阅读说明：本技术 一种高纯薄荷脑的制备方法 (Preparation method of high-purity menthol ) 是由 方胜 汪莉萍 李友谊 于 2020-06-28 设计创作，主要内容包括：本发明涉及薄荷脑生产技术领域,公开了一种高纯薄荷脑的制备方法,包括如下步骤：(1)一次冻析；(2)二次冻析；(3)脑油回收；(4)脱水过滤；(5)配料得到物料油；(6)结晶；(7)烘脑；(8)晾脑。本发明将回收利用的中间产物与经两次冻析后得到的脑油配料后再进行结晶,并严格控制生产过程中的各工艺的参数,可以保证最终得到的薄荷脑的纯度,提高产品质量,并且对毛素油、冰油、烘脑油、熔化油等原料的回收再利用,尤其是对杂质含量较多的毛素油中的薄荷脑进行提取利用,可以大大减少薄荷脑的损失,提高提取率。(The invention relates to the technical field of menthol production, and discloses a preparation method of high-purity menthol, which comprises the following steps: (1) performing primary freeze-out; (2) performing secondary freeze-out; (3) recovering naphtha; (4) dehydrating and filtering; (5) preparing materials to obtain material oil; (6) crystallizing; (7) drying the brain; (8) and (6) cooling the brain. The invention mixes the recycled intermediate product with the naphtha obtained after two times of freeze-out and then crystallizes, strictly controls the parameters of each process in the production process, can ensure the purity of the finally obtained menthol, improves the product quality, recycles the raw materials such as the crude oil, the ice oil, the oven oil, the molten oil and the like, particularly extracts and recycles the menthol in the crude oil with more impurity content, can greatly reduce the loss of the menthol and improve the extraction rate.)

1. The preparation method of the high-purity menthol is characterized by comprising the following steps:

(1) primary freeze-out: performing primary freezeout on the mint crude oil to obtain a primary camphor and a secondary oil;

(2) and (3) secondary freezing out: performing secondary freeze-out on the second oil to obtain second cerebrum and plain oil;

(3) naphtha recovery: re-extracting menthol in the wool oil to obtain recovered naphtha;

(4) dewatering and filtering: melting the primary naphtha and the secondary naphtha into primary naphtha and secondary naphtha, and carrying out vacuum dehydration on the primary naphtha, the secondary naphtha and the recovered naphtha in a dehydration tank and filtering;

(5) preparing materials to obtain material oil;

(6) and (3) crystallization: crystallizing the material oil in a crystallizing barrel to obtain wet brain;

(7) baking the brain: placing the wet brain in a crystallization barrel for drying the brain in five shifts to obtain dried brain, filtering the oil drained from the first shift, collecting the oil to obtain ice oil, filtering the oil drained from each shift, and collecting the oil to obtain dried brain oil;

(8) airing the brain: cutting off the brain head and brain foot of the dried brain, collecting brain blocks remained in the crystallization barrel, placing the dried brain on a brain airing table for airing the brain to obtain the high-purity menthol, and filtering after melting the brain head, brain foot and brain blocks to obtain the molten oil.

2. The method for preparing high-purity menthol according to claim 1, wherein the crude menthol oil in step (1) is allowed to stand in a standing tank at 40-60 ℃ for 24 hours or more before primary freezeout, and then primary freezeout is performed after water and impurities at the bottom of the tank are removed.

3. The preparation method of high-purity menthol according to claim 1 or 2, wherein the raw material in the primary freeze-out in the step (1) is a mixture of crude peppermint oil and ice oil, and the amount of the ice oil is 0-30% of the total mass of the raw material; the leaching amount of the second oil in the primary freeze-out is 40-50% of the total mass of the raw materials; the temperature of the cooling saline water during primary freeze-out is set to be-24 to-26 ℃, and the final oil temperature is controlled to be-4 to-10 ℃; the time from the beginning of cooling to the end of primary freeze-out is 21-27 h.

4. The method for preparing high-purity menthol according to claim 1, wherein the raw material for the second freeze-out in step (2) is a mixture of two oils and ice oil, and the mass ratio of the two oils to the ice oil is 1: (1-1.5); the leaching amount of the hair oil in the secondary freeze-out is 50-60% of the total mass of the two oils and the ice oil; the temperature of the cooling saline water during the secondary freeze-out is set to be-32 to-35 ℃, and the final oil temperature is controlled to be-21 to-26 ℃; and (4) from the beginning of cooling to the end of secondary freeze-out, wherein the time is 46-60 h.

5. The method for preparing high-purity menthol according to claim 1, wherein the recovery method in the step (3) comprises the following steps: adding the raw materials into the hair oil according to the mass ratio of 1: (7-10) stirring and reacting sodium borohydride at 55-65 ℃ for 3-5 h; then adding the mixture of the raw materials and the hair oil in a mass ratio of 1: (10-15) stirring and reacting the acetic anhydride for 12-24 hours; distilling the volatile component under reduced pressure, and collecting the rest part to obtain naphtha; adding sodium hydroxide into naphtha to enable the concentration of the sodium hydroxide to be 0.5-1 mol/L, stirring and reacting for 2-3 h, then distilling, and collecting distilled components to obtain the recovered naphtha.

6. The method for preparing high-purity menthol according to claim 1, wherein the temperature in the dehydration tank is 88 to 92 ℃ during dehydration in the step (4), the vacuum degree is-0.08 to-0.085 Mpa, and the dehydration time is 25 to 35 min.

7. The preparation method of high-purity menthol according to claim 1, wherein the material oil prepared by the blending in the step (5) comprises the following materials in parts by weight: 15-20 parts of primary naphtha, 8-12 parts of secondary naphtha, 5-10 parts of recovered naphtha, 5-8 parts of dried naphtha and 1-3 parts of melted oil.

8. The preparation method of high-purity menthol according to claim 1, wherein the temperature of the cooling saline during crystallization in the step (6) is-3 to-8 ℃, and the crystallization time is 14 to 16 days.

9. The preparation method of high-purity menthol according to claim 1, wherein the time of each shift in the process of drying menthol in step (7) is 8-10 h, the indoor temperature of the first shift is room temperature-38 ℃, and the temperature in the crystallization barrel is 10-18 ℃; the indoor temperature of the second shift is 38-40 ℃, and the temperature in the crystallization barrel is 15-28 ℃; the indoor temperature of the third shift is 40-42 ℃, and the temperature in the crystallization barrel is 24-37 ℃; the indoor temperature of the fourth shift is 40-43 ℃, and the temperature in the crystallization barrel is 36-39 ℃; the indoor temperature of the fifth shift is 40-44 ℃, and the internal temperature of the crystallization barrel is 39-40.5 ℃.

10. The preparation method of high-purity menthol according to claim 1, wherein the temperature of the environment is 18-26 ℃, the humidity is 45-65% RH, and the time for airing the menthol in the step (8) is 22-26 h.

Technical Field

The invention relates to the technical field of menthol production, in particular to a preparation method of high-purity menthol.

Background

Menthol is a saturated cyclic alcohol obtained from oleum Menthae Dementholatum, has effects of dispelling pathogenic wind, clearing heat, and removing toxic substance, and can be used for treating headache, conjunctival congestion, affection of exogenous wind-heat, sore throat, swelling and pain of teeth, headache, aphtha, rubella, measles, chest and abdomen distention, and early pregnancy. Has antiinflammatory and analgesic effects, can be used as irritant, acts on skin or mucous membrane, has refreshing and antipruritic effects, and can be used for preparing cooling oil, analgesic, and toothpaste.

The traditional menthol production process is generally obtained by separating and purifying raw peppermint oil, for example, the publication of "a process for producing menthol and peppermint oil" in Chinese patent literature has a publication number of CN102775277B, wherein mint powder or peppermint oil is used as a production raw material, and the raw material is liquefied in a drying room to form raw peppermint oil; pumping the liquefied mint raw oil into a dehydration tank for dehydration; entering a blending kettle, and adjusting to contain 87.5-88.5% of L-cerebrum; entering a filter press to filter impurities; throwing into a crystallization warehouse for crystallization; separating out semi-finished menthol and ice oil; drying the semi-finished menthol, cooling the menthol and packaging to obtain the finished menthol; separating out the wool oil by freezing out the ice oil; dehydrating the crude oil, distilling in a distillation still to separate out the peppermint oil and the residue, and filtering impurities in the peppermint oil in a filter press to obtain the peppermint oil.

But the menthol obtained by the traditional production process has more impurities and the purity is difficult to ensure; in addition, the menthol in the wool oil is wasted more in the production process, and the yield of the menthol is limited.

Disclosure of Invention

The invention aims to overcome the defects that the traditional menthol production process has more impurities and the purity is difficult to ensure; and the menthol in the crude oil is extracted in the preparation process and then crystallized together with the primary naphtha and the secondary naphtha, so that the waste of the menthol in the preparation process is reduced, and the yield and the purity of the menthol are improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of high-purity menthol comprises the following steps:

(1) primary freeze-out: performing primary freezeout on the mint crude oil to obtain a primary camphor and a secondary oil;

(2) and (3) secondary freezing out: performing secondary freeze-out on the second oil to obtain second cerebrum and plain oil;

(3) naphtha recovery: re-extracting menthol in the wool oil to obtain recovered naphtha;

(4) dewatering and filtering: melting the primary naphtha and the secondary naphtha into primary naphtha and secondary naphtha, and carrying out vacuum dehydration on the primary naphtha, the secondary naphtha and the recovered naphtha in a dehydration tank and filtering;

(5) preparing materials to obtain material oil;

(6) and (3) crystallization: crystallizing the material oil in a crystallizing barrel to obtain wet brain;

(7) baking the brain: placing the wet brain in a crystallization barrel for drying the brain in five shifts to obtain dried brain, filtering the oil drained from the first shift, collecting the oil to obtain ice oil, filtering the oil drained from each shift, and collecting the oil to obtain dried brain oil;

(8) airing the brain: cutting off the brain head and brain foot of the dried brain, collecting brain blocks remained in the crystallization barrel, placing the dried brain on a brain airing table for airing the brain to obtain the high-purity menthol, and filtering after melting the brain head, brain foot and brain blocks to obtain the molten oil.

Preferably, the peppermint crude oil in the step (1) is stood in a standing tank for more than 24 hours at 40-60 ℃ before primary freezeout, and then primary freezeout is carried out after water and impurities at the bottom of the tank are discharged.

Preferably, the raw material in the primary freeze-out in the step (1) is a mixture of peppermint crude oil and ice oil, and the amount of the ice oil is 0-30% of the total mass of the raw material; the leaching amount of the second oil in the primary freeze-out is 40-50% of the total mass of the raw materials; the temperature of the cooling salt water during the primary freeze-out is set to be-24 to-26 ℃, and the final oil temperature is controlled to be-4 to-10 ℃. The time from the beginning of cooling to the end of primary freeze-out is 21-27 h.

Preferably, the raw material for the second freeze-out in the step (2) is a mixture of the second oil and the ice oil, and the mass ratio of the second oil to the ice oil is 1: (1-1.5); the leaching amount of the hair oil in the secondary freeze-out is 50-60% of the total mass of the two oils and the ice oil; the temperature of the cooling salt water during the secondary freezing-out is set to be-32 to-35 ℃, and the final oil temperature is controlled to be-21 to-26 ℃. And (4) from the beginning of cooling to the end of secondary freeze-out, wherein the time is 46-60 h.

Preferably, the recovery method in step (3) is: adding the raw materials into the hair oil according to the mass ratio of 1: (7-10) stirring and reacting sodium borohydride at 55-65 ℃ for 3-5 h; then adding the mixture of the raw materials and the hair oil in a mass ratio of 1: (10-15) stirring and reacting the acetic anhydride for 12-24 hours; distilling the volatile component under reduced pressure, and collecting the rest part to obtain naphtha; adding sodium hydroxide into naphtha to enable the concentration of the sodium hydroxide to be 0.5-1 mol/L, stirring and reacting for 2-3 h, then distilling, and collecting distilled components to obtain the recovered naphtha.

Preferably, the temperature in the dehydration tank is 88-92 ℃ during dehydration in the step (4), the vacuum degree is-0.08-0.085 Mpa, and the dehydration time is 25-35 min.

Preferably, when the materials are mixed in the step (5), the use amounts of the materials in parts by weight in the material oil mixed in the step (5) are as follows: 15-20 parts of primary naphtha, 8-12 parts of secondary naphtha, 5-10 parts of recovered naphtha, 5-8 parts of dried naphtha and 1-3 parts of melted oil.

Preferably, the temperature of the cooling brine in the crystallization in the step (6) is-3 to-8 ℃, and the crystallization time is 14 to 16 d.

Preferably, in the step (7), the time of each shift in the brain drying process is 8-10 hours, the indoor temperature of the first shift is room temperature-38 ℃, and the temperature in the crystallization barrel is 10-18 ℃; the indoor temperature of the second shift is 38-40 ℃, and the temperature in the crystallization barrel is 15-28 ℃; the indoor temperature of the third shift is 40-42 ℃, and the temperature in the crystallization barrel is 24-37 ℃; the indoor temperature of the fourth shift is 40-43 ℃, and the temperature in the crystallization barrel is 36-39 ℃; the indoor temperature of the fifth shift is 40-44 ℃, and the internal temperature of the crystallization barrel is 39-40.5 ℃.

Preferably, the environment temperature is 18-26 ℃ and the humidity is 45-65% RH when the brain is dried in the step (8), and the brain drying time is 22-26 h.

The method comprises the steps of performing two times of freezeout, gradually separating menthol from peppermint crude oil and ice oil generated in the previous secondary production process, then recovering the menthol remained in the crude oil obtained by the secondary freezeout, dehydrating and filtering the separated primary naphtha, secondary naphtha and recovered naphtha, mixing the dehydrated and filtered primary naphtha, secondary naphtha and recovered naphtha with intermediate products which are obtained in the previous secondary production process and have more impurities and insufficient purity, and crystallizing, drying and airing the mixed material oil together to obtain the high-purity menthol.

In the preparation process, the intermediate product is reasonably utilized, and when the menthol in the wool oil is recovered, sodium borohydride is added firstly to reduce the menthone in the wool oil into menthol (namely the menthol), so that the content of the menthol in the wool oil is improved; then adding acetic anhydride to make acetic anhydride and menthol produce esterification reaction to produce menthyl acetate which is difficult to volatilize, removing volatile component by reduced pressure distillation, adding sodium hydroxide to make residual menthyl acetate hydrolyze, and distilling to obtain menthol. The method has the advantages that raw materials such as the wool oil, the ice oil, the oven oil and the molten oil are recycled, particularly, the menthol in the wool oil with more impurity content is extracted and utilized, the loss of the menthol can be greatly reduced, and the extraction rate is improved.

Meanwhile, the recycled intermediate products and the naphtha obtained after twice freeze-out are mixed and then crystallized, so that the purity of the finally obtained menthol can be ensured, and the product quality is improved. The parameters of each process are strictly controlled in the production process, and the leaching amount of the second oil and the plain oil is controlled during primary and secondary freeze-out, so that impurities are prevented from remaining in the first naphtha and the second naphtha, the purity of the first naphtha and the second naphtha is improved, and subsequent batching is facilitated; during the material preparation, the use amount of each material component is adjusted, so that the purity of the mixed material oil can obtain high-purity menthol after crystallization, and an intermediate product with lower purity can be fully utilized, so that the loss of the menthol is reduced; the temperature and the time of crystallization and drying are strictly controlled in the crystallization and drying processes, the purity of crystals is ensured, and finally the obtained menthol crystal has high purity, good quality and high extraction rate.

Therefore, the invention has the following beneficial effects:

(1) the raw materials such as the wool oil, the ice oil, the drying oil, the molten oil and the like are recycled, and particularly, the menthol in the wool oil with more impurity content is extracted and utilized, so that the loss of the menthol can be greatly reduced, and the extraction rate is improved;

(2) the recovered intermediate products and the naphtha obtained after twice freeze-out are mixed and then crystallized, and parameters of each process in the production process are strictly controlled, so that the purity of the finally obtained menthol can be ensured, and the product quality is improved.

Detailed Description

The invention is further described with reference to specific embodiments.