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CN-121974781-A - Multistage crystallization process of menthol

CN121974781ACN 121974781 ACN121974781 ACN 121974781ACN-121974781-A

Abstract

The invention discloses a multi-stage crystallization process of menthol, which comprises the steps of S1, preprocessing mint crude oil to obtain preprocessed mint crude oil, S2, performing multi-stage crystallization treatment on the preprocessed mint crude oil through pre-cooling crystallization, primary deep cooling crystallization, secondary deep cooling crystallization and tertiary deep cooling crystallization, and S3, performing primary recrystallization and secondary recrystallization on crude menthol to obtain menthol products. The multi-stage crystallization process of menthol can improve the purity and the yield of menthol, and the menthol product has good crystal morphology.

Inventors

  • HAN CHAOJIN
  • LI YONGLEI

Assignees

  • 安徽巨邦香料有限公司

Dates

Publication Date
20260505
Application Date
20260106

Claims (10)

  1. 1. A process for the multistage crystallization of menthol, comprising the steps of: s1, preprocessing mint crude oil to obtain preprocessed mint crude oil; S2, carrying out multistage crystallization treatment on the pretreated peppermint crude oil: S2.1, pre-cooling crystallization, namely adding seed crystals into the mixture at the temperature of 0-5 ℃ for crystallization to obtain a pre-cooling crystallization oil system; S2.2, preliminary deep cooling crystallization, namely preliminary cooling the pre-cooling crystallization oil system to-12 to-10 ℃ and crystallizing to obtain a preliminary crude brain and a preliminary deep cooling oil system; S2.3, secondary cryogenic crystallization, namely adding seed crystals into the primary cryogenic oil system, cooling to-20 to-18 ℃ for the second time, and crystallizing to obtain a secondary crude brain and a secondary cryogenic oil system; S2.4, performing triple cryogenic crystallization, namely adding seed crystals and crystallization agents into a secondary cryogenic oil system, cooling to-25 to-23 ℃ for the second time, and crystallizing under the magnetic field condition to obtain triple crude brains and Mao Suyou; s3, carrying out recrystallization treatment on the crude brain: S3.1, primary recrystallization, namely mixing and heating to melt the primary crude brain, the secondary crude brain and the tertiary crude brain, cooling to 10-15 ℃ again, adding seed crystals, slowly cooling to-4 to-2 ℃ again, and recrystallizing to obtain refined primary wet brain; S3.2, re-crystallizing, namely mixing the refined primary wet brain with absolute ethyl alcohol, heating and melting, rapidly re-cooling to-24 to-22 ℃ and re-crystallizing under the magnetic field condition to obtain a menthol product.
  2. 2. The multi-stage crystallization process of menthol crystals according to claim 1, wherein the seed crystal is L-menthol solid, and the purity is more than or equal to 99%.
  3. 3. The multi-stage crystallization process of menthol according to claim 1, wherein in step S2.4, the magnetic field strength is 0.38 to 0.45t.
  4. 4. The process of claim 1, wherein the rate of cooling is lower than the rate of cooling for the second time and higher than the rate of cooling for the third time, and the rate of cooling is less than or equal to 2 ℃ per hour.
  5. 5. The multi-stage crystallization process of menthol crystals according to claim 4, wherein in step S2.2, the preliminary cooling rate is 0.75-1.25 ℃ per hour, in step S2.3, the second cooling rate is 1.5-2 ℃ per hour, and the third cooling rate is 0.5-1 ℃ per hour.
  6. 6. The process according to claim 1, wherein in step S3, the rate of re-cooling is greater than the rate of continuing re-cooling and less than the rate of rapid re-cooling, and the rate of re-cooling is less than or equal to 5 ℃ per hour, the rate of continuing re-cooling is <2 ℃ per hour, and the rate of rapid re-cooling is >0.25 ℃ per minute.
  7. 7. The multi-stage crystallization process of menthol crystals according to claim 6, wherein in step S3.1, the rate of re-cooling is 3-5 ℃ per hour, the rate of slow re-cooling is 0.5-1.5 ℃ per hour, and the rate of rapid re-cooling is 0.5-1 ℃ per minute.
  8. 8. The multi-stage crystallization process of menthol crystals according to claim 1, wherein in step S2, the seed amount in the pre-cooling crystallization, the secondary cryogenic crystallization and the tertiary cryogenic crystallization is 0.25-0.5% of the weight of the pretreated peppermint crude oil, and the seed amount in the process from the pre-cooling crystallization, the secondary cryogenic crystallization to the tertiary cryogenic crystallization is gradually reduced; The crystallization agent in the step S2.4 is low-temperature ethanol, the low-temperature ethanol is absolute ethanol at the temperature of-18 to-15 ℃, and the dosage of the crystallization agent is 8-12% of the weight of the pretreated peppermint crude oil.
  9. 9. The multi-stage crystallization process of menthol crystals according to claim 1, wherein in step S3.1, the amount of seed crystals used in the primary recrystallization is 0.1-0.15% of the weight of the pretreated crude menthol crystals, and in step S3.2, the amount of absolute ethyl alcohol added is 10-15% of the amount of refined primary wet menthol crystals.
  10. 10. A process for the multistage crystallization of menthol according to claim 1, wherein in step S3.2, the washing is carried out with a 90% aqueous ethanol solution at-5~0 ℃.

Description

Multistage crystallization process of menthol Technical Field The invention relates to a multistage crystallization process of menthol, and belongs to the technical field of menthol production. Background Menthol, also called menthol, is a cyclic monoterpene, is colorless needle-like or prismatic crystal or white crystalline powder, and has special fragrance of peppermint. Menthol is very soluble in ethanol, chloroform, diethyl ether, liquid paraffin or volatile oil, and very slightly soluble in water. Menthol is extracted from natural mint crude oil, so that the pure natural characteristics of the menthol can be better maintained, but the menthol obtained by extracting the natural mint crude oil at present often contains more impurities. In order to obtain menthol with higher purity, the crystallization condition needs to be strictly controlled in the extraction process, and repeated crystallization and impurity removal are needed, so that the loss of menthol is increased, the waste is caused, and the crystallization rate of menthol is reduced. Disclosure of Invention At least one problem of the prior art is to provide a multi-stage crystallization process of menthol, which can improve the purity and yield of menthol, and the menthol product has good crystal morphology. In order to achieve the purpose, the invention adopts the following technical scheme that the multi-stage crystallization process of menthol comprises the following steps: s1, preprocessing mint crude oil to obtain preprocessed mint crude oil; S2, carrying out multistage crystallization treatment on the pretreated peppermint crude oil: S2.1, pre-cooling crystallization, namely adding seed crystals into the mixture at the temperature of 0-5 ℃ for crystallization to obtain a pre-cooling crystallization oil system; S2.2, preliminary deep cooling crystallization, namely preliminary cooling the pre-cooling crystallization oil system to-12 to-10 ℃ and crystallizing to obtain a preliminary crude brain and a preliminary deep cooling oil system; S2.3, secondary cryogenic crystallization, namely adding seed crystals into the primary cryogenic oil system, cooling to-20 to-18 ℃ for the second time, and crystallizing to obtain a secondary crude brain and a secondary cryogenic oil system; S2.4, performing triple cryogenic crystallization, namely adding seed crystals and crystallization agents into a secondary cryogenic oil system, cooling to-25 to-23 ℃ for the second time, and crystallizing under the magnetic field condition to obtain triple crude brains and Mao Suyou; s3, carrying out recrystallization treatment on the crude brain: S3.1, primary recrystallization, namely mixing and heating to melt the primary crude brain, the secondary crude brain and the tertiary crude brain, cooling to 10-15 ℃ again, adding seed crystals, slowly cooling to-4 to-2 ℃ again, and recrystallizing to obtain refined primary wet brain; S3.2, re-crystallizing, namely mixing the refined primary wet brain with absolute ethyl alcohol, heating and melting, rapidly re-cooling to-24 to-22 ℃ and re-crystallizing under the magnetic field condition to obtain a menthol product. Preferably, in step S2.4, the magnetic field strength is 0.38 to 0.45t. Preferably, the seed crystal is L-menthol solid, and the purity is more than or equal to 99 percent. Preferably, the crystallization agent is low-temperature ethanol, and the low-temperature ethanol is absolute ethanol at the temperature of-18 to-15 ℃. Preferably, in step S2, the seed amount in the pre-cooling crystallization, the secondary cryogenic crystallization and the tertiary cryogenic crystallization is 0.25-0.5% of the weight of the pretreated peppermint crude oil, and the seed amount in the process from the pre-cooling crystallization, the secondary cryogenic crystallization to the tertiary cryogenic crystallization is gradually reduced. Preferably, in the step S2, the usage amount of the crystallization agent for three times of cryogenic crystallization is 8-12% of the weight of the pretreated peppermint crude oil. Preferably, in the step S3.1, the seed crystal dosage in the primary recrystallization is 0.1-0.15% of the weight of the pretreated peppermint crude oil. Preferably, in step S2, the rate of the first cooling is lower than that of the second cooling and higher than that of the third cooling, and the cooling rate is less than or equal to 2 ℃ per hour. Preferably, in the step S2.2, the primary cooling rate is 0.75-1.25 ℃ per hour. Preferably, in the step S2.3, the second cooling rate is 1.5-2 ℃ per hour. Preferably, in the step S2.4, the rate of the third cooling is 0.5-1 ℃ per hour. Preferably, in step S3.1, in step S3, the rate of re-cooling is greater than the rate of continuing re-cooling and less than the rate of rapidly re-cooling, and the rate of re-cooling is less than or equal to 5 ℃ per hour, the rate of continuing re-cooling is <2 ℃ per hour, and the rate of rapidly re-cooling is >0.25 ℃ per minute. Preferably, i