Device and method for producing aromatic amines

1. A method for producing organic amino compounds of formula (II)

in which R1 and R2 independently of each other denote hydrogen, methyl or ethyl, wherein R1 can additionally denote NH 2 , from organic nitro compounds of formula (I)

in which R2 and R3 independently of each other denote hydrogen, methyl or ethyl, wherein R3 can additionally denote NO 2 , comprising:

(a) continuously feeding the organic nitro compound and a hydrogen-containing gas stream to a reaction chamber containing a catalyst,

(b) hydrogenating the organic nitro compound to the organic amino compound in the reaction chamber,

(c) continuously discharging from the reaction chamber a gas phase comprising 0.1 to 10 wt. % of the hydrogen from the hydrogen-containing gas stream,

(d) determining a concentration of one or more gaseous secondary products in the continuously discharged gas phase, and

(e) increasing the catalyst hydrogenating activity if the concentration of the one or more gaseous secondary products falls below a predefined minimum concentration,

wherein the hydrogenating activity of the catalyst is increased by a method selected from the group consisting of (i) increasing the volumetric flow rate of the hydrogen-containing gas steam to the reaction chamber, (ii) throttling the feed of organic nitro compound to the reaction chamber, (iii) increasing the pressure in the reaction chamber, (iv) increasing the temperature in the reaction chamber, (v) increasing the residence time of the organic nitro compound in the reaction chamber, (vi) adding further catalyst to the reaction chamber, or (vii) a combination thereof.

2. The method according to claim 1 , wherein the gaseous secondary product has a boiling point under normal pressure of 200° C. or less.

3. The method according to claim 1 , wherein the gaseous secondary product is selected from the group consisting of methane, ammonia, an aliphatic amine which is not one of the organic amino compounds of formula (II), and mixtures thereof, the minimum concentration of the gaseous secondary product being:

in the case of methane at least 2 mg/kg of organic nitro compound,

in the case of ammonia at least 2 mg/kg of organic nitro compound, and

in the case of the aliphatic amine at least 1 mg/kg of organic nitro compound.

4. The method according to claim 1 , wherein the concentration of the gaseous secondary product is determined by means of a gas probe or by spectroscopy.

5. The method according to claim 1 , wherein water vapor present in the gas phase is removed by condensation before determining the concentration of the gaseous secondary product.

6. The method according to claim 1 , wherein the gaseous secondary product is passed through a separating apparatus prior to determining the concentration.

7. The method according to claim 1 , wherein spent catalyst is continuously discharged.

8. The method according to claim 1 , wherein the organic nitro compound is produced by nitration of an organic compound.

9. The method according to claim 1 , wherein the organic nitro compound is dinitrotoluene, which is hydrogenated to toluylene diamine.

10. The method according to claim 1 , wherein the hydrogenating is performed at a temperature from 80 to 200° C. and/or the hydrogenating is performed under a pressure from 5 to 120 bar.

11. The method of claim 1 , wherein the hydrogenating activity of the catalyst is increased by a method selected from the group consisting of (i) increasing the volumetric flow rate of the hydrogen-containing gas steam to the reaction chamber, (ii) throttling the feed of organic nitro compound to the reaction chamber (iv) increasing the temperature in the reaction chamber, (v) increasing the residence time of the organic nitro compound in the reaction chamber, (vi) adding further catalyst to the reaction chamber, or (vii) a combination thereof.

12. A device configured to produce organic amino compounds, comprising:

(a) a reaction chamber configured to hydrogenate an organic nitro compound by means of a catalyst;

(b) a reactant line configured to continuously feed an organic nitro compound to the reaction chamber, wherein the organic nitro compound is of the formula (I)

in which R2 and R3 independently of each other denote hydrogen, methyl or ethyl, wherein R3 can additionally denote NO 2

(c) a hydrogen line configured to continuously feed a hydrogen-containing gas stream to the reaction chamber;

(d) a line configured to continuously discharge from the reaction chamber a gas phase comprising 0.1 to 10 wt. % of the hydrogen from the hydrogen-containing gas stream; and

(e) an apparatus configured to monitor the reaction course of the hydrogenation by analysing secondary products forming during the hydrogenation,

wherein the monitoring apparatus is configured to determine a concentration of gaseous secondary product(s) in a gas phase continuously discharged from the reaction chamber, and

wherein the monitoring apparatus is coupled to a control apparatus which is configured to increase hydrogenating activity of the catalyst if the concentration of the gaseous secondary product(s) falls below a predefined minimum concentration by increasing the volumetric flow rate of the hydrogen-containing gas stream to the reaction chamber, by throttling the feed of the organic nitro compound to the reaction chamber, by increasing the pressure in the reaction chamber, by increasing the temperature in the reaction chamber, by increasing the residence time of the organic nitro compound in the reaction chamber, by adding further catalyst to the reaction chamber, or a combination thereof.

13. The device according to claim 12 , wherein the monitoring apparatus (G) is connected to the reaction chamber (A) via an analytical gas line.

14. Device according to claim 13 , wherein a condensation apparatus for condensing water vapor is connected upstream of the monitoring apparatus (G).

15. The device of claim 12 wherein the control apparatus is configured to increase hydrogenating activity of the catalyst if the concentration of the gaseous secondary product(s) falls below a predefined minimum concentration by increasing the volumetric flow rate of the hydrogen-containing gas stream to the reaction chamber, by throttling the feed of the organic nitro compound to the reaction chamber, by increasing the temperature in the reaction chamber, by increasing the residence time of the organic nitro compound in the reaction chamber, by adding further catalyst to the reaction chamber, or a combination thereof.