JPH0657669B2 - Method for producing quinones - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing quinones corresponding to phenols by oxidizing them with molecular oxygen. More specifically, parabenzoquinone, particularly unsubstituted parabenzoquinone The present invention relates to a method for producing industrially useful compounds, which can produce corresponding hydroquinones used in the photographic industry by hydrogenation thereof.

[Conventional technology]

It is known to produce a benzoquinone or a substituted benzoquinone by reacting a phenol or a substituted phenol with oxygen in the presence of a copper salt in a solvent. However,
According to a conventionally known method, it is difficult to say that the yield of benzoquinone is sufficient. For example, according to JP-A-58-24537, acetonitrile is used as a solvent and a divalent copper salt selected from the group of halides and nitrates is used as a copper salt.
This is an improved method for obtaining enhanced selectivity by promoting this copper catalyst with an alkali metal base, but the yield of parabenzoquinone is about 55% at most according to this method. According to JP-A-60-51144, an alkylphenol is used as a phenol, methanol is used as a solvent, cupric halide is used as a copper salt, and the copper catalyst is used as an alkali metal or alkaline earth metal. Is an improved method for obtaining enhanced selectivity by promoting with the hydroxides and alkali metal or alkaline earth metal halides, but this method also produces the corresponding parabenzoquinone from unsubstituted phenols. In this case, it is hard to say that the yield is sufficient.

[Problems to be solved by the invention]

The present invention seeks to increase the low yield of parabenzoquinone according to the prior art by using a specific solvent and a specific catalyst.

[Means for solving problems]

The present inventors have solved the above-mentioned problems by using alcohol as a solvent and carrying out in the presence of cupric chloride and a chloride of an alkali metal. That is, the present invention provides a method for producing a benzoquinone or a substituted benzoquinone by reacting a phenol or a substituted phenol with oxygen in a solvent in the presence of a copper salt. 2. A process for producing quinones, which is carried out in the absence of copper and alkali metal hydroxides, in the presence of alkali metal chlorides, and in the absence of alkali metal hydroxides.

The phenol or substituted phenol used in the present invention has a general formula (Wherein R ₁ , R ₂ , R ₃ and R ₄ are the same or different and are hydrogen, halogen, cyano, alkyl or alkoxy containing 1 to 12 carbon atoms, 6 to 16 carbon atoms And an unsubstituted or substituted phenyl group or an unsubstituted or substituted phenoxy group), wherein R is hydrogen, chlorine, cyano, methyl, ethyl, propyl, butyl, pentyl, methoxy, ethoxy, phenyl. , Phenoxy, etc. Preferred phenols used in the present invention include phenol, o-chlorophenol, o-cresol, m-cresol and 2
-Tertiary butylphenol, 2,6-dimethylphenol, 2,3-dimethylphenol, 2,6-ditertiarybutylphenol, o-phenylphenol, o-benzylphenol, 2,6-dichlorophenol, 2-3-5
Examples include trimethylphenol and 2-3-6-trimethylphenol.

The concentration of phenols is about 0.05 to 20 mol / mol with respect to the reaction solution. If it is less than 0.05 mol / volume efficiency of the reactor is poor, and if it is 20 mol / mol or more, the selectivity decreases.

As the oxygen source, in addition to pure oxygen, air or oxygen diluted with nitrogen can be used. In the present invention, a monoalcohol of C ₁ -C ₄ as the alcohol. Specific examples include methanol, ethanol, n-propanol, isopropanol and butanol. Of these, methanol is particularly preferable.

In the present invention, cupric chloride is used as the copper salt. Do not use cupric bromide or cuprous chloride because the benzoquinone yield is low. The amount of cupric chloride used is 0.001 to 10 mol, preferably 0.01 to 1 mol, per 1 mol of phenols.
More preferably, 0.05 to 0.2 mol is used. If the amount used is less than 0.001 mol, the oxidation rate of phenols is slow, while if it is more than 10 mol, the selectivity to parabenzoquinones is low, which is not preferable.

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. When these are used in combination with cupric chloride, the oxidation rate of phenols increases,
And the yield of the corresponding benzoquinone is increased. Selectivity to benzoquinone does not increase with other chlorides, such as chlorides of alkaline earth metals.

The amount of this alkali metal chloride used is 0.1 to 20 mol per 1 mol of cupric chloride. If it is less than 0.1 mol, the effect is small, and the use of 20 mol or more does not increase the yield of benzoquinone.

Preferably, 0.5 to 10 mol, more preferably 2 to 6 mol is used. Lithium chloride is preferred as the alkali metal chloride.

Lithium chloride has a higher solubility in alcohol than chlorides of other alkali metals, so that the concentration in the solution can be made higher, and thus the oxidation rate of phenol becomes higher, which is preferable.

In the method of the present invention, the oxygen pressure is 1 to 500 kg / cm ² . Usually, the higher the oxygen pressure, the higher the oxidation rate of phenol and the higher the selectivity of benzoquinone. Considering the equipment cost for benzoquinone production, the oxygen pressure is 20 to 15
0 kg / cm ² is preferred.

The reaction temperature varies depending on the phenols used, but is usually 0 to 120 ° C, preferably 20 to 80 ° C.
Since the reaction rate of alkylphenol is higher than that of unsubstituted phenol, the reaction is carried out at a lower temperature. In addition, the alkylphenol has a higher selectivity to the corresponding benzoquinone than the unsubstituted phenol.

The reaction time is usually about 0.5 to 10 hours. This method can be performed by a batch method or a flow method. The product and the catalyst are separated, for example, by separating methanol from the liquid after the reaction by distillation, and then extracting with water and an organic solvent immiscible with water, respectively, an aqueous layer containing the catalyst and an organic solvent containing the product. This can be done by separating the layers and separating the benzoquinone from the organic solvent layer.

〔Example〕

Example 1 In a 70 ml stainless steel autoclave equipped with a stirrer, which contained a glass beaker, 0.941 g of phenol (0.01 mol), 0.134 g of cupric chloride (0.001 mol), and lithium chloride of 0.
170 g (0.004 mol) and 20 g of methanol were charged. Then, nitrogen was pressed up to 50 kg / cm ² G, and then oxygen gas was injected up to 100 kg / cm ² G.

(Oxygen partial pressure 50 kg / cm ² ) Heat this autoclave to 70
C. and held for 3 hours. Then, the sample was cooled to room temperature, depressurized and the contents were taken out and analyzed. The results are shown in Table 1.

Examples 2 to 8 The reaction was performed under exactly the same conditions as in Example 1 except that the amount of lithium chloride added was changed. The results are shown in Table 1.

Comparative Example 1 Lithium chloride was not added, and the reaction was carried out under exactly the same conditions as in Example 1 except for the above. The results are shown in Table 1.

Examples 9 to 12 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 1. The results are shown in Table 2.

Comparative Examples 2 to 4 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 1. The results are shown in Table 2.

Example 13 The reaction was carried out under the same conditions as in Example 3 except that ethanol was used instead of methanol. The results are shown in Table 3.

Comparative Example 5 The reaction was carried out under the same conditions as in Example 13 except that lithium chloride was not added. The results are shown in Table 3.

Comparative Example 6 The reaction was carried out under exactly the same conditions as in Example 3 except that cuprous chloride was used instead of cupric chloride. The results are shown in Table 4.

Comparative Example 7 The reaction was carried out under exactly the same conditions as in Comparative Example 6 except that lithium chloride was not added. The results are shown in Table 4.

Example 14 The reaction was carried out under exactly the same conditions as in Example 1 except that 2,6-dimethylphenol was used instead of phenol.

2,6-Dimethylphenol conversion 100% 2,6-Dimethyl-parabenzoquinone yield 97.8% Comparative row 8 In addition to Example 3, 0.001 mol of lithium hydroxide was added, and other than that was exactly the same as Example 3. The reaction was carried out under the conditions. The results are shown in Table 5.

[Effects of the Invention] From the results in Table 1, when lithium chloride was not added, the conversion of phenol was low and the selectivity to benzoquinone was low, but lithium chloride was 0% with respect to 1 mol of cupric chloride. ．
When 5 to 10 mol is added, the conversion of phenol is high and the yield of benzoquinone is high.

This result is shown on page 5, left column, lines 15 to 17 of JP-A-58-24537, showing that "alkali metal halide is relatively ineffective in improving selectivity in the absence or presence of water. This is a surprising result, and this difference is based on the difference in the solvent between the two methods. That is, in JP-A-58-24537, acetonitrile is used as a solvent, but the present invention uses alcohols such as methanol.

Thus, the benzoquinone can be produced in high yield only by the combination of the specific solvent and the specific catalyst.

The results shown in Table 2 show that sodium chloride, potassium chloride, rubidium chloride and cesium chloride have the same addition effect as lithium chloride, but magnesium chloride, calcium chloride and barium chloride do not have the effect of improving the selectivity of benzoquinone.

From the results of Table 3, even when ethanol is used as a solvent, by adding lithium chloride to cupric chloride,
It can be seen that the oxidation rate of phenol can be significantly increased and the selectivity to parabenzoquinone can be improved.

Comparing the results of Example 3 in Table 4 and Table 1, when cuprous chloride is replaced with cuprous chloride, the rate of oxidation of phenol is slow and the yield of benzoquinone is low. Only when cupric chloride is used as the copper compound,
Parabenzoquinone is obtained in high yield.

As shown in Example 14, the substitution of a phenol with an alkyl group increases the yield to the corresponding parabenzoquinone.

From the results in Table 5, the method described in JP-A-60-51144, that is, cupric halide and hydroxide of alkali metal were used as catalysts, and halides of alkali metal were used as promoters. The method used (the method of Comparative Example 8) greatly reduces both the selectivity and the yield of parabenzoquinone, as compared with the method of the present invention which does not use an alkali metal hydroxide.

This is described in JP-A-60-51144, page 2, lower left column, 10
Lines 14 to 14 read, "If the amount of these hydroxides is too large, the reaction to quinone does not proceed, and if it is too small, it does not proceed. The above catalyst concentration does not affect the selectivity of quinone formation. It is completely unpredictable when viewed from the description.

In the method of the present invention, it was surprisingly found that the reaction proceeds even in the absence of alkali metal hydroxide, and that the selectivity of quinone formation is higher in the absence of alkali metal hydroxide. It has been completed.

Claims (4)

[Claims] 1. A method for producing a benzoquinone or a substituted benzoquinone by reacting a phenol or a substituted phenol with oxygen in a solvent in the presence of a copper salt, wherein the reaction is carried out in an alcohol as a solvent and as a copper salt. A process for producing quinones, which is carried out in the presence of cupric acid and chloride of an alkali metal and in the absence of a hydroxide of an alkali metal. 2. The method according to claim 1, wherein methanol is used as the alcohol. 3. The method according to claim 1, wherein lithium chloride is used as the alkali metal chloride. 4. The method according to any one of claims 1 to 3, wherein the molar ratio of the chloride of the alkali metal to cupric chloride is 0.5 to 10.