JPH0776192B2 - Method for producing quinones - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for oxidizing phenols with molecular oxygen to produce quinones corresponding thereto. Parabenzoquinone Particularly, parabenzoquinone having no substituent can produce a corresponding hydroquinone by hydrogenation, and the hydroquinone is an industrially useful compound as used in the photographic industry and the like.

[Conventional technology]

It is known to produce quinones, i.e. unsubstituted benzoquinones or substituted benzoquinones, by reacting phenols, i.e. unsubstituted phenols or substituted phenols with oxygen in the presence of copper salts and in a solvent. However, according to the conventionally known method, it is difficult to say that the yield of quinones is sufficient. For example, in JP-A-48-434, substituted phenols substituted with a methyl group are used as phenols, and the corresponding quinones are oxidized by oxygen gas in a solvent in the presence of copper and halogen ions. , But the yield is low.

[Problems to be solved by the invention]

The present invention intends to improve the low yield of parabenzoquinone by using a specific solvent and a specific catalyst as compared with this prior art.

[Means for solving problems]

The present inventors have solved the above problems by using methyl alcohol as a solvent and carrying out the reaction in the presence of specific concentrations of cupric chloride and chlorides of alkali metals. That is, the present invention is a method for producing a quinone, that is, an unsubstituted benzoquinone or a substituted benzoquinone, by reacting a phenol, that is, an unsubstituted phenol or a substituted phenol with oxygen in a solvent in the presence of a copper salt,
In methyl alcohol as solvent, methyl alcohol
In the presence of 0.002 to 0.167 mol of cupric chloride per 1000 g, and in the presence of 0.5 to 10 mol of oxide of alkali metal per mol of cupric chloride, in the absence of hydroxide of alkali metal The method for producing quinones is characterized by carrying out the above reaction.

The phenols used in the present invention, that is, an unsubstituted phenol or a substituted phenol, has the general formula (I) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and are hydrogen, halogen, cyano, alkyl or alkoxy containing 1 to 12 carbon atoms, 6 to 16
Represented by an unsubstituted or substituted phenyl or an unsubstituted or substituted phenoxy group containing carbon atoms), particularly hydrogen, chlorine, bromine, iodine as R ₁ , R ₂ , R ₃ and R ₄ , Cyano, methyl, ethyl, propyl,
Examples include butyl, pentyl, methoxy, ethoxy, phenyl and phenoxy. Preferred phenols used in the present invention include phenol, that is, unsubstituted phenol, o
-Chlorophenol, 2,6-dichlorophenol, o-
Cresol, m-cresol, 2-tertiary butylphenol, 2,6-dimethylphenol, 2,3-dimethylphenol, 2,6-ditertiarybutylphenol, 2,3,5-trimethylphenol, 2,3,6 -Trimethylphenol, o-phenylphenol, o-benzylphenol and the like.

The concentration of phenols is about 0.5 to 70% by weight based on the reaction solution. If it is less than 0.5% by weight, the volumetric efficiency of the reactor is poor, and if it exceeds 70% by weight, crystals of quinones are precipitated during the reaction, resulting in poor operability. As the oxygen source, in addition to pure oxygen, oxygen diluted with air or nitrogen can be used. In the present invention, methyl alcohol is used as the solvent. In ethyl alcohol and propyl alcohol, the selectivity for quinones is lower than when methyl alcohol is used as a solvent.

In the present invention, cupric chloride is used as the copper salt. The amount used is 0.002-0.167 for 1000g of methyl alcohol.
Use moles. If it is less than 0.002 mol, the oxidation rate of phenols is slow. On the other hand, at a high concentration exceeding 0.167 mol, side reactions increase and the yield of the desired quinones is low. Preferably 0.050 to 0.140 mol is used. Within this range,
It has a high oxidation rate of phenols and a high selectivity to quinones.

The present invention is carried out in the presence of an alkali metal chloride together with cupric chloride. Examples of chlorides of alkali metals include lithium chloride, sodium chloride, potassium chloride, rubidium chloride, and cesium chloride.The combined use of these with cupric chloride increases the oxidation rate of phenols, and the corresponding quinones Higher yield.

The amount of the alkali metal chloride used is 0.5 to 10 mol per mol of cupric chloride. If it is less than 0.5 mol, the effect is small, and if it exceeds 10 mol, the oxidation rate of phenols is rather lowered and the selectivity to the corresponding quinones is also lowered. More preferably, 2.5 mol to 5 mol is used. In this range, the oxidation rate of phenols is high and the selectivity to the corresponding quinones is high. Lithium chloride is preferred as the alkali metal chloride. Lithium chloride is preferable because it has a higher solubility in methyl alcohol than chlorides of other alkali metals, and thus has a high concentration in the solution.

In the method of the present invention, the reaction pressure may be normal pressure, and may be increased pressure or reduced pressure if desired. However, oxygen pressure is 0.1 to 5
It is 00 kg / cm ² . Generally, the higher the oxygen pressure, the higher the rate of oxidation of the unsubstituted phenol and the higher the selectivity to the corresponding unsubstituted benzoquinone. Alkyl- or alkoxy-substituted substituted phenols have a higher oxidation rate than the unsubstituted phenols at the same oxygen pressure and a higher selectivity to the corresponding substituted benzoquinones. That is, lower oxygen pressures can be used.

In the case of unsubstituted phenol, the oxygen pressure is 30 kg / cm ²
The above is preferable, and considering the equipment cost for producing unsubstituted benzoquinone, the oxygen pressure is preferably 200 kg / cm ² or less.

The reaction temperature will differ depending on the phenols used, but is usually 0 to 120 ° C, preferably 20 to 100 ° C. Substituted phenols substituted with alkyl or alkoxy have a higher reaction rate than unsubstituted phenols, and thus can be reacted at a lower temperature. Further, the substituted phenol substituted with alkyl or alkoxy has higher selectivity to the corresponding substituted benzoquinone than the unsubstituted phenol.

The reaction time is usually about 0.5 to 10 hours. This method can be performed in a batch system or a flow system.

The product and the catalyst can be separated by, for example, separating methyl alcohol from the liquid after the reaction by distillation, and then extracting with water and an organic solvent that is immiscible with water to separate the aqueous layer containing the catalyst and the product. It can be carried out by separating the organic solvent layer containing the benzoquinone from the organic solvent layer.

Examples Example 1 Phenol 18.82 g (0.200 mol), cupric chloride 1.34 g (0.010 mol), lithium chloride 1.
70 g (0.040 mol) and 90 g of methanol were charged. Then, pressurize with nitrogen to 40 kg / cm ² G, and then add oxygen gas.
It was pressed up to 100 kg / cm ² G (at room temperature, the oxygen pressure at this point was 60 kg / cm ² ). This autoclave was heated to 70 ° C, and pure oxygen was constantly introduced into the reactor from the time when oxygen was consumed by the reaction and the total pressure became 100 kg / cm ² G,
The total pressure was kept at 100 kg / cm ² G. The reaction time was 3 hours after the temperature was raised to 70 ° C. Then, the mixture was cooled to room temperature, depressurized, the contents were taken out and analyzed by liquid chromatography. The results are shown in Table 1.

Examples 2 to 6 and Comparative Example 1 Reaction was performed under exactly the same conditions as in Example 1 except that the amounts of cupric chloride and lithium chloride added were changed. The results are shown in Table 1.

Example 7 Into a 70 ml stainless steel autoclave with a stirrer filled with a glass beaker, 0.941 g (0.01 mol) of phenol, 0.134 g (0.001 mol) of cupric chloride, and lithium chloride
1.70 g (0.004 mol) and 20 g of methyl alcohol were charged. After that, it was pressurized to 50 kg / cm ² G with nitrogen, and then oxygen gas was injected to 100 kg / cm ² G (oxygen pressure was 50 kg / cm ²
cm ² . The autoclave was heated to 70 ° C and then held for 3 hours. Then, the mixture was cooled to room temperature, depressurized, the contents were taken out and analyzed by gas chromatography. The results are shown in Table 2.

Examples 8 to 15 Only the amount of lithium chloride added was changed, and the others were changed to Example 7.
Were reacted under exactly the same conditions as. The results are shown in Table 2.

Comparative Example 2 Lithium chloride was not added, and the reaction was carried out under the same conditions as in Example 7 except for the above. The results are shown in Table 2.

Examples 16 to 19 Instead of lithium chloride, 0.001 mol of sodium chloride, potassium chloride, rubidium chloride or cesium chloride was added, and the reaction was carried out under exactly the same conditions as in Example 7. The results are shown in Table 3.

Comparative Examples 3 to 5 Magnesium chloride, calcium chloride or barium chloride was added in an amount of 0.0005 mol instead of lithium chloride, and the reaction was carried out under exactly the same conditions as in Example 7. The results are shown in Table 3.
It was shown to.

Example 20 The reaction was carried out under exactly the same conditions as in Example 7 except that 2,3,6-trimethylphenol was used instead of phenol.

Conversion of 2,3,6-trimethylphenol 100% Selectivity to 2,3,5-trimethylbenzoquinone 99.5% Comparative Example 6 20% sulfolane was used as a solvent instead of methyl alcohol.
g was used and the reaction was carried out under exactly the same conditions as in Comparative Example 2 except for the above. The results are shown in Table 4.

Comparative Example 7 0.003 mol of lithium chloride was added, and the reaction was carried out under the same conditions as in Comparative Example 6 except for the above. The results are shown in Table 4.

Example 21 The reaction was carried out under the same conditions as in Example 1 except that the initial pressure of nitrogen charged in the autoclave was 62 kg / cm ² G (70
Total pressure 100 kg / cm ² G at ° C., oxygen pressure was 30kg / cm ^2), the following results were obtained.

Phenol conversion 87.5% Selectivity to benzoquinone 73.9% Selectivity to hydroquinone 4.1% Comparative Example 8 In Example 9, 0.001 mol of lithium hydroxide was further added,
Other than that, the reaction was carried out under exactly the same conditions as in Example 9,
The following results were obtained.

Phenol conversion 98.9% Selectivity of total benzoquinone + hydroquinone 64.8% [Effect of the invention] From the results in Table 1, cupric chloride was converted to methyl alcohol 1000 g.
In the reaction system in which 0.002 mol to 0.167 mol was added and lithium chloride was added, the selectivity to benzoquinone is high. On the other hand, the amount of cupric chloride added was 10
When it is 0.222 mol per 00 g, it is outside the range of the present invention, and the selectivity for benzoquinone is low despite the addition of lithium chloride.

From the results shown in Table 2, when lithium chloride was not added, the conversion of phenol was low and the selectivity to benzoquinone was low, but lithium chloride was added to 0.5 mol of cupric chloride.
When mol to 10 mol is added, the conversion of phenol is high and the selectivity to benzoquinone is high.

The results shown in Table 3 show that sodium chloride, potassium chloride, rubidium chloride and cesium chloride have the same effect of addition as lithium chloride, but magnesium chloride, calcium chloride and barium chloride do not have the effect of improving the selectivity to benzoquinone.

As shown in Example 20, substituted phenols substituted with alkyl groups have increased selectivity to the corresponding parabenzoquinones.

From the results of Table 4, when sulfolane is used as the solvent, the conversion of phenol is lowered and the selectivity to benzoquinone is lowered by adding lithium chloride. Thus, benzoquinone can be produced in high yield for the first time by combining a specific solvent and a specific catalyst.

Example 1 (oxygen pressure at 70 ° C. was 55 kg / cm ² ) and Example
From 21 (oxygen pressure at 70 ℃ is 30 kg / cm ² ), it is clear that lowering the oxygen pressure lowers the conversion of phenol and lowers the selectivity to benzoquinone. In the present invention, the oxygen pressure is preferably 30 kg / cm ² or more.

Claims (4)

[Claims] 1. A method for producing quinones by reacting phenols with oxygen in the presence of a copper salt in a solvent, wherein methyl alcohol 10 is used in methyl alcohol as a solvent.
In the presence of 0.002-0.167 mol of cupric chloride to 00 g,
And 0.5 mol of alkali metal chloride per mol of cupric chloride
A process for producing a quinone, which comprises carrying out the above reaction in the presence of -10 mol and in the absence of an alkali metal hydroxide. 2. The method according to claim 1, wherein the chloride of the alkali metal is 2.5 to 5 mol per mol of cupric chloride. 3. The method according to claim 1 or 2, wherein the phenols are unsubstituted phenols. 4. The method according to claim 3, wherein an oxygen pressure of 30 kg / cm ² or more is used when the phenols are reacted with oxygen to produce quinones.