A method for extracting peppermint oil

Abstract

The application discloses a kind of extraction methods for peppermint oil, belong to the technical field of peppermint oil production, for solving the phase separation of the extraction process of peppermint oil in prior art in complex emulsion system, and the targeting recognition accuracy of separation carrier under the interference of strong impurities is further improved, specific steps include the following: dry peppermint leaf is crushed to 40-60 mesh, and immersed with deionized water according to the impregnation ratio 1:25-30 for 1-2h, suction filtration, filter cake is distilled with deionized water for 2-3h, and oil-water mixed emulsion is extracted.The application is to construct a grafted menthol imprinted layer of magnetic mesoporous silica filler, added to the pretreated emulsion, low-loss desorption is realized by acid-base microenvironment regulation, and the extraction efficiency and purity of peppermint oil in complex system are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of peppermint oil production technology, and more specifically to a method for extracting peppermint oil. Background Technology

[0002] Peppermint oil, a natural plant essential oil with extremely high economic value, is widely used in medicine, food, and daily chemical industries. Early extraction methods mainly relied on traditional steam distillation and organic solvent extraction. Although these methods initially achieved the enrichment of peppermint oil, the volatility and heat sensitivity of essential oil components often resulted in the loss of effective components and high energy consumption. In recent years, with the development of chemical separation technology, new processes such as supercritical fluid extraction and microwave-assisted extraction have emerged, which have improved the overall crude extraction yield to a certain extent. However, regardless of the pretreatment process used, peppermint oil often coexists with water, plant lipids, and colloidal impurities in the extract, forming an extremely complex and stable oil-water emulsion system. Therefore, how to achieve efficient phase separation and high-purity enrichment of target components in such a complex system has become a bottleneck restricting the further improvement of peppermint oil extraction process performance.

[0003] To overcome the separation barriers posed by the emulsion system, porous adsorption materials are often introduced as solid-phase extraction carriers. Commonly used materials include macroporous resins, conventional silica gel, activated carbon, and zeolite molecular sieves, which promote the enrichment of essential oil components on the carrier surface. Although these conventional hydrophobically modified carriers can improve the adsorption capacity of lipid-soluble substances to some extent, their adsorption mechanism is limited to non-specific hydrophobic interactions or simple pore size sieving. When faced with complex mixtures containing a large number of terpene homologues with similar polarity and molecular size, as well as other plant impurities, these traditional materials have extremely poor targeting selectivity and are prone to severe competitive adsorption, making it difficult for the purity of the final extract to meet high industrial standards.

[0004] Currently, traditional modified materials lack specific binding domains on their surfaces that are highly matched with the target peppermint oil molecules in terms of spatial conformation and hydrogen bonding sites. This makes it impossible to accurately extract the target components in the context of strong impurities. Furthermore, phase separation in complex emulsion systems is difficult, and conventional powders or porous fillers are prone to agglomeration and pore blockage in viscous emulsions, making it difficult to achieve low-loss extraction of peppermint oil.

[0005] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems in the existing peppermint oil extraction process, such as phase separation in complex emulsion systems and the need to further improve the targeting accuracy of the separation carrier under strong impurity interference.

[0007] The objective of this invention can be achieved through the following technical solution: a method for extracting peppermint oil, comprising the following steps:

[0008] S1. Crush dried peppermint leaves to 40-60 mesh, soak them in deionized water at a soaking ratio of 1:25-30 for 1-2 hours, filter them, and steam distill the filter cake with deionized water for 2-3 hours to extract an oil-water emulsion.

[0009] S2. Add the oil-water emulsion to the reaction vessel and stir. Add sodium chloride and stir for 0.5-1 h. Let it stand and separate into layers. Take the upper layer of crude peppermint oil and magnetic composite filler and place them in the reaction vessel and stir. Add citric acid-sodium citrate buffer solution to adjust the pH to 5.5-6.5. Shake and adsorb for 1-2 h. Post-process to obtain peppermint oil-supported composite filler.

[0010] S3. Peppermint oil-supported composite filler, sodium bicarbonate aqueous solution and ethanol are placed in a reaction vessel and shaken at room temperature for 0.5-1h to desorb, and then processed to obtain peppermint oil.

[0011] Furthermore, in step S1, the moisture content of the dried mint leaves is 5-10%, the ratio of dried mint leaves to deionized water is 1g:8-12mL, the temperature of steam distillation is 95-100℃, and the distillation pressure is 0.10-0.12MPa.

[0012] Furthermore, in step S2, the ratio of the crude oil-water mixed emulsion, sodium chloride, and magnetic composite packing is 80-100mL:0.5-1.0g:2-4g, the pH of the citric acid-sodium citrate buffer solution is 5.2, and the post-treatment step includes: after adsorption, placing a magnetic separation device on the outer wall of the reaction vessel to separate and discard the supernatant to obtain peppermint oil-loaded composite packing.

[0013] Further, in step S3, the ratio of the peppermint oil-supported composite filler, sodium bicarbonate aqueous solution, and ethanol is 1-2g:15-25mL:3-8mL, the concentration of the sodium bicarbonate aqueous solution is 0.3-0.5mol / L, and the post-processing steps include: after desorption, placing a magnetic separation device on the outer wall of the reaction vessel to separate and recover the desorbed solution loaded with peppermint oil, extracting the recovered mixed solution with ethyl acetate 2-4 times, and removing the ethyl acetate from the organic phase by rotary evaporation to obtain peppermint oil.

[0014] Furthermore, the magnetic composite filler is prepared by the following steps:

[0015] A1. Magnetic responsive mesoporous silica nanoparticles and toluene were placed in a reaction vessel under nitrogen atmosphere and stirred. 3-(methacryloyloxy)propyltrimethoxysilane was added. The reaction vessel was heated to 105-115℃ and kept at the temperature for 20-24h. After post-treatment, olefin-modified magnetic nanofillers were obtained.

[0016] A2. Menthol, methacrylic acid and 4-vinylpyridine were placed in a reaction vessel under nitrogen atmosphere and stirred. Olefin-modified magnetic nanofiller was added and stirred at room temperature for 25-35 min. Ethylene glycol dimethacrylate and azobisisobutyronitrile were added. The reaction vessel was heated to 55-65℃ and kept at that temperature for 20-24 h. The magnetic composite filler was obtained after post-treatment.

[0017] Further, in step A1, the ratio of the magnetically responsive mesoporous silica nanoparticles, toluene, and 3-(methacryloyloxy)propyltrimethoxysilane is 1-2g:80-100mL:3-5g. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with toluene and ethanol, transferred to an oven at 40-50℃, and dried to constant weight to obtain modified magnetically responsive mesoporous silica nanoparticles.

[0018] Further, in step A2, the ratio of menthol, methacrylic acid, 4-vinylpyridine, acetonitrile, 4-vinylpyridine, acetonitrile, olefin-modified magnetic nanofiller, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 0.1-0.3g:0.8-1g:0.5-1g:60-80mL:1-2g:1-2g:0.03-0.05g. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with 4-vinylpyridine, the product is placed in a Soxhlet extractor, and a mixture of methanol and glacial acetic acid with a volume ratio of 9:1 is used as the eluent. The mixture is continuously extracted at 60-65℃ for 48h, and then transferred to an oven at 50-60℃ and dried for 6-8h to obtain the magnetic composite filler.

[0019] Furthermore, the magnetically responsive mesoporous silica nanoparticles are prepared by the following steps:

[0020] B1. Place deionized water, ferric chloride hexahydrate and ferrous chloride tetrahydrate in a three-necked flask under nitrogen atmosphere and stir. Heat the three-necked flask to 75-85℃, keep it at the temperature and stir for 3-5 minutes. Add ammonia solution and keep it at the temperature for 1-2 hours. Post-treatment yields magnetic iron oxide nanoparticles.

[0021] B2. Magnetic iron oxide nanoparticles, deionized water and ethanol are placed in a reaction vessel and stirred. Cetyltrimethylammonium bromide is added. The reaction vessel is heated to 35-45℃. Ammonia solution is added. The mixture is kept warm and stirred for 5-10 min. Tetraethyl orthosilicate is added dropwise. The reaction is kept warm for 4-6 h. After post-treatment, magnetic core-shell particles are obtained.

[0022] B3. Place the magnetic core-shell particles, ethanol aqueous solution and dilute hydrochloric acid in a reaction vessel and stir. Heat the reaction vessel to 75-85℃ and keep it at that temperature for 10-12 hours. After post-treatment, obtain magnetically responsive mesoporous silica nanoparticles.

[0023] Further, in step B1, the ratio of deionized water, ferric chloride hexahydrate, ferrous chloride tetrahydrate, and ammonia solution is 350-450 mL: 10-12 g: 3-5 g: 35-45 mL, and the concentration of ammonia solution is 20-30 wt%. The post-processing steps include: after the reaction is completed, wait for the reaction system to cool to room temperature, place a strong magnet on the outer wall of the three-necked flask, and after the black particles are completely adsorbed onto the flask wall, pour out the supernatant, add 200 mL of deionized water to the three-necked flask, ultrasonically disperse for 10 min, and perform magnetic separation again with a magnet. Repeat this water washing step 3 times, add 200 mL of ethanol, and repeat the above magnetic separation washing step 2 times. Transfer the black solid product to a vacuum drying oven and vacuum dry at 50-60℃ for 10-12 h to obtain magnetic iron oxide nanoparticles.

[0024] Further, in step B2, the ratio of the magnetic iron oxide nanoparticles, deionized water, ethanol, hexadecyltrimethylammonium bromide, ammonia solution, and tetraethyl orthosilicate is 1-2g:35-45mL:150-250mL:0.5-1.5g:8-10mL:4-6g, and the concentration of the ammonia solution is 20-30wt%. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water and ethanol, transferred to a vacuum drying oven, and vacuum dried at 50-60℃ for 10-12h to obtain magnetic core-shell particles.

[0025] Further, in step B3, the ratio of the magnetic core-shell particles, the ethanol aqueous solution, and the dilute hydrochloric acid is 2-4g:140-160mL:1-2mL, the concentration of the ethanol aqueous solution is 95-98wt%, and the concentration of the dilute hydrochloric acid is 5-10wt%. The post-processing steps include: after the reaction is completed, the reaction system is cooled to room temperature, filtered, the filter cake is washed 2-4 times with deionized water and ethanol, transferred to a vacuum drying oven, and vacuum dried at 50-60℃ for 10-12h to obtain magnetically responsive mesoporous silica nanoparticles.

[0026] The present invention has the following beneficial effects:

[0027] 1. This invention establishes a synergistic mechanism for efficient mass transfer and rapid solid-liquid separation in complex liquid matrices based on the composite assembly of superparamagnetic iron oxide (Fe3O4) crystal nuclei and mesoporous silica shells. The dense mesoporous silica framework is in-situ coated on the surface of the magnetic nuclei, and the soft template agent is removed by acid extraction, exposing a regular pore network. This cross-linked silica shell effectively inhibits the dissolution and oxidation of the magnetic nuclei in complex emulsion extraction matrices, ensuring the physicochemical stability of the carrier in complex chemical environments. Simultaneously, the in-situ activated high specific surface area and large pore volume significantly broaden the internal mass transfer channels of the target molecules. This composite architecture not only establishes extremely rapid separation efficiency driven by an external magnetic field through superparamagnetic response, but also greatly simplifies the recovery process, increases the specific surface area of ​​traditional magnetic carriers, reduces mass transfer resistance, and enhances the loading capacity and interfacial mass transfer rate of peppermint oil.

[0028] 2. This invention also constructs a highly selective stereotargeting recognition matrix by covalently bridging the interface modification layer and the specific molecularly imprinted polymer network. It uses a silane coupling agent to anchor polymerizable double bonds on the surface of mesoporous silica, thereby guiding the functional monomers, crosslinking agents and menthol template pre-assemblies to undergo free radical graft copolymerization. Finally, in-situ demolding forms specific pores. The covalent modification tightly bridges the inorganic mesoporous framework and the organic crosslinked imprinted phase. Based on the template-guided synthesis, the pores construct a three-dimensional recognition microenvironment with a high degree of matching between spatial size and hydrogen bond sites. This composite modification not only inhibits the physical peeling and swelling of the adsorption layer under high-intensity fluid elution and establishes the long-term structural stability of the interface, but also endows the composite filler with the matching and enrichment of peppermint oil components in complex oil-water dispersion matrices, thereby improving the extraction efficiency of peppermint oil. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The menthol used in this invention was purchased from Wuxi Qianjuheng Trading Co., Ltd., with the product model BASF-L-Menthol, CAS number 2216-51-5, and brand name BASF.

[0031] Example 1

[0032] This embodiment provides a method for preparing magnetically responsive mesoporous silica nanoparticles, specifically including the following steps:

[0033] Step I: Preparation of magnetic iron oxide nanoparticles

[0034] Weigh out 3500 mL of deionized water, 100 g of ferric chloride hexahydrate, and 30 g of ferrous chloride tetrahydrate and place them in a three-necked flask under a nitrogen atmosphere. Stir the mixture and heat it to 75°C. Keep the mixture at this temperature and stir for 3 min. Add 350 mL of 20 wt% ammonia solution and keep the mixture at this temperature for 1 h. After the reaction is complete, let the reaction system cool to room temperature. Place a strong magnet on the outer wall of the three-necked flask. After the black particles are completely adsorbed onto the wall of the flask, pour out the supernatant. Add 2000 mL of deionized water to the three-necked flask and sonicate for 10 min. Perform magnetic separation again using a magnet. Repeat this water washing step 3 times. Add 2000 mL of ethanol and repeat the above magnetic separation washing step 2 times. Transfer the black solid product to a vacuum drying oven and vacuum dry it at 50°C for 10 h to obtain magnetic iron oxide nanoparticles.

[0035] Step II: Preparation of magnetic core-shell particles

[0036] Weigh 10g of magnetic iron oxide nanoparticles, 350mL of deionized water, and 1500mL of ethanol and place them in a reaction vessel. Stir, add 5g of hexadecyltrimethylammonium bromide, heat the reaction vessel to 35℃, add 80mL of 20wt% ammonia solution, keep warm and stir for 5min, add 40g of tetraethyl orthosilicate dropwise, keep warm and react for 4h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake twice with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry at 50℃ for 10h to obtain magnetic core-shell particles.

[0037] Step III: Preparation of magnetically responsive mesoporous silica nanoparticles

[0038] Weigh 20g of magnetic core-shell particles, 1400mL of 95wt% ethanol aqueous solution and 10mL of 5wt% dilute hydrochloric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 75℃ and keep it at that temperature for 10h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake twice with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry it at 50℃ for 10h to obtain magnetically responsive mesoporous silica nanoparticles.

[0039] Under a nitrogen atmosphere, ferric and ferrous salts undergo a co-precipitation reaction in an alkaline ammonia system to generate magnetically responsive iron(III) oxide nanocrystals. Further, using the cationic surfactant hexadecyltrimethylammonium bromide as a structure-directing agent and soft template, the precursor tetraethyl orthosilicate undergoes hydrolysis and condensation reactions under ammonia catalysis. It then co-assembles with hexadecyltrimethylammonium bromide micelles on the surface of the magnetic nuclei, forming template-containing magnetic core-shell particles. Finally, an acidic ethanol aqueous solution is used to disrupt the electrostatic interaction between the silicon-oxygen framework and the magnetic core-shell particles, removing the organic template agent from the pores and exposing the mesoporous structure, ultimately yielding magnetically responsive mesoporous silica nanoparticles.

[0040] The synthesis of iron oxide crystal nuclei endowed the adsorption matrix with superparamagnetism, established a rapid solid-liquid separation mechanism driven by an external magnetic field in the extraction system, simplified the carrier recovery process, and provided a highly cross-linked silicon-oxygen protective layer for the core-shell structure constructed by the hydrolysis and polycondensation of tetraethyl orthosilicate. This effectively inhibited the dissolution and oxidation of the magnetic nuclei in the complex extraction matrix, while also anchoring abundant reaction sites for the subsequent grafting of adsorption functional groups. The acidic extraction and removal of the organic template agent in situ activated the regular mesoporous network, endowing the material with high specific surface area and large pore volume, significantly broadening the spatial accommodation limit and internal mass transfer channels of peppermint oil molecules, and improving the loading capacity and mass transfer rate of peppermint oil.

[0041] Example 2

[0042] This embodiment provides a method for preparing magnetically responsive mesoporous silica nanoparticles, specifically including the following steps:

[0043] Step I: Preparation of magnetic iron oxide nanoparticles

[0044] Weigh out 4000 mL of deionized water, 110 g of ferric chloride hexahydrate, and 40 g of ferrous chloride tetrahydrate and place them in a three-necked flask under a nitrogen atmosphere. Stir the mixture and heat it to 80 °C. Keep the mixture at this temperature and stir for 4 min. Add 400 mL of 25 wt% ammonia solution and keep the mixture at this temperature for 1.5 h. After the reaction is complete, let the reaction system cool to room temperature. Place a strong magnet on the outer wall of the three-necked flask. After the black particles are completely adsorbed onto the wall of the flask, pour off the supernatant. Add 2000 mL of deionized water to the three-necked flask and sonicate for 10 min. Perform magnetic separation again using a magnet. Repeat this water washing step 3 times. Add 2000 mL of ethanol and repeat the above magnetic separation washing step 2 times. Transfer the black solid product to a vacuum drying oven and vacuum dry it at 55 °C for 11 h to obtain magnetic iron oxide nanoparticles.

[0045] Step II: Preparation of magnetic core-shell particles

[0046] Weigh 15g of magnetic iron oxide nanoparticles, 400mL of deionized water, and 2000mL of ethanol and place them in a reaction vessel. Stir, add 10g of hexadecyltrimethylammonium bromide, heat the reaction vessel to 40℃, add 90mL of 25wt% ammonia solution, keep warm and stir for 7min, add 50g of tetraethyl orthosilicate dropwise, keep warm and react for 5h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake three times with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry at 55℃ for 11h to obtain magnetic core-shell particles.

[0047] Step III: Preparation of magnetically responsive mesoporous silica nanoparticles

[0048] Weigh 30g of magnetic core-shell particles, 1500mL of 97wt% ethanol aqueous solution and 15mL of 7.5wt% dilute hydrochloric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 80℃ and keep it at that temperature for 11h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake three times with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry it at 55℃ for 11h to obtain magnetically responsive mesoporous silica nanoparticles.

[0049] Example 3

[0050] This embodiment provides a method for preparing magnetically responsive mesoporous silica nanoparticles, specifically including the following steps:

[0051] Step I: Preparation of magnetic iron oxide nanoparticles

[0052] Weigh out 4500 mL of deionized water, 120 g of ferric chloride hexahydrate, and 50 g of ferrous chloride tetrahydrate and place them in a three-necked flask under a nitrogen atmosphere. Stir the mixture and heat it to 85°C. Keep the mixture at this temperature and stir for 5 min. Add 450 mL of 30 wt% ammonia solution and keep the mixture at this temperature for 2 h. After the reaction is complete, let the reaction system cool to room temperature. Place a strong magnet on the outer wall of the three-necked flask. After the black particles are completely adsorbed onto the wall of the flask, pour off the supernatant. Add 2000 mL of deionized water to the three-necked flask and sonicate for 10 min. Perform magnetic separation again using a magnet. Repeat this water washing step 3 times. Add 2000 mL of ethanol and repeat the above magnetic separation washing step 2 times. Transfer the black solid product to a vacuum drying oven and vacuum dry it at 60°C for 12 h to obtain magnetic iron oxide nanoparticles.

[0053] Step II: Preparation of magnetic core-shell particles

[0054] Weigh 20g of magnetic iron oxide nanoparticles, 450mL of deionized water, and 2500mL of ethanol and place them in a reaction vessel. Stir, add 15g of hexadecyltrimethylammonium bromide, heat the reaction vessel to 45℃, add 100mL of 30wt% ammonia solution, keep the temperature and stir for 10min, add 60g of tetraethyl orthosilicate dropwise, keep the reaction temperature and react for 6h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake 4 times with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry at 60℃ for 12h to obtain magnetic core-shell particles.

[0055] Step III: Preparation of magnetically responsive mesoporous silica nanoparticles

[0056] Weigh 40g of magnetic core-shell particles, 1600mL of 98wt% ethanol aqueous solution and 20mL of 10wt% dilute hydrochloric acid and place them in a reaction vessel and stir. Heat the reaction vessel to 85℃ and keep it at that temperature for 12h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter it, wash the filter cake four times with deionized water and ethanol, transfer it to a vacuum drying oven, and vacuum dry it at 60℃ for 12h to obtain magnetically responsive mesoporous silica nanoparticles.

[0057] Example 4

[0058] This embodiment provides a method for extracting magnetic composite fillers, specifically including the following steps:

[0059] Step 1: Preparation of olefin-modified magnetic nanofillers

[0060] Weigh 10g of the magnetically responsive mesoporous silica nanoparticles prepared in Example 1 and 800mL of toluene and place them in a reaction vessel under a nitrogen atmosphere and stir. Add 30g of 3-(methacryloyloxy)propyltrimethoxysilane, heat the reaction vessel to 105℃, and keep it at this temperature for 20h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake twice with toluene and ethanol, transfer it to an oven at 40℃, and dry it to constant weight to obtain olefin-modified magnetic nanofiller.

[0061] Step 2: Preparation of magnetic composite filler

[0062] Weigh out 1g of menthol, 8g of methacrylic acid, 5g of 4-vinylpyridine, and 600mL of acetonitrile and place them in a nitrogen-protected reactor. Stir the mixture and add 10g of olefin-modified magnetic nanofiller. Stir at room temperature for 25min. Add 10g of ethylene glycol dimethacrylate and 0.3g of azobisisobutyronitrile. Heat the reactor to 55℃ and maintain the temperature for 20h. After the reaction is complete, let the reaction system cool to room temperature, filter, wash the filter cake twice with 4-vinylpyridine, and place the product in a Soxhlet extractor. Use a 9:1 (v / v) methanol and glacial acetic acid mixture as the eluent and extract continuously at 60℃ for 48h. Transfer the extract to an oven at 50℃ and dry for 6h to obtain the magnetic composite filler.

[0063] The free silanol groups on the surface of magnetically responsive mesoporous silica nanoparticles undergo a condensation reaction with 3-(methacryloyloxy)propyltrimethoxysilane at high temperature, covalently grafting polymerizable carbon-carbon double bonds onto the particle surface, thus completing the olefin modification of the support. Subsequently, the template molecule menthol and the functional monomers methacrylic acid and 4-vinylpyridine complete pre-assembly through non-covalent interactions such as hydrogen bonding. After the modified support is added, under the pyrolysis of the initiator azobisisobutyronitrile, the functional monomers, crosslinking agent ethylene glycol dimethacrylate, and the double bonds on the support surface undergo a free radical graft copolymerization reaction, constructing a highly crosslinked polymer layer on the surface of the magnetic support. Finally, Soxhlet extraction is performed using a methanol-glacial acetic acid mixed solvent to disrupt the non-covalent bonds between the polymer backbone and the template molecules, and the menthol template is removed in situ. Specific imprinted pores matching the spatial structure and binding sites of the target molecules are exposed on the material surface and within the pores, ultimately obtaining a magnetic composite filler.

[0064] The silanization covalent modification of the nanoparticle carrier surface bridges the inorganic mesoporous framework and the organic imprinted phase, inhibiting the physical exfoliation of the adsorbed layer under high-shear fluid extraction and elution conditions, and establishing the structural stability of the composite material interface. Based on menthol template-guided surface graft copolymerization, a cross-linked framework with highly compatible spatial dimensions and hydrogen bond interaction sites is constructed around the magnetic carrier, laying the stereochemical basis for targeted recognition. Soxhlet extraction demolding operation realizes the in-situ emptying of specific pores and complete activation of recognition sites, endowing the magnetic composite filler with conformational matching and high selective enrichment efficiency for the core target molecules of peppermint oil in complex oil-water emulsion systems.

[0065] Example 5

[0066] This embodiment provides a method for extracting magnetic composite fillers, specifically including the following steps:

[0067] Step 1: Preparation of olefin-modified magnetic nanofillers

[0068] Weigh 15g of the magnetically responsive mesoporous silica nanoparticles prepared in Example 2 and 900mL of toluene and place them in a reaction vessel under a nitrogen atmosphere and stir. Add 40g of 3-(methacryloyloxy)propyltrimethoxysilane, heat the reaction vessel to 110℃, and keep it at this temperature for 22h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake three times with toluene and ethanol, transfer it to an oven at 45℃, and dry it to constant weight to obtain olefin-modified magnetic nanofiller.

[0069] Step 2: Preparation of magnetic composite filler

[0070] Weigh out 2g of menthol, 9g of methacrylic acid, 7.5g of 4-vinylpyridine, and 700mL of acetonitrile and place them in a nitrogen-protected reactor. Stir the mixture and add 15g of olefin-modified magnetic nanofiller. Stir at room temperature for 30min. Add 15g of ethylene glycol dimethacrylate and 0.4g of azobisisobutyronitrile. Heat the reactor to 60℃ and maintain the temperature for 22h. After the reaction is complete, let the reaction system cool to room temperature, filter, wash the filter cake three times with 4-vinylpyridine, and place the product in a Soxhlet extractor. Use a 9:1 (v / v) methanol and glacial acetic acid mixture as the eluent and extract continuously at 63℃ for 48h. Transfer the extract to an oven at 55℃ and dry for 7h to obtain the magnetic composite filler.

[0071] Example 6

[0072] This embodiment provides a method for extracting magnetic composite fillers, specifically including the following steps:

[0073] Step 1: Preparation of olefin-modified magnetic nanofillers

[0074] Weigh 20g of the magnetically responsive mesoporous silica nanoparticles prepared in Example 3 and 1000mL of toluene and place them in a reaction vessel under nitrogen atmosphere and stir. Add 50g of 3-(methacryloyloxy)propyltrimethoxysilane, heat the reaction vessel to 115℃ and keep it at that temperature for 24h. After the reaction is complete, wait for the reaction system to cool to room temperature, filter, wash the filter cake 4 times with toluene and ethanol, transfer it to an oven at 50℃ and dry it to constant weight to obtain olefin-modified magnetic nanofiller.

[0075] Step 2: Preparation of magnetic composite filler

[0076] Weigh out 3g of menthol, 10g of methacrylic acid, 10g of 4-vinylpyridine, and 800mL of acetonitrile and place them in a nitrogen-protected reactor. Stir the mixture and add 20g of olefin-modified magnetic nanofiller. Stir at room temperature for 35min. Add 20g of ethylene glycol dimethacrylate and 0.5g of azobisisobutyronitrile. Heat the reactor to 65℃ and maintain the temperature for 24h. After the reaction is complete, let the reaction system cool to room temperature, filter, and wash the filter cake four times with 4-vinylpyridine. Place the product in a Soxhlet extractor and use a 9:1 (v / v) methanol and glacial acetic acid mixture as the eluent. Extract continuously at 65℃ for 48h. Transfer the product to an oven at 60℃ and dry for 8h to obtain the magnetic composite filler.

[0077] Example 7

[0078] This embodiment provides a method for extracting peppermint oil, specifically including the following steps:

[0079] Step ①: Prepare an oil-water emulsion

[0080] Weigh out 10g of dried peppermint leaf powder with a moisture content of 5%, crush it to 40 mesh, soak it in deionized water at a soaking ratio of 1:25 for 1 hour, filter it, and steam distill the filter cake with 80mL of deionized water for 2 hours to extract an oil-water emulsion.

[0081] The temperature for steam distillation is 95℃, and the distillation pressure is 0.10MPa.

[0082] Step 2: Preparation of peppermint oil-supported composite filler

[0083] Weigh out 800 mL of the oil-water emulsion and add it to the reaction vessel. Stir, add 200 g of sodium chloride, stir for 0.5 h, let stand and separate into layers. Take the upper layer of crude peppermint oil and 5 g of the magnetic composite filler prepared in Example 4 and place them in the reaction vessel. Stir, add citric acid-sodium citrate buffer solution to adjust the pH to 5.5, and shake to adsorb for 1 h. After the adsorption is completed, place a magnetic separation device on the outer wall of the reaction vessel to separate and discard the supernatant to obtain peppermint oil-supported composite filler.

[0084] Step 3: Prepare peppermint oil

[0085] Weigh out 10g of peppermint oil-supported composite filler, 150mL of 0.3mol / L sodium bicarbonate aqueous solution and 30mL of ethanol and place them in a reaction vessel. Shake at room temperature for 0.5h to desorb. After desorption, place a magnetic separation device on the outer wall of the reaction vessel to separate and recover the desorbed solution loaded with peppermint oil. Extract the recovered mixed solution twice with ethyl acetate. Remove the ethyl acetate from the organic phase by rotary evaporation to obtain peppermint oil.

[0086] The volatile peppermint components are co-distilled and precipitated with steam using the principle of steam distillation. The condensation system forms an oil-water emulsion. Sodium chloride is added to increase the ionic strength of the aqueous phase, which disrupts the double electric layer and hydration film of the emulsion particles, initiating salting-out and demulsification to achieve oil-water separation. Under a weakly acidic buffer system, target molecules in the free crude oil phase are directionally recognized and bound by the specific imprinted pores of the magnetic composite packing material through non-covalent forces such as hydrogen bonds. Finally, a mixed desorption solution of weakly alkaline sodium bicarbonate and ethanol is used to disrupt the interfacial hydrogen bond network, causing the target molecules to desorb and release from the imprinted pores. Based on the principle of like dissolves like, low-boiling-point solvents are removed by ethyl acetate liquid-liquid extraction and vacuum rotary evaporation, completing the separation and purification of peppermint oil.

[0087] Gas-liquid co-distillation achieved mild phase transfer and preliminary enrichment. Salting out promoted microemulsion aggregation and phase separation, improving the purity of the crude oil phase and the mass transfer driving force of subsequent interfaces. The weakly acidic microenvironment stabilized the non-covalent binding conformation between the imprinted framework and the target molecules. The synergistic stereo-size matching of specific pores established the spatial anchoring of peppermint oil characteristic components in the complex liquid matrix. The weakly basic alcohol-water desorption phase triggered the dissociation of the hydrogen bond network at the interface through competitive site substitution. Combined with polarity-controlled liquid-liquid extraction and low-pressure temperature-switching desolvation process, the low-loss recovery of high-purity peppermint oil was achieved.

[0088] Example 8

[0089] This embodiment provides a method for extracting peppermint oil, specifically including the following steps:

[0090] Step ①: Prepare an oil-water emulsion

[0091] Weigh out 10g of dried peppermint leaf powder with a moisture content of 7.5%, crush it to 50 mesh, soak it in deionized water at a soaking ratio of 1:27 for 1.5h, filter it, and steam distill the filter cake with 100mL of deionized water for 2.5h to extract an oil-water emulsion.

[0092] The temperature for steam distillation was 97℃, and the distillation pressure was 0.11MPa.

[0093] Step 2: Preparation of peppermint oil-supported composite filler

[0094] Weigh out 900 mL of the oil-water emulsion and add it to the reaction vessel. Stir, add 225 g of sodium chloride, stir for 1 h, let stand and separate into layers. Take the upper layer of crude peppermint oil and 7.5 g of the magnetic composite filler prepared in Example 5 and place them in the reaction vessel and stir. Add citric acid-sodium citrate buffer solution to adjust the pH to 6.0, shake and adsorb for 1.5 h. After the adsorption is completed, place a magnetic separation device on the outer wall of the reaction vessel to separate and discard the supernatant to obtain peppermint oil-supported composite filler.

[0095] Step 3: Prepare peppermint oil

[0096] Weigh out 15g of peppermint oil-supported composite filler, 200mL of 0.4mol / L sodium bicarbonate aqueous solution and 50mL of ethanol and place them in a reaction vessel. Shake at room temperature for 1h to desorb. After desorption, place a magnetic separation device on the outer wall of the reaction vessel to separate and recover the desorbed solution loaded with peppermint oil. Extract the recovered mixed solution three times with ethyl acetate. Remove the ethyl acetate from the organic phase by rotary evaporation to obtain peppermint oil.

[0097] Example 9

[0098] This embodiment provides a method for extracting peppermint oil, specifically including the following steps:

[0099] Step ①: Prepare an oil-water emulsion

[0100] Weigh out 10g of dried peppermint leaf powder with a moisture content of 10%, crush it to 60 mesh, soak it in deionized water at a soaking ratio of 1:30 for 2 hours, filter it, and steam distill the filter cake with 120mL of deionized water for 3 hours to extract an oil-water emulsion.

[0101] The temperature for steam distillation is 100℃, and the distillation pressure is 0.12MPa.

[0102] Step 2: Preparation of peppermint oil-supported composite filler

[0103] Weigh out 1000 mL of the oil-water emulsion and add it to the reaction vessel. Stir, add 250 g of sodium chloride, stir for 1 h, let stand and separate into layers. Take the upper layer of crude peppermint oil and 10 g of the magnetic composite filler prepared in Example 6 and place them in the reaction vessel. Stir, add citric acid-sodium citrate buffer solution to adjust the pH to 6.5, and shake to adsorb for 2 h. After the adsorption is completed, place a magnetic separation device on the outer wall of the reaction vessel to separate and discard the supernatant to obtain peppermint oil-supported composite filler.

[0104] Step 3: Prepare peppermint oil

[0105] Weigh out 20g of peppermint oil-supported composite filler, 250mL of 0.5mol / L sodium bicarbonate aqueous solution and 80mL of ethanol and place them in a reaction vessel. Shake at room temperature for 1h to desorb. After desorption, place a magnetic separation device on the outer wall of the reaction vessel to separate and recover the desorbed solution loaded with peppermint oil. Extract the recovered mixed solution with ethyl acetate 4 times. Remove the ethyl acetate from the organic phase by rotary evaporation to obtain peppermint oil.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 9 is that the template molecule menthol was omitted in step (2) when preparing the magnetic composite filler.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 9 is that, in step (1) when preparing the olefin-modified magnetic nanofiller, magnetic core-shell particles are used in an equal amount to replace the magnetically responsive mesoporous silica nanoparticles.

[0110] Performance testing:

[0111] The specific surface area of ​​the magnetic composite fillers used in Examples 7-9 and Comparative Examples 1-2 was determined in accordance with the standard GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method".

[0112] The saturation magnetization of the magnetic composite fillers used in Examples 7-9 and Comparative Examples 1-2 was determined in accordance with the standard GB / Z 26082-2010 "Method for Measurement of DC Magnetic Susceptibility (Magnetic Moment) of Nanomaterials".

[0113] The extraction rates of peppermint oil extracted in Examples 7-9 and Comparative Examples 1-2 were determined according to General Chapter 2204 "Determination of Volatile Oils" in the 2025 edition of the Chinese Pharmacopoeia.

[0114] The relative densities of the peppermint oils extracted in Examples 7-9 and Comparative Examples 1-2 were determined according to the method specified in the 2025 edition of the Chinese Pharmacopoeia, Volume IV, under the peppermint oil section. The relative density was used to characterize the purity of the peppermint oils. The specific data are shown in Table 1.

[0115] Table 1 - Performance Test Data of Samples

[0116]

[0117] Comparative analysis of the data in Table 1 above shows that the specific surface area of ​​the magnetic composite filler prepared in this invention is 172.1 m². 2 ·g -1 The saturation magnetization is 1.266 × 10⁻⁶. 6 A·m -1 The extraction rate of peppermint oil was 92.3%, and the relative density was 0.901, all of which were better than the comparative sample.

[0118] This invention constructs magnetically responsive mesoporous silica nanoparticles as a carrier using a soft template method, and covalently grafts a molecularly imprinted layer with menthol as a template onto the surface of these nanoparticles to activate specific recognition pores. This magnetic composite filler is then directly introduced into an emulsion pretreated by gas-liquid co-distillation and salting-out demulsification. By relying on the reversible regulation of the microenvironment through weak acid anchoring adsorption and weak base competitive elution, the target component is desorbed with low loss. This invention not only enables rapid recovery of the filler by relying on an external magnetic field, but also accurately extracts and desorbs peppermint oil in complex mixtures, improving the extraction efficiency and purity of peppermint oil.

[0119] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method of extracting oil from peppermint, characterized by, Includes the following steps: S1. After pretreatment of dried peppermint leaves, steam distillation is carried out with deionized water for 2-3 hours to extract an oil-water emulsion. S2. Add the oil-water emulsion to the reaction vessel and stir. Add sodium chloride and stir for 0.5-1 h. Let it stand and separate into layers. Take the upper layer of crude peppermint oil and magnetic composite filler and place them in the reaction vessel and stir. Add citric acid-sodium citrate buffer solution to adjust the pH to 5.5-6.

5. Shake and adsorb for 1-2 h. Post-process to obtain peppermint oil-supported composite filler. S3. Peppermint oil-supported composite filler, sodium bicarbonate aqueous solution and ethanol are placed in a reaction vessel and shaken at room temperature for 0.5-1h to desorb, and then processed to obtain peppermint oil.

2. The method for extracting peppermint oil according to claim 1, characterized in that, In step S1, the moisture content of the dried peppermint leaves is 5-10%, the ratio of dried peppermint leaves to deionized water is 1g:8-12mL, the temperature of steam distillation is 95-100℃, and the distillation pressure is 0.10-0.12MPa.

3. The method for extracting peppermint oil according to claim 1, characterized in that, In step S2, the ratio of crude oil-water mixed emulsion, sodium chloride and magnetic composite filler is 80-100mL:0.5-1.0g:2-4g, and the pH of the citric acid-sodium citrate buffer solution is 5.

2.

4. The method for extracting peppermint oil according to claim 1, characterized in that, In step S3, the ratio of peppermint oil-supported composite filler, sodium bicarbonate aqueous solution, and ethanol is 1-2g:15-25mL:3-8mL, and the concentration of sodium bicarbonate aqueous solution is 0.3-0.5mol / L.

5. The method for extracting peppermint oil according to claim 1, characterized in that, The magnetic composite filler is prepared by the following steps: A1. Magnetic responsive mesoporous silica nanoparticles and toluene were placed in a reaction vessel under nitrogen atmosphere and stirred. 3-(methacryloyloxy)propyltrimethoxysilane was added. The reaction vessel was heated to 105-115℃ and kept at the temperature for 20-24h. After post-treatment, olefin-modified magnetic nanofillers were obtained. A2. Menthol, methacrylic acid, 4-vinylpyridine and acetonitrile were placed in a reaction vessel under nitrogen atmosphere and stirred. Olefin-modified magnetic nanofiller was added and stirred at room temperature for 25-35 min. Ethylene glycol dimethacrylate and azobisisobutyronitrile were added. The reaction vessel was heated to 55-65℃ and kept at that temperature for 20-24 h. The magnetic composite filler was obtained after post-treatment.

6. The method for extracting peppermint oil according to claim 5, characterized in that, In step A1, the ratio of the magnetically responsive mesoporous silica nanoparticles, toluene, and 3-(methacryloyloxy)propyltrimethoxysilane is 1-2g:80-100mL:3-5g; in step A2, the ratio of the menthol, methacrylic acid, 4-vinylpyridine, acetonitrile, 4-vinylpyridine, olefin-modified magnetic nanofiller, ethylene glycol dimethacrylate, and azobisisobutyronitrile is 0.1-0.3g:0.8-1g:0.5-1g:60-80mL:1-2g:1-2g:0.03-0.05g.

7. The method for extracting peppermint oil according to claim 5, characterized in that, The magnetically responsive mesoporous silica nanoparticles were prepared by the following steps: B1. Place deionized water, ferric chloride hexahydrate and ferrous chloride tetrahydrate in a three-necked flask under nitrogen atmosphere and stir. Heat the three-necked flask to 75-85℃, keep it at the temperature and stir for 3-5 minutes. Add ammonia solution and keep it at the temperature for 1-2 hours. Post-treatment yields magnetic iron oxide nanoparticles. B2. Magnetic iron oxide nanoparticles, deionized water and ethanol are placed in a reaction vessel and stirred. Cetyltrimethylammonium bromide is added. The reaction vessel is heated to 35-45℃. Ammonia solution is added. The mixture is kept warm and stirred for 5-10 min. Tetraethyl orthosilicate is added dropwise. The reaction is kept warm for 4-6 h. After post-treatment, magnetic core-shell particles are obtained. B3. Place the magnetic core-shell particles, ethanol aqueous solution and dilute hydrochloric acid in a reaction vessel and stir. Heat the reaction vessel to 75-85℃ and keep it at that temperature for 10-12 hours. After post-treatment, obtain magnetically responsive mesoporous silica nanoparticles.

8. The method for extracting peppermint oil according to claim 7, characterized in that, In step B1, the ratio of deionized water, ferric chloride hexahydrate, ferrous chloride tetrahydrate, and ammonia solution is 350-450 mL: 10-12 g: 3-5 g: 35-45 mL, and the concentration of ammonia solution is 20-30 wt%.

9. The method for extracting peppermint oil according to claim 7, characterized in that, In step B2, the ratio of the magnetic iron oxide nanoparticles, deionized water, ethanol, hexadecyltrimethylammonium bromide, ammonia solution, and tetraethyl orthosilicate is 1-2g:35-45mL:150-250mL:0.5-1.5g:8-10mL:4-6g, and the concentration of the ammonia solution is 20-30wt%.

10. The method for extracting peppermint oil according to claim 7, characterized in that, In step B3, the ratio of the magnetic core-shell particles, the ethanol aqueous solution, and the dilute hydrochloric acid is 2-4g:140-160mL:1-2mL, the concentration of the ethanol aqueous solution is 95-98wt%, and the concentration of the dilute hydrochloric acid is 5-10wt%.

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