JPS6046385A - Oxidation of organic compound - Google Patents

Abstract

PURPOSE:To enhance oxidation reactivity, in preparing phenols by oxidizing benzene in the presence of a compound of Cu or Ti, by bringing a part of a Cu or Ti-ion to a low valency state by electrolytic reduction in a reaction system. CONSTITUTION:A solvent mixture, of which the volumetric ratio of 0.1N sulfuric acid and acetonitrile is 9:1, is introduced into an electrolytic cell, wherein a graphite rod is used as a cathode and a platinum plate as an anode, as an electrolytic medium and a solution mixture of cupric sulfate and benzene is further added to the cathode side. Air is blown into the cell while this cathode solution is stirred and benzene is oxidized with O2 in air to prepare phenols. In this case, at least a part of a cupric ion is reduced to a cuprous ion at the cathode by electrolytic reaction. Phenols can be prepared from benzene through one-stage reaction in the presence of this copper ion. Furthermore, Ti may be used in place of Cu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of oxidizing an organic compound with an oxidation-containing gas in the presence of a metal compound selected from copper compounds or titanium compounds.

More specifically, the present invention relates to a method for oxidizing an organic compound, which comprises maintaining at least a portion of the copper ions or titanium ions in the metal compound in a low valence state by performing electrolytic reduction within the reaction system.

Aromatic hydrocarbons such as benzene are generally stable against both oxidation and reduction and are considered to be poorly reactive. The production of phenols by oxidizing benzene etc. is no exception, and the current situation is that it generally requires two or three or more steps.

For this reason, the need for phenol synthesis by one-step oxidation of benzene has been advocated, and research is progressing in various places, but the main trend seems to be high-temperature oxidation using solid catalysts.

On the other hand, attempts have been made to directly oxidize liquid phase benzene to produce phenol, and B. Fleszar et al.
Roczniki Ohem, +50+271 (19
76) reported that in a system in which metallic copper was immersed in an aqueous sulfuric acid solution containing benzene and corroded, a considerable amount of phenol was obtained, and at the same time, a small amount of dihydroxybenzene was obtained. This reaction is carried out at room temperature and atmospheric pressure, and the species that attacks benzene is predicted to be a hydroxyl radical represented by the following formula.

Cu + H202→Ou + .OH+ OH However, in this document, -valent copper ions and hydrogen z<-ogicide are not experimentally confirmed.

Moreover, it is not clear whether the metal surface of the corroded copper is essential for this reaction.

As a result of studying this reaction, the present inventors found that metallic copper is not required for this reaction, and furthermore, that the essential conditions for this reaction are a combination of -valent penal ions and a suitable oxygen source. Oxygen oxidation of benzene using 0-valent copper efficiently produces phenol even under mild conditions, but monovalent copper is also oxidized and deactivated by the reaction. The deactivation of -valent copper is not only due to its effective use in the oxidation of benzene, but also due to the fact that monovalent copper is oxidized to divalent copper by the supplied oxygenation. Therefore, even if a monovalent copper compound is added to the system from the beginning, the proportion effectively utilized for the reaction is at most 1.
Similarly, when an organic compound is oxidized with an oxidation-containing gas in the presence of a titanium compound, titanium becomes highly valent and deactivated.

In addition, methods for directly oxidizing organic compounds using metal compounds selected from copper compounds or titanium compounds include hydroxylation by direct oxidation of aromatic hydrocarbons such as benzene and toluene, and direct oxidation of alicyclic compounds such as cyclohexanone. Oxidation and other reactions are used, but as mentioned above, the metal in the metal compound is in a high valence state, and the efficiency of the reaction is not necessarily good.

For this reason, the present inventors investigated the possibility of reducing and reusing these deactivated copper compounds or titanium compounds. By electrolytically reducing these deactivated copper compounds or titanium compounds directly in the reaction system, copper ions or By discovering that at least a portion of titanium ions become low-valent, and by simultaneously performing oxidation of the organic compound and electrolytic reduction of the metal compound used in this process, it is possible to oxidize the organic compound continuously over a long period of time. I found out that it can be implemented.

A method of oxidizing an organic compound by maintaining at least a part of the copper ions or titanium ions in the metal compound in a low valence state by performing electrolytic reduction in the reaction system. Regarding the method.

As long as the copper compound or titanium compound used in the present invention can be converted into a low-valent copper or titanium compound such as a monovalent copper compound by electrolytic reduction within the reaction system as described above, It is not particularly limited. Specific examples of copper compounds include halogenated steel such as copper chloride and copper bromide, mineral acid salts such as copper sulfate, silver phosphate, and copper borate, and carboxylic acid salts such as copper formate and copper acetate. These can be used not only for -valent copper but also for divalent copper. Among these, copper sulfate or copper halide is preferably used.

Similarly, titanium compounds include titanium tetrachloride, titanium tetrabromide, and the like.

In the reaction of the present invention, a reaction medium is used together with the above metal compound. As the reaction medium, an aqueous solution of sulfuric acid, phosphoric acid, boric acid, tungstic acid, heteropolymer, formic acid, acetic acid, etc. is usually used, and among these, an aqueous solution of sulfuric acid is particularly preferably used.

In addition, in order to stably maintain the low valence state of the metal in the metal compound described above, it is necessary to add approximately 30 volumes of charcoal to the aqueous solution of the above acid as a reaction medium. It is desirable to use a reaction medium consisting of an aqueous solution of an acid containing in proportions of up to %.

Specific examples of the nitrile used include acetonitrile, propionitrile, butyronitrile, benzonitrile, etc., and specific examples of the amide include acetamide, N,N-dimethylacetamide, N, IJ
-dimethylformamide, etc., and specific examples of ketones include acetone, methyl ethyl ketone,
Examples include diethyl ketone and methyl isobutyl ketone. These organic media can be used alone or in combination of two or more. In the present invention, nitriles, especially acetonitrile, are particularly suitable.

The reaction of the present invention is carried out while at least a portion of the copper ions or titanium ions in the metal compound are kept in a low valence state by electrolytic reduction. During the reaction, 1. In a reaction system consisting of an organic compound, a metal compound, and a reaction medium, which are usually in a liquid phase,
This is done by introducing oxygen-containing gas. Further, it is desirable that each component of the reaction system is mixed by stirring, and preferably the reaction is carried out in a suspended state.

As the oxygen-containing gas, oxygen or air with increased oxygen concentration in the air can also be used, but from an industrial perspective it is desirable to use air as it is.

In the present invention, when producing phenols such as phenol and hydroquinone by directly oxidizing liquid benzene with an oxygen-containing gas in the presence of a copper compound, the ratio of benzene to the reaction medium is particularly limited. Although it is not something that
Usually about 0% benzene is added to 100 parts by volume of reaction medium.
．． It is often used in a proportion of 0.05 to about 20 parts by volume. The proportion of copper compound used depends on its type and the efficiency of electrolytic reduction, but it is usually about 10-4 per mole of benzene.
7 (approximately 10-1 mol.) When using air as the oxygen-containing gas to be fed, the total amount of the charged reaction solution 1
Usually about 0.1 to about 1.5 J? /m1n(
25° C., 1 atm), and increasing the amount of aeration more than this often results in a decrease in yield. The reaction temperature is usually about 20°C to about 70°C, and the pressure is about normal pressure to several atmospheres.

The treatment by electrolytic reduction in the present invention is directly carried out on a reaction system containing an organic compound, a reaction medium, a metal compound, or an oxidation product. Usually, electrolytic reduction is carried out by immersing an electrode pair in a reaction mixture in a reaction apparatus in which an oxidation reaction is carried out.

The cathode is usually made of carbon, platinum, lead, lead oxide, etc., and the anode is usually made of carbon such as graphite, as well as metals from group 1b, metals from group Ⅰ, and metals from group ① of the periodic table. Mention may be made of metals selected from the group consisting of group metals.

Of the metals used as anodes, the first in the periodic table is
Examples of group B metals include copper, silver, and gold; examples of group II metals include tin, lead, titanium, zirconium, and the like; Examples include iron, metal, nickel, ruthenium, rhodium, /fragilum, osmium, iridium, and platinum. Further, electrolytic reduction can be carried out in the absence of a diaphragm, or supporting electrolyte ions can be passed between both electrodes. It can also be carried out in the presence of a diaphragm that does not allow the passage of benzene or phenols.

It is preferable to carry out electrolytic reduction in the presence of a diaphragm because current efficiency is improved. As a diaphragm, there are ion exchange membranes such as Nafyon (manufactured by DuPont) and Selemion (manufactured by Asahi Glass), Gama gas filters (Y3 to A5),
Unglazed boards can also be used.

In addition, during electrolytic reduction, it is effective to feed hydrogen gas to the anode side in order to maintain the pH on the cathode side within an appropriate range and to lower the electrolytic voltage.0 The conditions for electrolytic reduction are as follows: Depending on the proportion of the metal compound, the shape of the reactor, the type and combination of electrodes, the raw material organic compound, the concentration of the oxidation product, the type of reaction medium, etc., conditions for good yield of the target compound and/or electrolytic efficiency can be determined. Just set it. For example, when graphite is used for the electrode pair, the pH is preferably about 1 to about 2, and the temperature is about 20.
to about 70°C, and the cathode electrode potential (vs. 5OK) depends on the pH of the reaction system, but is usually about -0.1 to about +0.
．． It is about 2v.

As a result, high valence metal ions in the metal compound are reduced to a lower valence state, and the metal in the metal compound in the reaction system can be maintained in a low valence state.

In the present invention, the oxidation of organic compounds and the electrolytic reduction of metal ions can be carried out alternately,
In particular, if the oxidation of organic compounds and the electrolytic reduction of metal ions are carried out simultaneously, it is possible to perform the oxidation reaction and at the same time activate the metal compounds deactivated by the reaction.
Oxidation of organic compounds can be carried out continuously over long periods of time.

For example, in the presence of a copper compound, liquid phase benzene is directly oxidized with an oxygen-containing gas to produce ferls, and at the same time, at least a portion of the divalent copper ions generated in the reaction system are electrolyzed. Phenols can be produced continuously over a long period of time by reduction to monovalent copper ions. In this case, the electrolytic reduction conditions can be determined with priority given to conditions that are suitable for producing the desired phenols.

The oxidation reaction of the organic compound of the present invention can be carried out either batchwise or continuously as described above.

Furthermore, the reaction of the present invention can be applied to the oxidation of various organic compounds, such as a method for directly oxidizing aromatic hydrocarbons such as benzene and toluene to hydroxylate them to produce phenols such as phenol and hydroquinone; A method for producing an unsaturated alicyclic compound such as cyclohexenone by directly oxidizing an alicyclic compound such as cyclohexanone,
Examples include a method of producing a ketone by oxidizing a secondary alcohol.

Organic compounds produced by the reaction of the present invention, such as phenols such as phenol and hydroquinone, are separated from the reaction system by conventionally known methods such as distillation, extraction, crystallization, etc.

According to the present invention, a deactivated metal compound can be activated as it is within the reaction system, so that no complicated operation is required to replace the catalyst. Furthermore, by carrying out electrolytic reduction and oxidation reaction simultaneously, the oxidation reaction can be carried out continuously for a long period of time.

Example 1 An H-type cell in which the cathode side and the anode side are separated by a molten glass material was used as a reactor, a graphite rod (diameter 13 mm, length 20 mm) was used as the cathode, and a platinum plate was used as the counter electrode. there was. 0 for the medium. A mixed solvent with a volume ratio of IN H2SO4 and acetonitrile of 9:1 was used, and cupric sulfate (0.8-b (11.2 mmol)) was further added to the cathode side to prepare a catholyte.

The reaction was carried out by stirring the catholyte with a magnetic stirrer and adding 7 mj of air through a glass capillary tube. This was carried out while feeding at a rate of /min.

During the reaction, the cathode potential was controlled at 0.0 to 0.1 volt (vs. 5GIE) by a potentiostat, and the reaction temperature was set at 25°C.
Ta. The reaction was carried out for 2 hours at a cathode current density of 10 mA/α.

The reaction mixture was subjected to high pressure liquid chromatography (column: DuPont ZORBAX ODS, 4.6 mm x 150 m
As a result of analysis with m), phenol 0.65 mmol,
Hydroquinone 0. ”+6 mmol and 0.04 mmol of catechol were produced.

Example 2 An H-type cell (cathode chamber internal diameter 20 mm) containing 10% by volume acetonitrile. I N , 25 ml of sulfuric acid and 2. cupric sulfate. Qmmol was charged. In addition, graphite (surface area 18α) was used for both electrodes, and the reaction temperature was 25°C in a nitrogen atmosphere.
Electrolytic reduction of Cu++ ions was carried out for 1.5 hours by employing a constant potential electrolysis method at a temperature of 0.degree. C., a pressure of 1 atm, and a cathode electrode potential of 10 o.iv (vs. sam).

Add 1.0 m of toluene to this electrolytically reduced solution.
mol was added, the reaction solution was stirred under air atmosphere, and the reaction was continued under suspension conditions for about 30 minutes.

After the reaction was completed, the liquefied product in the reaction mixture was analyzed by liquid chromatography, and the following compound was found to have been produced.

0-cresol 18μmol1 m-cresol 10 p-cresol 7.2 benzyl alcohol 10 benzaldehyde 1.3 benzoic acid 4.7 Example 6 In Example 2, instead of adding 1 mmol of toluene, cyclohexanone was added. The same conditions were used except that 1 mmol was added. As a result, 0.056 mmol of cyclohexenone was produced in the reaction solution.

Example 4 In Example 2, instead of adding 1 mmol of toluene, 5 mmol 'fl of isopropyl alcohol was added.
The same conditions as in Example 2 were used except that fi was added.

As a result, 0.7 mmol of acetone was produced in the reaction solution.

Applicant: Mitsui Petrochemical Industries, Ltd. Agent: Patent Attorney Kazu Yamaguchi

Claims (1)

[Claims] (1) In a method of oxidizing an organic compound with an oxygen-containing gas in the presence of a metal compound selected from copper compounds or titanium ions, the copper ions or titanium in the metal compound are oxidized by electrolytic reduction in the reaction system. A method for oxidizing an organic compound, characterized by keeping at least a portion of the ions in a low valence state.