JPS601149A - Production of alpha-tetralone - Google Patents

Abstract

PURPOSE:To obtain the titled substance useful as a raw material of agricultural chemicals, etc., in high conversion and yield, without precipitating the insoluble solid chromium salt, by the liquid-phase oxidation of tetraline with molecular oxygen in the presence of a catalyst composed of a soluble chromium salt and a 2-pyrrolidone compound under mild condition. CONSTITUTION:The titled compound is produced by reacting tetraline with molecular oxygen or an oxygen-containing gas at 30-160 deg.C, preferably 60-130 deg.C in the presence of a catalyst composed of (A) a soluble chromium salt and (B) a 2- pyrrolidone compound of formula (R1, R2, R3, R4, R5, R6 and R7 are H or alkyl) or its mixture. The volume ratio of the 2-pyrrolidone compound used as the catalyst to tetraline is preferably 1:20-5:1, and the amount of the soluble chromium salt is preferably 0.001-0.05mol/l. The partial pressure of oxygen is preferably >=0.1atm.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing α-tetralone by a liquid phase oxidation reaction of tetralin, and in particular, a method for producing α-tetralone by oxidizing tetralin in the presence of a catalyst system containing a chromium salt. It's about how to do it.

α-tetralone is a useful substance with high utility value as a dye intermediate, a raw material for agricultural chemicals, a raw material for rubber anti-aging agents, etc.

Conventionally, the method for producing α-tetralone is to acetate tetralin with oxygen in the presence of a chromium-amine complex catalyst such as a combination of chromium acetate and 2-ethyl-5-methylpyridine to obtain α-tetralone. (U.S. Pat. No. 3,404,185). however,
This method has low solubility of chromium acetate in the reaction solution.
The catalyst concentration in the reaction solution is substantially low, and therefore the reaction rate is slow. Therefore, in order to obtain a suitable reaction rate, it is necessary to increase the reaction temperature and oxygen partial pressure, and as a result, the selectivity for α-tetralone tends to be low. Furthermore, this catalyst has the disadvantage that in continuous reactors, which are important as an industrial production method, chromium salts have a low solubility and precipitate as one piece, depositing in the reaction line and causing blockage of the X-beam. There is.

The fusible threads containing chromium salts that have been proposed to date include: (1) chromium-amine complex S medium represented by a combination of chromium naphthenate and 2,4-lutidine; (2) chromium acetylacetonate and N; Chromium-N represented by N-dimethylacetamide.

Examples include N-dialkyl acid amide complex catalysts.

Among these, catalyst (2) has improved solubility of chromium salt in the reaction solution compared to the above-mentioned chromium-amine complex catalyst of chromium acetate and 2-ethyl-5-methylpyridine, but the conversion rate is Increasing the α-tetralone selectivity decreases. Similarly, when comparing the catalyst (2) with the above-mentioned catalyst of chromium acetate and 2-methyl-5-ethylpyridine,
The solubility of chromium salt in the reaction solution was improved, and the selectivity of α-tetralone was 90% at a conversion rate of 20-25%.
However, if you try to further increase the conversion rate, the selectivity will decrease.

The present inventors conducted intensive research to further improve the solubility of this chromium salt in the reaction solution and the selectivity of α-tetralone in order to produce α-tetralone by liquid-phase oxidation of tetralin, and as a result, the present invention was developed. reached.

That is, the present invention oxidizes tetralin in a liquid phase with molecular oxygen or a molecular oxygen-containing gas under mild conditions in the presence of a catalyst consisting of a soluble chromium salt and 2-pyrrolidones, so that the insoluble solid of the chromium salt is oxidized. The present invention provides a method for producing α-tetralone fI4i without precipitation, with a high conversion rate, and with a high selectivity.

The 2-pyrrolidones used in the present invention are represented by the general formula. In this formula, R,, R8, R8, R4-.

R5* Re + R7Lt represents a hydrogen atom or an alkyl group, especially an alkyl group such as methyl, ethyl, or propyl.

Lower alkyl groups such as butyl are preferred. Specifically, 2-
Pyrrolidone, N-methyl-2-pyrrolidone.

Examples include N-ethyl-2-pyrrolidone.

Not only one type of 2-pyrrolidones but also a mixture of two or more types may be used.

The 2-pyrrolidones are used in a volume ratio of 1:10D to 1O:1, preferably 1:20 to 5:1, with respect to the raw material tetralin. If too little acid is used in the 2-pyrrolidones, the solubility of the chromium salt in the anti-IIS liquid will be reduced, and the effective catalyst arsenic will therefore be reduced, resulting in an increase in the formation of the by-product α-tetralyl hydroperoxide; In addition, if too many companies use 2-pyrrolidones, the concentration of raw material tetralin in the reaction solution decreases, resulting in a decrease in the cardiac velocity and α-tetralin. -Productivity of tetralone deteriorates.

The soluble chromium salts used in the present invention include β-dikene complex salts (complex salts with acetylacetone, dibenzoylmethane, etc.), organic chromium salts such as acetates, naphthenates, etc. bromides, etc.), nitrates, sulfates, hydroxides, etc., but other salts can be used as long as they are soluble in the reaction solution.

The acid used for the chromium salt is o, o o o a mole/1 or more, preferably 0. OU ranges from 1 to 0.05 mol/l. If too little acid is used in the chromium salt, the production capacity of α-tetralyl hydroperoxide will increase, and the selectivity of α-tetralone, which is the target product, will decrease.
If too much chromium salt is used, the chromium salt exceeding its solubility will precipitate in the reaction solution and block the line, which is undesirable for plant operation.The oxidizing agent in this reaction is molecular oxygen. It may be a pure gas, or it may be a mixed gas with the gas (I), such as air. The oxygen partial pressure G is at least 0.01 atm, preferably at least 0.1 atm. In this reaction, since the rate of dissolution of oxygen into the reaction liquid affects the reaction rate, an appropriate oxygen partial pressure and/or appropriate gas-liquid contact is required.

The reaction temperature is 30-160"C1, preferably 60-130"
"The range of C is good. If the reaction temperature is too low, the reaction rate will be slow; if it is too high, side reactions will occur, oxidizing 2-pyrrolidones, reducing the catalytic ability, and lowering the selectivity of α-tetralone. .

The reactor format for this reaction can be either a batch type or a continuous type.

Examples of the present invention will be shown below, but the present invention is not limited thereto unless it goes beyond the gist of the present invention.

<Example 1> 800-Glass I glass with gas disperser and condenser 1+5'? +'fz, Tetralin 125fl/,
25 ml of N-methyl-2-pyrrolidone, and chromium (1
') Acetylacetonate 0.15729 was charged.

Immerse the reactor in a constant temperature bath at 80°C, and add pure oxygen gas to 7'0
It was flowed at a flow rate of 4. After 2 hours, the reactor was removed from the thermostat and quenched with cold water. The analysis results of the reaction solution are shown in Table 1.

<Examples 2 to 6> In Example 2, the reaction temperature was 90°C, in Example 8, chromic acetate (1,09519) was used as the chromium salt, and in Example 4, 2-pyrrolidone was used as the 2-pyrrolidone. Using lolidon,
And the reaction temperature was 90°C, Example 5 used N-ethyl-2-pyrrolidone as the 2-pyrrolidones, and Example 6
An experiment was conducted in the same manner as in Example 1 except that N-methyl-2-pyrrolidone 15- and N-ethyl-2-pyrrolidone IO- were used as the 2-pyrrolidones. The results are shown in Table 1.

<Reference Example 1> An experiment was conducted in the same manner as in Example 1 except that N,N-dimethylacetamide was used instead of N-methyl-2-pyrrolidone. The results are shown in Table 1. Reference Example 2> Tetralin 14 B, 5 tg, 2.4-lutidine 1.
5ml, and chromium naphthenate (3% chromium content) (
1, Jil 50 D 9 was placed in the same reactor as in Example 1, and incubation was carried out for 2 hours at a reaction temperature of 90"C and a pure oxygen gas flow rate of 404. The results are shown in Table 1. .

<Reference Example 3> Tetralin 148.5-12-methyl-5-ethylpyridine 1.5" and chromic acetate U, 0518 were placed in the same reactor as in Example 1, and the reaction temperature was 125.
The reaction was carried out for 0.5 hours at a pure oxygen gas flow rate of 70'C. The results are shown in Table 1.

In Table 1, the catalysts of Examples 1 to 8 in which a chromium salt and N-methyl-2-pyrrolidone were combined are compared with the known catalysts of Reference Examples 1 to 3. The selectivity of α-tetralone is
Even with the same degree of tetralin conversion, Example 1.8 shows a higher value than Reference Examples 1 to 8. Further, even in Example 2 where the tetralin conversion rate was increased to 50%, a high conversion rate of 85% was maintained. Also, chromium salt, 2-pyrrolidone or N-ethyl-2-pyrrolidone, or N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone
- Example 4 using a catalyst combined with a mixture of pyrrolidones
-6 and Reference Examples 1-8 are also compared, Examples 4-6
has a higher selectivity of 90% or more. Therefore, it was found that, compared to the conventional catalyst containing a chromium salt, the catalyst in which a chromium salt and 2-pyrrolidones were combined according to the present invention G had an extremely high conversion rate and a high selectivity.

Claims (1)

[Claims] In producing α-tetralone V4 by liquid-phase oxidation of L-tetralin with molecular oxygen or molecular oxygen-containing gas, a soluble chromium salt and the general formula (wherein, Rlt R2r R, B s R4, Rs h
1. A method for producing α-tetralone, which comprises using a catalyst system comprising 1f7iJX of 2-pyrrolidones represented by (Ra and R7 represent a hydrogen atom or an alkyl group) or a mixture of two or more thereof.