude 1,1-difluoroethane containing less than 1 mol of hydrogen chloride per mole of 1,1-difluoroethane.

1 - 10 . (canceled)  
     
     
         11 . A process for producing 1,1-difluoroethane (HFC-152a), comprising 
 a) a reaction between hydrogen fluoride and a chloro precursor of 1,1-difluoroethane, optionally in the presence of a hydrofluorination catalyst, this reaction giving rise to a crude reaction product; and    b) a separation of hydrogen chloride from the crude reaction product, said HCl separation being carried out in a distillation column with removal of HCl from the top of the column, lateral extraction of the crude HFC-152a product substantially depleted of HCl, and withdrawl of a tail fraction containing products heavier than 1,1-difluoroethane, this tail fraction optionally being returned into step a).    
     
     
         12 . The process of  claim 11 , wherein the tail fraction contains HF and synthetic intermediates.  
     
     
         13 . The process of  claim 11 , wherein the tail fraction contains HF and 1,1-chlorofluoroethane (HCFC-151 a) and 1,1-dichloroethane (HCC-150a).  
     
     
         14 . The process according to  claim 11 , wherein the crude HFC-152a product contains less than 1 mole HCl per mole HFC-152a.  
     
     
         15 . The process according to  claim 13 , wherein the crude HFC-152a product contains less than 0.1 mole HCl per mole HFC-152a.  
     
     
         16 . The process according to  claim 11 , wherein the crude HFC-152a product contains less than 0.1 mole HCl per mole HFC-152a.  
     
     
         17 . The process according to  claim 11 , wherein the crude HFC-152a product contains less than 0.03 mole HCl per mole HFC-152a.  
     
     
         18 . The process according to  claim 11 , wherein the distillation column consists of a head section mounted on the hydrofluorination reactor.  
     
     
         19 . The process according to  claim 11 , characterized in that it comprises an additional distillation of the said crude HFC-152a product, substantially depleted of HCl obtained from the said HCl distillation column, with withdrawl from the top of the column of HFC-152(a) product and withdrawal, from the bottom of the column, of a tail fraction, containing products heavier than 1,1-difluoroethane, this tail fraction optionally being returned into step a).  
     
     
         20 . 1,1-difluoroethane (HFC-152a), obtained by hydrofluorination of a chlorohydrocarbon, having a purity of greater than 99.8% and a vinyl chloride content of less than 10 mg/kg.  
     
     
         21 . The HFC-152a as claimed in  claim 20 , obtained by hydrofluorination of a chlorohydrocarbon, having a purity of greater than 99.9%, and a vinyl chloride content of less than 5 mg/kg.  
     
     
         22 . A method for making a plastic foam which comprises using the HFC-152a of  claim 20  as swelling agent.  
     
     
         23 . A method for making a plastic foam which comprises using the HFC-152a of  claim 21  as swelling agent.  
     
     
         24 . The method according to  claim 22 , wherein the plastic foam is a polystyrene foam produced by extrusion.  
     
     
         25 . The method according to  claim 23 , wherein the plastic foam is a polystyrene foam produced by extrusion.