Synthesis of perfluoroolefins

Abstract

A gold-lined pyrolysis reactor is used to pyrolyze compounds to form fluoroolefins like tetrafluoroethylene and hexafluoropropylene in high yield, with minimum to no formation of perfluoroisobutylene, chlorotrifluoroethylene, coke, salts, or polymer.

What is claimed is:  
     
         1 . A reactor for the pyrolysis of reactants that can produce fluoromonomers, comprising a reaction zone, the surface of which reaction zone comprises gold.  
     
     
         2 . The reactor of  claim 1  further comprising a quench zone, the surface of which quench zone comprises gold.  
     
     
         3 . The reactor of  claim 1  wherein said reaction zone comprises a lining of comprised of gold backed by heat-resistant thermally conductive metal.  
     
     
         4 . The reactor of  claim 3  wherein the heat-resistant thermally conductive metal is an alloy of nickel.  
     
     
         5 . The reactor of  claim 1  wherein the ratio of volume to surface area of said reaction zone is at least about 0.08 cm 3 /cm 2 .  
     
     
         6 . A process comprising feeding at least one reactant which can produce fluoromonomers into a reactor having a reaction zone, the surface of which reaction zone comprises gold, under conditions sufficient to produce fluoromonomers, including tetrafluoroethylene and hexafluoropropylene.  
     
     
         7 . The process of  claim 6  wherein said reactor further comprises a quench zone, the surface of which comprises gold.  
     
     
         8 . The process of  claim 6  wherein the reactant comprises compounds that can provide at least one moiety selected from the group consisting of a CF 2 : moiety, a CF 3 CF: moiety, and a CF 2 CF 2 : moiety.  
     
     
         9 . The process of  claim 6  wherein said reactant comprises monocarbon compounds that can provide a CF 2 : moiety together with a) dicarbon compounds selected from the group consisting of compounds that can provide a CF 3 CF: moiety and a CF 2 CF 2 : moiety, and tetrafluoroethylene and/or b) perfluorocyclobutane.  
     
     
         10 . The process of  claim 6  wherein said reactant comprises C 2 HClF 4  and perfluorocyclobutane in a molar ratio of C 2 HClF 4  to perfluorocyclobutane from about 1:10 to about 10:1, and wherein a molar ratio of CHClFCF 3  to CHF 2 CClF 2  is at least about 1:1.  
     
     
         11 . The process of  claim 10  wherein the C 2 HClF 4  is a mixture of isomers produced by vapor phase fluorination of tetrachloroethylene.  
     
     
         12 . The process of  claim 6  wherein said reactant consists essentially of C 2 HClF 4  and a molar ratio of CHF 2 CClF 2  to CHClFCF 3  in said C 2 HClF 4  is at least about 9:1.  
     
     
         13 . The process of  claim 6  wherein said conditions include temperature and residence time selected to produce a product containing less than about 1 mole % perfluoroisobutylene.  
     
     
         14 . The process of  claim 6  wherein the reactant comprises chlorodifluoromethane and perfluorocyclobutane and optionally 1-chloro-1,1,2,2-tetrafluoroethane, and wherein hexafluoropropylene and tetrafluoroethylene are produced in a molar ratio of at least about 1:19.  
     
     
         15 . The process of  claim 6  wherein said reactant is fed to said reaction zone as a gas, the temperature of said reaction zone is from about 600° C. to about 1000° C. and the residence time in said reaction zone is less than about one second.  
     
     
         16 . The process of  claim 6  wherein perfluoroisobutylene and chlorotrifluoroethylene are formed in a combined amount no greater than about 5 wt % based on the combined amount of said tetrafluoroethylene and hexafluoropropylene that are formed.  
     
     
         17 . The process of  claim 6  wherein said reactant has a residence time in the reaction zone of no more than about one second.  
     
     
         18 . The process of  claim 6  wherein at least one of said at least one reactant is preheated to a temperature less than its pyrolysis temperature.  
     
     
         19 . The process of  claim 6  wherein said reactant is fed to said reactor as a gaseous mixture of said at least one reactant and an inert gas which is free of oxygen and hydrogen.  
     
     
         20 . The process of  claim 6  further comprising turbulent flowing of said reactant in said reaction zone.  
     
     
         21 . The process of  claim 20  and creating obstructions in the reaction zone to cause said turbulent flowing.  
     
     
         22 . A process for producing at least one fluoroolefin selected from the group consisting of tetrafluoroethylene and hexafluoropropylene, comprising: 
 pyrolyzing a gaseous feed containing C 2 HClF 4  and perfluorocyclobutane at a temperature of from about 600° C. to about 1000° C. in a reactor wherein surfaces exposed to said pyrolysis comprise gold; wherein a molar ratio of C 2 HClF 4  to perfluorocyclobutane in said feed is from about 1:10 to about 10:1, and a molar ratio of CHClFCF 3  to CHF 2 CClF 2  in said feed is at least about 1:1.    
     
     
         23 . A process for producing a polymer comprising at least one monomer selected from the group consisting of tetrafluoroethylene and hexafluoropropylene, characterized by producing said tetrafluoroethylene and/or said hexafluoropropylene by the process of claim  6 .