JPS61103851A - Production of benzophenone polycarboxylic acid - Google Patents

Abstract

PURPOSE:In producing the titled substance useful as a raw material for polyimide, etc., by nitric acid oxidation method for aromatic hydrocabon, to reduce an amount of nitric acid used by the use of a by-product and to improve yield, by oxidizing a nitrogen oxide as a by-product with oxygen fed to raise concentration of nitric acid and to promote the oxidation reaction. CONSTITUTION:An aromatic hydrocarbon [e.g., bis(dimethylphenyl)ethane, etc.] shown by the formula (R1-R6 are H, or 1-3C alkyl, and at least two of R1-R6 are alkyl; R7 are 1-3C alkylene) as a raw material is reacted with nitric acid. The oxidation reaction is carried out in a pressure reactor, and the reaction pressure is 30-100kg/cm<2>. Then, the reaction is continuously done in the presence of oxygen, to give the aimed compound. The reaction temperature of the secondary oxidation reaction is preferably 160-200 deg.C, the pressure is 30-80kg/cm<2>, and an amount of oxygen fed is 0.05-5mol, preferable 0.1-2mol based on 1mol aromatic hydrocarbon.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing benzophenone polycarboxylic acid, which is useful as a raw material for polyimide, polyamide, polyester, and the like.

BACKGROUND ART Conventionally, it has been known that the corresponding benzophenone polycarboxylic acid can be obtained by oxidizing the aromatic hydrocarbon represented by the general formula (1, .) using nitric acid. (hereinafter referred to as "nitric acid oxidation method"). For example, U.S. Pat.
, 173. No. 573 describes that 3.3',4.4'-benzophenonetetracarboxylic acid can be obtained by heating bis(3,4-dimethylphenyl)ethane with an aqueous nitric acid solution in a pressure vessel. has been done. This type of nitric acid oxidation process does not require any special oxidation catalyst, the product can be separated relatively easily, and the reaction vessel can be made of easily available stainless steel, making it an advantageous reaction and method. be.

Problems to be Solved by the Invention However, in the conventional nitric acid oxidation method, waste gas containing a large amount of nitrogen oxides is generated during the oxidation reaction, but it is difficult to release this gas into the atmosphere for pollution prevention reasons. Not beaten,
Therefore, a separate membrane must be installed in the waste gas treatment equipment. Furthermore, the nitric acid oxidation method requires a large amount of nitric acid for the oxidation reaction, and has the disadvantage that the basic unit of nitric acid is high.

The present invention was made against the background of these conventional technical problems, and its purpose is to reduce the amount of nitric acid used as an oxidizing agent, and to suppress the amount of nitrogen oxides produced to an extremely low level. It is an object of the present invention to provide a method for producing benzophenone polycarboxylic acid that is possible and that can increase the yield of the desired product.

A means for solving the problem, that is, the present invention is characterized in that an aromatic hydrocarbon represented by the following general formula (1) is oxidized using nitric acid, and then the reaction is continued in the presence of oxygen. A method for producing benzophenone polycarboxylic acid is provided.

(In the general formula (I), R1 to R are hydrogen atoms or alkino groups having 1 to 3 carbon atoms, and at least two of R+''-Rb are alkyl groups, and R1 is , is an alkylene group having 1 to 8 carbon atoms.) The oxidation reaction using nitric acid of the aromatic hydrocarbon represented by the above general formula (1) (hereinafter simply referred to as "aromatic hydrocarbon"), for example, Taking bis(3,4-dimethylphenyl)ethane as an example of a hydrocarbon, it can be considered that the following two types of reactions mainly proceed in parallel.

+35/3H, O+34/3N O +4715Hz O+1715Nz In this way, in the nitric acid oxidation method of aromatic hydrocarbons, in addition to the target benzophenone polycarboxylic acid, carbon dioxide,
Water, nitrogen oxide, nitrogen, etc. are produced, and other low molecular weight compounds such as nitrogen dioxide, nitrous oxide, and carbon oxide are produced in very small amounts.

The present invention was made with attention to this point, and the produced nitrogen monoxide, nitrogen dioxide, etc. are oxidized to nitric acid by coexisting water and oxygen supplied from the outside, and the nitric acid concentration in the oxidation reaction system is reduced. The main objective is to reduce the amount of nitric acid consumed by suppressing the decrease in nitric acid consumption, and to significantly reduce the content of nitrogen monoxide and nitrogen nitride in the exhaust gas, thereby reducing the need for after-treatment of the exhaust gas.

Examples of aromatic hydrocarbons in the present invention include bis(
dimethylphenyl)ethane, bis(dimethylphenyl)
Propane, bis(dimethylphenyl)butane, bis(diethylphenyl)octane, bis(diethylphenyl)
Examples include ethane, bis(trinotylphegor)ethane, bis(methylphenyl)ethane, trimethylphenyldimethyphenylethane, and the like.

These aromatic hydrocarbons can be obtained, for example, by subjecting an alkylbenzene such as toluene, xylene, cumene, cymene, and pseudocumene to a condensation reaction with an aliphatic aldehyde such as acetaldehyde using sulfuric acid.

For example, when 0-xylene and acetaldehyde are reacted in the presence of sulfuric acid, bis(3,4-dimethylphenyl) is produced.
Ethane can be synthesized.

In the present invention, the benzophenone polycarboxylic acid obtained by oxidizing the aromatic hydrocarbon with nitric acid is an oxide corresponding to the aromatic hydrocarbon, such as hensiphenonetetracarboxylic acid, benzophenone hexacarboxylic acid, etc. Examples include carboxylic acid, hensifhenonedicarboxylic acid, and the like.

In the present invention, such aromatic hydrocarbons are first oxidized using nitric acid, and the reaction temperature at this time is usually 140 to 140°C.
The temperature is 220°C, preferably 160-200°C. (This oxidation reaction is sometimes referred to as the "first oxidation reaction" below)
.

If the temperature of this primary oxidation reaction is less than 140°C, a yellow compound is likely to be produced as a by-product, while if it exceeds 220°C, the yield of benzophenone polycarboxylic acid obtained will decrease.

Note that nitric acid used as an oxidizing agent usually has a concentration of 20
It is used as a weight liquid of ~40 weight percent.

If the nitric acid concentration is less than 20% by weight, the reaction rate will be slow, the nitric acid concentration will be too low and a large amount of nitric acid aqueous solution will have to be used, resulting in poor usage efficiency of the reaction vessel and the concentration of the reaction product liquid after the reaction.
Precipitation or separation of benzophenone polycarboxylic acid requires a large amount of energy. On the other hand, the nitric acid concentration is 40% by weight.
If the reaction rate exceeds 100%, the reaction rate becomes too high and there is a risk that the reaction will run rampant.

The amount of nitric acid charged is 100 nitric acid per mole of aromatic hydrocarbon.
The amount is preferably 5 to 20 mol, particularly preferably 10 to 15 mol, in terms of weight % nitric acid.

If the amount of nitric acid charged is less than 5 moles per mole of aromatic hydrocarbon, the oxidation reaction will not proceed sufficiently;
Large amounts of nitric acid in excess of a molar amount are unnecessary and are disadvantageous in post-reaction processing.

Such oxidation reaction is carried out in a closed system, that is, in a pressure-resistant reaction vessel, the atmosphere during the reaction may be nitrogen, air, etc., the reaction pressure is usually 30 to 100 kg/-, and the reaction time is Usually 0.05 to 10 hours, preferably 0.05 to 10 hours.
1 to 5 hours, and the filling rate of the raw material liquid in the reaction vessel at this time is not particularly limited, but is generally 50 to 70
%.

When aromatic hydrocarbons and nitric acid are filled into a reaction vessel in this way and heated while stirring, an oxidation reaction usually occurs from around 100°C! An increase in tightening pressure is observed.

In the present invention, after performing the first oxidation reaction, oxygen or a gas containing oxygen (for example, air) is then supplied to the reaction system, and the reaction is continued (this reaction is hereinafter referred to as "second oxidation reaction"). Sometimes).

Thus, in such a secondary oxidation reaction, nitrogen oxides such as nitrogen monoxide and by-product nitrogen dioxide generated during the primary (and secondary) oxidation reaction are combined with coexisting water and supplied oxygen. At the same time, the aromatic hydrocarbon is reduced to nitric acid, and the oxidation reaction of the aromatic hydrocarbon to hensifhenone polycarboxylic acid is carried out in parallel, and the pressure in the reaction system is also reduced compared to the first oxidation reaction. (When using air, there is no pressure reduction due to the low oxygen concentration).

The reaction temperature of the second oxidation reaction is usually 140 to 220°C, preferably 160 to 200°C, for the same reason as the first oxidation reaction temperature, and the reaction pressure is usually
30-80kg/ctK, reaction time is usually 0.05
-10 hours, preferably 0.1-5 hours.

In the second oxidation reaction, the amount of oxygen supplied is 0.605 to 5 mol, preferably 0.05 to 5 mol per mol of aromatic hydrocarbon.
．． It is 1 to 2 moles.

The amount of oxygen supplied is 0.0% per mole of aromatic hydrocarbon.
If the amount is less than 5 moles, it is insufficient to reduce the produced nitrogen oxides to nitric acid, while if it exceeds 5 moles, the effect will not increase proportionally and on the contrary, the pressure of the reaction system will increase excessively. It will be necessary to do so.

In addition, oxygen is supplied to the reaction system after the aromatic hydrocarbon has been converted to benzophenone polycarboxylic acid or an intermediate pair to some extent, but as a guideline for when to supply oxygen to the reaction system, the pressure of the reaction system is ~90 kg/cffl or the reaction time is 0.5 kg/cffl after the start of the first oxidation reaction.
05 to 10 hours, preferably 0.1 to 5 hours.

After the reaction is completed, the reaction product liquid obtained is preferably 10 to 5
A pale yellow aqueous solution or suspension is obtained by cooling to about 0°C, releasing and notarizing the gas, and returning the reaction system to normal pressure. The separated gas contains almost no nitrogen oxides such as nitrogen oxide or nitrogen dioxide other than the carbon dioxide produced, and the gas can be treated with a slight treatment or as it is. It is possible to release it into the atmosphere.

Note that unreacted nitric acid in the reaction product liquid can be neutralized with an alkaline substance, but it is also possible to recycle such nitric acid to the oxidation reaction system, and there is no particular need for neutralization.

Also, the reaction product liquid after gas separation is, for example, concentrated, cooled, or? The crude benzophenone polycarboxylic acid is precipitated and separated by cooling after 1IIW, and then the obtained crude benzophenone polycarboxylic acid can be purified by recrystallization using water as a recrystallization solvent, for example.

Effect of the present invention When obtaining hensifhenone polycarboxylic acid by the nitric acid oxidation method of aromatic hydrocarbons, the produced nitrogen oxides (in addition to the above-mentioned nitrogen oxides, nitrogen oxides such as by-produced nitrogen dioxide) are mixed with coexisting water. and oxygen supplied from the outside to oxidize to nitric acid, increasing the nitric acid concentration in the oxidation reaction system and lowering the concentration of water and nitrogen oxides produced, promoting the oxidation reaction of aromatic hydrocarbons with nitric acid as a whole. It is something that makes you

Example The present invention will be explained in more detail with reference to Examples.

In addition, in the examples, % is based on weight.

Example 1 In a stainless steel autoclave with an internal volume of 100 cc,
5 g of bis(3,4-dimethylphenyl)ethane with a purity of 98% and 60 g of a nitric acid aqueous solution with a concentration of 30% were charged, stirred and heated, and the temperature was rapidly raised to 120°C.
The temperature was slowly raised at a rate of 180°C to an internal temperature of 180°C.

The internal pressure at this time was 52kg/cI+! Met.
After 11 hours, the internal pressure was 68 kg/cot, but at this point, when oxygen was slowly injected into the system from an oxygen cylinder, the internal pressure temporarily dropped to about 43 kg/C1A, but the pressure in the system was 65 kg/cn ( Further oxygen was injected until

After oxygen injection, the reaction was continued at 180°C for another 2 hours, and then allowed to cool, and after the reaction system had cooled to room temperature.

The valve was gradually opened to release the gas. This gas is colorless, and gas chromatogram analysis shows that both nitrogen monoxide and nitrogen dioxide are 5 ppm and 31 ppm, respectively.
It was a trace amount.

The resulting reaction product liquid was distilled under reduced pressure to remove moisture and concentrated to about 30 cc to obtain a bottom liquid.

This canned liquid was allowed to cool to room temperature and left to stand day and night to precipitate crude 3.3', 4.4'-benzophenonetetracarboxylic acid, which was separated into the crude benzophenonetetracarboxylic acid and the filtrate.

Approximately 30 cc of this crude benzophenone tetracarboxylic acid
After washing with distilled water and separating by filtration, it was dried in a dryer at 125° C. for 16 hours, and its weight was measured to be 5.80 g.

On the other hand, when the amount of unreacted nitric acid was measured by electrical conductivity titration analysis, it was found that 0.05 g was present in the distilled water during the vacuum Fujidome, 9.90 g in the filtrate, and 1.03 g in the waste water during washing.
A total of 10.98 g of unreacted nitric acid was recovered. As a result,
It was found that only 7.02 g of nitric acid was consumed in this example.

That is, it was found that the consumed nitric acid corresponded to only 1.21 g per 1 g of crude hensifhenonetetracarboxylic acid.

Example 2 31.5 g of filtrate obtained in Example 1 (8.91 g of nitric acid
14.9 g of a nitric acid aqueous solution with a concentration of 61V6 and 13.6 g of distilled water were added to the nitric acid aqueous solution with a concentration of 30%. This aqueous solution has 98% purity bis(3,
5 g of 4-dimethylphenyl)ethane was added, and the reaction was carried out in the same manner as in Example 1. After the reaction was completed, the reaction product was allowed to cool, the gas was discharged, and the reaction product liquid was taken out and post-treated in the same manner as in Example 1 to obtain 5.82 g of crude 3.3'.

4.4'-hensiphenotetracarboxylic acid was obtained. In addition, when the amount of nitric acid consumed was measured in the same manner as in Example 1, it was found to be 6.45 g, which corresponds to only 1.11 g per 1 g of crude hensiphenonetetracarboxylic acid obtained.

The results show that it is also possible to reuse the filtrate as a raw material and reuse unreacted nitric acid.

Comparative Example 1 The reaction was carried out in the same manner as in Example 1, except that oxygen was not injected during the reaction and the reaction was carried out at 180°C for 3 hours. After the reaction was completed, the autoclave was allowed to cool and the gas was released, and yellow nitrogen dioxide gas was released, indicating that at least a large amount of nitrogen monoxide and nitrogen dioxide were contained within the autoclave. This reaction product liquid was post-treated in the same manner as in Example 1 to obtain crude 3.3', 4.4' benzophenone tetracarboxylic acid. The obtained crude hensifenonetetracarboxylic acid was 4.92 g, which was 85 g of Example 1.
It only corresponded to %.

Further, the amount of nitric acid consumed was measured in the same manner as in Example 1, and it was found to be 9.01 g, which corresponds to 2.33 g per 1 g of crude hensiphenonetetracarboxylic acid obtained.

Comparative Example 2 5 g of bis(3,4-dimethylphenyl)ethane with a purity of 98% and a concentration of 3 were added to the autoclave used in Example 1.
0% nitric acid water? Prepare 60g of 8 liquid and further inject oxygen to raise the internal pressure to 50kg/cn! After that, while stirring, boil it to 120
It was rapidly heated to 180°C, and then the internal temperature was slowly raised to 180°C at a rate of 1.5°C/min. After reacting at this temperature for 3 hours, the mixture was left to cool as in Example 1 to release gas. The released gas was completely colorless and was analyzed in the same manner as in Example 1, but only trace amounts of -nitrogen oxide and nitrogen dioxide were detected. This reaction product solution was treated in the same manner as in Example 1! Crude 3.3' and 4.4' benzophenone tetracarboxylic acids were obtained. The amount of crude hensifhenonetetracarboxylic acid obtained was only 3.50 g, which was significantly less than that in Example 1. Further, the amount of nitric acid consumed was measured in the same manner as in Example 1, and was found to be 5.21 g.

The results show that supplying oxygen from the beginning of the nitric acid oxidation reaction inhibits the reaction.

Example 3 Into the autoclave used in Example 1, 97% pure bis(1,3,4-1-dimethylphenyl)ethane 3.
2g and 30% nitric acid solution? 60 g of a was charged, and the reaction was carried out in the same manner as in Example 1. After the reaction was completed, the reaction system was allowed to cool down to room temperature, and then the valve was gradually opened to release the gas. This gas was colorless, and analysis by gas chromatography showed trace amounts of nitrogen monoxide and nitrogen dioxide, 6 ppm and 36 ppm, respectively. The resulting reaction product liquid was boiled in a vacuum distiller while boiling the can.
After distilling under reduced pressure at 0 Torr to remove moisture and concentrating until the can becomes almost solid, the concentrated liquid was taken out onto a vacuum filtration funnel, washed with about 10 cc of distilled water, and dried for 5 days. and 1.90g of coarse 1. l'.

3.3',4.4'-hensiphenone hexacarboxylic acid was obtained.

On the other hand, when the amount of unreacted nitric acid was measured in the same manner as in Example 1, a total of 14.00 g of unreacted nitric acid was recovered. As a result, only 4.00 nitric acid was consumed in this example.
It turned out to be g.

Example 4 The autoclave used in Example 1 was charged with 8.0 g of bis(methylphenyl)ethane with a purity of 98% and 60 g of a nitric acid aqueous solution with a concentration of 30%, and reacted in the same manner as in Example 1.

After the reaction was completed, the reaction system was allowed to cool down to room temperature, and then the valve was gradually opened to release the gas.

This gas is colorless, and gas chromatogram analysis shows that both nitrogen monoxide and nitrogen dioxide each contain 5p.
pm and 40 ppm, which was a trace amount.

After releasing the gas, the reaction product liquid was taken out and post-treated in the same manner as in Example 1 to obtain 8.9 g of crude hensifenonedicarboxylic acid. Furthermore, when the amount of nitric acid consumed was measured in the same manner as in Example 1, it was found that this amount corresponded to only 1.0 Og per gram of crude benzophenonedicarboxylic acid obtained.

Effects of the Invention As described above, according to the present invention, (i) the yield of benzophenone polycarboxylic acid, which is the desired product obtained, is increased, (ii) the amount of nitric acid consumed is significantly reduced, (
iii) The gas produced after the reaction ends contains only a small amount of nitrous oxide, and the amount of nitrogen oxides such as nitrogen oxide and nitrogen dioxide is negligible, making waste gas treatment much easier. It has many advantages, such as being able to be simplified.

Claims (1)

[Claims] 1. An aromatic hydrocarbon represented by the following general formula [I],
1. A method for producing benzophenone polycarboxylic acid, which comprises oxidizing it with nitric acid and then continuing the reaction in the presence of oxygen. ▲There are mathematical formulas, chemical formulas, tables, etc.▼... [I] (In the general formula [I], R_1 to R_6 are the same or different hydrogen atoms or alkyl groups having 1 to 3 carbon atoms, and R_1 to At least two of R_6 are alkyl groups, and R_7 is an alkylene group having 1 to 8 carbon atoms.)