Method for producing diaminotoluene

Patent metadata

Field	Value
Publication number	US-2016244402-A1
Application number	US-201415027327-A
Country	US
Kind code	A1
Filing date	Oct 2, 2014
Priority date	Oct 8, 2013
Publication date	Aug 25, 2016
Grant date	—

Abstract

The invention relates to an industrial-scale method for the vapor-phase hydrogenation of dinitrotoluene (DNT). According to said method, a stream containing DNT is sprayed into a carrier-gas stream containing hydrogen, optionally in the presence of an atomizing gas, unevaporated liquid droplets are extracted from the substantially gaseous stream that is obtained and the resultant gas stream is catalytically hydrogenated to form diaminotoluene.

First claim

1 . A continuous process for preparing toluenediamine by hydrogenation of dinitrotoluene in the gas phase, comprising:
(I) spraying of a dinitrotoluene-comprising stream into a hydrogen-containing carrier gas stream in a vaporization apparatus, where
a) the temperature of the dinitrotoluene-comprising stream is from 70° C. to 150° C. and the temperature of the hydrogen-containing carrier gas stream is from 140° C. to 300° C.,
b) the absolute pressure of the dinitrotoluene-comprising stream is from 3.0 bar to 30 bar and the absolute pressure of the hydrogen-containing carrier gas stream is from 1.0 bar to 10 bar, where the pressure of the dinitrotoluene-comprising stream is higher than that of the hydrogen-containing carrier gas stream, and
c) the molar ratio of hydrogen to dinitrotoluene is from 6.0:1 to 900:1.
so as to give a stream comprising dinitrotoluene and hydrogen;
(II) removing or targetedly decomposing the liquid droplets present in the stream comprising dinitrotoluene and hydrogen from step (I) to give a gas stream which comprises dinitrotoluene and hydrogen and has been depleted in liquid droplets; (III) reacting the dinitrotoluene present in the gas stream which comprises dinitrotoluene and hydrogen and has been depleted in liquid droplets with hydrogen in at least one reaction space in the presence of a catalyst at an absolute pressure of from 1.0 bar to 10 bar, a temperature of from 140° C. to 300° C. and a residence time in the reaction space of from 0.1 s to 10 s, so as to give a toluenediamine-containing gas stream, (IV) separating the toluenediamine-containing gas stream obtained in step (III) after passing through the last reaction space into a toluenediamine-comprising liquid phase and a hydrogen-comprising gas phase by condensation; and (V) recirculating at least part of the hydrogen-comprising gas phase obtained in step (IV) into the first vaporization apparatus of step (I).

2 . The process of claim 1 , wherein the spraying of the dinitrotoluene-comprising stream into the hydrogen-containing carrier gas stream in step (I) is carried out by means of at least one two-fluid nozzle through which a stream of an atomizing gas which is under a pressure of from 1.0 bar to 20 bar higher than the absolute pressure prevailing in the surroundings on the nozzle exit side is passed in addition to the dinitrotoluene-comprising stream.

3 . The process of claim 2 , wherein steam, nitrogen, fresh hydrogen, part of the hydrogen-comprising gas phase, part of the hydrogen-containing carrier gas stream or a mixture of two or more of the abovementioned gases is used as atomizing gas.

4 . The process claim 1 , wherein the condensation in step (IV) is carried out fractionally with a gradually decreasing condensation temperature so that a plurality of toluenediamine-comprising liquid phases are obtained.

5 . The process of claim 1 , further comprising:
(VI) working up the toluenediamine-comprising liquid phase and/or the toluenediamine-comprising liquid phases obtained in step (IV) by distillation in order to obtain pure toluenediamine.

6 . The process of claim 5 , wherein the condensation in step (IV) is carried out fractionally with a gradually decreasing condensation temperature so as to give a plurality of toluenediamine-comprising liquid phases which are, in step (VI), introduced separately from one another into various places in the work-up by distillation.

7 . The process claim 1 , wherein the dinitrotoluene in the dinitrotoluene-comprising stream has the following composition:
from 99.00% by mass to 99.94% by mass of dinitrotoluene, >5 ppm of nitrocresols, >20 ppm of trinitrotoluene, and >500 ppm of other impurities comprising water, mononitrotoluene, sulfuric acid and salts of sulfuric acid, in each case based on the total mass of the dinitrotoluene in the dinitrotoluene-comprising stream.

Assignees

• Covestro Deutschland Ag

Inventors

• Pennemann Bernd
• Moussa Amgad Salah
• Mahr Bastian

Classifications

• C07C209/36 Primary

  by reduction of nitro groups bound to carbon atoms of six-membered aromatic rings {in presence of hydrogen-containing gases and a catalyst} · CPC title

• C07C211/50

  with at least two amino groups bound to carbon atoms of six-membered aromatic rings of the carbon skeleton · CPC title

• C07C209/86

  Separation · CPC title