JPH06135879A - Production of naphthaldehyde - Google Patents

Abstract

PURPOSE:To obtain a naphthaldehyde compound in high yield by oxidation of a methylnaphthalene compound in a specific solution in the presence of cobalt, cerium and bromine using molecular oxygen. CONSTITUTION:The objective naphthaldehyde compound can be obtained by oxidation of methylnaphthalene (alpha- or beta-modification) or a substituted methylnaphthalene in a lower carboxylic acid-contg. solvent (pref. acetic acid solution) in the presence of 0.0005-0.1mol per 100ml of the solvent of cobalt plus cerium (the atomicratio of cerium to cobalt being 0.1 to 10) and bromine using molecular oxygen pref. at 40-120 deg.C.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing naphthaldehydes by oxidizing methylnaphthalenes such as methylnaphthalenes or methylnaphthalenes having other substituents.

These naphthaldehydes are used as modifiers for engineering plastics, various pharmaceuticals, synthetic intermediates for agricultural chemicals, and the like.

[0003]

2. Description of the Related Art As a method for producing naphthaldehyde, a method has been proposed in which methylnaphthalene is oxidized with molecular oxygen in a solvent of acetic acid using a cobalt salt and a soluble bromine compound as a catalyst [JP-A-55-55]. 7235, Synthetic Organic Chemistry, Vol. 37, No. 8, p. 667 (197
9)]. However, the above conventional method has a problem that the conversion rate of methylnaphthalene is low and the selectivity is low, so that the yield of aldehyde is low.

[0004]

The present invention has solved the above problems, and an object of the present invention is to provide a method capable of producing naphthaldehydes in a high yield with a high conversion and a high selectivity. It is in.

[0005]

DISCLOSURE OF THE INVENTION According to the present invention, methylnaphthalene or methylnaphthalene having another substituent is dissolved in a solution containing a lower aliphatic carboxylic acid, and cobalt and cerium are added in an atomic ratio of cerium to cobalt. 0.
It is a method for producing naphthaldehydes, which is present in a ratio of 1 to 10 and is oxidized by molecular oxygen in the presence of a bromine compound.

Methylnaphthalene, which is a raw material of the present invention, has two kinds of isomers, an α-form and a β-form. In the present invention, either a single substance or a mixture can be used. Further, in the present invention, methylnaphthalene having another substituent in which 1 to 7 nitro groups, methoxy groups, halogen groups and the like, which are functional groups relatively stable to oxidation, are substituted on the methylnaphthalene is also the same. It can be used as a raw material.

Cobalt and cerium are used in the form of a simple substance or a compound which can be dissolved or dispersed in a reaction solvent containing a lower aliphatic carboxylic acid, and examples thereof include metal powders, metal oxides, metal salts, etc., particularly preferably , Metal fatty acid salt,
A metal halide or the like can be used.

The bromine may be either a simple substance or a compound of bromine, and molecular bromine, alkyl bromide, alkali bromide, ammonium bromide, hydrogen bromide, metal bromide salts and the like are preferable, but bromine is particularly preferable. Alkali oxide is preferred.

Although the aldehyde selectivity tends to improve as the total amount of cobalt and cerium increases, the total amount of cobalt and cerium is 0.10 with respect to 100 ml of solvent in consideration of solubility in a solvent and economic efficiency. 0005-0.1 mol,
It is particularly preferable to set the amount to 0.002 to 0.05 mol.

The ratio of cobalt to cerium is 0.1 to 10 in terms of atomic ratio of the amount of cerium to cobalt, and particularly preferably 0.4 to 4. If cerium is present in a larger amount than cobalt in this range, cerium has an extremely low oxidation activity as compared with cobalt, so that the oxidation reaction rate decreases and the conversion rate of methylnaphthalene compounds decreases. On the other hand, when cobalt is present in a larger amount than cerium in an amount exceeding the above range, the oxidation reaction rate is increased, naphthaldehydes are oxidized to naphthoic acids, and naphthaldehyde selectivity is reduced.

Further, bromine is necessary for efficiently proceeding the oxidation reaction, and sufficient oxidation activity cannot be obtained without bromine. The amount of bromine is 0.001 or more in terms of atomic ratio with respect to the total amount of cobalt and cerium, and particularly 0.01 to
It is preferably 1.

In the present invention, a solvent containing a lower aliphatic carboxylic acid is used as a reaction solvent, and examples of the lower aliphatic carboxylic acid include acetic acid, propionic acid and butyric acid. These can be used alone or as a mixture of two or more kinds, and also include benzene compounds such as chlorobenzene, bromobenzene, dichlorobenzene and nitrobenzene, and lower aliphatic monocarboxylic acids such as alkyl halides, acetic anhydride, water and alcohols. It can also be used as a mixed solvent with a solvent miscible with an acid. However, considering the recovery and reuse of the solvent, the lower aliphatic monocarboxylic acid alone is preferable, and the acetic acid alone is particularly preferable.

The molecular oxygen used in the reaction is preferably oxygen or a mixed gas obtained by diluting it with an inert gas. Industrially, it is preferable to use air from the viewpoint of cost. In this case, it is sufficient that the oxygen partial pressure is 0.2 kg / cm ² (absolute pressure) or more, but the higher the partial pressure, the faster the reaction proceeds.

This oxidation reaction is preferably carried out at 220 ° C. or lower, particularly preferably 40 to 120 ° C. When the reaction temperature increases, the oxidation reaction rate increases, naphthaldehydes are oxidized to naphthoic acids, and the selectivity of naphthaldehydes decreases, and when the reaction temperature decreases, the oxidation reaction rate decreases, and The conversion rate of naphthalene will decrease.

The method of the present invention can be carried out in any of a batch system, a semi-batch system and a continuous system, but it is a semi-batch system or a semi-batch system in that the production of by-products can be suppressed and the production can be carried out efficiently. It is better to do it continuously.

After completion of the reaction, the reaction mixture is concentrated by vacuum distillation or the like to precipitate a product, which can be separated and recovered by a known solid-liquid separation method such as filtration. By adding water after concentration, precipitation of the product can be promoted. The obtained crude naphthaldehydes can be purified by a conventionally known technical means such as distillation.

[0017]

EXAMPLES The present invention will be further described below with reference to examples. Incidentally, the conversion rate of methylnaphthalene in Examples and Comparative Examples,
The selectivity and yield of naphthaldehyde are determined by the internal standard method of gas chromatography.

Example 1 2-Methylnaphthalene 6.22
g (43.8 mmol), acetic acid 50 ml, cobalt acetate tetrahydrate 0.952 g (3.84 mmol), cerium acetate monohydrate 0.5
51 g (1.64 mmol), sodium bromide 0.0563 g (0.06)
(548 mmol) was placed in a reaction vessel and heated to 88 ° C. under normal pressure conditions. Pure oxygen gas was blown into the reaction solution at a rate of 300 ml / min while stirring to carry out a reaction for 2.5 hours.

After completion of the reaction, the reaction solution was concentrated under reduced pressure, water was added thereto, and the precipitated solid substance was collected by filtration and dried to obtain naphthaldehyde. The conversion rate, selectivity and yield at this time are shown in Table 1.

(Example 2) Cobalt acetate tetrahydrate was added to 0.2%.
682 g (2.74 mmol), cerium acetate monohydrate 0.91
Naphthaldehyde was obtained in the same manner as in Example 1 except that 8 g (2.74 mmol), the heating temperature was 80 ° C., and the reaction time was 8 hours. The conversion rate, selectivity and yield at this time are shown in Table 1.

(Example 3) Cobalt acetate tetrahydrate 1.3
64 g (5.48 mmol), cerium acetate monohydrate 1.837 g
(5.48 mmol), a heating temperature of 70 ° C. and a reaction time of 8 hours were repeated to obtain naphthaldehyde in the same manner as in Example 1. The conversion rate, selectivity and yield at this time are shown in Table 1.

(Comparative Example 1) The same procedure as in Example 1 was repeated except that the amount of cobalt acetate tetrahydrate was 1.364 g (5.48 mmol), and cerium acetate monohydrate was not added. , Naphthaldehyde was obtained. The conversion rate, selectivity and yield at this time are also shown in Table 1.

Comparative Example 2 Example 1 was repeated except that the cerium acetate monohydrate was 1.837 g (5.48 mmol) and the reaction was carried out for 8 hours without adding cobalt acetate tetrahydrate. In the same manner as above, naphthaldehyde was obtained. The conversion rate, selectivity and yield at this time are also shown in Table 1.

(Comparative Example 3) A naphthaldehyde was obtained in the same manner as in Example 1 except that sodium bromide was not added and the heating temperature was 80 ° C and the reaction time was 8 times. The conversion rate, selectivity and yield at this time are also shown in Table 1.

[Table 1]

[0025]

INDUSTRIAL APPLICABILITY The present invention has the effect that naphthaldehydes can be produced in high yield.

Claims (1)

[Claims] 1. A ratio of methylnaphthalene or methylnaphthalene having another substituent in a solution containing a lower aliphatic carboxylic acid such that cobalt and cerium have an atomic ratio of cerium to cobalt of 0.1 to 10. And a method for producing naphthaldehydes, which comprises oxidizing with molecular oxygen in the presence of bromine. [0001]