Method an system for recovery of catalysts and process and unit for production of perfluoroalkyl iodide telomers

Abstract

A solid catalyst used in, for example, production of a perfluoroalkyl iodide telomer is effectively and continuously recovered and the recovered catalyst is continuously recycled to the reactor for reuse. A slurry containing a reaction product and the catalyst is drawn from the reaction system, and the catalyst in the drawn slurry is classified by means of a hydrocyclone, whereby a high-concentration slurry whose catalyst concentration is higher than that of the drawn slurry and a low-concentration slurry whose catalyst concentration is lower than that of the drawn slurry are obtained, and the high-concentration slurry is recycled to the reaction system.

1 . A method for recovering a catalyst which has been used for a chemical reaction, which comprises: 
 drawing a slurry containing a reaction product in a liquid phase and the catalyst in a solid phase from a reaction system; and    classifying the catalyst in the drawn slurry by means of a centrifugal classifier to give a high-concentration slurry having a catalyst concentration higher than that of the drawn slurry.    
     
     
         2 . The method according to  claim 1 , wherein the centrifugal classifier is a hydrocyclone.  
     
     
         3 . The method according to  claim 1 , wherein the chemical reaction is a telomerization reaction of perfluoroalkyl iodide with tetrafluoroethylene.  
     
     
         4 . A method for producing a perfluoroalkyl iodide telomer by a telomerization reaction of a perfluoroalkyl iodide with tetrafluoroethylene catalyzed with a solid catalyst, which comprises: 
 drawing a slurry containing the perfluoroalkyl iodide telomer and the catalyst from a reaction system;    classifying the catalyst in the drawn slurry by a centrifugal classifier to give a high-concentration slurry having a catalyst concentration higher than that of the drawn slurry and a low-concentration slurry having a catalyst concentration lower than that of the drawn slurry; and    recycling the high-concentration slurry to the reaction system.    
     
     
         5 . The method for according to  claim 4 , wherein the centrifugal classifier is a hydrocyclone.  
     
     
         6 . The method for according to  claim 5 , wherein the catalyst is classified by two or more hydrocyclones which are connected in series.  
     
     
         7 . The method for according to  claim 4 , wherein the catalyst is copper particles.  
     
     
         8 . The method for according to  claim 4 , wherein 90% by weight of the catalyst is distributed in the high-concentration slurry by classification.  
     
     
         9 . The method for according to  claim 4 , wherein the catalyst concentration is constant in the reaction system.  
     
     
         10 . A system for recovering a catalyst comprising: 
 a hydraulic classifier;    a line which is connected to a reactor and through which a slurry containing a reaction product in a liquid phase and the catalyst in a solid phase is delivered from the reactor to the hydraulic classifier; and    a line through which a high-concentration slurry is delivered to the reactor, the high-concentration slurry having a catalyst concentration higher than that of the slurry delivered from the reactor, and being obtained by classifying the catalyst contained in the slurry delivered from the reactor with use of the classifier.    
     
     
         11 . The system according to  claim 10 , wherein the hydraulic classifier is a hydrocyclone.  
     
     
         12 . An apparatus for producing a perfluoroalkyl iodide telomer by a telomerization reaction of a perfluoroalkyl iodide with tetrafluoroethylene catalyzed with a solid catalyst, which comprises: 
 a reactor;    a hydraulic classifier;    a line which passes a slurry containing the perfluoroalkyl iodide telomer and the catalyst from the reactor to the hydraulic classifier; and    a line which passes a high-concentration slurry to the reactor, the high-concentration slurry having a catalyst concentration higher than that of the slurry delivered from the reactor, and being obtained by classifying the catalyst contained in the slurry delivered from the reactor with use of the classifier.    
     
     
         13 . The apparatus according to  claim 12 , wherein the hydraulic classifier is a hydrocyclone.