JPS63277646A - Production of acyloxyaromatic carboxylic acid - Google Patents

Abstract

PURPOSE:To simply improve yield of acyloxyaromatic carboxylic acid, by reacting an acyloxyalkyl aromatic compound with oxygen in the presence of an oxidation catalyst and a specific compound in a solvent while removing water, when acyloxyalkyl aromatic compound is oxidized by a molecular oxygen containing gas to provide the titled compound of synthetic resin raw material. CONSTITUTION:An acyloxyalkyl aromatic hydrocarbon expressed by the formula (Ar is monocyclic or polycyclic aromatic hydrocarbon; R<1> and R<2> are 1-5C alkyl; n and m are 1-4) which is a raw material is subjected to oxidation reaction in at least one kind of solvent selected from benzene, cyclohexane, chlorobenzene, dichlorobenzene and carbon tetrachloride in the presence of an aliphatic carboxylic acid of 0.5-2 times mol. based on the raw material compound and an oxidation catalyst using a molecular oxygen containing gas at 100-170 deg.C and pressure from ordinary pressure to 200kg/cm<2>G and <=40kg/cm<2> as oxygen partial pressure while removing produced water out of system by reaction distillation to provide the aimed compound.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing an acyloxyaromatic carboxylic acid by liquid phase oxidation of an acyloxyalkyl aromatic compound using a molecular oxygen-containing gas.

Acyloxy aromatic carboxylic acids are used as they are or by hydrolyzing the acyloxy group to form a hydroxy group, and are useful as raw materials for synthetic resins or synthetic fibers.

(Prior art) As a method for producing acyloxyaromatic carboxylic acids by air oxidation of acyloxyalkyl aromatic compounds, Japanese Patent Publication No. 1984-849 describes p-cresyl acetate in a soluble inert solvent and a cobalt catalyst. Presence 100-140
As an improved method of obtaining p-acetoxybenzoic acid by oxidation at ℃, Japanese Patent Publication No. 50-35066 uses an organic carboxylic acid or its anhydride as a solvent and three components of a bromine compound, a cobalt compound and a manganese compound as a catalyst. A method of using the system is described.

Furthermore, JP-A-51-108030 describes a method of air oxidizing 5-acyloxymethaxylene to 5-acyloxyisophthalic acid in the presence of an organic carboxylic acid and an acid anhydride. In No. 61-24541, in a mixed solvent consisting of an organic carboxylic acid and its anhydride,
A method for producing acyloxynaphthoic acid by air oxidation of an acyloxyalkylnaphthalene compound in the presence of a bromine compound, a cobalt compound, and a manganese compound, an improved method of which is disclosed in JP-A-61-40242 and JP-A-61
No. 286342 describes a method of oxidizing an acylalkylnaphthalene compound with a peroxide and air-oxidizing the obtained acyloxyalkylnaphthalene compound.

(Problems to be Solved by the Invention) The method disclosed in Japanese Patent Publication No. 42-849 has a conversion rate of p-cresyl acetate of only 12%, and
Although the reaction rate of p-cresyl acetate has been improved in No. 66, it is still not sufficient, and the selectivity of p-acetoxybenzoic acid is about 50%.

Further, the method of JP-A-51-108030 requires an expensive acid anhydride, and the acid anhydride is consumed in an amount at least equimolar to the water produced in the oxidation reaction.

The method of JP-A No. 61-24541 also has a low reaction rate of acyloxyalkylnaphthalene and a low selectivity of acyloxynaphthoic acid. In addition, the improved method requires a complicated process, such as treating the raw material acyloxyalkylnaphthalene with acetic anhydride before air oxidation, or using acyloxynaphthalene produced under special conditions. Only limited raw materials are available.

The purpose of the present invention is to eliminate the need for such complicated steps,
The objective is to directly oxidize acyloxyalkyl aromatic compounds without restrictions on raw materials to obtain the corresponding acyloxyaromatic carboxylic acids in high yield and high selectivity.

(Means for Solving the Problem) The inventors have intensively investigated a method of directly oxidizing acyloxyalkyl aromatic compounds, and using benzene, cyclohexane, chlorobenzene, dichlorobenzene, or carbon tetrachloride as a solvent, the It has been discovered that acyloxy aromatic carboxylic acids can be obtained in high yield by performing a reaction in the presence of a carboxylic acid while removing produced water by a reactive distillation method, leading to the present invention.

That is, the present invention has the general formula (R'), Ar (OCOR
”), (Ar is a monocyclic or polycyclic aromatic hydrocarbon, R1
o and R2 represent an alkyl group having 1 to 5 carbon atoms, and n and m are integers of 1 to 4). , in the presence of an aliphatic carboxylic acid and an oxidation catalyst in an amount of 0.1 to 10 times the mole of the acyloxyalkyl aromatic compound in at least one solvent selected from the group of chlorobenzene, dichlorobenzene and carbon tetrachloride, This is a method for producing acyloxy aromatic carboxylic acids, characterized by carrying out the reaction while removing produced water by a reactive distillation method.

The acyloxyalkyl aromatic compound used in the present invention is represented by the general formula (R'), Ar (CUR''). In this general formula, Ar represents an aromatic compound such as benzene, naphthalene, anthracene, phenanthrene, and biphenyl. group hydrocarbon, R' and R2 are linear or branched alkyl groups having 1 to 5 carbon atoms, and m and n are 1 to 5 carbon atoms.
It is an integer of 4.

Examples of the acyloxyalkyl aromatic compound represented by this general formula include mono- or diacyloxy compounds such as toluene, xylene, mesitylene, etc., mono- or diacyloxy compounds such as monoalkylnaphthalene, dialkylnaphthalene, monoalkylbiphenyl, dialkylbiphenyl, etc. be done. These acyloxyalkyl aromatic compounds can be easily produced, for example, by acylation of the corresponding hydroxy compound.

The solvent used in the method of the present invention is inert to the reaction and insoluble in water, and one or more solvents selected from the group of benzene, cyclohexane, chlorobenzene, dichlorobenzene, and carbon tetrachloride are used. be done. The amount used varies depending on the type of raw material acyloxyalkyl aromatic compound, but is at least 2 times the weight of the raw material acyloxyalkyl aromatic compound, preferably 5 to
100 times by weight is used.

Further, the organic carboxylic acid in the present invention is an aliphatic carboxylic acid having 1 to 10 carbon atoms, preferably an aliphatic carboxylic acid having 2 to 4 carbon atoms. The amount of this organic carboxylic acid to be used is variously selected depending on the type of raw material acyloxyalkyl aromatic compound and the amount of solvent, but is 0.1 to 10 times the mole of the raw material acyloxyalkyl aromatic compound, preferably 0.5 to Twice the molar amount is used. If the amount of organic carboxylic acid is too large or too small, the selectivity of acyloxy aromatic carboxylic acid will decrease.

The oxidation catalyst used in the present invention includes a Br compound and a C
A two-component system consisting of an O compound or a three-component system in which a Mn compound is added to the catalyst is used, and each Br, C
The o and Mn compounds are selected from compounds that are soluble in the solvent.

Examples of Br compounds include acetyl bromide, benzyl bromide, tetrabutylammonium bromide,
Organic bromides such as bromoform, acetyl bromide, and tetrabromeedane are used. The amount used is B based on the solvent.
300 ppm or more, preferably 1000 to 11 r atoms
0000pp.

As the Co compound, cobalt naphthenate, cobalt acetylacetonate, cobalt carbonyl, cobalt oxalate, cobalt stearate, etc. are used, and the amount used is 50 ppm or more as Co atoms, preferably 200 to 5000 ppm relative to the solvent. .

As the Mn compound, manganese naphthenate, manganese acetylacetate, manganese carbonyl, manganese oxalate, manganese stearate, manganese benzoate, etc. are used. The amount used is 5 Mn atoms relative to the solvent.
The concentration is less than ooppm.

The molecular oxygen-containing gas used in this reaction may be pure oxygen gas or oxygen gas diluted with an inert gas, but air is generally used.

The reaction temperature in the present invention is 100 to 170°C.

At a temperature lower than 100°C, the reaction does not proceed sufficiently, and at a temperature higher than 170°C, the selectivity decreases. The reaction pressure is from normal pressure to 200 kg/cm2G, and the oxygen partial pressure is 40 kg/cm'G or less.

In the present invention, it is necessary to carry out the reaction while removing produced water from the reaction system by reactive distillation. It is preferable to remove the water produced by the reaction while azeotropically distilling it with the solvent.

To separate the acyloxy aromatic carboxylic acid from the reaction solution, a general method such as recrystallization or extraction after concentration is used.

(Effects) The present invention does not require expensive acid anhydrides or complicated steps such as treatment with peroxides, and can easily convert acyloxyalkyl aromatic compounds by liquid phase oxidation using molecular oxygen-containing gas. Acyloxy aromatic carboxylic acids can be obtained in high yield and high selectivity.

Acyloxy aromatic compounds obtained by the method of the present invention, such as 4-acetoxybenzoic acid and 2-acetoxy-6-naphthoic acid, have recently attracted attention as high-strength polyester resins. Since the present invention advantageously produces such acetoxy aromatic carboxylic acids, it has great industrial significance.

(Example) Next, the present invention will be specifically explained with reference to Examples.

Example 1 1.0 g of p-cresyl acetate and 19 benzene solvent
．． 6 g 1 acetic acid 0.40 g, and cobalt naphthenate (CO content 6.0 wt%) 0.17 g as an oxidation catalyst (
CO concentration in the solvent 510 ppm), manganese naphthenate (Mn content 9.0 wt%) 0.11 g (M in the solvent
n concentration 500 ppm), acetyl bromide pro? It (B
rCH2COBr) 0.07 g (Br concentration in solvent 2
7? Oppm) was charged into a 100 mA titanium autoclave equipped with a condenser for the generated steam and a separator for the condensate, and stirred air at 2 kg/cm'G at 120°C.
It was introduced and reacted so as to maintain the temperature.

The condensate was separated into an upper oil phase and a lower aqueous phase in a separator, and only the oil phase containing benzene was returned to the reaction system.

The absorption of oxygen was completed in about 1.5 hours, but the reaction was continued for an additional 30 minutes. This reaction solution was analyzed by liquid chromatography and the following results were obtained.

p-Cresyl acetate reaction rate 100% p-acetoxybenzoic acid selectivity 88.2% p-hydroxybenzoic acid selectivity 0.1% p-acetoxybenzaldehyde selectivity 0.1% Example 2 As described in Example 1 The reaction was carried out in the same manner as in Example 1, except that the amount of acetic acid added was 2.0 g, and the following results were obtained.

p-Cresyl acetate reaction rate 100% p-acetoxybenzoic acid selectivity 83.0% p-hydroxybenzoic acid selectivity 0.1% p-acetoxybenzaldehyde selectivity 2.3% Example 3 Used in Example 1 Alternative to p-cresyl acetate 6
Using -acetoxy-2-methylnaphthalene, the reaction was carried out under the same conditions as in Example 1, and the following results were obtained.

6-acetoxy-2-methylnaphthalene reaction rate 100%
6-acetoxy-2-naphthoic acid selectivity 85.0
%6-acetoxy-2-naphthaldehyde selectivity 1.
2% 6-hydroxy-2-naphthoic acid selectivity 0
．． 1% Comparative Example 1 The reaction was carried out under the same conditions as in Example 1 except that acetic acid was not added, and the following results were obtained.

p-cresyl acetate reaction rate 100% p-acetoxybenzoic acid selectivity 64.7% p-hydroxybenzoic acid selectivity trace p-acetoxybenzaldehyde selectivity 2.3% Comparative Example 2 Lower aqueous phase in condensate separator was returned to the reactor and reacted in the same manner as in Example 1 except that the water produced by the reaction was not removed, and the following results were obtained.

p-cresyl acetate reaction rate 43.2% p-acetoxybenzoic acid selectivity 33.2% p-hydroxybenzoic acid selectivity 2.1% p-acetoxybenzaldehyde selectivity 21.8% Comparative Example 3 In Example 1 A reaction was carried out under the same conditions as in Example 1, using 20 g of acetic acid instead of benzene, but no reaction occurred. Therefore, the amount of acetic anhydride corresponding to the amount of water produced by the reaction is 0.
55g was added and reacted, and the following results were obtained.

Claims (1)

[Claims] General formula (R^1)_nAr(OCOR^2)_m(Ar
is a monocyclic or polycyclic aromatic hydrocarbon, R^1 and R^2
represents an alkyl group having 1 to 5 carbon atoms, and n and m are 1 to 5.
When oxidizing an acyloxyalkyl aromatic compound represented by (which is an integer of 4) with a molecular oxygen-containing gas,
In at least one solvent selected from the group of benzene, cyclohexane, chlorobenzene, dichlorobenzene and carbon tetrachloride, 0.1 to 10 times the mole of aliphatic carboxylic acid and oxidation catalyst to the acyloxyalkyl aromatic compound. A method for producing an acyloxy aromatic carboxylic acid, characterized by carrying out the reaction while removing produced water by a reactive distillation method in the presence of an acyloxyaromatic carboxylic acid.