Gas-phase phosgenation process
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.