JPH034055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides m-phenylenediamine (hereinafter m-
Abbreviated as PDA. ). More specifically, crude m-dinitrobenzene (hereinafter m-
Abbreviated as DNB. ) to produce m-PDA of higher purity.

m-PDA is an important compound as an intermediate for pharmaceuticals and, in recent years, as a raw material for heat-resistant resins.
-DNB has been obtained by catalytic hydrogenation reaction in the presence of a catalyst. Furthermore, m-DNB can be obtained by nitrating benzene or nitrobenzene with a strong mixed acid.
-Dinitrobenzene (hereinafter abbreviated as p-DNB) is produced as a by-product, and usually has a purity of about 90% as m-DNB. Known methods for separating these isomers include a method using the difference in solubility in alcohol or benzene, a method of heat treatment with sodium sulfite and sodium bisulfite, and a method of heat treatment with an aqueous caustic alkali solution. The product purity of the m-DNB obtained was only about 99% at most, and complete separation of o-DNB and p-DNB was impossible.

Therefore, m-PDA obtained by hydrogenating m-DNB contains impurities such as o- and p-isomers, so it needs to be purified by rectification etc. Because the difference in boiling point between the two bodies is small, severe rectification using dozens of rectification columns and post-purification steps such as recrystallization are required.

Even in trace amounts, impurities such as o- and p-isomers are
-If it is contained in PDA, it not only causes discoloration of m-PDA over time, but also only resins of poor quality can be obtained, especially when m-PDA is used as a heat-resistant resin raw material.

As a result of intensive studies to solve the above problems, the present inventors found that when crude m-DNB is reacted with a lower alcohol in the presence of a base, there is virtually no loss of m-DNB, and o- and m-DNB are reacted. It has been found that only -DNB can be selectively and almost completely converted to lower alkoxynitrobenzene. Furthermore, if this reaction mixture is hydrogenated by a conventional method without separating m-DNB from these reaction mixtures, and the obtained hydrogenated reaction product is separated by a conventional distillation method, We have completed the present invention by discovering that purified m-PDA of high purity can be obtained much more easily than by separating m-PDA and o- and p-isomers.

That is, the method of the present invention uses crude m-DNB and hydrogenates it to obtain high-purity refined m-PDA.
-Provides a method for manufacturing a PDA.

In the method of the present invention, the alkoxylation reaction of crude m-DNB is carried out as follows.

The types of alcohol used include lower aliphatic monohydric alcohols such as methanol, ethanol, and isopropanol, alicyclic alcohols such as cyclohexanol, aromatic alcohols such as benzyl alcohol, and lower polyhydric alcohols such as ethylene alcohol. However, the rate of alkoxy reaction and the separation efficiency of o- and p-alkoxynitrobenzene and m-DNB or o- and p-alkoxyaniline and m-PDA after hydrogenation of them are Considering this, lower aliphatic monohydric alcohols are preferred, and aliphatic monohydric alcohols having 3 or less carbon atoms are more preferred.

The amount of alcohol used is not particularly limited as long as it is at least equimolar to the total amount of o-DNB and p-DNB contained in the crude m-DNB. o if it is less
-, and P-DNB may remain, and if there is a large excess, the volumetric efficiency of the reactor will deteriorate, and it is not advisable to take time to recover the alcohol. o-,
It is preferable to carry out the reaction in an autosolvent of the alcohol used, using a 10 to 90-fold molar excess with respect to the total amount of p-DNB and p-DNB.

The reaction temperature is selected to give a suitable reaction rate below the boiling point of the reaction system. The range is preferably from around room temperature to the boiling point of the alcohol used.
Although it is possible to carry out the process under pressure and at a higher temperature, it is not economical, and the yield and quality of purified m-DNB are reduced due to tarring, alkoxylation, etc. of m-DNB.

The basic compounds used are caustic soda,
Examples include hydroxides of alkali metals and alkaline earth metals such as caustic potash and calcium hydroxide, or their carbonates, bicarbonates, sulfites, and bisulfites. Particularly preferred is caustic soda, which is inexpensive and has a strong basicity. The amounts of these basic compounds used are o- and p- in the crude m-DNB.
It is sufficient if the amount is stoichiometrically equivalent to the total amount of DNB. If the amount used is too large, m-DNB may become tarred, leading to a decrease in yield and quality, and preferably 1.0 to 2.0 equivalents is sufficient. When adding these, there is no problem whether they are used as solids or in aqueous solutions, but depending on the separation and purification method, it is advantageous to use them in aqueous solutions in consideration of removal of residual basic compounds, etc.

The crude m-DNB containing o- and p-alkoxynitrobenzene obtained in this way can be hydrogenated using a known method, for example, using an organic solvent such as alcohol or toluene in the presence of a noble metal catalyst at normal pressure or under pressure. After the reaction mixture is added and the corresponding amine compound is converted into a mixed reactant, it is subsequently separated and purified by distillation. At that time, by converting o- and p-DNB into o- and p-alkoxynitrobenzene as in the present invention, the hydrogenation reaction products can be separated from m-PDA and o- and p-alkoxyaniline. It can be easily done between. For example, in the case of separation of o- and p-methoxyaniline and m-PDA, conventional m-PDA and o- and p-
Compared to the separation method for PDA isomers, the boiling points of m-PDA and o- and p-methoxyaniline are
There is a much larger difference, and separation and purification becomes possible much more economically than in the past.

Also, when separating alcohol into ethoxyaniline, propoxyaniline, etc. using ethanol, propanol, etc., during hydrogenation,
Alternatively, the separation efficiency can be increased by extracting these alkoxyanilines with a non-aqueous solvent after the completion of the reaction and then distilling this.

The specific method of the present invention will be explained below with reference to Examples.

Example 1 Crude m-DNB (o-DNB9.0%, m-DNB88.6
%, p-DNB2.4%) 200.0g, methanol 146.0
g, (33.5 mole times relative to o-DNB and p-DNB) and 32.0 g of 20% caustic soda water were charged into a reaction tank equipped with a stirrer, and reacted for 3 hours at the boiling point of the solvent (about 70°C). This reaction mass was analyzed from time to time, and the point at which o- and p-DNB became undetectable was defined as the end point of the reaction. Analysis of the reaction mass revealed that m-DNB±
176.6g (99.7% recovery rate), o-nitroanisole
16.0g (yield 97.7%), p-nitroanisole 4.1
g (yield 94.6%), o- and p-DNB
The reaction between and methanol has been completed, and m-
It was confirmed that DNB could be recovered almost quantitatively without loss.

Subsequently, after removing the solvent, in order to remove remaining basic compounds, etc., the mixture was washed with about 100 g of hot water, followed by oil-water separation, and the oil layer was used as it was as a raw material for the following hydrogenation step.

195.1g of the above oil layer (m-DNB in this is 173.2g)
), methanol 97.5g and 5% Pd-carbon
Pour 0.25g into a stainless steel autoclave,
Hydrogenation was carried out at a reaction temperature of ±100° C. and a hydrogen pressure of 40 Kg/cm ² G. The reaction was completed in 55 minutes. After cooling, residual hydrogen was released, and the reaction solution was filtered to separate the catalyst.

After removing the solvent, the above liquid (which contained 102.0 g of m-PDA) was subjected to batch distillation at a reduced pressure of 15 mmHg and a reflux ratio of 10 to 20 in a rectification column with 10 theoretical plates, and the boiling point was 121.
o- and p-methoxyaniline up to
p-methoxyaniline 240-242℃) distillate 15.2g
and m-PDA with a boiling point of 162° (literature value boiling point at normal pressure)
88.1 g of a fraction (282-284°C) (86.4% yield in the distillation process) was obtained. This m-PDA fraction has a light transmittance of 98 at 450 mμ compared to methanol.
%, and the purity by gas chromatography is
It was 99.99%.

Comparative Example 1 The crude m-DNB described in Example 1 was directly hydrogenated under the same conditions as Example 1 without the step of reacting with methanol. The reaction was completed in 60 minutes.
After cooling, residual hydrogen was released, and the reaction solution was filtered to separate the catalyst.

The above liquid was heated in the same rectification column as in Example 1 and under the same distillation conditions to form m-PDA, o- and p-isomers (the boiling points of these literature values at normal pressure are 256-258°C for the o-isomer,
P-isomer (267°C) was batch distilled to obtain m-PDA with a purity of 99.99% as determined by gas chromatography, but the yield during distillation was only 41.5%. Furthermore, the light transmittance of this m-PDA at 450 mμ with methanol as a control was only 86.0%.

In addition, in order to achieve a extraction yield of about 85% during distillation, a rectification column with 50 theoretical plates is used, and the reflux ratio is 20 to 20.
I needed 30.

Example 2 Same as Example 1 except that 200.0 g of ethanol was used instead of methanol, but the boiling point of the solvent (approx.
Ethoxylation was carried out for 6 hours at 100°C. When this reaction mass was analyzed, o- and p-DNB were not detected, m-DNB176.9g (recovery rate 99.8%), o-nitrophenetol 17.4g (yield 97.0%), p-nitrophenetol There were 4.4 g of phenetol (93.2% yield).

Subsequently, after removing the solvent, the mixture was washed with about 100 g of molten water to remove residual basic compounds, followed by oil-water separation, and the oil layer was used as it was as a raw material for the following hydrogenation step.

194.7g of the above oil layer (m-DNB in this is 172.7g)
), toluene 170g and 5% Pd-carbon 0.25g
g was placed in a stainless steel autoclave, and hydrogenated at a reaction temperature of 100° and a hydrogen pressure of 40 kg/cm ² G. The reaction was completed in 60 minutes. After cooling, residual hydrogen was released, and the reaction solution was filtered to separate the catalyst.

The above solution (which contained 103.2 g of m-PDA) was separated, and 170 g of toluene was added to extract o- and p-ethoxyaniline.
After concentrating the aqueous layer, batch distillation was carried out at a reflux ratio of 5 to 10 using a rectification column with a pressure reduction degree of 15 mmHg and 10 theoretical plates.
PDA fraction 93.9g (removal yield in distillation process 91.0
%) was obtained. This m-PDA fraction showed a light transmittance of 96% at 450 mμ with methanol as a control, and the purity by gas chromatography was 99.98.
It was %.

Claims (1)

[Claims] 1. Crude m-dinitrobenzene containing o- and p-dinitrobenzene is reacted with a lower alcohol in the presence of a basic compound to obtain substantially o-,
Only p-dinitrobenzene and p-dinitrobenzene are selectively converted into the corresponding alkoxynitrobenzene, hydrogenation reaction is performed as it is without separating m-dinitrobenzene from the obtained reaction mixture, and then the obtained m-phenylenediamine is A method for producing high-purity m-phenylenediamine, which comprises separating it by distillation. 2. The method according to claim 1, wherein the lower alcohol is an aliphatic monohydric alcohol having 3 or less carbon atoms.