JPH0529384B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing 2,6-dimethyl-p-benzoquinone, which is useful as a synthetic intermediate for functional polymers, pharmaceuticals, and the like. More specifically, the present invention uses a catalyst consisting of a combination of a copper compound and various nitrogen compounds in the liquid phase, namely salts of hydroxylamines and inorganic acids or mixtures thereof or mixtures of oximes and inorganic acids, Using an aliphatic alcohol or a mixture of aromatic carbon hydrogen and lower aliphatic alcohol as a solvent, 2,6-dimethylphenol (hereinafter abbreviated as DMP) is efficiently oxidized with oxygen to produce 2,6
The present invention relates to a method for producing -dimethyl-p-benzoquinone (hereinafter abbreviated as DMQ). [Prior art] DMQ is an important substance that is a raw material for functional polymers such as liquid crystal polymers and pharmaceuticals.
At present, a high efficiency synthesis method has not yet been established. Furthermore, many studies have been made on methods for producing benzoquinones by oxidizing alkyl-substituted phenols in one step.
Methods using oxidizing agents such as hypohalous acid (Japanese Patent Publication No. 60-81135) and hydrogen peroxide (Eur. Pat. Appl. 107176) have been proposed. However, even these methods have problems in terms of generation of harmful gases, use of expensive oxidizing agents, and generation of by-products. For these reasons, methods using oxygen as an oxidizing agent have been studied, and various catalyst systems for this oxidation reaction have been proposed. Although it has high activity, it has the disadvantage that the catalyst life is extremely short.
In addition, in the method using copper halide as a catalyst, the reaction rate,
Although high values for both selectivity and selectivity have been obtained, there are various fundamental drawbacks that need to be resolved. For example, in the method of oxidizing phenols using a copper salt in a nitrile or tertiary amide solvent (Japanese Patent Application Laid-open No. 49-36641),
The yield of benzoquinones is about 75%, and other by-products such as polyphenylene oxide are generated, and the benzoquinone must be separated from polymers that are difficult to process, so it cannot be said to be an efficient manufacturing method. Method for oxidizing phenols in an organic solvent in the presence of a catalyst consisting of copper and halogen ions (Japanese Patent Publication No. 53-17585)
No.) is an excellent method in terms of high yield, but
Since the activity of the catalyst is extremely low, it is necessary to carry out the reaction for a long time using approximately the same molar amount of catalyst as the phenols, and furthermore, this large amount of catalyst must be recycled, resulting in high utility consumption. It has fatal flaws such as: In order to improve these drawbacks, several patents (for example, JP-A No. 50-93931, JP-A No. 59-225137, or JP-A No. 63-280040 have been published regarding phenol oxidation methods using copper and halogen catalysts). (No.), but all of them only show methods to facilitate the cyclical use of catalysts; the reaction rate itself is small, and there is no evidence of improvement in the fundamental problem of catalyst activity itself. It is not allowed. [Problems to be solved by the invention] Therefore, the present inventors oxidized DMP with oxygen.
As a result of intensive research on oxidation catalysts and oxidation reaction solvents for producing DMQ, we have found that copper compounds and various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids, or mixtures thereof, oximes, or oximes and inorganic A high yield can be achieved by using a catalyst consisting of a mixture with an acid and a mixture of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms as a solvent. The inventors discovered that the desired DMQ could be produced at a relatively low rate, and based on this knowledge, the present invention was accomplished. [Means for solving the problem] That is, the present invention oxidizes DMP with oxygen.
In producing DMQ, a catalyst consisting of a copper compound and various nitrogen compounds, i.e., a salt of hydroxylamine and an inorganic acid or a mixture thereof, or a combination of oximes or a mixture of an oxime and an inorganic acid is used, and a solvent is used. carbon number 1~
The present invention provides a method for producing DMQ, characterized in that a mixture of a lower aliphatic alcohol having 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms is used. In the present invention, DMP is dissolved in a mixed solvent of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms, and molecular oxygen and a catalytic amount of a copper compound and This is easily achieved by simple stirring at room temperature to 200°C in the presence of various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids or mixtures thereof, or oximes or mixtures of oximes and inorganic acids. This is a simple and safe oxidation method. In the present invention, in order to oxidize DMP, molecular oxygen is used as an oxidizing agent, and a copper compound and various nitrogen compounds are used as catalysts, i.e., salts of hydroxylamines and inorganic acids, or mixtures thereof, or oximes or oximes and inorganic acids. A combination of mixtures of As the molecular oxygen source, either pure oxygen gas or air may be used, and it is effective in the range of normal pressure to 30 kg/cm ² . The copper compound used as a catalyst component may be an inorganic salt, an organic salt, etc., and is not particularly limited, but chlorides such as cuprous chloride and cupric chloride show particularly good reaction results. Hydroxylamines, which are nitrogen compounds used as other components of the catalyst, include hydroxylamine itself, N,N-dialkylhydroxylamines such as N,N-dimethylhydroxylamine, and N-dialkylhydroxylamines such as N-methylhydroxylamine. -alkylhydroxylamines,
Various hydroxylamine derivatives such as O-alkylhydroxylamines such as O-methylhydroxylamine can be used, but in particular hydroxylamine, hydroxyurea or low molecular weight N,N-dialkylhydroxylamines have shown good reaction results. show. Regarding oximes, acetone, dialkyl ketones such as methyl ethyl ketone and diethyl ketone, cyclic ketones such as cyclohexanone and cyclooctanone, acetophenone,
Any ketones such as aromatic ketones such as propiophenone, diketones such as diacetyl, acetylacetone, cyclic diketones such as dimedone, aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, phenyl acetaldehyde, etc. Oximes of any of the aromatic aldehydes can be used, but oximes with relatively low molecular weights such as acetaldoxime, benzaldoxime, acetone oxime, and 2-butanone oxime have particularly good reaction results. give. Also,
When using the salts with these inorganic acids, various inorganic acids such as sulfuric acid and halogen acid can be used and are not particularly limited, but hydrochloric acid or sulfuric acid gives relatively good results. Addition of this inorganic acid is not essential, and sufficient catalytic activity can be obtained with a system of copper compound and oximes, but catalytic activity is often improved by further adding an inorganic acid. Furthermore, it is not necessary to prepare and use a mixture of hydroxylamines, oximes, amines, and inorganic acids in advance, and they may be added separately, and in either case, there are no particular restrictions on the composition ratio of each. However, a range of 0.2 to 5 moles of inorganic acid per mole of hydroxylamines and oximes gives good reaction results. There is no particular restriction on the amount of hydroxylamines and oximes to be used with respect to the copper compound, but if it is too little or too much, the reaction rate will be low, so in any case, it should be in the range of 0.3 to 3 mol per 1 mol of the copper compound. preferable. There is no particular limit to the amount of the catalyst obtained in this way, but if it is too small, the reaction rate will be low, and if it is too large, problems will arise with separation after the reaction, so the amount of copper compound should be 0.01 per mole of DMP. The use of ˜0.1 molar amounts gives favorable reaction results. In the method of the present invention, as for the solvent used in the reaction, lower aliphatic alcohols having 1 to 8 carbon atoms include methanol, ethanol, 1-
Propanol, isopropanol, 1-butanol, 2-butanol, tert-butanol, 1-amyl alcohol, 2-amyl alcohol, 3-amyl alcohol, sec-amyl alcohol, tert
-amyl alcohol, 1-hexanol, 1-octanol, 2-octanol, etc., including but not limited to, tert-butanol,
Tertiary alcohols such as tert-amyl alcohol give favorable results. When using a mixed solvent of aromatic hydrocarbons and lower aliphatic alcohols having 1 to 8 carbon atoms, there are no particular restrictions on the aromatic hydrocarbons; Those that are stable against oxidation are preferred. At this time, a mixture of one or more of the above-mentioned lower aliphatic alcohols having 1 to 8 carbon atoms and one or more aromatic hydrocarbons is used as a solvent. These solvents have excellent effects on dissolving copper compounds as catalysts, hydroxylamines, oximes, and/or inorganic acids, DMP as raw materials, and oxygen, and can dissolve the desired DMQ simply by bringing them into contact. Generate extremely effectively. The composition ratio of aromatic hydrocarbons and lower aliphatic alcohols cannot be determined unconditionally as it varies depending on the combination, but the volume ratio of lower aliphatic alcohols to aromatic hydrocarbons is
It is preferably 0.2 to 1.5, particularly preferably 0.25 to 0.8. The above catalysts can be used by directly dissolving them in these mixed solvents, but they can also be used as an aqueous solution. In addition, as the aliphatic alcohol having 1 to 8 carbon atoms used in this case, there is no particular problem as long as it has low water solubility, and butanol, pentanol, hexanol, heptanol, octanol, etc. containing various isomers can be used. be. In either case, dissolved in the solvent
In order to efficiently bring DMP into contact with the catalyst dissolved in the aqueous phase and oxygen in the gas phase, it is necessary to provide an efficient stirring device and aeration device. The temperature of the reaction in the method of the invention is room temperature to 20°C
It can be carried out at temperatures around 80°C, but if the temperature is too low, the reaction rate will be slow, while if it is too high, there will be a lot of solvent loss or side reactions.
Preferably, the temperature is within the range of .degree. The reaction time is
Although it depends on the reaction temperature, oxygen pressure, and amount of catalyst used, 1 to 10 hours is usually sufficient. [Effects of the Invention] According to the method of the present invention, lower fats having 1 to 8 carbon atoms are produced using copper compounds such as cupric chloride and nitrogen compounds such as hydroxylamine and acetone oxime, which are inexpensive commercially available general reagents, as catalysts. When the reaction is carried out using a mixed liquid formed with a preferable composition of a group alcohol or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms as a solvent, and a catalyst as an aqueous solution, the above-mentioned mixed liquid or a lower aliphatic alcohol having 1 to 8 carbon atoms is used as the solvent.
In addition to being able to obtain DMQ in one step by oxidizing DMP with molecular oxygen using an aliphatic alcohol with relatively low water solubility in No. 8 as a solvent, and with an extremely high reaction rate and yield, This method is suitable as an industrial method for producing DMQ because it eliminates the need to circulate a large amount of catalyst, which was a drawback of the conventional method. Since the activity of the catalyst used in the present invention is extremely high, it is sufficient to use a small amount of catalyst, and it is not necessarily necessary to reuse the catalyst by circulation, but if this is necessary, the catalyst can be used as an aqueous solution. Can be used repeatedly. in this case,
During the reaction, under stirring, in a mixed solvent system, due to the lipophilicity of aromatic hydrocarbons and the hydrophilicity of lower aliphatic alcohols, aliphatic alcohols, which are poorly water-soluble, are mixed with the lipophilicity of long-chain alkyl groups in the solvent. Due to the hydrophilic nature of the hydroxyl group, it forms a good suspension state with the catalyst in the aqueous phase, allowing the three-phase reaction of aqueous phase - organic phase - gas phase to proceed smoothly. However, if stirring is stopped after the reaction is completed, the organic phase and the aqueous phase, and the catalyst in the aqueous phase can be separated and recovered for reuse. At the same time, the solvent can be removed from the organic phase by means such as distillation to produce the product DMQ.
can be easily isolated. [Example] Next, the present invention will be explained in more detail with reference to Examples. Note that the examples of the present invention are representative examples for easier understanding of the present invention, and the present invention is not limited to these examples. In addition, the DMP shown in the following examples and comparative examples
The conversion rate of and the yield of DMQ were determined by gas chromatography using o-dichlorobenzene as an internal standard. Examples 1 to 7 2 mmol of DMP in a glass container with an internal volume of 10 ml,
0.2 mmol of cupric chloride dihydrate as a catalyst, various additives in predetermined amounts, and 2 ml of n-hexanol as a solvent were charged, and the reaction temperature was 60°C and the oxygen pressure was 860°C.
The reaction was carried out while maintaining the temperature at mmHg, and the amount of oxygen absorbed was measured using a gas filter. After the amount of oxygen absorption had almost stopped, the reaction was continued for about 1 to 2 hours to complete the reaction, and the products in the reaction solution were analyzed. DMP
Table 1 shows the conversion rate of and the yield of DMQ produced. Comparative Examples 1 and 2 The reaction was carried out in the same manner as in Examples 1 to 7 without adding an additive or using lithium chloride as an additive. Table 1 shows the conversion rate of DMP and the yield of DMQ produced.

[Table] The abbreviations used for additives in Table 1 indicate the following compounds. HAH = Hydroxylamine hydrochloride (NH ₂ OH.
HCl), HAS=hydroxylamine sulfate ( _NH2
OH) ₂ . H ₂ SO ₄ ), AO = acetone oxime (CH ₃ ) ₂ C = NOH) and 36% hydrochloric acid aqueous solution was used as HCl. Examples 8 to 10 In Examples 1 to 7, cupric chloride dihydrate was
The reaction was carried out in the same manner as in Examples 1 to 7 using 0.1 mmol and 2 ml of tertiary butanol as a solvent at a reaction temperature of 40°C. Table 2 shows the conversion rate of DMP and the yield of DMQ produced. Comparative Examples 3 to 4 Reactions were carried out in the same manner as in Examples 8 to 10 without adding any additives or using lithium chloride or diethylamine hydrochloride as additives. DMP
Table 2 shows the conversion rate of and the yield of DMQ produced.

[Table] In Table 2, the abbreviations used for converting agents indicate the following compounds. HAH = Hydroxylamine hydrochloride (NH ₂ OH.
HCl), HAS=hydroxylamine sulfate ( _NH2
OH) ₂ . H ₂ SO ₄ ), AO=acetone oxime ((CH ₃ ) ₂ C=NOH), and 36% hydrochloric acid aqueous solution was used as HCl. Examples 11-13 In Example 9, using various aliphatic alcohols instead of tertiary butanol as the solvent,
The reaction was carried out in the same manner as in Example 9. Table 3 shows the conversion rate of DMP and the yield of DMQ produced.

[Table] In Table 3, the abbreviations used for solvents indicate the following compounds. i-PrOH=isopropanol, i-BuOH=
Isobutyl alcohol and 2-PeOH=2-pentanol. Examples 14 to 19 In Example 10, the reaction was carried out in the same manner as in Example 10, using various aliphatic alcohols or a mixed solvent of an aliphatic alcohol and an aromatic hydrocarbon instead of tertiary butanol as the solvent. Ivy. DMP
Table 4 shows the conversion rate of and the yield of DMQ produced.

【table】

[Table] Example 20 In Example 9, a reaction was carried out for 2 hours in the same manner as in Example 9, using isopropanol and 0.2 mmol of cupric chloride dihydrate as the solvent instead of tertiary butanol. However, the DMP conversion rate was 96.2%.
A value of 64.2% DMQ yield was obtained. Examples 21 to 23 In Example 20, 0.1 mmol of hydroxylamine sulfate was used instead of 0.2 mmol of hydroxylamine hydrochloride as an additive, and various aliphatic alcohols or a mixed solvent of an aliphatic alcohol and an aromatic hydrocarbon were used as a solvent. The reaction was carried out in the same manner as in Example 20. Conversion rate of DMP and produced
The yield of DMQ is shown in Table 5.

【table】

Claims (1)

[Claims] 1. In producing 2,6-dimethyl-p-benzoquinone by oxygen-oxidizing 2,6-dimethylphenol, salts of copper compounds and various nitrogen compounds, namely hydroxylamines, and inorganic acids are used. 2,6-dimethyl-p, characterized in that it uses a catalyst consisting of a mixture thereof, or a combination of oximes or a mixture of an oxime and an inorganic acid.
- A method for producing benzoquinone. 2 2,6-dimethylphenol is converted to oxygen using a catalyst consisting of a copper compound and various nitrogen compounds, i.e., salts of hydroxylamines and inorganic acids, or mixtures thereof, or combinations of oximes or mixtures of oximes and inorganic acids. Oxidize 2,
A method for producing 6-dimethyl-p-benzoquinone, characterized in that a mixture of a lower aliphatic alcohol having 1 to 8 carbon atoms or an aromatic hydrocarbon and a lower aliphatic alcohol having 1 to 8 carbon atoms is used as a solvent. A method for producing 2,6-dimethyl-p-benzoquinone.