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 . A process for purifying 1,1-difluoroethane of any vinyl chloride, comprising treatment, with hydrogen fluoride, of a crude 1,1-difluoroethane containing less than 1 mol of hydrogen chloride per mole of 1,1-difluoroethane.  
     
     
         2 . The process of  claim 1 , in which the crude 1,1-difluoroethane has, per kg of 1,1-difluoroethane, a 1-chloro-1-fluoroethane content of less than 50 g and a 1,1-dichloroethane content of less than 20 g.  
     
     
         3 . The process of  claim 1 , in which the treatment is carried out in the liquid phase in a reaction medium containing at least 200 g of HF per kg, preferably at least 500 g of HF per kg.  
     
     
         4 . The process of  claim 1 , in which the treatment is carried out in the presence of a hydrofluorination catalyst chosen from the group comprising derivatives from groups IIIa, IVa, IVb, Va, Vb and VIb of the Periodic Table of the Elements, and mixtures thereof, preferably from tin, molybdenum, titanium, vanadium, antimony and tungsten derivatives.  
     
     
         5 . The process of  claim 1 , in which the crude 1,1-difluoroethane is subjected to the said treatment continuously, at a flow rate of from 0.01 to 5 kg per hour and per liter of reaction medium.  
     
     
         6 . A process for producing 1,1-difluoroethane, 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;    b) a separation of hydrogen chloride from the crude reaction product; and    c) a further treatment of the crude reaction product, which is substantially depleted of HCl, with hydrogen fluoride, this further treatment giving rise to a formation of purified 1,1-difluoroethane.    
     
     
         7 . The process of  claim 6 , wherein the HCl separation is carried out in a distillation column with removal of HCl from the top of the column and withdrawal of the crude reaction product, substantially depleted of HCl, intended for the further treatment, from the bottom of the column.  
     
     
         8 . The process of  claim 6 , wherein the HCl separation is carried out in a distillation column with removal of HCl from the top of the column, lateral extraction of the crude reaction product substantially depleted of HCl, intended for the further treatment, and withdrawal of a tail fraction containing products heavier than 1,1-difluoroethane, this tail fraction optionally being returned into step a).  
     
     
         9 . The process of  claim 7 , comprising an additional distillation of the said crude reaction product, substantially depleted of HCl, obtained from the said HCl distillation column, with withdrawal, from the top of the column, of the product intended for the further treatment, 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).  
     
     
         10 . Difluoroethane, obtained by hydrofluorination of a chlorohydrocarbon, having a purity of greater than 99.8%, preferably greater than 99.9%, and a vinyl chloride content of less than 10 mg/kg, preferably less than 5 mg/kg.