Preparation method of L-menthol

A technology of menthol and menthol ester, applied in the field of preparation of bulk spice L-menthol, can solve the problems of low splitting efficiency of L-menthol, complicated purifying enzyme process, difficult to obtain raw materials, etc. Synthesis efficiency, easy operation, and the effect of reducing energy consumption

Inactive Publication Date: 2012-11-28
SHANGHAI INST OF TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

From 2008 to 2010, Zheng et al. used the purified recombinant whole-cell esterase (Escherichia eoli BL-1) to transesterify D,L-menthol. The results showed that the substrate / enzyme mass ratio S / C, Under the condition of >50, compared with acrylic acid and n-butyric esterifying agent, the effect of acetic esterifying agent is the best (Esterase to menthyl acetate E>100), and through recovery, the immobilized enzyme can be reused up to 4 times ~5 times. These split results show that the purified enzyme has relatively high enzyme activity, but due to the complicated process of purified enzyme, it is also easy to cause enzyme inactivation, so most of them directly use crude enzyme for splitting, but the crude enzyme activity is low
[0012] (4) In addition, sodium is usually used to reduce menthone in liquid ammonia to obtain menthol, but the raw materials used in this method are relatively difficult to obtain, and the reaction process Need to use more dangerous metal sodium, therefore, this method also has obvious disadvantages
[0013] In summary, in the current preparation method of L-menthol, there are problems such as raw materials are not easy to obtain, D, L-menthol resolution efficiency is not high, etc.

Method used

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  • Preparation method of L-menthol

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Experimental program
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Effect test

Embodiment 1

[0033] D, the preparation of L-menthol, concrete steps are as follows:

[0034] In a 1L autoclave with a stirrer, add thymol (250g, 1.67mol), dissolve it with 200mL of methanol, then add 2.5g of 10% palladium carbon catalyst, seal the reaction kettle, replace the air in the kettle with hydrogen , and then fill the reaction system with hydrogen to make the pressure of the reaction system to 3.0-4.0MPa, and then heat the reaction system until the reaction temperature is 120-130°C. During the reaction, the pressure of the reaction system will continue to decrease as the reaction progresses, so , continuously add hydrogen under stirring, maintain the pressure of the reaction system at 3.0-4.0 MPa, stop heating when the hydrogen is no longer absorbed, adjust the temperature of the reaction system to room temperature, stop stirring, vent the reaction kettle, open the autoclave, Take out the material, filter, and reclaim the palladium-carbon catalyst for the next reaction. The filtra...

Embodiment 2

[0036] D, the preparation of L-menthol, concrete steps are as follows:

[0037] In a 1L autoclave with a stirrer, add thymol (250g, 1.67mol), dissolve it with 200mL of ethanol, then add 5gW-2 Raney nickel catalyst, seal the reactor, and replace the air in the reactor with hydrogen , and then fill the reaction system with hydrogen to make the pressure of the reaction system to 3.0-4.0MPa, and then heat the reaction system until the reaction temperature is 120-130°C. During the reaction, the pressure of the reaction system will continue to decrease as the reaction progresses, so , continuously add hydrogen under stirring, maintain the pressure of the reaction system at 3.0-4.0 MPa, stop heating when the hydrogen is no longer absorbed, adjust the temperature of the reaction system to room temperature, stop stirring, vent the reaction kettle, open the autoclave, Take out the material, filter, reclaim the Raney nickel catalyst and can be used for the next reaction, the filtrate is co...

Embodiment 3

[0039] D, the preparation of L-menthol, concrete steps are as follows:

[0040] In a 1L autoclave with a stirrer, add thymol (250g, 1.67mol), dissolve it with 200mL of ethanol, add 5g of copper-chromium catalyst, seal the reactor, replace the air in the reactor with hydrogen, and then fill Hydrogen makes the pressure of the reaction system to 3.0-4.0MPa, and then heats the reaction system until the reaction temperature is 120-130°C. During the reaction, as the reaction progresses, the pressure of the reaction system will continue to decrease. Therefore, when stirring Continue to add hydrogen under high pressure to maintain the pressure of the reaction system at 3.0-4.0MPa. When the hydrogen is no longer absorbed, stop heating, adjust the temperature of the reaction system to room temperature, stop stirring, vent the reactor, open the autoclave, and take out the materials. Filtration, recovery of copper chromium catalyst can be used for the next reaction, the filtrate is concen...

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Abstract

The invention discloses a preparation method of L-menthol. The preparation method comprises the following steps that thymol undergoes a catalytic hydrogenation reaction in the presence of a precious metal catalyst to produce a menthol mixture; the menthol mixture is rectified so that D, L-menthol is obtained; the D, L-menthol and an acylation reagent undergo an esterification reaction in the presence of one or more alkalis to produce D, L-menthol ester; and D, L-menthol ester undergoes a hydrolysis reaction in the presence of a hydrolase to produce L-menthol. The preparation method of L-menthol has the advantages that thymol as a raw material is easily available and has a low price; operation is simple; three wastes produced in production are less; environmental protection pressure is small; a yield is high; and the preparation method is suitable for industrial production.

Description

technical field [0001] The invention relates to the field of perfume synthesis, in particular to a method for preparing bulk perfume L-menthol. Background technique [0002] Menthol, common name menthol, scientific name 5-methyl-2 isopropyl-cyclohexanol. Menthol is widely used in medicine and hygiene, daily chemical flavor, tobacco flavor and food flavor. In 2007, the output of menthol was close to 20,000 tons. In recent years, the output has continued to increase, and it has become one of the largest single spices in output. Now because the output of naturally extracted menthol can no longer meet the growing industrial demand, chemically synthesized menthol is becoming more and more important. [0003] Menthol has historically been isolated primarily from natural peppermint oil. Natural menthol is greatly affected by natural conditions, such as weather, sunshine, etc. Its output and quality will fluctuate, and the price will also fluctuate thereupon, and the production c...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C12P41/00C12P7/02
Inventor 潘仙华何锡敏刘烽于万盛
Owner SHANGHAI INST OF TECH
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