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Preparation method of L-menthol

A technology of menthol and menthyl, applied in the preparation field of L-menthol, can solve problems such as low ee value of L-menthyl benzoate, industrialized yield, large solvent consumption, etc., to avoid intermittent crystallization mode, The effect of improving production efficiency and reducing the use of solvents

Inactive Publication Date: 2019-11-15
SHANDONG NHU PHARMA
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0013] In summary, in the preparation method of L-menthol at present, there are following problems in the resolution process of D benzoate, L-menthyl ester: the solvent consumption is large, the recovery energy consumption is high, and in the crystallization process, a large amount of Solute, although it can be recovered, affects the yield of industrialization; the ee value of the L-menthyl benzoate obtained by the separate resolution process is low, and it needs to be combined with the recrystallization process to improve the ee value of the L-menthyl benzoate

Method used

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  • Preparation method of L-menthol
  • Preparation method of L-menthol

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Embodiment 1

[0048] A kind of preparation technology of embodiment 1 L-menthol

[0049] Include the following steps:

[0050] (1) Preparation of D,L-menthyl benzoate

[0051] Add 200.0g of D,L-menthol, 300.0g of methyl benzoate, 10g-40g of strong acidic sulfonic acid resin to a 1000ml three-necked flask, and pull a vacuum on the reaction system. Control the vacuum degree at 2000pa-10000pa and control the reaction temperature at 80 ℃, reacted for 5 hours, and the light components after the reaction under vacuum are more conducive to timely separation, which greatly accelerates the speed of the reaction. After filtration, the filtrate enters the rectification system, and the resin is recovered mechanically; The methyl benzoate that has reacted, D, L-menthyl benzoate, the molar yield of this step is shown in the following table:

[0052]

[0053] (2) split

[0054] as attached figure 1 As shown, add 5 L each of D benzoate and L-menthyl to the primary melting crystallizer 1 and secondar...

Embodiment 2

[0079] A kind of preparation technology of embodiment 2 L-menthol

[0080] Include the following steps:

[0081] (1) Preparation of D,L-menthyl phenylacetate

[0082] Add 200.0g of D,L-menthol, 330.0g of methyl phenylacetate, 10-40g of strong acidic sulfonic acid resin into a 1000ml three-necked flask, and pull a vacuum on the reaction system. ℃, reacted for 5 hours, and the light components after the reaction under vacuum are more conducive to timely separation, which greatly speeds up the reaction speed. After filtration, the filtrate enters the rectification system, and the resin is recovered and applied mechanically; Finished methyl phenylacetate, D, L-menthyl phenylacetate, the actual molar yield of this step is shown in the following table:

[0083]

[0084] (2) split

[0085] as attached figure 1 As shown, add 10L of D,L-menthyl phenylacetate to the primary melting crystallizer 1 and the secondary melting crystallizer 2 (each crystallizer has a volume of 5L, just o...

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Abstract

The invention provides a preparation method of L-menthol. The preparation method comprises esterification, resolution and hydrolysis. According to the process, a resolution route is optimized, a meltcrystallization mode is adopted, and continuous production is realized, so that a complex intermittent crystallization mode is avoided, the use of a large amount of solvents is reduced, resolution efficiency of the process is improved by 40%, energy consumption is reduced by 20%, and production efficiency is improved by 40%. According to the method, recrystallization and freezing crystallization are not needed in the resolution process, meanwhile, the ee value of aromatic L-menthyl ester is increased to 99% or above, and the ee value of aromatic D-menthyl ester is increased to 98% or above. The one-way molar yield of aromatic D-menthyl ester in the resolution procedure is 50.25%-50.75%, the one-way molar yield of aromatic L-menthyl ester is 49.25%-49.75%, and the method is suitable for industrial production and use.

Description

technical field [0001] The invention relates to the technical field of perfume synthesis, in particular to a preparation method of L-menthol. Background technique [0002] Menthol, the scientific name is 5-methyl-2-isopropyl-cyclohexanol, also known as menthol, which is a colorless transparent needle-like crystal; L-menthol, also known as L-menthol, melting point: 44 ° C, boiling point : 216.4℃, specific rotation [α]d: =-48 o ; Refractive index: 1.458; Slightly soluble in water, soluble in conventional organic solvents such as cyclohexane, ethanol and benzene. With a light and sweet pungent smell, it has a strong cooling effect; while d-menthol has a pungent pungent smell and has almost no cooling effect. Therefore, levomenthol is basically widely used, which can be used as local anesthetics, cosmetics, fungicides, cigarette spices, refreshing drinks and food in medicine and hygiene, food industry and daily fine chemicals. [0003] Due to the high stability and high econo...

Claims

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Application Information

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IPC IPC(8): C07C29/09C07C35/12
CPCC07B2200/07C07C29/095C07C67/03C07C67/52C07C2601/14C07C35/12C07C69/78
Inventor 马啸于安德李耀林于明宦关生郝小雷孙孝晖李国庆包新军
Owner SHANDONG NHU PHARMA
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