JPS6253945A - Manufacture of aromatic amino compound - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic reduction method, more specifically a method for catalytic reduction of an aromatic nitro compound to a corresponding amino compound (
For example, it relates to a method for reducing nitrobenzene to aniline).

Reduction of aromatic nitro compounds is conveniently carried out by passing a hydrogen-containing gas stream through a liquid nitro compound in which the catalyst is suspended or a solution of the nitro compound in a suitable solvent. , the amino product is removed from the reaction mixture by distillation.

The commonly used catalyst is usually nickel in finely divided form, which is usually supported on an inert oxide-based material such as poly-JL diatomaceous earth. Such catalysts involve impregnating a support with a pyrolyzable nickel salt, such as a nitrate, calcination to convert the nickel salt to nickel oxide, and then reducing the nickel oxide to the active metal with a hydrogen-containing gas stream. It can be manufactured by Alternatively,
Nickel can be produced by precipitating it on a support in the form of a hydroxide or carbonate, which is then calcined to form the hydroxide or carbonate into nickel oxide. In a typical commercial catalyst precursor made in this manner, nickel is present in less than about 60 of the total number of atoms (other than oxygen atoms) in the precursor.

GB 1,342,020 proposes the use of a nickel catalyst for the reduction of nitrobenzene, prepared by reduction of a precursor pelleted from calcined precipitated crystals of the formula:

Ni 1s, o CrO,COs (OH)1a ・
4H20 Therefore, the active metal, i.e. nickel atoms, in such a catalyst accounts for about 75 of the total number of metal atoms in the catalyst.
%.

We have found that certain catalysts with higher contents of active metals are particularly useful.

Accordingly, the present invention provides a catalyst comprising at least one metal of group Ⅰ of the periodic table of elements selected from cobalt and nickel in close contact with at least one refractory metal oxide. and the hydrogen-containing aromatic nitro compound in the presence of a catalyst such that the atoms of said Group (I) metal constitute 80 to 98 of the total number of atoms excluding oxygen and (if present) hydrogen in the catalyst. A method for preparing the corresponding aromatic amino compounds is provided, which comprises reduction in a gas stream.

The aromatic nitro compound is preferably phosphorous and preferably has a single nitro substituent, such as nitrobenzene. The aromatic nucleus may have other substituents such as alkyl groups such as methyl groups, as in nitrotoluenes.

The catalyst may be used in the form of a fixed bed, for example a fixed bed of pellets, but the nitro compound and optionally the solvent of the nitro compound (
(often suitably reduction products of nitro compounds)
Preferably, it is used in finely divided form, suspended in a liquid phase consisting of: The reaction is carried out by passing a stream of hydrogen gas-containing gas into the liquid phase, preferably with vigorous stirring, while maintaining the liquid phase at a temperature at which the product is distilled off from the reaction mixture. preferable. Examples of gases containing hydrogen gas include hydrogen, or hydrogen and an inert diluent (
Example: Nitrogen). The henitro compound is added continuously to the reaction mixture, and the product is removed by distillation from the reaction mixture at a rate corresponding to the rate of product formation.

When such distillation operations are used to remove amino products, the reaction temperature is governed by the boiling point of the product and the applied pressure. The pressure is a reaction temperature of 100-250℃,
In particular, it is preferable to keep the temperature within the range of 140 to 200°C. By using such a distillation method, the heat of reaction can be utilized as at least part of the heat of vaporization of the amino product.

The catalyst in the present invention consists of at least one Group (III) metal selected from cobalt and nickel intimately mixed (in contact) with one type of refractory metal oxide. Sometimes the catalyst has high activity and good selectivity. When the group II metal is cobalt, the activity may not be as high but the selectivity is even better. Mixtures of cobalt and nickel,
In particular, by using mixtures with a Ni:Co atomic ratio of 0.5 to 5, an advantageous compromise between high activity and very good selectivity is achieved. The catalyst of the present invention has a relatively high Group 1 metal content. Therefore, the Group III metal is the total number of atoms other than oxygen and (if present) carbon atoms in the catalyst (i.e., the total number of Group III metal atoms and the metal atoms of the refractory metal oxide). 80 to 98 yen, preferably 85 to 95%.

The refractory metal oxide may be any oxide of a metal in subgroup A other than group 1A of the periodic table, preferably metals in group 1 [IA (e.g., rare earths, doria, urania). etc.) or of Group 1 VA. It is preferred that two or more such oxides are present, particularly combinations of oxides of aluminum and one or more rare earths (especially lanthanum and/or cerium). So-called industrial grade materials consisting of rare earth mixtures can also be used as raw materials.

Although the catalyst should be substantially free of other metals or oxides, small amounts of these may in fact be present as impurities.

Intimate contact between the active metal, i.e. the group I metal, and the refractory oxide can be brought about by precipitation (e.g. in the form of the respective hydroxide and/or carbonate) or by a highly adsorptive state. (More than 50ml/g, especially 100m/!
applying a solution of a compound of an active metal to a refractory oxide with a surface area greater than or equal to i', then reducing the Group I metal compound to metal and, if necessary, decomposing the subgroup A metal compound to It is brought about by using it as a reducing compound.

The catalyst of the invention can be precipitated sequentially or especially co-precipitated in the form of hydroxide and/or carbonate and then calcined with A.
It is preferably obtained by decomposing the subgroup metal compound to form an oxide and further reducing the group (I) metal compound to a metal.

Reduction to the active metal is usually accomplished by heating the catalyst precursor in a hydrogen-containing gas stream, but this can in some cases be carried out in a nitro compound reduction reaction vessel, e.g. Suspending the calcined precursor in a liquid nitro compound, or e.g. This can also be done by passing the Preferably, the reduction of the precursor to the active metal is carried out off-line. In particular, the activity of the catalysts of the present invention tends to improve as the temperature used for the reduction of the precursor to the active metal increases, and the reduction to the active metal typically occurs during the nitro compound reduction reaction. It has been discovered that optimal activity is obtained when carried out at temperatures significantly higher than those encountered. Preferably the catalyst precursor is 600-750°
α is reduced to the active metal, especially at temperatures in the range from 350 to 700°C. To facilitate handling of the catalyst (precursor) before, during, or after reduction to the active metal, it may be desirable to form the precursor into pellets prior to reduction to the active metal. When the catalyst is produced by a precipitation method, the precipitation mixture is preferably pelletized after calcination to decompose the precipitate into an oxide. However, pelletization may be facilitated if the calcination prior to pelletization is incomplete, such that the calcination mixture contains hydroxides and/or carbonates. Additional heating of the pellet to complete decomposition to oxides leads to
It can be carried out before or during the reduction of the group metal compound. Preferably, such additional heating is performed before reduction. This is because otherwise methanation of the released carbon dioxide would occur during the reduction, resulting in a significant exotherm, which would make it difficult to control the reduction temperature.

To facilitate handling before use, the reduced catalyst can also be stabilized by treatment with a stream of inert gas containing a small amount of oxygen during cooling from the reduction temperature. If such a pelletized and stabilized catalyst is to be used as a catalyst suspension, the pellets are crushed or ground in an inert medium to form fine particles before use.

Preferably, the surface area of the active metal in the reduction catalyst is at least 30 yi per gram of catalyst.

One of the particular advantages found with the use of catalysts with a high Group I metal content is that the selectivity of the nitro compound reduction reaction is significantly improved.

Therefore, when reducing nitrobenzene to aniline,
Some phenol is produced, probably resulting from hydrolysis of some of the aniline product by the water produced in the nitrobenzene reduction. Some phenylcyclohexylamino is also produced as a result of the hydrogenation and condensation reactions. Compared to catalysts commonly used for the reduction of nitro compounds, the high Group I metal content catalysts of the present invention yield significantly reduced proportions of such by-product hydrocarbons.

The present invention will be explained below with reference to Examples.

6 Examples 1 to 11 A small precipitation vessel contains 3229/l of nickel nitrate hexahydrate, 2">, 6 g/l of aluminum nitrate nonahydrate and BA9/l of cerium nitrate hexahydrate. An aqueous solution at about 70° C. was fed continuously and an aqueous solution at 70° C. containing 15 rH1/!l of sodium carbonate hydrate was fed in an amount to maintain the pH value in the vessel at about 7. Precipitate is continuously removed from the container, hot filtered, washed and 110
It was dried at ℃ for 16 hours. The dried precipitate was then heated to 350
It was baked at 'C for 4 hours. This fired product had the following composition after ignition at 90°C.

Oxide Weight % NiO93.1 hl, o, 3.7 Cen23. The ignition loss of INa, OQ at 1900°C was 11.3% by weight. The nickel atoms therefore comprised approximately 93 of the total number of atoms (excluding oxygen atoms) in this calcined catalyst precursor. Moreover, this fired product had the following powder characteristics.

BIT (nitrogen) cloth area 213 m/, Si' helium method density 5.07 g/crl mercury method density 2.44 g/d pore volume
0.21m/9 fired product by 1.2m of its weight.
Mixed with 5 inches of graphite and compressed to a diameter of 6.7
Balls were formed into cylindrical pellets with a height of 3.3 mm. A 3 F deep bed of the pellets, supported on a piece of fused (sintered) alumina, was loaded into a 2.5 caliber experimental reactor.

The reactor was heated to the desired reduction temperature and an equal volume mixture of hydrogen and nitrogen was flowed at 1001/hr (N
TP) was passed through the bed.

This nitrogen/hydrogen gas flow is then heated to 2001/hour (NTP)
The reactor was switched to a nitrogen gas flow at a flow rate of about 10
Cooled to 0°C. After 1 hour at 100° C., 0.5 volume percent air was mixed into the nitrogen gas stream for about 2 hours. The concentration of air in the gas stream was then doubled every 30 minutes until the proportions of air and nitrogen in the gas stream were approximately equal. The gas flow rate was then reduced to 401/hr and the reactor was cooled to room temperature.

This reduction and stabilization operation was repeated on new samples of pellets to obtain a series of reduced catalysts at several temperatures within the range of 300-700<0>C. The nickel surface area of these catalysts was determined by adsorption method on crushed samples after 2 hours of re-reduction at 260°C.

The activity of these catalyst samples was assayed by the following procedure.

2 g of the stabilized pellets were ground with a pestle and needle under 5 Q ml of purified aniline, and the resulting slurry was then transferred with an additional 5 Q ml of aniline to a 250 ml flask with a stirrer. The flask was heated in an oil bath to drive air out of the flask.

The flask contents were maintained at 157°C. Hydrogen was passed into the vigorously stirred mixture over a period of 2 hours at a flow rate of 180 l/h. Small samples were taken from time to time and analyzed for phenylcyclohexylamino content by gas chromatography. The flask contents were then cooled to 145°C and 1
0rnl of nitrobenzene was added and the hydrogen flow was continued for 2 hours during which time samples were taken to determine the residual nitrobenzene content.

In the table below, the activity for catalysts reduced at various temperatures; Activity for standard commercially available catalysts;
are listed.

The activity is expressed in grams of aniline produced per hour per gram of stable catalyst used. During a series of experiments, different types of nitrobenzene (A, B, C) with possibly different purities were used. Such differences in raw material purity may account for the variations in activity shown in the table.

In the case of Example B, the production rate of phenylcyclohexylamino per 1 g of catalyst was 0.2 g 7 h, that is, the value obtained with the standard commercially available catalyst was 1.9 to 2.1. ! It was about one-tenth of 9/hour. In another embodiment of the invention, the rate of formation of phenylcyclohexylamino is
It was less than 0.1 g/hour.

Example 12 The precipitation procedure used in the previous example was repeated, but the mixed nitrate solution of this example contained the following components:

Cobalt (as nitrate) 65.3f! /1 aluminum nitrate nonahydrate 22.9 &/1 cerium nitrate hexahydrate 7.99/11 The precipitate was filtered, washed, dried and calcined as in the previous example, but in this example the drying temperature was The temperature was 120°C and the firing temperature was 300°C.

The fired product (after ignition at 900°C) had the following composition:

Oxide Weight% Coo 92.2 A1. o, 3.2 Ce02 3.8 Naz　O＜　0.1 The ignition loss at 900°C was 6.7% by weight.

Therefore, the cobalt atoms comprised about 93.5% of the total number of atoms (excluding oxygen atoms) in the calcined catalyst precursor. This fired product had the following powder characteristics.

BET (nitrogen) method area 132 m/g Helium method density 5.07 i/lyd Mercury method density
0.9ON/d pore volume
The calcined product was pelletized as in the previous example, reduced (at a reduction temperature of 450° C.), stabilized with air, and tested.

Its activity was only 46% that of the standard commercially available catalyst, and the rate of phenylcyclohexylamino formation was only 0.7% that of the standard commercially available catalyst.

(5 other people)

Claims (9)

[Claims] (1) A catalyst comprising at least one metal of Group VIII of the Periodic Table of Elements selected from cobalt and nickel in close contact with at least one refractory metal oxide, and said Group VIII metal. The metal atoms account for 80-98% of the total number of atoms other than oxygen and hydrogen, if present, in the catalyst.
A process for the preparation of corresponding aromatic amino compounds, which comprises reducing an aromatic nitro compound in a hydrogen-containing gas stream in the presence of a catalyst such as. (2) The method according to claim 1, wherein the refractory metal oxide is alumina. (3) The refractory metal oxide is alumina and at least one
3. A method according to claim 1 or 2, comprising a rare earth species. (4) A method according to claim 1, 2 or 3, wherein the catalyst comprises a mixture of nickel and cobalt and has a nickel:cobalt atomic ratio within the range of 0.5 to 5. (5) The catalyst is obtained by calcining an intimate mixture of precipitated hydroxides and/or carbonates of nickel and/or cobalt and at least one metal that is a refractory oxide. In addition, it is obtained by reducing nickel and/or cobalt oxide in an intimate mixture with at least one refractory metal oxide at a temperature within the range of 300 to 750°C. A method according to any one of claims 1 to 4. (6) The method according to any one of claims 1 to 5, wherein the catalyst has a metal surface area of at least 30 m^2/g. (7) The reduction of the aromatic nitro compound is carried out by continuously passing a hydrogen-containing gas stream through a liquid phase consisting of the aromatic nitro compound in which a catalyst is suspended in a finely divided state. 6. The method according to any one of items 6 to 6. (8) The reduction of the aromatic nitro compound is carried out by adding the aromatic nitro compound to the reaction mixture and distilling off the product amino compound at a rate corresponding to its production rate. the method of. (9) The method according to any one of claims 1 to 8, wherein the reduction of the aromatic nitro compound is carried out at a temperature within the range of 100 to 250°C.