DE4102860C1 - Aniline prodn. at reduced cost - by redn. of nitrobenzene with hydrogen in liq. phase, by reaction in aq. medium - Google Patents

Abstract

Prodn. of aniline by the redn. of nitrobenzene (I) with H2 in the liq. phase comprises reacting (I) in an aq. medium at 39.23-245.2 bar at 240-375 deg.C using Zr cpd. as catalyst. The hydrogen is generated in situ in the presence of lower alcohol or aliphatic hydrocarbon. ADVANTAGE - Reduced cost, as the amt. of water required is less, sepn. is easier, and a separate H2 generator is not required. The H2 is formed by the steam reformation process

Description

The present invention relates to a method for manufacturing of organic amines by reducing the associated ones Nitro compounds. The one needed for the reduction Hydrogen is generated "in situ" by the so-called steam Reforming process generated, so that both hydrogen generation like reduction in the same reactor and in liquid water at elevated pressure and temperature.

Under the steam reforming process one understands what is also known as steam splitting Steam reforming process for the most complete possible Conversion of hydrocarbons into water vapor endothermic reaction to methane, hydrogen, carbon monoxide and Carbon dioxide according to the water gas balance. It deals the technically most important process for the production of Hydrogen and hydrogen-containing gas mixtures.

By far the largest amount of aniline is used in the chemical industry by reducing nitrobenzene with the help of hydrogen manufactured as a reducing agent. This happens in the Gas phase with a suitable catalyst at moderately elevated Pressure, usually between 1 to 10 bar overpressure, and at Temperatures from 275 to 400 ° C in the presence of hydrogen. To avoid that the reduction achieved If heat becomes too high, it is necessary to use one over the other Production of nitrobenzene very large excess of hydrogen to drive. This is very costly and energy consuming, because hydrogen outside the reaction system in one separate procedures must be created and because it is necessary is the excess hydrogen after removal of reaction products with the help of compressors. Despite this measure (attempt to limit the temperature to keep the catalyst deactivated due to coal formation and must therefore be regenerated from time to time. During this Regeneration cannot produce aniline which is synonymous with a loss of production.  

There has now been a process for making aniline Reduction of nitrobenzene with hydrogen in the liquid phase at elevated temperature and under pressure in the presence of a Catalyst found, which is characterized in that nitrobenzene in an aqueous medium at 39.23 to 245.2 bar and 240-375 ° C in the presence of a zirconium compound as Reduced catalyst, the to Reduction required hydrogen in situ in the presence of low molecular weight alcohols or aliphatic hydrocarbons is produced.

To the need for an expensive, separate Avoiding the hydrogen generation system is done the hydrogen required for the reduction in situ the so-called steam reforming reaction. To further at the same time Controlling the temperature increase will be the case with Reduction of nitrobenzene to aniline by heat absorbs the water in the reactor.

So both can be used to create a separate hydrogen Save reactor while maintaining a more accurate reactor temperature achieve without the costly hydrogen over to have a shot.

Suitable as organic steam reforming starting materials low alcohols and aliphatic Hydrocarbons.

example

A reactor is hourly, at 200 bar and 330 ° C, 6.06 kg of nitrobenzene and a mixture of 2.43 kg of methanol and 0.97 kg of water. During the process hourly at a suitable location 11.5 kg of water supplied at 20 ° C to increase the temperature to be checked (see sketch).

Yield 4.6 kg aniline per hour.

Explanation of the sketch:

1st Starting material for the steam reforming reaction.
2nd Organic nitro compounds
3rd Pump for 1
4th Pump for 2
5 . Heat exchanger
6 . Combined reactor for hydrogen production and reduction
7 . exit

Claims (1)

A process for the preparation of aniline by reduction of nitrobenzene with hydrogen in the liquid phase at elevated temperature and under pressure in the presence of a catalyst, characterized in that nitrobenzene in an aqueous medium at 39.23 to 245.2 bar and 240-375 ° C in Reduced presence of a zirconium compound as a catalyst, wherein the hydrogen required for the reduction is generated in situ in the presence of low molecular weight alcohols or aliphatic hydrocarbons.