JPH0853391A - Production of aromatic carboxylic acid - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject compound in high yield at a low cost by using a specific catalyst in oxidizing an aromatic compound containing an alkyl substituent group with a gas containing molecular oxygen in an aqueous medium. CONSTITUTION:This method for producing an aromatic carboxylic acid is to oxidize an aromatic compound containing an alkyl substituent group or a partially oxidized alkyl substituent group (e.g. p-xylene) with a gas containing molecular oxygen in an aqueous medium using a compound in which a transition metal (preferably Cr, Mn, Fe, etc.) integrated into a heteropoly acid skeleton having a deficient structural site {preferably a deficient type hexametalate-form ion, etc., of the formula [M5O18]<n-> [M is Mo or W; (n) is an integer]} as a catalyst. Furthermore, the reaction is preferably carried out at 150-230 deg.C under 10-80atm for 1-5hr and the amount of the catalyst used is preferably 100-5000ppm based on the reactional solution.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aromatic carboxylic acid industrially useful as a resin raw material, a raw material for medicines and agricultural chemicals, etc. by oxidizing an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent. The present invention relates to a method of manufacturing.

[0002]

2. Description of the Related Art Conventionally, as a method for industrially producing an aromatic carboxylic acid, an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent, for example, a heavy metal compound such as cobalt or manganese, And a method in which a lower alkanoic acid such as acetic acid is used as a solvent in the liquid phase in the presence of a catalyst containing bromine or a bromine compound. However, in this method, since a lower alkanoic acid such as acetic acid used as a solvent is consumed in a considerable amount due to oxidation, combustion, etc., there is a problem that the manufacturing cost becomes high.

In order to solve such a problem, a method of using water as a solvent instead of lower alkanoic acid has been proposed (Japanese Patent Publication No. 39-13921 and Japanese Patent Laid-Open No. 58/1983).
-85840, JP-A-60-18403, etc.), the reaction rate is slow and not practical. Therefore, a method using ruthenium oxide as a catalyst (JP-A-3-130247), a method using a heavy metal and a bromine compound as a catalyst, and a heteropoly acid such as silicotungstic acid or phosphomolybdic acid as a co-catalyst (JP-A-2-200656), etc. A method for improving the above with a water solvent has been proposed.

[0004]

However, the above-mentioned improvement method has not reached the stage of practical use, and further improvement is desired. An object of the present invention is to propose an industrially more advantageous and practical method for producing an aromatic carboxylic acid at low cost and in high yield.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent in an aqueous medium. It was found that the target aromatic carboxylic acid can be obtained in a high yield in a short time by using a specific compound in which a transition metal is incorporated in a heteropolyacid skeleton having a defective structural site as a catalyst during oxidation. The invention was reached. That is, the present invention is a method for producing an aromatic carboxylic acid by oxidizing an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent with a gas containing molecular oxygen in an aqueous medium, A method for producing an aromatic carboxylic acid is characterized by using a compound having a transition metal incorporated in a heteropolyacid skeleton having a defective structural site as a catalyst.

Hereinafter, the present invention will be described in detail. In the present invention, an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent is used as a raw material. The alkyl substituent has usually 1 to 8 carbon atoms.
Although those having a degree of about 1 to 3 are used, an alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, an n-propyl group and an i-propyl group is preferable. The partially oxidized alkyl group having a carbon number of about 1 to 8 is usually used, and examples thereof include a formyl group, a carboxyl group and a hydroxyalkyl group. The number of these substituents is not limited to one, and two or more may be substituted. Further, in the case of having a plurality of substituents, each substituent may be the same or different. The aromatic nucleus includes not only a single ring such as a benzene ring but also a polycyclic aromatic nucleus such as a naphthalene ring.

Aromatic compounds containing the above alkyl substituents or partially oxidized alkyl substituents include toluene, ethylene, isopropylbenzene, 4,4'-dimethylbiphenyl, o-, m-, or p-xylene. , O-, m-,
Or an aromatic compound substituted with an alkyl group such as p-diisopropylbenzene, pseudocumene (1,2,4-trimethylbenzene), and 2,6-dimethylnaphthalene; benzaldehyde, o-, m-, or p-tolualdehyde, Formyl group-substituted aromatic compounds such as 2,4-dimethylbenzaldehyde and 2,4,5-trimethylbenzaldehyde; Hydroxyalkyl group-substituted aromatic compounds such as benzyl alcohol; o-, m-, or p-toluyl Acid, o-, m-, or p-
Examples thereof include compounds substituted with a carboxyl group such as carboxybenzaldehyde, 2,6-naphthalenedicarbaldehyde and 1-naphthalenedicarbaldehyde, and mixtures thereof, but are not limited thereto.

In the present invention, a compound in which a transition metal is incorporated in a heteropolyacid skeleton having a defective structural site is used as a catalyst. As the transition metal, one or more kinds selected from the elements of the groups 5 to 10 are usually selected, and preferably V of the group 5 and Cr, Mo, W of the group 6 and Mn of the group 7 are selected. , Group 8 Fe, Ru, Group 9 Co, Rh, Group 10 P
d. . These transition metals are described, for example, by R. Neumann et
al., J. Am. Chem. Soc., 112 (1990) 6025. and the like, and the like are incorporated into a heteropolyacid skeleton having a defective structural site. In addition, the heteropolyacid compound catalyst containing a transition metal is separately supplied to the reaction system by a transition metal salt such as chloride and a defective heteropolyacid compound in addition to the method of providing the reaction system after the preparation, and the transition in the reaction system is performed. A method of forming a heteropolyacid compound containing a metal is also possible.

Examples of the heteropolyacid skeleton having this defective structure site include, for example, the general formula [M ₅ O ₁₈ ] ^n- (M = Mo,
W; n is an integer) deficient hexametallate ion, represented by the general formula [YM ₁₁ O ₃₉ ] ^n- (M = Mo, W; Y = S
i, P, Ge; where n is an integer), a defective Keggin-type polyacid ion represented by the general formula [Y ₂ M ₁₇ O ₆₁ ] ^n- (M = Mo,
W; Y = Si, P, Ge; n is an integer) and is selected from a deficient Dawson type polyacid ion or the like. Note that n in the above formula is usually in the range of 1 to 20. The counter cation of the heteropolyacid compound containing these transition metals is not particularly limited, and examples thereof include protons, alkali metal ions such as Na ⁺ and K ⁺ , and tetraalkylammonium cations (NR ₄ ⁺ ).

The amount of these catalysts used is usually 10 to 10,000 ppm, preferably 100 per reaction solution.
~ 5000 ppm. In order to stabilize the heteropolyacid compound catalyst containing these transition metals, a deficient heteropolyacid compound can coexist with the catalyst. The coexisting addition amount thereof is usually 0.01 to 10 times equivalent, preferably 0.1 to 5 times equivalent to the heteropolyacid compound containing a transition metal.

The reaction of the present invention is carried out in a liquid phase in an aqueous medium, and as the aqueous medium, water or a solution containing water as a main component is used. The weight ratio of the aqueous medium and the aromatic compound as the reaction substrate is usually selected in the range of 1: 1 to 100: 1. Examples of the molecular oxygen-containing gas used in the reaction include oxygen alone or a mixed gas with an inert gas such as nitrogen, and air. These gases are usually supplied while continuously blowing into the reaction system.

As the reaction conditions, the reaction temperature is usually 100.
To 300 ° C., preferably 150 to 230 ° C., and the reaction pressure may be equal to or higher than the pressure at which the liquid phase can be retained in the reactor at the reaction temperature, and usually normal pressure to 100 atm (0.1 to 10 MPa). ), Preferably 10 to 80 atm (1 to 8 MPa). The reaction time is usually 0.
It is selected in the range of 1 to 8 hours, preferably 1 to 5 hours.

Separation and purification of the aromatic carboxylic acid obtained by the present invention is carried out by a conventional method such as filtration, centrifugation or distillation. The catalyst or the solution containing the catalyst after separating the product can be reused in the reaction.

[0014]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. (Example of catalyst synthesis) Synthesis flask deficient silicate tungstate _{Na 2 WO 4 · 2H 2 O} 182g (0.55
(2 mol) and 300 ml of water were charged and refluxed. While vigorously stirring this reflux liquid, 165 m of 4N hydrochloric acid
1 was added dropwise over about 1 hour. Next, N
_{a 2 SiO 3 · 9H 2 O} 14.23g (0.05mo
l) Aqueous solution 100 ml was added. Further, 50 ml of 4N hydrochloric acid was quickly added and refluxed for 1 hour. After cooling to room temperature and filtering the precipitated impurities, 150 g of KCl was added for salting out. Precipitated white solid K ₈ SiW ₁₁ O ₃₉
After separation of 13H ₂ O, K ₈ SiW ₁₁ O ₃₉ was further extracted from the mother liquor.
・ 13H ₂ O was recovered. The total yield is 123 g (0.03
8 mol) and the yield was 76%. 2. Synthesis of Ru-containing silicotungstate In a round bottom flask, K ₈ SiW ₁₁ O ₃₉ · 13H ₂ O 3.2
6 g (1.0 mmol) and 95 ml of water were weighed and stirred at about 80 ° C. for 15 minutes to uniformly dissolve them.
To this solution was added RuCl3. nH2O
294 mg (1.12 mmol) was slowly added, and about 9
The reaction was carried out at 0 ° C for 40 minutes. After allowing to cool, MeOH 1
00 ml was added, and a brown solid K ₅ SiRu (H ₂ O) W ₁₁ was added.
O ₃₉ was precipitated. It was washed with methanol and acetone and air dried. Also, from the mother liquor, after concentrating the mother liquor to about 10 ml, 50 ml of methanol was added to the mixture to give K ₅
SiRu (H ₂ O) W ₁₁ O ₃₉ was recovered. Total yield is 1.
It was 53 g (0.47 mmol) and the yield was 47%.

Example 1 A 500 ml titanium autoclave equipped with a reflux condenser and a stirrer was charged with 150 ml of water and 10.35 of p-xylene.
g and Ru-containing silicotungstate K ₅ SiRu (H ₂
O) W ₁₁ O ₃₉ (Ru concentration = 1000 ppm) was charged. After replacing the inside of the autoclave with nitrogen, the temperature was raised to 200 ° C by heating. When the temperature reaches 200 ° C, pressurize the air,
Air was continuously supplied for 2 hours at a rate of 39 Nl / Hr under a pressure of 60 atm. The reactor was then cooled, the contents removed and the product filtered off. The obtained product was analyzed by high performance liquid chromatography and gas chromatography. As a result, the conversion rate of p-xylene was 87%, and the yield of terephthalic acid based on the charged p-xylene was 52%. The main by-product was CO ₂ produced by combustion.

Example 2 The reaction was carried out in the same manner as in Example 1 except that 10.35 g of p-xylene and 4.0 g of p-toluic acid were used as the reaction substrates. As a result, the conversion rate of p-xylene was 71.
%, And the yield of terephthalic acid based on the charged p-xylene was 44%. The main by-product was CO ₂ produced by combustion.

Example 3 RuCl ₃ .nH ₂ O as a catalyst and deficient silicotungstate K ₈ SiW ₁₁ O ₃₉ .13H ₂ O (Ru concentration = 100
0 ppm, molar ratio = 1: 1) was charged separately to the reactor,
The reaction was carried out as in Example 1. As a result, the conversion rate of p-xylene was 85%, and the yield of terephthalic acid based on the charged p-xylene was 49%. The main by-product was CO ₂ produced by combustion.

Comparative Example 1 RuCl as a catalyst₃・ NH₂O (Ru concentration = 1000p
pm) only, no defective heteropolyacid is present
The reaction was carried out in the same manner as in Example 2 except for the above. as a result,
The conversion rate of p-xylene is 50%,
The yield of terephthalic acid based on len was 7%. What
The main by-product is CO produced by combustion. ₂Met.

Comparative Example 2 Ru-free deficient silicotungstate K₈Si
W₁₁O₃₉・ 13H₂Using 4.78 g of O as a catalyst,
The reaction was carried out by the same operation as in Example 2. as a result,
The conversion rate of p-xylene was 24%,
The yield of terephthalic acid based on len was 1%. What
The main by-product is CO produced by combustion. ₂Met.

Comparative Example 3 As a catalyst, RuO ₂ .nH ₂ O (Ru concentration = 1000 pp
The reaction was carried out in the same manner as in Example 2 except that only m) was added and no deficient heteropolyacid was present. As a result, p-
The conversion rate of xylene was 31%, and the yield of terephthalic acid based on the charged p-xylene was 16%. The main by-product was CO ₂ produced by combustion.

[0021]

According to the present invention, an aromatic carboxylic acid can be efficiently produced at low cost.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 27/199 X C07C 51/265 63/26 F 9450-4H // C07B 61/00 300

Claims (3)

[Claims] 1. A method for producing an aromatic carboxylic acid by oxidizing an aromatic compound containing an alkyl substituent or a partially oxidized alkyl substituent with a gas containing molecular oxygen in an aqueous medium to produce an aromatic carboxylic acid. A method for producing an aromatic carboxylic acid, which comprises using a compound having a transition metal incorporated in a heteropolyacid skeleton having a structural site as a catalyst. 2. A heteropolyacid skeleton having a deficient structural site, a deficient hexametallate ion represented by the general formula [M ₅ O ₁₈ ] ^n- (M = Mo, W; n is an integer), a general formula [Y
M ₁₁ O ₃₉ ] ^n- (M = Mo, W; Y = Si, P, Ge; n
Is a defective Keggin-type polyion ion represented by the general formula [Y ₂ M ₁₇ O ₆₁ ] ^n- (M = Mo, W; Y = Si, P,
Ge; n is one or more kinds selected from deficient Dawson type polyacid ions represented by () is the method for producing an aromatic carboxylic acid according to claim 1. 3. The method for producing an aromatic carboxylic acid according to claim 1, wherein the transition metal is one or more selected from Group 5 to 10 elements.