JPS59211585A - Electrolytic oxidation of xylene - Google Patents

Abstract

PURPOSE:To obtain tolualdehyde or methyl benzyl nitrate at a high conversion by oxidizing electrolytically xylene in an acetonitrile solvent in the presence or absence of oxygen by using a platinum anode and an electrolyte of metallic nitrate. CONSTITUTION:Xylene is electrolytically oxidized in an acetonitrile solvent by using platinum for an anode and metallic nitrate as an electrolyte to be dissolved in an electrolytic soln. while supplying oxygen to the acetonitrile solvent, by which tolualdehyde is obtd. Methyl benzyl nitrate is obtd. by oxidizing electrolytically xylene in the acetonitrile solvent in nitrogen atmosphere or non- supply of oxygen in the above-mentioned method. The temp. of the electrolytic bath in the synthesis of said tolualdehyde is preferably as low as about <=45 deg.C and the concn. of the metallic nitrate in the electrolyte is preferably about >=0.1mol/l. The temp. of the electrolytic bath in the production of the methyl benzyl nitrate is preferably an ordinary temp. or relatively high temp. and the moisture in the reaction vessel is preferably about <=5vol%.

Description

[Detailed description of the invention] The present invention relates to a novel method for electrolytic oxidation of xylene.

More specifically, the present invention relates to a method for selectively producing tolualdehyde and/' or (J methyl benzyl nitrate ester) by electrolytically oxidizing xylene in an acetonitrile solvent and appropriately adopting limited conditions.

Methylbenzyl nitrate ester can be easily and quantitatively obtained by hydrolyzing it at 1.0%.

1-rualdehyde and methylbensyl)'runyl has wide application as an intermediate for various organic chemicals. For example, tolualdehyde has been used in the field of functional polymers, such as polymer stabilizers and monomers for polymerization, and has been used in the field of feces and chemicals, such as agricultural and medical intermediates with sterilization and antibacterial properties. It is used in a wide range of applications, and like methylpenzyl alcohol, it has a wide range of uses, such as solvents, dyes, medicines and agricultural chemicals, plasticizers, etc.

Various methods have been proposed as methods for synthesizing these compounds.

For example, common methods for producing these compounds include chlorinating the methyl substituent to produce the corresponding henzyl chloride and henzylidene chloride compounds, and hydrolyzing them, or synthesizing them by partial oxidation of the methyl substituent. It's a method.

It is as complicated as the title Method CJ I, and there are many problems such as recovery of by-product hydrochloric acid gas, so it is difficult to say that it is a practically preferred industrial production method. In addition, the latter method is a catalytic oxidation method at a relatively high temperature in the gas phase oxidation method, and in the liquid phase oxidation method, it is a catalytic oxidation method in several solvents, mainly acetic anhydride. The common disadvantages of these two methods are that the catalysts used are expensive in most cases, and even when these expensive catalysts are used, the selectivity is low or the conversion rate is poor. In most cases, the main product in these reactions is oxidized to the carboxyl group, and phenylaldehydes, benzyl alcohols, etc. are not only produced as by-products as impurities in this reaction, but they are also used industrially. The manufacturing method was difficult to describe.

Therefore, rather than improving the synthesis method, the method for obtaining these aromatic aldehydes and aromatic alcohols is to separate and purify the mixed product of partial oxidation reaction containing them by making full use of various methods. I was focusing on how to get it.

For example, when tolualde and/or methylbenzyl alcohol is prepared from xylene, it is oxidized in the presence of HA in an acetic acid solvent using a compound such as cobalt, chromium, molybdenum, tungsten, vanadium, manganese + lIf + mercury as a catalyst. A method was adopted to separate various impurities and isomers from the reaction product by utilizing differences in physical properties.

However, as mentioned above, these methods had very poor conversion rates and selectivity, and could hardly be called practical and industrial production methods.

Under these circumstances, the present inventors conducted extensive research in order to solve these problems and establish a new industrial production method for these significant compounds, and finally completed the present invention.

That is, the present invention [1] Using platinum as an anode in an acetonitrile solvent and using a nitrate metal salt as an electrolyte dissolved in an electrolytic solution,
This is an electrolytic oxidation method for xylene in which xylene is electrolytically oxidized in the presence or absence of oxygen. jJIJ aldehyde
'A method of 1) above.

3) The method of 1 above, in which xylene is oxidized to produce methyl benzyl nitrate in a water atmosphere or in the absence of oxygen supply in an acetate solvent.

-There is C.

Furthermore, in accordance with Rev. 9111, synthesis of tolualdehyde in J3 does not necessarily need to be carried out under oxygen pressure, but may be carried out simply by aeration or by aeration into the liquid. In addition, the oxygen used is not only pure oxygen gas, but also air or gases such as monomorphic nitrogen acid or carbon dioxide, which are incompatible with one reaction.
It doesn't matter if it's there.

The temperature of the electric iW bath is normal: 1, room temperature -C, especially the regulation is 4F, but when there is oxygen 2 million slili, a relatively low temperature is preferable /l! 1℃ or less, d: L < 1, 1.1
A good method is to maintain the temperature below 0°G while changing the current to MYnu.

Regarding the anode potential, when it becomes 1.4 port t-vsscE or more with respect to the standard U water electrode (hereinafter referred to as SCE), the effect of the present invention decreases and current efficiency or low tossie (unreacted material increases, and When the .8 pol hvsscl is 30 or more, the selectivity of tolualdehyde decreases.

The molar concentration of metal nitrate, which is an electrolyte to be dissolved in the electrolytic solution, in the electrolytic cell should be 0.1 mol/ILX 10C, and 0.1 mol/ILX1C.
When the amount is less than 1 mol/'1, the selectivity of tolualdehy 1~ becomes low. In addition to silver nitrate, preferred electrolytes to be dissolved in the electrolytic solution include metal nitrates such as niracle nitrate and iron nitrate.

Further, although the water content in the electrolytic cell is extremely large and does not affect the production rate of 1-heraldehyde, it is better to have less water in comparison.

On the other hand, in the case of producing methyl nitrate pencil ester, which can quantitatively yield J, trimethylhenzylalnylene, by hydrolysis, it is preferable to carry out the process in the absence of oxygen; It is not necessary to take any special method in advance such as completely removing oxygen from the gas, but it is possible to use a forced one-gas method using an oxygen-containing gas.

In addition, the temperature of the electrolytic cell does not need to be particularly limited7, but when conducting in air, active measures such as cooling are not required to prevent an increase in dissolved oxygen. Target temperature is good.

Also, it is better that there is no moisture in the reaction tank, and 9r
Preferably, it is 5% by volume or less.

EXAMPLES In order to explain the present invention in more detail, Examples will be given below, but the scope of the present invention is not limited only to these Examples.

Example A beaker-type electrolytic cell with a total capacity of 50 m1 equipped with a glass frit diaphragm on a medium flame was used, a platinum electrode was used as the anode, a carbon electrode was used as the cathode, and 15% of the solvent aretonyl-1-lyl was used as the electrode.
1. and an electrolyte to be dissolved in the electrolytic solution to a predetermined concentration, and 0-xylene was added as a substrate to the anode at a concentration of 0.00.
5 mol/15 ml of 1-acetonitrile was added, and a predetermined constant potential electrolytic oxidation reaction was carried out while keeping the electrolytic cell at a constant temperature in a constant temperature bath.

In Examples 1 to 21, J3 was carried out without oxygen or air aeration from 15 minutes before the start of the reaction until the end of the reaction.

The reaction product was separated into υ1 parts by the gas chromatography method, and the results are shown as the production ratio.

Examples 1 to 4 Silver nitrate, which is an electrolyte, is dissolved in an electrolytic solution at a concentration of 0.6 mol/
'1-acetonyl-1-lyl was added and analyzed after applying a current of 965 corons using a constant potential method using a predetermined anode potential. Reaction temperature: Note 1) In Example 3, air aeration was performed.

Note 2) A is tolualdehyde and B is methylbenzyl nitrate, which will be abbreviated as A and F3 below.

Examples 5-9 The effect of the amount of electrolyte dissolved in the electrolyte was examined while maintaining the anode potential at 2.3 volts vs S CE. Other example 1
0 to 12 Keep the electrolytic cell at a predetermined temperature and set the anode potential to 2 or 3 volts.
s3 CL, and the other conditions were the same as in Example 1. The results are shown in the table on the next page.

Examples 13 to 17 Reactions were carried out at an anode potential of 2.3 volts vs S CE , an electrolytic cell temperature of 30° C., and various amounts of water in the solvent acetonitrile. Other next month will be Example 1
8-19 It is an electrolyte to be dissolved in the electrolytic solution (adjust the temperature of the nitrate ion of the irl acid metal salt to 0.6 mol/'1, keep the anode potential at 2.3 pol hvsSCE, Examples 20~
21 Example 1 and Examples 22 to 23 where the substrate was changed while keeping the anode potential at 2.3pol 1 vs SCL and the electric field temperature at 30°C? b The reaction was carried out under the same conditions as in Example 4, except that the inside of the cracking tank was not aerated with oxygen or was covered with a nitrogen stream. The results were reported to the dwarf, and 1.0 mol/concentration of silver nitrate was added to Example 24-26.

Using an anode potential of 2.1 volts VSS CE, a substrate of 0-xylene (1,005 mol), and platinum (2.0 cm2) for the anode, constant potential electrolysis was performed by changing the temperature of the electrolytic cell and keeping the anode potential constant. The results are shown in the table above.

Example 27 The anode potential is 2.1% vs. 3%, and the nitrate ion of the electrolyte dissolved in the electrolyte is 11%! 1.0 mol/'1-
Acetonitrile, electrolytic cell temperature 30°C 2 groups i''! i
The reaction was carried out under the conditions of 0.005 mol of o-xylene,
Look at the influence of the type of nitrate metal salt Ic Q The results are shown in the table below Examples 28 to 29 Anode potential 2.3 pol 1-VSS CE, electrolytic cell temperature 3
0℃.

Silver nitrate 0.6 mol/' as an electrolyte dissolved in the electrolytic solution
The reaction was carried out in the same manner as in Example 22, except that the reaction mixture was adjusted to 1-acenitrile and the water content in the solvent ace1-2[-nitrile was varied. The results are shown in the table below.

Examples 30 to 31 LI'-U-i' constant potential electrolysis was carried out in the same manner as in Example 22, except that the substrate was changed. I received the results in 1. Table.

Claims (1)

[Claims] 1) In an acetonitrile solvent, using platinum as an anode and as an electrolyte dissolved in an electrolytic solution, gold nitrate Its JJA
1. A method for electrolytically oxidizing xylene, which comprises electrolytically oxidizing xylene in the presence or absence of oxygen. 2) The invention according to claim 1, characterized in that xylene is electrolytically oxidized while supplying oxygen to an acetonitrile solvent to produce l-raldehyde. 3) The method of claim 1 is to electrolytically oxidize xylene in an acetonitrile solvent under a nitrogen atmosphere or in the absence of oxygen supply to produce methylbenzyl nitrate ester.
The invention described in Section 1.