JPH09169696A - Production of acetoxybenzene dicarboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject compound good in the color in high selectivity and in a good yield by adding a catalyst and a zirconium compound to a reaction system, esterifying a dialkylphenol with acetic anhydride and subsequently oxidizing the ester with a molecular oxygen-containing gas. SOLUTION: (G) A dialkylphenol is acetylated and oxidized with a molecular oxygen-containing gas in the presence of a catalyst containing (C) a cobalt compound, (D) a manganese compound, (E) a zirconium compound and (F) a bromine compound in the coexistence of (B) acetic anhydride in (A) acetic acid solvent to obtain the acetoxybenzenedicarboxylic acid. The components A and B are preferably used in amounts of 0.5-10 pts.wt. and 2.5-8 moles, respectively, per pt.wt. of the component G. The amount of the used component C is 0.05-0.5wt.% based on the total amount of the components A and B in terms of the metals, and the amount of the component D is preferably 0.2-40wt.% based on the cobalt metal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing acetoxybenzenedicarboxylic acid from dialkylphenol. Acetoxybenzenedicarboxylic acid is industrially regarded as important as a raw material for medicines and agricultural chemicals such as hydroxybenzenedicarboxylic acid and polymers.

[0002]

2. Description of the Related Art Since dialkylphenol is a dialkylated product of phenol, it exhibits an oxidation-inhibiting effect which is a characteristic of phenols, and it is difficult to oxidize an alkyl group to a carboxyl group by an ordinary oxidation reaction with molecular oxygen. is there. Therefore, a method is adopted in which the phenolic hydroxyl group is protected by esterification to cancel its oxidation suppressing effect.

Regarding the method for producing a hydroxybenzenedicarboxylic acid by esterifying a dialkylphenol with acetic anhydride and oxidizing it with a gas containing molecular oxygen, Japanese Examined Patent Publication No.
No. 7-15737, JP-A No. 7-109246, and the like.

[0004]

However, in all of these methods, a large amount of by-products are produced, so that the selectivity of hydroxybenzenedicarboxylic acid is not sufficient, and crystals of hydroxybenzenedicarboxylic acid separated from the reaction product solution are not formed. ,
The purity is low and it is markedly colored. Furthermore, when a reaction filtrate containing hydroxybenzenedicarboxylic acid or a catalyst is used in the next oxidation reaction, there is a problem that the yield of hydroxybenzenedicarboxylic acid is significantly reduced, and it is hard to say that this is a preferable method.

[0005]

Means for Solving the Problems Accordingly, the present inventors have:
With the aim of developing a method for obtaining a target product with good color tone at a high selectivity in a high yield in a method for producing acetoxybenzenedicarboxylic acid by esterifying a dialkylphenol with acetic anhydride and oxidizing with a gas containing molecular oxygen. After extensive studies, cobalt, which has been used as a catalyst,
The inventors have found that the object can be achieved by allowing a zirconium compound to be present in the reaction system in addition to a variable valence metal compound such as manganese and a bromine compound, and have reached the present invention.

[0006] That is, the present invention is a dialkylphenol in the acetic acid solvent in the presence of acetic anhydride, a cobalt compound,
Using a catalyst containing a manganese compound and a bromine compound,
A method for producing acetoxybenzenedicarboxylic acid, which is characterized in that a zirconium compound is allowed to exist in a reaction system in the method for producing acetoxybenzenedicarboxylic acid, which is performed by successively performing acetylation and oxidation with a gas containing molecular oxygen.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be specifically described below.

In the method of the present invention, a dialkylphenol is acetylated with acetic anhydride in an acetic acid solvent and then contacted with a molecular oxygen-containing gas in the presence of a catalyst.

Examples of the dialkylphenol used in the present invention include xylenol, ethylmethylphenol, diethylphenol, isopropylmethylphenol, isopropylethylphenol, diisopropylphenol, n-propylmethylphenol, n-propylethylphenol and di ( Examples include n-propyl) phenol and the like. Among them, xylenol, especially 3,5
-Xylenol is preferably used.

The amount of acetic acid used is 0.5 to 10 times by weight, preferably 1.5 to 8 times by weight that of dialkylphenol. If the amount of acetic acid used is less than 0.5 times by weight, a sufficient oxidation rate cannot be obtained, and the reaction product becomes a slurry of high concentration, which is difficult to handle, and a target product with a satisfactory level of quality. It is difficult to get stable. On the other hand, when the amount of acetic acid used is 10 times by weight or more, the economical burden due to combustion decomposition of acetic acid increases, and the volumetric efficiency of the reactor is unnecessarily lowered, which is disadvantageous. Acetic anhydride may be used in an amount sufficient to acetylate the dialkylphenol and further remove water by-produced by oxidation, and the amount used is 2.5 to 8 mole times the dialkylphenol, preferably Is 3.3 to 4.5 molar times.

As the catalyst, a cobalt compound and a bromine compound are used as main constituents, and a manganese compound is used together with them in order to enhance the catalytic activity. In this case, the cobalt compound and the manganese compound are soluble in and interfere with the reaction product such as a bromide, hydroxide, carbonate, a salt of a lower aliphatic carboxylic acid such as acetic acid, a salt of naphthenic acid, and acetylacetonate. Compounds containing no such counterion are suitable.

As the bromine compound, bromine, hydrogen bromide, cobalt bromide, manganese bromide, ammonium bromide,
Inorganic bromine compounds such as alkali metal bromides and organic bromine compounds such as tetrabromoethane, bromacetic acid and benzyl bromide can be used.

The amount of the cobalt compound used is such that the amount of the cobalt compound used is 0.001 with respect to the total amount of acetic acid and acetic anhydride.
It is preferable to set it in the range of 05 to 0.5% by weight. If the amount of the cobalt catalyst used is less than 0.05% by weight, a sufficient reaction rate cannot be obtained, and if it exceeds 0.5% by weight, the time and effort required for separating the cobalt catalyst from the target product increase and the coloring impurities It is not preferable because by-products increase.

In the present invention, a manganese compound is used in combination with the cobalt compound, but the manganese compound is used so that the amount of the manganese metal used is in the range of 0.2 to 40% by weight based on the cobalt metal. Is preferred. If the amount of the manganese compound used is less than the above range, the catalytic activity will be lowered, and if it is more than the above range, by-products of coloring impurities will increase, which is not preferable.

The amount of the bromine compound used is preferably in the range of 0.6 to 5 times by weight, particularly 1 to 3 times by weight, as the amount of bromine atom used relative to the cobalt metal.

When the amount of the bromine compound used is less than 0.6 times by weight, sufficient catalytic activity cannot be obtained, and when it exceeds 5 times by weight, the catalytic activity tends to decrease and contamination of the product with bromine and catalyst This is not preferable because the cost burden becomes significant.

In the present invention, in addition to the above-mentioned cobalt compound, bromine compound and manganese compound, a zirconium compound is further present in the reaction system. The present inventors have found that the use of a zirconium compound in combination increases the catalytic activity and reduces the amount of coloring impurities by-produced.

Suitable zirconium compounds are zirconium compounds which are soluble in acetic acid and do not contain counterions which interfere with the reaction, such as zirconium bromide, zirconyl acetate and zirconium acetate. The amount of zirconium compound used is preferably such that the amount of zirconium metal used is equivalent to 7.5 to 30% by weight, more preferably 8 to 20% by weight, based on the cobalt metal used as the catalyst constituent. Is the amount. If the amount of the zirconium compound used is less than this range, the effect of addition becomes weak, and if it is more than this range, the cost burden and the labor of separation increase, but no particular effect can be obtained, which is disadvantageous.

In carrying out the present invention, first, the inside of the reactor is replaced with nitrogen, and the reaction temperature is 60 ° C. or higher, preferably 80 ° C.
It is preferable to maintain the above for about 1 to 2 hours to complete the acetylation. If the reaction temperature is too low, the protection by the esterification of the phenolic hydroxyl group will be insufficient and the oxidation inhibiting effect of the phenols will be exhibited, so that the subsequent oxidation reaction will stop at a low conversion rate. The reaction temperature in oxidation is 80 to 1
80 ° C. is preferable, and more preferably 100 to 150 ° C.
Is appropriate. At a temperature lower than 80 ° C., the reaction rate becomes remarkably slow, while at a reaction temperature higher than 180 ° C., decomposition of the reaction product into carbon dioxide and by-products of coloring impurities increase, which is not preferable.

As the molecular oxygen-containing gas used as an oxidizing agent in the next oxidation step, pure oxygen or industrial exhaust gas can be used, but industrially, normal air or a mixed gas of air and industrial exhaust gas is suitable. ing.

Regarding the oxygen partial pressure of the reaction system, the total reaction pressure is in the range of 490 to 4000 kPa, particularly 780 to 290.
It is preferably in the range of 0 kPa, and it is preferable to operate so that the oxygen concentration of the exhaust gas from the reactor is in the range of 1 to 8% by volume. When the reaction pressure exceeds 40 atm, no special advantage can be obtained despite the increase in the equipment cost and the power cost for compressing the molecular oxygen-containing gas, and conversely the decomposition of the reaction product into carbon dioxide. It is disadvantageous as it tends to increase. Further, if the oxygen concentration of the exhaust gas exceeds 8% by volume, there is a strong possibility that the gas phase portion of the reactor will form an explosive mixed gas, and from the viewpoint of safety measures, it is preferable that the oxygen concentration of the exhaust gas be 8% by volume or less. .

The reactor used in the present invention is preferably a forced mixing type rather than a simple bubble column type. That is, in order to perform a good gas-liquid mixture of the molecular oxygen-containing gas and the reaction solution, to promote the dissolution of the molecular oxygen in the reaction solution, and to facilitate the mutual contact of the reactants in the reactor, It is preferable to use a reactor provided with a gas inlet having a large number of pores in the lower part of the reactor and in which forced stirring by a rotating stirring blade or forced circulation by a circulation pump outside the reactor is performed.

A reflux condenser is provided in the upper part of the reactor so that the exhaust gas is discharged through the reflux condenser to condense solvent acetic acid, acetic anhydride, unreacted acetoxydialkylbenzene and the like contained in the exhaust gas. Circulate in reactor.

The reaction system may be a batch system, a semi-continuous system or a continuous system.

The target substance, hydroxybenzenedicarboxylic acid, can be obtained from the reaction product mixture obtained by the method of the present invention by the following method. That is,
The reaction product is cooled and optionally further concentrated to crystallize acetoxybenzenedicarboxylic acid, and solid-liquid separation is performed. The isolated acetoxybenzenedicarboxylic acid is washed with a solvent and optionally recrystallized to purify it to a desired purity, and then acidified with sulfuric acid, hydrochloric acid, acetic acid or the like, or with sodium hydroxide or the like. The acetoxy group is hydrolyzed with an alkaline aqueous solution to convert it into a hydroxy group. At that time, it is particularly preferable to perform hydrolysis using an aqueous acetic acid solution. Then, solid-liquid separation is performed again,
The desired hydroxybenzenedicarboxylic acid can be obtained by carrying out purification such as solvent washing and recrystallization as necessary.

On the other hand, the mother liquor from which the acetoxybenzenedicarboxylic acid has been separated contains the solubility of acetoxybenzenedicarboxylic acid, reaction intermediates, catalysts, and excess organic substances such as acetic anhydride. Therefore, the catalyst and acetic anhydride can be replenished and circulated in the reaction system for repeated use.

The method of the present invention described in detail above makes it possible to produce a good quality hydroxybenzenedicarboxylic acid in a high yield.

The present invention will be specifically described below with reference to examples.

[0029]

【Example】

Example 1 A titanium pressure-resistant reactor equipped with a reflux condenser and a rotary blade stirrer was charged with 3,5-xylenol (Wako Pure Chemical, special grade) 120.
Part, acetic anhydride (Kanto Chemical, first grade) 330.9 parts (3,5
-3.3 mol times with respect to xylenol), 169.1 parts of acetic acid (Katayama Chemical, first grade) (1.4 times times with respect to 3,5-xylenol), cobalt acetate tetrahydrate (Wako Pure Chemical, special grade) 3.128 parts (0.15% by weight of cobalt metal based on the total amount of acetic anhydride and acetic acid), manganese acetate tetrahydrate (Wako Pure Chemical Industries, Ltd.) 0.172 parts (manganese to cobalt 5. 0% by weight), zirconyl acetate (Hanai Chemical,
0.185 parts (10% by weight of zirconium for cobalt), sodium bromide (Wako Pure Chemical Industries, special grade)
80 parts (1.9 weight times bromine to cobalt) was charged, the inside of the reactor was replaced with nitrogen, the pressure was increased to 392 kPa gauge, the temperature was raised to 95 ° C., and heating was continued for 90 minutes.

After that, the pressure was increased to 1373 kPa gauge with a mixed gas of 5% oxygen and 95% nitrogen, and heating was continued while blowing the mixed gas. When 5 minutes later, oxygen absorption started at 115 ° C., so the gas to be blown in. Was changed to air, and the blowing of air was continued at a flow rate such that the oxygen concentration in the exhaust gas was 8% or less. After 7 hours, the oxygen concentration in the exhaust gas rose to 8%, so the blowing of air was stopped.

After the reaction was completed, 703 parts by weight of the reaction product was cooled to around room temperature and solid-liquid separated to obtain 238 parts by weight of wet crude crystals (5-acetoxyisophthalic acid, yield 90.7%) containing 30% water. When washed with 350 parts of acetic acid and dried, 196.7 parts of white crystals of 5-acetoxyisophthalic acid (yield 8
9.3%). The purity of this product determined by high performance liquid chromatography was 99.7%. Also, acquired 5
-2.00 g of crystals of acetoxyisophthalic acid were dissolved in 20 ml of a 2N aqueous potassium hydroxide solution, and the light transmittance at 460 nm measured with a 10 mm cell was 82.0%.

Further, 469 parts by weight of the filtrate contained 9.5 parts by weight of 5-acetoxyisophthalic acid and 3.2 parts by weight of acetic anhydride, but 5-acetoxy-m-xylene was not detected. .

As a result, the reaction yield of 5-acetoxyisophthalic acid was 94.7%, and the amount of acetic anhydride consumed was 3.27 mol times that of 3,5-xylenol.

Example 2 From 469 parts by weight of the reaction filtrate obtained in Example 1 to 284
120 parts by weight of 3,5-xylenol was added to 185 parts by weight of the residual liquid obtained by distilling parts by weight, and 330.9 parts by weight of acetic anhydride was added to make the ratio of 3,5-xylenol, acetic acid and acetic anhydride. A reaction solution was prepared in the same manner as in Example 1. All catalysts were supplemented with 15% of the amount added in Example 1.

The above prepared solution was reacted in the same manner as in Example 1,
After cooling, solid-liquid separation, washing, and drying were carried out to obtain 204.0 parts of white crystals of 5-acetoxyisophthalic acid (yield 93.0).
%). The purity of the obtained 5-acetoxyisophthalic acid is 99.6%, and the light transmittance at 460 nm is 80.
It was 6%.

Further, 441 parts by weight of the filtrate contained 10.0 parts by weight of 5-acetoxyisophthalic acid and 2.6 parts by weight of acetic anhydride, but 5-acetoxy-m-xylene was not detected. .

As a result, the reaction yield of 5-acetoxyisophthalic acid (the yield excluding 5-acetoxyisophthalic acid contained in the reaction filtrate of Example 1) was 92.9%.
The acetic anhydride consumption was 3,5 with respect to 3,5-xylenol.
It was 27 molar times.

Comparative Example 1 When zirconyl acetate was not added in Example 1, the reaction yield of 5-acetoxyisophthalic acid decreased to 89.7%. The yield of isolated 5-acetoxyisophthalic acid also dropped to 84.6%, and the light transmittance at 460 nm was measured and found to be 74.5%.

Comparative Example 2 From 441 parts by weight of the reaction filtrate obtained in Comparative Example 1 to 256
185 parts by weight of the residual liquid obtained by distilling parts by weight was supplemented with 3,5-xylenol, acetic acid, acetic anhydride, and all the catalysts in the same manner as in Example 2, and the reaction was carried out. Oxygen absorption was stopped, and the reaction yield of 5-acetoxyisophthalic acid (the yield excluding p-acetoxybenzoic acid contained in the reaction filtrate of Comparative Example 1) was 59.2%.

[0040]

According to the present invention, high-purity hydroxybenzenedicarboxylic acid can be obtained in high yield without coloring.

Claims (5)

[Claims] 1. A dialkylphenol is continuously acetylated and oxidized by a molecular oxygen-containing gas in an acetic acid solvent in the presence of acetic anhydride in the presence of a catalyst containing a cobalt compound, a manganese compound, a zirconium compound and a bromine compound. A method for producing acetoxybenzenedicarboxylic acid, which comprises carrying out. 2. The amount of acetic acid used is 0.5 to 10 times by weight that of dialkylphenol, the amount of acetic anhydride is 2.5 to 8 times that of dialkylphenol, and the amount of cobalt compound used is 0.05 to 0.5% by weight based on the total amount of acetic acid and acetic anhydride in terms of cobalt metal, and the amount of the manganese compound used is 0.2 to 40% by weight in terms of cobalt metal in terms of manganese metal. Oxidation in the presence of a catalyst whose amount used is 0.6 to 5 times by weight that of cobalt metal in terms of bromine atoms, and the amount of zirconium compound used is 7.5 to 30% by weight of cobalt metal in terms of zirconium metal. The method for producing acetoxybenzenedicarboxylic acid according to claim 1, wherein 3. The method for producing acetoxybenzenedicarboxylic acid according to claim 1, wherein the dialkylphenol is xylenol. 4. The method for producing acetoxybenzenedicarboxylic acid according to claim 3, wherein the dialkylphenol is 3,5-xylenol. 5. A method for producing hydroxybenzenedicarboxylic acid, characterized in that the acetoxybenzenedicarboxylic acid obtained by the method according to any one of claims 1 to 4 is hydrolyzed with an aqueous acetic acid solution.