CN111004093A - Method for purifying menthol - Google Patents
Method for purifying menthol Download PDFInfo
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- CN111004093A CN111004093A CN201911109756.9A CN201911109756A CN111004093A CN 111004093 A CN111004093 A CN 111004093A CN 201911109756 A CN201911109756 A CN 201911109756A CN 111004093 A CN111004093 A CN 111004093A
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- NOOLISFMXDJSKH-UHFFFAOYSA-N DL-menthol Natural products CC(C)C1CCC(C)CC1O NOOLISFMXDJSKH-UHFFFAOYSA-N 0.000 title claims abstract description 82
- 229940041616 menthol Drugs 0.000 title claims abstract description 81
- 238000000034 method Methods 0.000 title claims abstract description 36
- NOOLISFMXDJSKH-UTLUCORTSA-N (+)-Neomenthol Chemical compound CC(C)[C@@H]1CC[C@@H](C)C[C@@H]1O NOOLISFMXDJSKH-UTLUCORTSA-N 0.000 title claims 9
- 239000002131 composite material Substances 0.000 claims abstract description 73
- 239000013078 crystal Substances 0.000 claims abstract description 50
- 239000002994 raw material Substances 0.000 claims abstract description 40
- 239000002904 solvent Substances 0.000 claims abstract description 27
- 238000002425 crystallisation Methods 0.000 claims abstract description 18
- 230000008025 crystallization Effects 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims description 55
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 30
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 30
- 230000002378 acidificating effect Effects 0.000 claims description 21
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 18
- 238000001914 filtration Methods 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 12
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 claims description 11
- 239000001768 carboxy methyl cellulose Substances 0.000 claims description 11
- 238000002156 mixing Methods 0.000 claims description 11
- 235000019812 sodium carboxymethyl cellulose Nutrition 0.000 claims description 11
- 229920001027 sodium carboxymethylcellulose Polymers 0.000 claims description 11
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 9
- 239000003795 chemical substances by application Substances 0.000 claims 1
- NOOLISFMXDJSKH-KXUCPTDWSA-N (-)-Menthol Chemical compound CC(C)[C@@H]1CC[C@@H](C)C[C@H]1O NOOLISFMXDJSKH-KXUCPTDWSA-N 0.000 abstract description 80
- 230000003287 optical effect Effects 0.000 abstract description 9
- 238000000746 purification Methods 0.000 abstract description 7
- 230000006911 nucleation Effects 0.000 abstract description 4
- 238000010899 nucleation Methods 0.000 abstract description 4
- 238000009210 therapy by ultrasound Methods 0.000 abstract description 3
- 239000000203 mixture Substances 0.000 description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 238000001514 detection method Methods 0.000 description 4
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- 235000006679 Mentha X verticillata Nutrition 0.000 description 3
- 235000002899 Mentha suaveolens Nutrition 0.000 description 3
- 235000001636 Mentha x rotundifolia Nutrition 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008014 freezing Effects 0.000 description 2
- 238000007710 freezing Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- OHVLMTFVQDZYHP-UHFFFAOYSA-N 1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-2-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound N1N=NC=2CN(CCC=21)C(CN1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)=O OHVLMTFVQDZYHP-UHFFFAOYSA-N 0.000 description 1
- LDXJRKWFNNFDSA-UHFFFAOYSA-N 2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound C1CN(CC2=NNN=C21)CC(=O)N3CCN(CC3)C4=CN=C(N=C4)NCC5=CC(=CC=C5)OC(F)(F)F LDXJRKWFNNFDSA-UHFFFAOYSA-N 0.000 description 1
- YLZOPXRUQYQQID-UHFFFAOYSA-N 3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-1-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]propan-1-one Chemical compound N1N=NC=2CN(CCC=21)CCC(=O)N1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F YLZOPXRUQYQQID-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 1
- 229940057995 liquid paraffin Drugs 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000711 polarimetry Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000341 volatile oil Substances 0.000 description 1
- 239000008782 xin-kang Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
- C07C29/78—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by condensation or crystallisation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
- C07B2200/00—Indexing scheme relating to specific properties of organic compounds
- C07B2200/13—Crystalline forms, e.g. polymorphs
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2601/00—Systems containing only non-condensed rings
- C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
- C07C2601/14—The ring being saturated
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention belongs to the technical field of menthol purification, and particularly relates to a method for purifying menthol, which comprises the steps of preparing a composite solution by using a composite solvent and a menthol raw material, and assisting ultrasonic treatment in a crystallization process; the purification degree of the menthol is improved by a plurality of crystallization processes. Compared with the prior art, the invention has the following advantages: by reasonably preparing the solvent and matching with the action of the ultrasonic generator, the properties of a crystal growth interface can be influenced, the size and the structural form of a growth element of the crystal can be effectively controlled, the nucleation time can be further shortened, the purity of the menthol crystal is improved, the optical rotation is improved, and the content of the L-menthol crystal is improved, and the quality of the menthol crystal is greatly improved.
Description
Technical Field
The invention belongs to the technical field of menthol purification, and particularly relates to a method for purifying menthol.
Background
The menthol is colorless transparent crystal or crystalline powder, contains menthol as main chemical component, has melting point of 41-44 deg.C, is extracted from leaf and stem of herba Menthae, is easily volatile, and is easily dissolved in ethanol, chloroform, diethyl ether, liquid paraffin or volatile oil; china is a main natural mint producing country, the annual output of the mint oil reaches 2000-3000t, and the application is wide; the purity of the commercially available menthol is about 95%, and the quality of the menthol can be influenced by trace impurities; therefore, the menthol needs to be further purified, the prior art adopts a freezing crystallization technology to purify the menthol, the cooling speed needs to be controlled in the cooling crystallization process, and the mint oil can be condensed and not crystallized when the cooling is too fast; therefore, how to improve the purity of menthol while shortening the crystallization time is a problem to be further studied.
Disclosure of Invention
The invention aims to provide a method for purifying menthol, aiming at solving the problem of complexity of the existing freezing and crystallizing technology.
In order to solve the problems, the invention prepares the composite solution by using the composite solvent and the menthol raw material, heats the composite solution to dissolve the menthol raw material, and adjusts the pH value of the composite solution, thereby being beneficial to leading the composite solution to reach a supersaturated state; the ultrasonic generator is reasonably arranged, so that the molecular motion in the solution is accelerated, and the rapid formation of crystal nuclei can be facilitated; the sodium carboxymethyl cellulose has certain viscosity, and can prevent coarse crystals caused by too fast molecular motion in a solution in the treatment process of an ultrasonic generator; the menthol crystals in the invention can be separated out at a temperature above zero, which is beneficial to effective purification of the menthol.
The invention is realized by the following technical scheme: a method for purifying menthol, which is used for purifying a menthol raw material with the purity of 95-98 percent, comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 26-30 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.25-0.35g/mL, adjusting the pH value of the composite solution to 5.6-6.0 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 18-24 parts of dimethylformamide, 4-6 parts of ethyl acetate and 0.8-1.6 parts of sodium carboxymethylcellulose; at least two ultrasonic generators are arranged outside the crystallizer, the ultrasonic generators are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 300-;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 2-4 ℃/min, cooling to 6-8 ℃, preserving the temperature, filtering and distilling the separated crystals after crystals are not increased any more to obtain the purified menthol.
Further, the pH value of the acidic composite solution is 5.7.
Further, the plurality of ultrasonic generators are controlled by the control device to synchronously operate; the ultrasonic generator is arranged close to the upper position of the outer wall of the crystallizer and can uniformly and effectively act on crystals.
Compared with the prior art, the invention has the following advantages: by reasonably preparing the solvent and matching with the action of the ultrasonic generator, the properties of a crystal growth interface can be influenced, the size and the structural form of a growth element of the crystal can be effectively controlled, the nucleation time can be further shortened, the purity of the menthol crystal is improved, the optical rotation is improved, and the content of the L-menthol crystal is improved, and the quality of the menthol crystal is greatly improved.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The menthol raw material used in the examples is provided by Wuhan Xinkang fine chemical Co., Ltd, and the menthol content in the menthol raw material is 98%; detecting according to a method for detecting the purity and recovery rate of the menthol crystals in Chinese pharmacopoeia, detecting the mass of the L-menthol according to GC-MS analysis conditions, and calculating to obtain the purity of the menthol crystals; performing optical rotation measurement on the solvent crystal of the sample by using a WZZ-2SS automatic polarimeter; dissolving a purified menthol sample with 75% ethanol, standing for 15 minutes, detecting in a polarimeter, repeatedly detecting each sample for three times, and then taking an average value, wherein the wavelength of a light source sodium light is 589nm during detection, the temperature during detection is 25 ℃, the length of a detection tube is 2dm, and the concentration of a solution is 0.02 g/mL;
specifically, the purity of menthol = (mass of L-menthol/mass of raw material) × 100%;
the formula for calculating the optical rotation is:
wherein α is the reading of the polarimeter during measurement, t is the temperature during measurement, D is the wavelength of the light source, C is the concentration of the solution, and L is the length of the measuring tube.
Example 1
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.3g/mL, adjusting the pH value of the composite solution to 5.8 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide, 5 parts of ethyl acetate and 1.2 parts of sodium carboxymethylcellulose; three ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 400W;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 3 ℃/min, cooling to 7 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Detection shows that the time for generating crystal nuclei in the step (2.2) is about 2 hours, and the detected optical rotation is-48.69 +/-0.13 degrees; the optical rotation is in positive correlation with the content of L-menthol, and the optical rotation is higher than that of the prior art
Example 2
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 26 ℃ to dissolve the mixture to obtain a composite solution with the menthol raw material concentration of 0.25g/mL, adjusting the pH value of the composite solution to 5.6 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 24 parts of dimethylformamide, 4 parts of ethyl acetate and 1.6 parts of sodium carboxymethylcellulose; two ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 500W;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 2 ℃/min, cooling to 8 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Example 3
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 26-30 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.25-0.35g/mL, adjusting the pH value of the composite solution to 5.6-6.0 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 18 parts of dimethylformamide, 6 parts of ethyl acetate and 0.8 part of sodium carboxymethylcellulose; three ultrasonic generators are arranged outside the crystallizer, and the ultrasonic power of the ultrasonic generators is 300W and can be continuously adjusted;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 4 ℃/min, cooling to 6 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Example 4
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the menthol raw material concentration of 0.32g/mL, adjusting the pH value of the composite solution to 5.7 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide, 5 parts of ethyl acetate and 1.2 parts of sodium carboxymethylcellulose; three ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 400W;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 3 ℃/min, cooling to 7 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Control group 1
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the menthol raw material concentration of 0.3g/mL, and adding the composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide, 5 parts of ethyl acetate and 1.2 parts of sodium carboxymethylcellulose; three ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 400W;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 3 ℃/min, cooling to 7 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Control group 2
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.3g/mL, adjusting the pH value of the composite solution to 5.8 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide and 6 parts of ethyl acetate; three ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 400W;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 3 ℃/min, cooling to 7 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Control group 3
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.3g/mL, adjusting the pH value of the composite solution to 5.8 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide, 5 parts of ethyl acetate and 1.2 parts of sodium carboxymethylcellulose; three ultrasonic generators are arranged outside the crystallizer and are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 400W;
(2) the crystallization process is divided into three stages
(2.1) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.2) controlling the cooling speed to be 3 ℃/min, cooling to 7 ℃, preserving the temperature, filtering and distilling the separated crystals after the separated crystals are not increased any more, and obtaining the purified menthol.
Control group 4
A method for purifying menthol comprises the following steps:
(1) mixing a composite solvent and a menthol raw material, heating to 28 ℃ to dissolve the mixture to obtain a composite solution with the concentration of the menthol raw material of 0.3g/mL, adjusting the pH value of the composite solution to 5.8 by using sodium carbonate to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 21 parts of dimethylformamide, 5 parts of ethyl acetate and 1.2 parts of sodium carboxymethylcellulose;
(2) filtering the obtained acidic composite solution with a filter press to remove impurities, adding into a crystallization tank, crystallizing at 5 deg.C to separate out crystals which are not increased, and filtering and distilling to obtain purified menthol.
Control group 5
A method for purifying menthol comprises the following steps:
(1) mixing an ethanol solution with the mass concentration of 75% and a menthol raw material to prepare a composite solution, heating to 28 ℃ to dissolve the composite solution to obtain the composite solution with the concentration of the menthol raw material of 0.3 g/mL;
(2) filtering the obtained composite solution with a filter press, adding into a crystallization warehouse, crystallizing at-8 deg.C to obtain crystals which are not increased, filtering, and distilling to obtain purified Mentholum.
The nucleation time, menthol purity and optical rotation of each group were measured and observed according to the method described above, and the following data were obtained:
TABLE 1
| Group of | Time to nucleation (h) | Menthol purity (%) | Degree of optical rotation (°) |
| Example 1 | 2 | 99.46 | -49.05 |
| Example 2 | 2 | 99.51 | -49.01 |
| Example 3 | 2 | 99.47 | -49.04 |
| Example 4 | 2 | 99.65 | -49.22 |
| Control group 1 | 5 | 99.39 | -48.67 |
| Control group 2 | 2 | 97.26 | -45.21 |
| Control group 3 | 1.5 | 98.24 | -45.36 |
| Control group 4 | 20 | 98.95 | -45.73 |
| Control group 5 | 28 | 99.02 | -46.18 |
As can be seen from the data in Table 1, the composite solvent can ensure that the crystallization can be realized at a temperature above zero, and the setting of the control group 1 shows that the adjustment of the pH value of the composite solvent has certain influence on the time of crystal nucleus generation, but has little influence on the purification performance; as can be seen from the arrangement of the control group 2, the sodium carboxymethyl cellulose affects the crystal structure and further affects the optical rotation; the control group 3 shows that the early ultrasonic treatment can help to precipitate crystal nuclei earlier, but can affect the purity of the menthol; the arrangement of the control group 4 shows that the ultrasonic treatment can help to shorten the crystallization time and has certain influence on the purification of the menthol crystal; the control group 5 can be basically regarded as the prior purification technology, crystals can be separated out only when the temperature is below zero, the menthol can be further purified, but the time is long; in the actual production, corresponding adjustment can be carried out according to the actual production conditions and requirements.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (6)
1. A method for purifying menthol is used for purifying a menthol raw material with the purity of 95-98 percent, and is characterized by comprising the following steps:
(1) mixing a composite solvent and a menthol raw material, heating and dissolving to obtain a composite solution with the concentration of the menthol raw material of 0.25-0.35g/mL, adjusting the pH value of the composite solution to 5.6-6.0 to obtain an acidic composite solution, and adding the acidic composite solution into a crystallizer for later use; the composite solvent comprises the following raw materials in parts by weight: 18-24 parts of dimethylformamide, 4-6 parts of ethyl acetate and 0.8-1.6 parts of sodium carboxymethylcellulose; at least two ultrasonic generators are arranged outside the crystallizer, the ultrasonic generators are uniformly distributed on the same horizontal height, and the ultrasonic power of the ultrasonic generators is continuously adjustable at 300-;
(2) the crystallization process is divided into three stages
(2.1) controlling the cooling speed to be 1 ℃/min, and cooling to 24 ℃;
(2.2) starting the ultrasonic generator, controlling the cooling speed to be 0.5 ℃/min, cooling to 20 ℃, preserving heat, and closing the ultrasonic generator after crystal nuclei appear;
(2.3) controlling the cooling speed to be 2-4 ℃/min, cooling to 6-8 ℃, preserving the temperature, filtering and distilling the separated crystals after crystals are not increased any more to obtain the purified menthol.
2. The method of claim 1, wherein the temperature for heating to dissolve menthol is 26-30 ℃.
3. The method of claim 1, wherein the agent used to adjust the pH is sodium carbonate.
4. The method of claim 1, wherein the pH of the acidic complex solution is 5.7.
5. The method for purifying menthol according to claim 1, wherein the plurality of ultrasonic generators are controlled by the control device to operate synchronously.
6. The method for purifying menthol according to claim 1, wherein the ultrasonic generator is installed at an upper position of the outer wall of the crystallizer.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101265162A (en) * | 2007-03-16 | 2008-09-17 | 高砂香料工业株式会社 | Process for purifying menthol |
| CN106542966A (en) * | 2016-10-12 | 2017-03-29 | 安徽丰乐香料有限责任公司 | A kind of industrial crystallization method of synthesis L Mentholums |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101265162A (en) * | 2007-03-16 | 2008-09-17 | 高砂香料工业株式会社 | Process for purifying menthol |
| CN106542966A (en) * | 2016-10-12 | 2017-03-29 | 安徽丰乐香料有限责任公司 | A kind of industrial crystallization method of synthesis L Mentholums |
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