JPH05331109A - Method for purifying m-dinitrobenzene - Google Patents

Abstract

PURPOSE:To obtain purified high-purity m-dinitrobenzene in high yield, simultaneously remarkably reduce the amount of an alcohol used and improve the productivity. CONSTITUTION:The method for purifying m-dinitrobenzene is characterized by substantially selectively reacting only the o- and p-isomers of crude m- dinitrobenzene with a lower alcohol in the presence of a basic compound and a phase-transfer catalyst and separating o- and p-alkoxynitrobenzenes from the resultant reactional mixture.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying m-dinitrobenzene (hereinafter abbreviated as m-DNB). m
-DNB is a raw material for m-phenylenediamine and m-nitroaniline, and is also important as an organic synthetic intermediate.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
m-DNB is obtained by nitrating benzene or nitrobenzene with a strong mixed acid, and isomers at that time, o-dinitrobenzene (hereinafter abbreviated as o-DNB) and p-dinitrobenzene (hereinafter p. -DNB) is a by-product, and the purity is usually about 90% as m-DNB.

Known methods for separating these isomers include a method utilizing the difference in solubility in alcohol or benzene, a method of heat treatment with an aqueous solution of caustic alkali, and a method of heating with sodium sulfite and sodium hydrogen sulfite. The product purity of m-DNB obtained in each case is 9
It was only about 9%, and complete separation of o-DNB and p-DNB was impossible.

These trace isomers are not preferred, especially when they are m-phenylenediamines, as they cause coloration of m-phenylenediamines over time, and it has been conventionally desired to sufficiently separate o-DNB and p-DNB. Further, in the reaction with the above-mentioned basic compound, there are drawbacks such that a considerable loss of m-DNB is unavoidable and the wastewater treatment cost is also increased, and its improvement has been demanded.

Further, the present inventors have reported that crude m-DNB and a lower alcohol can be used in the presence of a basic compound in o- and p-D.
A method for obtaining high purity m-DNB by selective reaction of only NB to convert it to the corresponding alkoxynitrobenzene and crystallization from the obtained crude m-DNB containing alkoxynitrobenzene by slow cooling crystallization, etc., was filed previously. (JP-A-59-134750). However, this method requires the use of a large amount of lower alcohol, and there is room for improvement industrially.

[0006]

Means for Solving the Problems As a result of further studies by the present inventors, the addition of a phase transfer catalyst during the alkoxylation reaction improves the alkoxylation reaction rate and reduces the amount of alcohol used. It was found that the present invention has been completed. That is, the present invention is characterized by adding a phase transfer catalyst during an alkoxylation reaction when purifying m-DNB by performing an alkoxylation reaction of an isomer in m-DNB with a lower alcohol in the presence of a basic compound. This is a purification method.

The types of alcohols used in the present invention include lower aliphatic monohydric alcohols such as methanol, ethanol and isopropanol, alicyclic alcohols such as cyclohexanol, aromatic alcohols such as benzyl alcohol, and ethylene glycol. Although lower polyhydric alcohols and the like can also be used, lower aliphatic monohydric alcohols are preferable, and more preferable when the alkoxylation reaction rate and the separation efficiency of the obtained o- and p-alkoxynitrobenzenes and m-DNB are taken into consideration. Is preferably an aliphatic monohydric alcohol having 3 or less carbon atoms.

The amount of alcohol used is crude m-DNB.
There is no particular limitation as long as it is at least equimolar to the total amount of o-DNB and p-DNB contained therein. When it is small, there is a possibility that o- and p-DNB may remain, when it is large, the volumetric efficiency of the reactor is deteriorated, and it is not a convenient measure for alcohol recovery, and preferably the sum of o- and p-DNB is used. It is preferable to carry out the reaction in an amount of 2 to 15 times mol, more preferably 3 to 10 times mol, based on the amount.

The reaction temperature in the present invention is selected so as to give an appropriate reaction rate below the boiling point of the reaction system. The boiling point of the alcohol used is preferably around room temperature. It can be carried out under pressure at a temperature higher than this, but it is not economical, and the yield and quality of the purified m-DNB are deteriorated due to tar-forming or alkoxylation of m-DNB.

The basic compounds used in the present invention include hydroxides of alkali metals such as caustic soda, caustic potash and calcium hydroxide, and alkaline earth metals or their carbonates, bicarbonates, sulfites and bisulfites. Examples include salt. It is particularly preferable to use caustic soda which is inexpensive and has a strong basicity. The amount of these basic compounds used is roughly m
-It is sufficient that the total amount of o- and p-DNB contained in DNB is stoichiometrically equivalent or more. M-D when used in large quantities
As a result, NB is tarred and the yield and quality are deteriorated. Therefore, 1.0 to 2.0 equivalents are preferable. When these are added, there is no problem whether they are used as a solid or as an aqueous solution, but depending on the separation and purification method, it is advantageous to use them as an aqueous solution to remove residual base compounds and the like. The phase transfer catalyst used in the present invention is represented by the general formulas (1) and (2)

[0011]

[Chemical 1]

[In the formula, each R represents an alkyl group, a phenyl group, a benzyl group or an alkoxy group, and X represents a halogen atom, a hydroxyl group, a sulfate group or an acetate group. ] A quaternary alkyl ammonium salt represented by, and amine oxides, for example, tetramethyl ammonium chloride, tetramethyl ammonium acetate, tetraethyl ammonium chloride, tetrabutyl ammonium bromide, tetraethyl ammonium iodide, tetraethyl ammonium bromide,
Tetrabutylammonium hydroxide, tetrabutylammonium iodide, trioctylmethylammonium chloride, tridodecylmethylammonium chloride, phenyltrimethylammonium chloride, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltriethylammonium chloride, benzyltributylammonium chloride, benzyl Examples thereof include tributylammonium bromide, cetyltrimethylammonium chloride, dimethyldodecylamine oxide, dimethyltetradecylamine oxide, dimethylhexadecylamine oxide, and dimethyloctadecylamine oxide.

This phase transfer catalyst may be used alone or in combination of several kinds, and the amount used is not particularly limited as long as it is 0.1% by weight or more based on the crude m-DNB. When it is small, o- and p-DNB may remain, and when it is large, it is economically disadvantageous. It is preferably 0.1 to 10% by weight, more preferably 0.5 to
It is 5% by weight.

To carry out the purification method of the present invention, the crude m-DNB containing o- and p-alkoxynitrobenzene obtained by the alkoxylation reaction is, for example, benzene,
A suitable amount of a generally used recrystallization solvent such as toluene or acetic acid ester is added, followed by crystallization by slow cooling followed by filtration, or distillation of excess alcohol from the reaction mass followed by steam distillation to obtain o- and p-alkoxynitrobenzene. The o- and p-alkoxynitrobenzene and m- are separated by a conventional separation method such as a method of separating m-DNB by distillation from water.
DNB can be easily separated, and high-quality purified m-DNB can be obtained.

[0015]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.
This will be specifically described. The raw material m-
The composition of DNB is m-DNB 88.6%, o-DNB
It was 9.0% and p-DNB 2.4%, and the analysis was carried out by gas chromatography.

Example 1 200.0 g of crude m-DNB, 20.0 g of methanol, 2
32.0 g of 0% caustic soda water and 2.0 g of trioctylmethylammonium chloride were charged into a reactor equipped with a stirrer and reacted under reflux (75 to 78 ° C.) for 3 hours. When this reaction mass was analyzed, o- and p-DNB were not detected, and the reaction with methanol was completed. Furthermore, 176.7 g of m-DNB (recovery rate 99.7%), o
-Nitroanisole 16.0 g (yield 97.6%), p
-4.1 g (yield 93.2%) of nitroanisole was quantified, and it was confirmed that m-DNB can be recovered almost quantitatively without loss.

The above reaction mass was transferred to a flask equipped with a stirrer,
100.0 g of methanol was added and the mixture was gradually cooled to about 10 ° C to crystallize m-DNB. Subsequently, filtration is performed, the filter cake is washed with a small amount of methanol, dried, and then purified m-DNB16
5.3 g (recovery rate 93.3%) was obtained. This product had a light yellow color and had a purity of 99.7%.

Example 2 A reaction was carried out in the same manner as in Example 1 except that 1.0 g of tetraethylammonium chloride was used instead of trioctylmethylammonium chloride. When analyzed 3 hours after the start of the reaction, o-DNB was not detected, but
Since a trace amount of p-DNB was detected, the reaction was continued for another hour. When this reaction mass was analyzed, p-DN
B was not detected and m-DNB 176.8 g (recovery rate 9
9.8%), 15.8 g of o-nitroanisole (yield 9
6.3%), and 4.0 g of p-nitroanisole (yield 90.9%) were quantified. Subsequently, the same treatment as in Example 1 was carried out to obtain 165.4 g of purified m-DNB (recovery rate 93.3%, purity 99.7%).

Example 3 A reaction was carried out in the same manner as in Example 1 except that 2.0 g of dodecyldimethylamine oxide was used instead of trioctyl ammonium chloride. When analyzed with a reaction time of 3 hours, o- and p-DNB were not detected, and m-DNB1
76.7 g (recovery rate 99.7%), o-nitroanisole 16.0 g (yield 97.6%) and p-nitroanisole 4.1 g (yield 93.2%) were quantified. Subsequently, the same treatment as in Example 1 was performed to obtain the purified m-DNB165.
2 g was obtained (recovery rate 93.2%, purity 99.7%).

Example 4 The reaction was carried out under reflux (80 to 82 ° C.) for 5 hours in the same manner as in Example 1 except that 28.7 g of ethanol was used instead of methanol. When the reaction mass was analyzed, o- and p-DNB were not detected, and 176.9 g of m-DNB (recovery rate 99.8%), 15.9 g of o-nitrophenetol.
(Yield 97.0%) 4.1 g of p-nitrophenetol
(Yield 93.2%) was quantified. Continuing, Example 1
161.2 g of purified m-DNB was obtained (recovery rate 91.0%, purity 99.9%).

Example 5 A reaction was carried out in the same manner as in Example 1 except that 1.0 g of tetrabutylammonium hydroxide and 1.0 g of dimethylhexadecylamine oxide were used in place of trioctylammonium chloride. When analyzed with a reaction time of 3 hours, o- and p-DNB were not detected, and m-D
NB176.6 g (recovery rate 99.7%), o-nitroanisole 15.9 g (yield 97.0%), and p-nitroanisole 4.1 g (yield 93.2%) were quantified. Subsequently, the same treatment as in Example 1 was performed to obtain the purified m-DNB16.
5.4 g was obtained (recovery rate 93.3%, purity 99.8).
%).

Example 6 The reaction mass having the composition described in Example 1 was heated as it was to distill off the remaining methanol, and then steam distillation was carried out at about 100 ° C. to distill o- and p-nitroanisole. The m-DNB remaining in the distillation flask and water were separated and dried, and then purified m-D
170.3 g of NB (recovery rate 96.1%) was obtained. This product had a light yellowish brown color and had a purity of 99.7%.

Comparative Example 1 The same reaction as in Example 1 was carried out without adding trioctylmethylammonium chloride. Analysis at 5 hours after the start of the reaction revealed that o- and p-DNB remained, so the reaction was continued for a further 6 hours.
Remained, and the reaction mass turned black with time.
The reaction was stopped after a total of 12 hours from the start of the reaction, and the reaction mass was analyzed. As a result, o-DNB 1.1 g, p-DNB 0.8 g, m
-DNB 170.1 g (recovery rate 96.0%), o-nitroanisole 10.4 g (yield 63.4%), and p-nitroanisole 2.9 g (yield 65.9%) were quantified. Subsequently, the same process as in Example 1 is performed to m-DNB.
160.0 g (recovery rate 90.3%) was obtained, which was m-DNB 98.8%, o-DNB 0.3%, p-D.
It had a composition of 0.1% NB and had a brown color.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that 150.0 g of methanol was used without adding trioctylammonium chloride. The total weight of the raw materials charged was 382.
The amount is 0 g, which is 1.5 times that of Example 1. When reacted for 3 hours in the same manner as in Example 1 and analyzed, o- and p-DNB were not detected, and m-DNB 176.7 g.
(Recovery rate 99.7%), o-nitroanisole 15.9
g (yield 96.6%), 4.0 g of p-nitroanisole
(91.5%) was quantified. The reaction mass was gradually cooled to about 10 ° C. to crystallize m-DNB. By subsequently filtering and washing the filter cake with a small amount of methanol,
165.1 g (recovery rate 93.1%) of purified m-DNB was obtained. This product had a light yellow color and had a purity of 99.7%.

[0025]

According to the present invention, o- and p-DNB contained in the crude m-DNB, which has not been achieved by the prior art, is obtained.
Can be sufficiently separated, and highly purified pure m-DNB can be obtained in a high yield. Furthermore, by adding a phase transfer catalyst during the alkoxylation reaction, the amount of alcohol used can be greatly reduced, leading to improved productivity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Teruyuki Nagata 30 Asmuta-cho, Omuta-shi, Fukuoka Mitsui Toatsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A corresponding alkoxynitrobenzene, which comprises reacting crude m-dinitrobenzene with a lower alcohol in the presence of a basic compound and a phase transfer catalyst to substantially selectively react only the o- and p-isomers. A method for purifying m-dinitrobenzene, which comprises separating o- and p-alkoxynitrobenzene from the reaction mixture obtained by converting