A synthetic process of L-menthol

A synthesis process, menthol technology, applied in the field of L-menthol synthesis process, can solve the problems of harsh reaction conditions, low efficiency, high reaction temperature and pressure, etc., to achieve improved esterification yield, easy operation, high yield high effect

Active Publication Date: 2016-04-06
ANHUI HAIHUA CHEM
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0009] In summary, in the current preparation method of L-menthol, there are the following problems: 1. The industrialization technology of the asymmetric hydrogenation reaction catalyzed by the chiral catalyst is relatively difficult, and can only be produced under laboratory conditions; 2. The efficiency of the original menthyl benzoate esterification process is low, the chemical resolution effect is relatively low, the efficiency of a single resolution is not high, and repeated crystallization is required; 3. The process reaction control stability is poor, and the reaction conditions Harsh, e.g. high reaction temperature and pressure

Method used

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  • A synthetic process of L-menthol

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0077] S1. Synthesis of d,l-menthol

[0078] In a 5L hydrogenation kettle, 1923g of thymol and 57.7g of Raney nickel were added, and hydrogen gas was introduced. The molar ratio of hydrogen to thymol was 1:4, and the pressure of the kettle was 2MPa. The reaction temperature is 190°C, and the hydrogenation reaction generates 20.37% of d,l-neomenthol, 65.58% of d,l-menthol, 1.84% of d,l-neoisomenthol, and 10.21% of d,l-isomenthol.

[0079] S2, d,l-menthol rectification

[0080] The above reaction was rectified under reduced pressure to obtain d,l-menthol 1311.6g, l-isomenthol, d,l-neomenthol, d,l-neo-menthol isomeric mixture 648.4g, this step The yield is 98% of theoretical.

[0081] S3, d,l-menthol esterification

[0082] Add 5109g of methyl benzoate, 1953.5g of d,l-menthol, 30% sodium methoxide and toluene into a 20L esterification reactor, wherein the molar weight of methyl benzoate is 3 times that of d,l-menthol, 30% Sodium methoxide 4508g, molar weight is d, 2 times of ...

Embodiment 2

[0094] S1. Synthesis of d,l-menthol

[0095] In a 5L hydrogenation kettle, 1923g of thymol and 38.5g of Raney nickel were added, and hydrogen was introduced. The molar ratio of hydrogen to thymol was 1:4, and the pressure of the kettle was 2MPa. The reaction temperature was 170°C, and the hydrogenation reaction produced 22.37% of d,l-neomenthol, 62.26% of d,l-menthol, 1.22% of d,l-neoisomenthol, and 11.15% of d,l-isomenthol.

[0096] S2, d,l-menthol rectification

[0097] The above reaction was rectified under reduced pressure to obtain d,l-menthol 1245.2g, l-isomenthol, d,l-neomenthol, d,l-neoisomenthol isomeric mixture 694.8g, this step The yield is 97% of theoretical.

[0098] S3, d,l-menthol esterification:

[0099] Add 3306g of methyl benzoate, 1919.1g of d,l-menthol, 30% sodium methoxide and toluene into a 20L esterification reactor, wherein the molar weight of methyl benzoate is 3 times that of d,l-menthol, 30% Sodium methoxide 4428.8g, molar weight is 2 times of d, l...

Embodiment 3

[0111] S1. Synthesis of d,l-menthol

[0112] In a 5L hydrogenation kettle, 1923g of thymol and 19.2g of Raney nickel were added, hydrogen was introduced, the molar ratio of hydrogen to thymol was 1:4, and the pressure of the kettle was 1MPa. The reaction temperature was 160°C, and the hydrogenation reaction produced 21.60% of d,l-neomenthol, 58.36% of d,l-menthol, 1.39% of d,l-neoisomenthol, and 13.65% of d,l-isomenthol.

[0113] S2, d,l-menthol rectification

[0114] The above reaction was rectified under reduced pressure to obtain 1167.2 g of d,l-menthol, 732.7.4 g of isomeric mixtures of d,l-neomenthol, d,l-neomenthol, and 1,167.2 g of l-isomenthol, respectively. The step yield is 95% of the theoretical yield.

[0115] S3, d,l-menthol esterification

[0116] Add 3262g of methyl benzoate, 1870.6.5g of d, l-menthol, 30% sodium methoxide and toluene in a 20L esterification reactor, wherein the molar weight of methyl benzoate is twice that of d, l-menthol, 30 % sodium metho...

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Abstract

The invention relates to the field of spice synthesis and particularly relates to a synthetic process of L-menthol. The process includes steps of d,l-menthol synthesizing, d,l-menthol rectification, d,l-menthol esterification, d,l-menthyl benzoate rectification, d,l-menthyl benzoate resolution, D-menthol synthesizing, menthol isomerization and L-menthol synthesizing. The process adopts thymol that is a simple, easily available and cheap chemical product as a raw material. Esterification conditions are optimized and the esterification and rectification are performed at the same time so as to allow the esterification to be converted into a way beneficial to d,l-menthyl benzoate production, thus increasing the esterification yield. Crystallization and resolution are optimized by utilization of the d,l-menthyl benzoate. Preparation of the L-menthol by the process is characterized by being high in yield, low in cost, simple and convenient in operation, suitable for continuous and large-scale production, and the like. According to the process, operation of the process is cyclic with a whole system being sealed, and the process is free of waste water, energy-saving and environmental friendly.

Description

technical field [0001] The invention relates to the field of perfume synthesis, in particular to a synthesis process of 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. 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] Due to the high economic value of synthetic menthol, there are many reports about L-menthol in the literature. At present, the synthetic route of menthol mainly contains: [0004] (1), an industrialized asymmetric synthesis route developed by Takasago Corporation in Japan, which uses myrcene as a raw material and reacts with lithium diethylamine to obtain N,N'-diethylgeranylamine, and then Citronellal enamine is obtained under the catalysis of the chiral ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C35/12C07C29/20C07C29/88C07C29/78C07C29/74
CPCC07C29/20C07C29/74C07C29/78C07C29/88C07C35/12
Inventor 解凤贤张其忠郝宗贤柏阳
Owner ANHUI HAIHUA CHEM
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