UV-activated chlorination process

Abstract

A method of producing alkanes containing chlorine by addition of chlorine to C—C double bonds or C—C triple bonds or by exchange of hydrogen for chlorine by contacting the starting compound in the gas or liquid phase with elemental chlorine and irradiating the reaction mixture with UV tight having a wavelength of λ≧280 nm. In this way pentachloroethane can be produced from trichloroethylene, CFC-113 from HCFC-123 or HFC-133 a, CFC-112 a from HCFC-142 b, or HCFC-123 from HCFC-133 a . The method also is suitable for separating photochlorinatable impurities from HFC-365- mfc to obtain purified HFC-365- mfc. Advantages include high yields and excellent selectivity.

What is claimed is:  
     
         1 . A process for producing a chlorine-containing alkane selected from the group consisting of pentachloroethane; 1,1,1 -trifluoro-2,2,2-trichloroethane and 1,1,1,2-tetrachloro-2,2-difluoroethane by addition of chlorine to trichloroethylene in liquid phase to produce pentachloroethane, or by exchange of hydrogen for chlorine in gas or liquid phase to produce 1,1,1-trifluoro-2,2,2-trichloroethane from 1,1,1-trifluoro-2-chloroethane or 1,1,1-trifluoro-2,2-dichloroethane, or to produce 1,1, 1,2-tetrachloro-2,2-difluoroethane from 2,2-difluoro-2-chloroethane, or to produce purified 1,1,1,3,3-pentafluorobutane from 1,1,1,3,3-pentafluorobutane that has been contaminated by unsaturated compounds with C—C double bonds or C—C triple bonds by chlorinating the unsaturated contaminating compounds, wherein a respective starting compound is contacted with elemental chlorine and irradiated with UV light having a wavelength of λ>280 nm.  
     
     
         2 . A process according to  claim 1 , wherein the process is carried out in the liquid phase.  
     
     
         3 . A process according to  claim 1 , wherein the process is carried out at a temperature in the range from room temperature to 200° C.  
     
     
         4 . A process according to  claim 1 , wherein the process is carried out at a pressure of 1 to 10 bar (absolute).  
     
     
         5 . A process according to  claim 1 , wherein l,1,1,3,3-pentafluorobutane is purified by converting unsaturated impurities into chlorine-containing impurities and separating the chlorine containing impurities.  
     
     
         6 . A process according to  claim 1 , wherein elemental chlorine is used in an amount that is 0.9 times to 1.3 times the stoichiometrically required amount.