Method and plant for producing tetrafluoropropene

Abstract

A plant for the manufacture of tetrafluoropropene comprises three reactors for reaction in the gas phase comprising a catalyst bed. The first and second reactor are each configured in order to be fed in turn by a device for feeding with a reaction stream comprising a compound B and hydrofluoric acid; and a device for feeding with a regeneration stream configured in order to feed the reactor with a regeneration stream comprising an oxidizing agent. The third reactor is configured in order to be fed in turn by a device for feeding with a reaction stream comprising a compound A and hydrofluoric acid; said compound A being different from said compound B; and a device for feeding with a regeneration stream configured in order to feed the reactor with a regeneration stream comprising an oxidizing agent.

That which is claimed is as follows: 
     
         1 . A plant for the manufacture of tetrafluoropropene comprising three reactors for reaction in the gas phase comprising a catalyst bed,
 the first reactor and the second reactor for reaction in the gas phase being each configured in order to be fed in turn by:
 a device for feeding with a reaction stream comprising a compound B and hydrofluoric acid; and 
 a device for feeding with a regeneration stream configured in order to feed the reactor with a regeneration stream comprising an oxidizing agent; and 
   the third reactor for reaction in the gas phase being configured in order to be fed in turn by:
 a device for feeding with a reaction stream comprising a compound A and hydrofluoric acid, and optionally an intermediate collecting device connected at the outlet of the first reactor or of the second reactor; said compound A being different from said compound B; and 
 a device for feeding with a regeneration stream configured in order to feed the reactor with a regeneration stream comprising an oxidizing agent. 
   
     
     
         2 . The plant as claimed in  claim 1 , configured so that, when the first reactor is fed by the device for feeding with reaction stream, the second reactor is fed by the device for feeding with a regeneration stream. 
     
     
         3 . The plant as claimed in  claim 1 , in which the device for feeding with the regeneration stream is connected at the top and at the bottom of the reactor. 
     
     
         4 . The plant as claimed in  claim 1 , configured so that the device for feeding with the regeneration stream feeds any one of the three reactors at the bottom and at the top alternately. 
     
     
         5 . The plant as claimed in  claim 1 , wherein the tetrafluoropropene comprises 2,3,3,3-tetrafluoropropene or 1,3,3,3-tetrafluoropropene. 
     
     
         6 . The plant as claimed in  claim 1 , wherein the compound A is selected from the group consisting of tetrachloropropenes, chlorotrifluoropropenes, pentachloropropanes, dichlorotrifluoropropanes, trichlorodifluoropropanes, tetrachlorofluoropropanes, dichlorodifluoropropenes, trichlorofluoropropenes and the mixtures of these; and the compound B is selected from the group consisting of chlorotrifluoropropenes, pentafluoropropanes, dichlorotrifluoropropanes, trichlorodifluoropropanes, tetrachlorofluoropropanes, dichlorodifluoropropenes, trichlorofluoropropenes and the mixtures of these. 
     
     
         7 . The plant as claimed in  claim 1 , comprising:
 a first reactor;   a second reactor;   a third reactor;   a device for collecting a stream of products resulting from the third reactor connected at the outlet of the third reactor;   a separation unit fed by the device for collecting the stream of products resulting from the third reactor;   a first collecting pipe and a second collecting pipe which are connected at the outlet of the separation unit, the first collecting pipe being configured in order to transport a stream comprising hydrochloric acid and tetrafluoropropene and the second collecting pipe being configured in order to transport a stream comprising hydrofluoric acid and the compound B;   an intermediate collecting device connected at the outlet of the first reactor or of the second reactor;   a first device for feeding the third reactor configured in order to feed the third reactor, this device being itself fed by the device for feeding with preliminary reaction mixture and optionally by the intermediate collecting device;   a second device for feeding with reaction medium configured in order to alternately feed the second reactor and the first reactor, this device being itself fed by the second collecting pipe and optionally by a device for feeding with hydrofluoric acid;   a device for feeding with the regeneration stream configured in order to feed the first reactor and the second reactor;   a device for feeding with the regeneration stream configured in order to feed the third reactor;   a device for collecting a stream of gas resulting from the regeneration of the first reactor and of the second reactor; and   a device for collecting a stream of gas resulting from the regeneration of the third reactor.   
     
     
         8 . The plant as claimed in  claim 1 , comprising:
 a first reactor;   a second reactor;   a third reactor;   a device for collecting a stream of products connected at the outlet of the first reactor and of the second reactor;   a separation unit fed by the device for collecting stream of products;   a first collecting pipe and a second collecting pipe which are connected at the outlet of the separation unit, the first collecting pipe being configured in order to transport a stream comprising hydrochloric acid and tetrafluoropropene and the second collecting pipe being configured in order to transport a stream comprising hydrofluoric acid and the compound B;   an intermediate collecting device connected at the outlet of the third reactor;   a first device for feeding with a reaction medium configured in order to feed the third reactor, this device being itself fed by the device for feeding with preliminary reaction mixture and optionally by the second collecting pipe;   a second device for feeding with a reaction medium configured in order to feed the first reactor or second reactor, this device being itself fed by the intermediate collecting device and optionally by a device for feeding with hydrofluoric acid;   a device for feeding with a regeneration stream configured in order to feed the first reactor and the second reactor;   a device for feeding with a regeneration stream configured in order to feed the third reactor;   a device for collecting a stream of gas resulting from the regeneration of the first reactor and of the second reactor; and   a device for collecting a stream of gas resulting from the regeneration of the third reactor.   
     
     
         9 . The plant as claimed in  claim 1 , wherein the reactors are made of steel and have an interior surface covered with an alloy comprising more than 30% by weight of nickel or with a fluoropolymer-type coating.