Gas-phase phosgenation process

Abstract

The present invention relates to a process for the phosgenation of amines in the gas phase, in which a specific type of heat exchanger is used for vaporizing the amines.

1 . A process for producing an isocyanate comprising phosgenating an amine in the gas phase in which at least one heat exchanger having 
 a. a heat transfer area per unit volume for the amine side of at least 1.000 m 2 /m 3  and    b. channels with a hydraulic diameter of from 5 to 10.000 μm for the flow of the amine    is used for liquid heating, vaporization and/or gas superheating of the amine.    
   
   
       2 . The process of  claim 1  in which the amine is flowed through a heat exchanger comprising at least one stacked channel micro heat exchanger having channels with a hydraulic diameter of from 30 to 500 μm, stacked channel plates with a diameter of from 100 to 1.000 μm and an individual channel length of from 0.5 to 400 cm.  
   
   
       3 . The process of  claim 1  in which the amine is flowed through a heat exchanger comprising at least one stacked channel micro heat exchanger or milli channel tube heat exchanger type having channels with a hydraulic diameter of from 2.000 to 5.000 μm and an individual channel length of from 10 to 400 cm.  
   
   
       4 . The process of  claim 1  in which the heat exchanger's heat transfer area per unit volume of the channels is from 1×10 3  to 1×10 5  m 2 /m 3 .  
   
   
       5 . The process of  claim 1  in which the channels of the heat exchanger through which amine is flowed contain internals.  
   
   
       6 . The process of  claim 5  in which channels or space of the heat exchanger for conveying a heating medium contain internals.  
   
   
       7 . The process of  claim 1  in which channels or space of the heat exchanger for conveying a heating medium contain internals.  
   
   
       8 . The process of  claim 1  in which the amine's mean residence time in the heat exchanger for heating and/or vaporizing is in each case from 0.01 to 10 s.  
   
   
       9 . The process of  claim 8  in which the amine's mean residence time in the heat exchanger for gas superheating is from 0.0005 to 1 s.  
   
   
       10 . The process of  claim 1  in which the amine's mean residence time in the heat exchanger for gas superheating is from 0.0005 to 1 s.  
   
   
       11 . The process of  claim 1  in which the amine is heated to a temperature of from 280 to 350° C. at an (absolute) pressure of from 800 to 1.600 mbar before entering the reactor.  
   
   
       12 . Process according to any of  claims 1  to  7 , characterized in that the phosgene is heated to a temperature of the phosgene stream of from 280 to 330° C. at an (absolute) pressure of from 700 to 1.500 mbar before entering the heat exchanger for phosgenation.  
   
   
       13 . The process of  claim 1  in which phosgene is used in a molar excess per amino group to be phosgenated of from 60 to 170%.  
   
   
       14 . The process of  claim 1  in which isophoronediamine (IPDA), hexamethylenediamine (HDA), bis(p-aminocyclohexyl)methane (PACM 20) or 1,8-diamino-4-(aminomethyl)octane(triaminononane) is the amine.