Preparation method of menthone

Abstract

The invention relates to a preparation method of menthone, which comprises the following steps: (1) taking a reaction product generated in production of menthol through thymol hydrogenation, introducing the reaction product into a fixed bed reactor, filling a copper-based catalyst with the particle size of 3 * 3mm in the fixed bed reactor according to the length-diameter ratio of (7-8): 1, and controlling the temperature at 220-240 DEG C and the feeding space velocity at 0.8-1.2 h <-1 >; (2) a rectifying tower is prepared, the column height of the rectifying tower is 140 cm, the inner diameter of the rectifying tower is 30 mm, packing is western tower ring packing 3 mm * 3 mm, and the suction rate of a vacuum pump is 2 L / min; and (3) adding the reaction liquid obtained in the step (1) into the tower kettle of the rectifying tower prepared in the step (2), and controlling the kettle temperature to be 120-135 DEG C, the vacuum degree to be 15-20 mmHg and the reflux ratio to be 20: 2-50: 2, so that qualified menthone can be extracted. According to the invention, a reaction product of production of menthol through thymol hydrogenation is used as a raw material, and hydroxyl on a benzene ring of the raw material is efficiently dehydrogenated through a fixed bed catalyst reaction to obtain menthone.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of menthone. BACKGROUND

[0002] Menthone is a flavoring ingredient for preparing geranium oil, used in trace amounts in citronellol or in floral flavors such as rose, has the effect of adjusting the floral flavor, and is used in lavender, jasmine, spice and other types of flavorings in appropriate amounts. It is a raw material for edible cooling flavor, used in fruit flavors such as raspberry, etc., to adjust the flavor and increase the fresh and clear taste while reducing the sweet taste. It is also a good flavor for toothpaste.

[0003] Menthone is mainly prepared by oxidation method, using menthol as raw material, and obtained by oxidation reaction. It can also be obtained from natural menthol, old heron grass, sweet vernal grass and other natural raw materials, by vacuum distillation to cut 204~212℃ fraction, converting it into oxime or semicarbazide, recrystallizing, and separating pure menthone or isomenthone, see Chinese patent CN105061175. Menthone can be obtained by reducing piperitone or piperonyl ketone. The menthone in the prior art needs to be synthesized and separated by a complex process.

[0004] Menthol, commonly known as menthol, is 5-methyl-2-isopropyl-cyclohexanol. Menthol is widely used in medicine, daily chemical flavor, tobacco flavor and edible flavor. At present, the yield of natural extracted menthol cannot meet the increasing industrial demand, so the chemical synthesized menthol becomes more and more important. Because of the high economic value of synthetic menthol, there are a large number of mature menthol production lines on the market, which produce excess menthol. At present, the synthesis route of menthol mainly adopts thymol hydrogenation method, see Chinese patent CN201510809332.9. The reaction will obtain neomenthol, isomenthol, isomenthol, DL menthol, these four main products, and by-products are menthone and isomenthone. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method of menthone, which uses the reaction product of thymol hydrogenation to produce menthol as raw material, and efficiently dehydrogenates the hydroxyl group on the benzene ring of the raw material by fixed bed catalyst reaction to obtain menthone.

[0006] To solve the above technical problems, the present application provides a preparation method of menthone, comprising the following steps:

[0007] (1) The reaction product of thymol hydrogenation to produce menthol is introduced into a fixed bed reactor, and a copper-based catalyst with a particle size of 3*3mm is loaded in the fixed bed reactor according to a length-diameter ratio of 7~8:1, the temperature is controlled at 220~240℃, and the feed air speed is 0.8~1.2h -1 ;

[0008] (2) Prepare a rectifying column, the column height of the rectifying column is 140 cm, the inner diameter is 30 mm, the filler is 3mm*3mm Westinghouse ring filler, and the air pumping capacity of a vacuum pump is 2L / min;

[0009] (3) The reaction liquid obtained in step (1) is put into the still kettle of the rectifying column prepared in step (2), the kettle temperature is controlled to be 120-135 DEG C, the vacuum degree is 15-20 mmHg, and the reflux ratio is 20:2-50:2, so that qualified menthone can be obtained.

[0010] The method has the advantages that the reaction product of thymol hydrogenation to produce menthol is used as raw material, the hydroxyl on the benzene ring of the raw material is dehydrogenated to obtain menthone through a fixed bed catalyst reaction, the reaction product of thymol hydrogenation to produce menthol has a large yield, the method can directly use the reaction product as raw material, greatly reduces production cost, and has the advantages of simple process, high product yield and low separation difficulty. DETAILED DESCRIPTION

[0011] Example One

[0012] A preparation method of menthone comprises the following steps:

[0013] (1) The reaction product of thymol hydrogenation to produce menthol is put into a fixed bed reactor, a copper-based catalyst with a particle size of 3*3mm is filled in the fixed bed reactor according to a length-diameter ratio of 7:1, the temperature is controlled to be 220 DEG C, and the feed air speed is 0.8h -1 ;

[0014] (2) A rectifying column is prepared, the column height of the rectifying column is 140 cm, the inner diameter is 30 mm, the filler is 3mm*3mm Westinghouse ring filler, and the air pumping capacity of a vacuum pump is 2L / min;

[0015] (3) The reaction liquid obtained in step (1) is put into the still kettle of the rectifying column prepared in step (2), the kettle temperature is controlled to be 120 DEG C, the vacuum degree is 15 mmHg, and the reflux ratio is 20:2, so that qualified menthone can be obtained.

[0016] Example Two

[0017] A preparation method of menthone comprises the following steps:

[0018] (1) The reaction product of thymol hydrogenation to produce menthol is put into a fixed bed reactor, a copper-based catalyst with a particle size of 3*3mm is filled in the fixed bed reactor according to a length-diameter ratio of 7.5:1, the temperature is controlled to be 230 DEG C, and the feed air speed is 1.0h -1 ;

[0019] (2) Prepare a rectifying column with a column height of 140 cm, an inner diameter of 30 mm, and a packing of Westinghouse ring packing 3 mm*3 mm. The vacuum pump has a pumping capacity of 2 L / min;

[0020] (3) Take the reaction liquid obtained in step (1) and pour it into the still kettle of the rectifying column prepared in step (2). The kettle temperature is controlled at 127°C, the vacuum degree is 17 mmHg, and the reflux ratio is 35:2. Qualified menthone can be obtained.

[0021] Example Three:

[0022] A method for preparing menthone, comprising the following steps:

[0023] (1) Take the reaction product of thymol hydrogenation to produce menthol and pass it into a fixed bed reactor. In the fixed bed reactor, fill copper-based catalyst with a particle size of 3*3 mm according to a length-diameter ratio of 8:1. The temperature is controlled at 240°C, and the feed air speed is 1.2 h -1 ;

[0024] (2) Prepare a rectifying column with a column height of 140 cm, an inner diameter of 30 mm, and a packing of Westinghouse ring packing 3 mm*3 mm. The vacuum pump has a pumping capacity of 2 L / min;

[0025] (3) Take the reaction liquid obtained in step (1) and pour it into the still kettle of the rectifying column prepared in step (2). The kettle temperature is controlled at 135°C, the vacuum degree is 20 mmHg, and the reflux ratio is 50:2. Qualified menthone can be obtained.

[0026] The copper-based catalyst used in the above examples is a copper-based catalyst prepared by co-precipitation as described in Chinese Patent CN117504885 A. The content of the aluminum carrier is 1-40% by weight, the content of copper is 10-70% by weight, and the content of zinc is 5-60% by weight.

[0027] Westinghouse ring packing is an existing product that can be purchased.

Claims

1. A method for preparing menthone, characterized in that, Includes the following steps: (1) The reaction product of hydrogenating thymol to produce menthol is fed into a fixed-bed reactor. The fixed-bed reactor is filled with copper-based catalyst with a particle size of 3*3mm at an aspect ratio of 7~8:

1. The temperature is controlled at 220~240℃ and the feed space velocity is 0.8~1.2h. -1 ; (2) Prepare a distillation column with a column height of 140cm, an inner diameter of 30mm, and packing material of 3mm*3mm West Tower ring packing. The vacuum pump has a pumping capacity of 2L / min. (3) Take the reaction solution obtained in step (1) and put it into the distillation column prepared in step (2). The temperature of the column is controlled at 120~135℃, the vacuum degree is 15~20 mmHg, and the reflux ratio is 20:2~50:2 to obtain qualified menthone.