JP3080776B2 - Method for producing 4-alkoxyanilines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a noble metal catalyst used in the production of 4-alkoxyanilines, which are important intermediates such as dyes and pharmaceuticals, from corresponding nitro compounds by utilizing a Bamberger-type rearrangement reaction. Recycling method.

[0002]

2. Description of the Related Art A method for producing 4-aminophenols and 4-alkoxyanilines in a single step by catalytic reduction using a Bamberger-type rearrangement reaction from nitrobenzenes has already been known (Japanese Patent Publication No. 45-29811, Japanese Patent Publication No. Kaisho 6
0-115556). At that time, since an expensive noble metal catalyst is used as a catalyst, it is recovered and reused. Usually, the solution is recovered from the end of the reduction reaction by filtration and reused. However, it is unavoidable that tar generated during the reaction adheres and deactivation due to air contact during the filtration operation. To improve these problems, Japanese Patent Publication No. 45-29811 (4 times higher than nitrobenzene)
-Aminophenol production method) proposes a method in which the reaction is stopped halfway, the noble metal catalyst contained in the unreacted nitrobenzene is separated, recovered and reused.

[0003]

In the production of 4-alkoxyanilines according to the present invention, the reaction solution does not become two-phase, and the conversion is reduced as in the production of 4-aminophenol. However, it is not possible to adopt a method of reusing and leaving a nitro compound which can contain almost all of the noble metal catalyst. Therefore, after the completion of the reaction, the solution is collected by filtration and reused, but deactivation is inevitable, and it is necessary to add a new catalyst by about 30%.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve these problems, and as a result, the activity of the recovered catalyst was improved by washing the recovered catalyst after the reaction with hot water. The present inventors have found that an additional amount of the catalyst is small and completed the present invention. That is, the present invention provides a compound represented by the general formula (1)

[0005]

Embedded image

[Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group, and when R is a substituent other than a hydrogen atom, it is in the o-position or m-position with respect to the nitro group.
Represents the position. n is an integer of 1 to 2] in a method of producing a 4-alkoxyaniline by catalytic hydrogenation of a nitrobenzene represented by the following formula in a lower aliphatic alcohol and sulfuric acid system in the presence of a noble metal catalyst. Characterized in that the precious metal catalyst recovered by filtration is washed with hot water and reused.
This is a method for producing an alkoxyaniline.

The nitrobenzenes used in the method of the present invention include, for example, nitrobenzene, o-chloronitrobenzene, m-chloronitrobenzene, o-nitrotoluene, m-nitrotoluene, o-nitroanisole and m-chlorotoluene.
-Nitroanisole, o-nitrophenetol, m-nitrophenetol and the like.

The mixed solvent of alcohol and sulfuric acid used in the method of the present invention has a water content of 2 to 30% by weight, and preferably contains 3 to 10% by weight of water. It is a mixed solvent. If the water content is out of this range, 4-hydroxyanilines and anilines are by-produced, which is not a measure.

Examples of the type of alcohol used in the present invention include lower alcohols such as methanol and ethanol. The amount of alcohol used is at least 10 times mol, preferably 20 to 100 times mol, of nitrobenzene as a raw material. More preferably, the molar ratio is 30 to 60 times.

The amount of sulfuric acid used in the present invention is 0.5 to 20 moles, preferably 1 to 20 moles per mole of the starting nitrobenzenes.
The molar ratio is preferably 10 to 10 times, more preferably 2 to 7 times.
When the amount of sulfuric acid is out of this range, an increase in anilines and unknown tar components is observed.

In the present invention, platinum, palladium, and a mixture thereof are used as the catalyst. These metal catalysts use an inert solid as a carrier, but carbon is advantageous as a carrier. It is preferable to use a catalyst containing 1 to 5% of platinum and / or palladium supported on activated carbon, but any catalyst containing 0.1 to 20% of these metals may be used. The amount used is 0.01 to 0.10% by weight of platinum, based on the nitrobenzenes to be reacted.
Alternatively, it is preferable to use a supported catalyst in a catalytic amount corresponding to palladium.

The reaction temperature in the catalytic hydrogenation is 0 ° C.
To the boiling point of the mixed solvent, preferably 30 to 60 ° C.
Is selected. The reaction pressure is practically in the range from atmospheric pressure to 2 kg / cm ² gauge pressure.

In the hot water washing treatment according to the present invention, the recovered catalyst filtered after the reaction may be washed with hot water as it is. However, the catalyst separated from the reaction solution by filtration is reslurried with hot water, filtered, and then re-slurried. It is more effective to use.

The temperature of the hot water used in the present invention is not particularly limited as long as it is 40 ° C. or higher. If it is less than this, the activity of the recovered catalyst will not be improved, and the added amount of the new catalyst will increase, so that it is preferably 40 to 90 ° C, more preferably 50 to 70 ° C. In addition, steam or hot water having a boiling point equal to or higher than the boiling point of water under pressure may be used, but a pressurizing device or the like is required, which is economically disadvantageous.

[0015] The amount of hot water used in the present invention is not particularly limited, but is preferably 10 or more times the weight of the recovered catalyst. If the amount is small, there is a disadvantage that the activity of the recovered catalyst is not improved. If the amount is large, it is economically disadvantageous, such as an increase in the amount of wastewater and the like, and preferably 50 to 200 times the weight of the recovered catalyst is sufficient, and more preferably 80 to 120 times.

In the present invention, the time of the hot water washing treatment is not particularly limited, but it is sufficient if it is several minutes or more. Also, the number of times of hot water washing is not particularly limited, but it is sufficient if it is performed once or more. Even if the above-mentioned amount of warm water is divided into several times, there is no problem.

Next, in order to carry out the present invention, the reaction mass obtained by a usual method, for example, a Bamberger-type rearrangement reaction is filtered, and the filtrate is sent to a purification step, and remains on a filter. The recovered catalyst may be reslurried with warm water, re-filtered, mixed with a small amount of water, and recycled to the reaction system.

[0018]

The present invention will be described in detail below with reference to examples and comparative examples. Example 1 In a 5 l glass reactor equipped with a stirrer, a thermometer, and a hydrogen inlet tube, 137.1 g of o-nitrotoluene, 264.5 g of 98% sulfuric acid, 68.6 g of distilled water, and 151 of methanol
8.0 g and 0.41 g of a 3% carbon-supported platinum catalyst were charged.

The reaction is carried out at 50 ° C. while adding hydrogen.
Performed under slight pressure maintained at 0-30 cm water column. The reaction time required 300 minutes, and the reaction was completed when 52.5 l of hydrogen was absorbed. At that time, almost no o-nitrotoluene remained in the reaction solution.

Subsequently, the reaction solution was filtered to separate the catalyst,
The recovered catalyst was transferred to a 50 ml beaker, about 40 ml of 70 ° C warm water was added, and the mixture was stirred for 10 minutes while maintaining the temperature at 60 to 65 ° C in a hot water bath. It was filtered again to obtain 0.81 g of a catalyst (including water) which had been washed with hot water. The filtrate after the hot water washing treatment had a dark brown color.

After the methanol was distilled off, the reaction solution from which the catalyst had been removed by filtration was added with 500 g of distilled water, neutralized with 28% aqueous ammonia, and then neutralized with a pH. 7.2. 200 g of toluene in the neutralized solution
And extracted. After the separated toluene layer was washed with dilute caustic water, the toluene layer was concentrated and distilled under reduced pressure to obtain 22.8 g of o-toluidine as an initial fraction and 96.8 as a main fraction.
g (70.0% yield) of 2-methyl-4-methoxyaniline was obtained. The purity of the main fraction determined by gas chromatography was 99.2%.

Examples 2 to 9 Using the recovered catalyst obtained in Example 1, the same hot water washing treatment as in Example 1 was carried out every time during recycling, and the recycled catalyst was used 9 times. The addition of the new catalyst was not performed until the fifth recycling, and the reaction was performed by adding 0.04 g of the new catalyst used in Example 1 every time after the sixth recycling. Table 1 shows the results.

[0023]

[Table 1]

Comparative Example 1 The same reactor as used in Example 1 was charged with exactly the same amounts of raw materials and catalyst as in Example 1, and reacted in the same manner as in Example 1. The time required for the reaction was 300 minutes.

Subsequently, the reaction solution was filtered to separate the catalyst,
The recovered catalyst was transferred to a 50 ml beaker, about 40.0 ml of water at 20 ° C. was added, and the mixture was stirred at room temperature for about 1 hour. 0.82 g of the filtered and washed catalyst (including water) was obtained again. The filtrate after the water washing treatment exhibited a light brown color.

The reaction solution from which the catalyst was filtered off was subjected to the same treatment as in Example 1, and the yield of 2-methyl-4-methoxyaniline obtained was 70.6% and the purity was 99.2%. .

Comparative Examples 2 to 10 Hereinafter, using the recovered catalyst obtained in Comparative Example 1, the same water washing treatment as in Comparative Example 1 was carried out every time during recycling, and the recycled catalyst was used 9 times. The addition of a new catalyst was not performed until the fifth recycle, and the reaction was performed by adding 0.08 g of the new catalyst used in Example 1 every time from the sixth to the eighth and adding 0.21 g of the new catalyst at the ninth time. Table 2 shows the results.

[0028]

[Table 2]

Comparative Example 11 The same reactor as used in Example 1 was charged with exactly the same amounts of raw materials and catalyst as in Example 1, and the reaction was carried out in the same manner as in Example 1. The time required for the reaction was 300 minutes.

Subsequently, the reaction solution was filtered to separate the catalyst,
The recovered catalyst was transferred to a 100 ml beaker, about 50 ml of methanol was added, and the mixture was stirred at room temperature for about 1 hour. The filtered and washed catalyst (including methanol and water) 0.8
0 g was obtained. The filtrate after the methanol treatment exhibited a light brown color.

The reaction solution from which the catalyst was filtered off was subjected to the same treatment as in Example 1. The yield of 2-methyl-4-methoxyaniline obtained was 70.5% and the purity was 99.3%. .

COMPARATIVE EXAMPLES 12-20 Hereinafter, using the recovered catalyst obtained in Comparative Example 11, the same methanol washing treatment as in Comparative Example 11 was carried out every time during recycling, and the recycled catalyst was used 9 times. The addition of the new catalyst was not performed until the fifth recycling, and the reaction was performed by adding 0.08 g of the new catalyst used in Example 1 every time until the sixth to eighth recycling, and adding 0.21 g at the ninth recycling. Table 3 shows the results.

[0033]

[Table 3]

[0034]

According to the present invention, a reduction in the activity of the recovered catalyst can be suppressed, and the amount of the new catalyst added can be reduced, whereby an economically advantageous improvement in productivity can be achieved. That is,
In Comparative Examples 1 to 20, which are out of the scope of the present invention, when the recovered catalyst is recycled, the activity of the recovered catalyst is clearly reduced, and the reaction rate cannot be maintained unless the amount of the new catalyst is increased. Which is economically disadvantageous. On the other hand, when the recovered catalyst is recycled, if the hot water washing treatment is performed as shown in Examples 1 to 9, the additional amount of the new catalyst can be reduced, and it is obvious that the productivity is greatly improved economically. And
The significance of the present invention is great.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-115556 (JP, A) JP-A-2-160048 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 217/84 B01J 23/96 B01J 38/48 C07C 213/00 C07B 61/00 300

Claims (1)

(57) [Claims] 1. A compound represented by the general formula (1): [Wherein, R represents a hydrogen atom, a halogen atom, a lower alkyl group or a lower alkoxy group, and when R is a substituent other than a hydrogen atom, it represents the o-position or the m-position with respect to the nitro group.
n is an integer of 1 to 2] in a method of producing a 4-alkoxyaniline by catalytic hydrogenation of a nitrobenzene represented by the following formula in a lower aliphatic alcohol and sulfuric acid system in the presence of a noble metal catalyst. A method for producing 4-alkoxyanilines, comprising washing and recycling a noble metal catalyst recovered by filtration.