JPS6019744A - Production of alpha-tetralone - Google Patents

Abstract

PURPOSE:To obtain alpha-tetralone useful as an intermediate of dyes, raw material of agricultural chemicals, raw material of the antioxidant for rubber, etc., in high conversion and selectivity, by the liquid-phase oxidation of tetralin with O2 or an O2-containing gas in the presence of a specific catalyst. CONSTITUTION:The objective compound is produced by the oxidizing tetralin with O2 or an O2-containing gas at 30-160 deg.C, preferably 60-130 deg.C, in the presence of a catalyst comprising a mixture of a soluble chromium salt (e.g. beta- diketone complex salt, acetate, etc.) and one or more compounds selected from N-acylpiperidines of formula (R1-R11 are alkyl or H) (e.g. N-formylpiperidine, N-acetyl-piperidine, etc.). The amount of the chromium salt is >=0.0003mol/l, and the volume ratio of N-acylpiperidine to tetralin is 1:100-10:1.

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.

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 8A production method for α-tetralone involves oxidizing tetralin with oxygen in the presence of a chromium-amine complex catalyst represented by a combination of lithium acetate and 2-methyl-5-ethylpyridine to produce α-tetralone. A method was proposed to obtain (
(U.S. Pat. No. 8,404,186). However, in this method, since the solubility of chromium acetate in the reaction solution is low, the catalyst concentration in the reaction solution is substantially low, and therefore the reaction rate is slow. Therefore, in order to obtain an appropriate reaction rate (9), it is necessary to increase the reaction temperature and oxygen partial pressure, and as a result, the selectivity of α-tetralone tends to be low. Furthermore, this catalyst has a serious drawback in that it has low solubility in continuous reactions, which are important as an industrial production method, and the tetramer salt precipitates as a solid and deposits in the reaction line, causing blockage of pipes, etc. have.

As a catalyst improved in these respects, a chromium-N,N-siakyl acid amide complex catalyst represented by chromium acetylacetonate and N,N-dimethylacetamide has been proposed. This catalyst combines the above-mentioned chromium acetate and 2
-Methyl-5-ethylpyridine paste When compared with p-mooramine complex catalyst, it dissolves well in the reaction solution, and almost no precipitation of chromium salt is observed. and the selectivity for α-tetralone is also high (at a conversion rate of 20 to 25 mo or less). However, N,N-dimethylacetamide, which is a co-catalyst, is partially oxidized, so it needs to be replenished, and it is also necessary to separate it from the oxidized product, which causes an increase in product costs. There is. Therefore, it was desired to develop a cocatalyst that is robust against oxidation as soon as possible.

The present inventors focused on this point, and as a result of intensive research into a robust co-catalyst that can sufficiently withstand meltification in order to produce α-tetralone by liquid-phase oxidation of tetralin, the present invention was achieved.

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 N-acylpiperidines, and the co-catalyst is liquefied.・No □, no precipitation of insoluble solids of chromium salt, and high conversion rate.
The present invention provides a method for producing α-tetralone with high selectivity.

The N-acylpiperidines used in the present invention are represented by the general formula. In this formula, R,, R2# R8, R4
°R,, R6, R,, R8, R,, R,. and R11 each represent an alkyl group or a hydrogen atom, and the alkyl group is preferably a lower alkyl group such as methyl, ethyl, propyl or butyl. Specifically, N-formylbiveridine, N-acetylpiperidine, N-probionylpiperidine and the like are exemplified.

The N-acylpiperidines may be used not only as a single type but as a mixture of two or more types. The amount of N-acylpiperidines to be used is such that the volume ratio to the raw material tetralin is "□": 100 to 1.
Used in the range of 0:1, preferably 1:20 to 5:
Used in the range 1. If the amount of N-acylpiperidine used is too small than the above range, the solubility of the chromium salt in the reaction solution will decrease and the amount of effective catalyst will decrease, resulting in an increase in the amount of α-tetralyl hydroperoxide produced. , the selectivity of the target α-tetralone decreases. Also, N
- If the amount of the acylpiperidine used is too much above the above range, the concentration of raw material tetralin in the reaction solution decreases, resulting in a decrease in volumetric efficiency and, therefore, a decrease in the productivity of α-tetralone.

The soluble chromium salt used in the present invention is β-diketone M
body salts (complex salts with acetylacetone, dibenzoylmethane, etc.), organic acid salts (acetates, naphthenates, etc.),
Halides (chlorides, bromides, etc.), nitrates, sulfur
Examples include salts and hydroxides, but other salts can be used as long as they are soluble in the reaction solution.

The amount of chromium salt used is 0.0008 mol/! or more, preferably in the range of 0.00i to 0.05 mol/l. The amount of chromium salt used is o, oooa moles/l.
If the amount is too small, the amount of α-tetralyl hydroperoxide produced increases, and the selectivity of the target product α-tetralone decreases. Furthermore, if the amount of the salt used exceeds the above range, the salt exceeding the solubility will precipitate in the reaction solution, which is unfavorable in terms of plant operation, such as clogging the line.

The oxidizing agent in this reaction is molecular oxygen, which may be a pure gas or a mixed gas with another gas such as air. The oxygen partial pressure is o, ol ''□atm or higher, preferably 0.1 atm or higher.In this reaction, the rate of dissolution of oxygen into the reaction solution affects the reaction rate, so the oxygen partial pressure and / Alternatively, appropriate gas-liquid contact is required.

The reaction temperature is 80-160°C, preferably 60-'18
A range of 0°C is preferable. If the reaction humidity is too low than this range, the reaction rate will be slow; if it is too high, side reactions will occur, reducing the selectivity of α-tetralone and further oxidizing N-acylpiperidines.

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) Tetralin 125gXtSN-acetylpiperidine 25w+l was placed in an 8009nl Rirasu reactor equipped with a condenser.
, and 0.0959 chromic acetate were added and heated to 80°C. Pure oxygen gas was flowed through the gas disperser at a flow rate of 701/hr to carry out the reaction for 2 hours. Analysis of the reaction solution revealed that the conversion rate of tetralin was 88.1%, the selectivity of α-tetralone was 88.9%, and the conversion rate of N-acetylpiperidine was 88.1%.
(The ratio was 99.7.

(Example 2) An experiment was carried out in the same manner as in Example 1, except that chromium (1) acetylacetonate 0°1579 was used instead of 0.09599 chromic acetate. The obtained results showed that the tetralin conversion rate was 81.2% and the α-tetralone selectivity was 87.2%.
8%, and N-acetylpiperidine recovery rate was 99.5%.
Met.

(Example 8) An experiment was conducted in the same manner as in Example 2 except that N-formylpiperidine 25tt/ was used instead of N-acetylpiperidine 25-. The obtained results were that the conversion of tetralin was 26.6%, the selectivity of α-tetralone was 80.7%, and the recovery of N-formylpiperidine was 100%.

(Example 4) An experiment was conducted in the same manner as in Example 1 except that N-formylpiperidine 10- and N-acetylpiperidine 15fnl were used instead of N-acetylpiperidine 25-. The obtained results were that the tetralin conversion rate was 85.8%, the α-tetralone selectivity was 87.0%, and the recovery rate of N-formylpiperidine and N-acetylpiperidine was 99.7%.

(Reference Example 1) An experiment was carried out in the same manner as in Example 1, except that N,N-dimethylacetamide was used instead of N-acetylpiperidine and the reaction temperature was changed from 80°C to 90°C. The obtained results were that the tetralin conversion rate was 85.0%, the α-tetralone selectivity was 87°5, and the N,N-dimethylacetamide recovery rate was 95.5% □. Compared with Example 1, Example 1 has a higher α-tetralone selectivity,
The tetralin conversion rate and the N,N-dimethylacetamide recovery rate show significantly improved values.

As described above, according to the present invention, as a catalyst system, a
q (and N-acylpiperidines, the conventional α
- Compared to the method for producing tetralone, both conversion and selectivity were improved despite liquid phase oxidation under mild conditions. Furthermore, since the N-acylpiperidines were sufficiently resistant to oxidation, the recovery rate was also approximately 1oos.

Patent applicant: Kawatetsu Chemical Co., Ltd. ・　9-30

Claims (1)

[Claims] 1. In producing α-tetralone by liquid phase oxidation of tetralin with molecular oxygen or molecular oxygen-containing gas,
Soluble chromium salt and general formula (wherein, R1, R2, R8, R
,,R5,R6,R1,R8°R8,R,. and R11
each represents an alkyl group or a hydrogen atom) A method for producing α-tetralone, characterized in that a catalyst system comprising one type or a mixture of two or more types of N-acylpiperidines represented by the following is used.