Fragrance purification method of leaf alcohol

Abstract

The invention relates to the technical field of purification of organic chemicals, in particular to an aroma purification method of leaf alcohol. Comprising the following steps: preparing a methanesulfonic acid magnetic catalyst; esterification of leaf alcohol; and alcoholysis and fractionation of the esterification solution. According to the method, acetic acid is used for esterification of leaf alcohol, then clear water and a sodium carbonate solution are used for washing, the clear water can effectively remove some water-soluble impurities and acidic byproducts, and the sodium carbonate solution not only can neutralize residual acidic substances, but also can promote siloxane impurities in initial leaf alcohol to be hydrolyzed and then taken away by a water phase, so that the content of the siloxane impurities in the leaf alcohol is reduced; in the subsequent process of producing leaf alcohol through alcoholysis of the organic phase I, pure water and ethanol, silyl ether impurities are hydrolyzed in a high-temperature and strong-alkali environment, products are dissolved in waste liquid to be removed, olefine aldehyde impurities with the boiling point lower than that of leaf alcohol are removed through azeotropic fractionation with ethanol, in conclusion, the impurities in the finished product leaf alcohol can be effectively reduced, and the yield of the finished product leaf alcohol is increased. And the prepared finished product leaf alcohol is high in purity and pure in fragrance.

Description

Technical Field

[0001] The present invention relates to the technical field of purification of organic chemicals, and specifically to an aroma purification method for leaf alcohol. Background Art

[0002] Leaf alcohol (geraniol) is an important aroma component widely used in the fragrance, cosmetics, and food industries. It is highly favored for its unique rose floral fragrance. However, during the synthesis or extraction of leaf alcohol, some trace impurities are often generated. These impurities have an adverse effect on the aroma purity of leaf alcohol. Especially in high-end fragrance applications, the presence of impurities can lead to an impure "top note" of the finished product aroma, affecting the product quality and market acceptance.

[0003] Common impurities include silanol impurities, siloxane impurities, silyl ether impurities, and hexenal impurities. These impurities produce irritating and unnatural odors that conflict with the natural aroma of leaf alcohol, resulting in a decrease in the fineness and layering of the aroma, thus making the "top note" impure and presenting a discordant chemical odor.

[0004] To remove these impurities, traditional purification methods mainly include multiple rectification and water washing treatments. Multiple rectification attempts to separate components by taking advantage of the boiling point differences of each component through rectification. However, since the boiling points of leaf alcohol and some impurities (such as decamethyltetrasiloxane, 2-ethyl-2-hexenal) are close, it is difficult to completely separate these impurities by rectification. In addition, there may be a risk of thermal decomposition during the rectification process. Especially at high temperatures, impurities may undergo side reactions with leaf alcohol. Although water washing can remove some polar impurities, its removal effect on non-polar or weakly polar impurities (such as silanol and siloxane compounds) is limited. Due to the strong hydrophobicity of these impurities, it is difficult to separate them through the aqueous phase, resulting in poor water washing treatment effects. Summary of the Invention

[0005] To solve the above technical defects, the present invention has developed an aroma purification method for leaf alcohol, which can effectively remove impurities in leaf alcohol, and can well reduce the loss of leaf alcohol during the treatment process, making the finished leaf alcohol have a more pure and natural aroma, and is suitable for the production of high-end fragrances and cosmetics.

[0006] An aroma purification method for leaf alcohol, comprising the following steps:

[0007] S1: Preparation of methylsulfonic acid magnetic catalyst

[0008] Mix nano-Fe3O4 and Tris-HCl solution evenly, then add dopamine hydrochloride, stir and filter to obtain a PDA-modified Fe3O4 carrier. Mix methanesulfonic acid and toluene evenly, add the PDA-modified Fe3O4 carrier, perform ultrasonic treatment and then carry out condensation reflux, then use magnetic separation to separate the product, wash the solid product with ether, and collect the separated product to obtain a methanesulfonic acid magnetic catalyst;

[0009] S2: Esterification of leaf alcohol

[0010] Add leaf alcohol and the methanesulfonic acid magnetic catalyst to a container, add glacial acetic acid under stirring, then heat and reflux to separate water, take samples regularly for GC detection, and end the reaction when the leaf alcohol peak < 0.5% to obtain an esterification mixture. After the esterification mixture is allowed to stand and cool, recover the methanesulfonic acid magnetic catalyst to obtain an esterification solution. The esterification solution is washed successively with water and Na2CO3 solution, stirred and allowed to stand for phase separation to separate out aqueous phase I and organic phase I. Aqueous phase I is transferred to the sewage treatment station, and organic phase I is transferred to the crude product tank for storage and standby;

[0011] S3: Alcoholysis and fractional distillation of the esterification solution

[0012] Place polyvinylpyrrolidone powder and N,N-dimethylformamide in a container and mix evenly, then add 1,4-diazabicyclo[2.2.2]octane, filter after heating and stirring to obtain a solid reactant. Wash, dry and grind the solid reactant evenly, then immerse it in NaOH solution and stir, wash, filter and dry to obtain a supported basic catalyst. Mix organic phase I, pure water and ethanol, add the supported basic catalyst, stir and then heat to reflux, recover ethanol at atmospheric pressure, and obtain an alcoholysis solution after the alcoholysis kettle cools down. After the alcoholysis solution is allowed to stand for liquid separation, perform suction filtration, discharge the waste liquid and adjust the pH of the remaining solution, and then perform suction filtration again to obtain aqueous phase II and organic phase II. Fractionally distill organic phase II to obtain the finished leaf alcohol.

[0013] Further, the preparation of the methanesulfonic acid magnetic catalyst in step S1 includes the following steps:

[0014] S1.1: Mix nano-Fe3O4 and Tris-HCl solution with a pH of 8 - 8.5 in a mass ratio of 1:(120 - 150) in a container and stir evenly, then add dopamine hydrochloride with a mass 2 - 3 times that of nano-Fe3O4, stir for 8 - 10 hours and then filter to obtain a PDA-modified Fe3O4 carrier;

[0015] S1.2: Mix 3 - 4 parts by weight of methanesulfonic acid and 80 - 100 parts by weight of toluene in a container and stir evenly. Then add 6 - 8 parts by weight of the PDA - modified Fe3O4 support. Place it in an ultrasonic disperser and ultrasonicate for 15 - 20 minutes, then heat up to 105 - 110 °C. Maintain the temperature and carry out condensation reflux at a stirring speed of 650 - 800 rpm for 12 - 15 hours. Then apply a magnetic field to separate the product to obtain a solid product. Wash the solid product with ether and then collect it by magnetic adsorption to obtain the methanesulfonic acid magnetic catalyst.

[0016] Further, the esterification of leaf alcohol in step S2 includes the following steps:

[0017] S2.1: Add 4 - 5 parts by weight of leaf alcohol and 0.2 - 0.3 parts by weight of the methanesulfonic acid magnetic catalyst to a container. Then add 3 - 4 parts by weight of glacial acetic acid under stirring, and control the stirring speed at 400 - 500 rpm. After the glacial acetic acid is completely added, heat - reflux at a temperature of 80 - 90 °C, and at the same time separate the water generated by the reaction through a water separator. Take samples of the mixture in the reaction kettle every 3 - 5 minutes and conduct GC detection. When the peak of leaf alcohol < 0.5%, end the reaction to obtain an esterification mixture.

[0018] S2.2: After the esterification mixture is allowed to stand and cool down, recover the methanesulfonic acid magnetic catalyst by a magnet to obtain an esterification solution. Wash the esterification solution once with water, then wash it with a Na2CO3 solution with a mass fraction of 10 - 15% until the pH is 10 - 10.5. Stir for 1 - 1.5 hours and then let it stand for stratification. Use a separatory funnel to separate the aqueous phase I and the organic phase I. Transfer the aqueous phase I to the sewage treatment station, and transfer the organic phase I to a crude product tank for storage and standby.

[0019] Further, the alcoholysis and fractionation of the esterification solution in step S3 include the following steps:

[0020] S3.1: Mix 1 - 2 parts by weight of polyvinylpolypyrrolidone powder and 40 - 50 parts by weight of N,N - dimethylformamide in a container and stir evenly. Then add 0.6 - 0.8 parts by weight of 1,4 - diazabicyclo[2.2.2]octane, and then heat to 75 - 80 °C and continuously stir for 20 - 24 hours. Filter to obtain a solid reactant. Wash the solid reactant with ethanol 2 - 3 times, then place it in a vacuum oven and dry at a temperature of 60 - 65 °C. Then grind it evenly and immerse it in a NaOH solution, stir for 18 - 20 hours, wash it with water and then filter, and then place it in a vacuum box and dry at a temperature of 60 - 65 °C to obtain a supported basic catalyst.

[0021] S3.2: Place the organic phase I, pure water, and ethanol in an alcoholysis kettle at a mass ratio of 1:(0.6 - 0.8):(0.3 - 0.4), then add a supported basic catalyst of 16 - 18 wt% and stir evenly. Heat under reflux at a temperature of 120 - 130 °C for 3 - 4 hours, and then fractionally distill to recover ethanol under normal pressure. Wait for the alcoholysis kettle to cool down to 30 - 40 °C to obtain an alcoholysis solution;

[0022] S3.3: Let the alcoholysis solution stand for liquid separation and then perform suction filtration. Discharge the waste liquid obtained from the suction filtration, adjust the pH of the remaining solution to 7, and then perform suction filtration again to obtain the aqueous phase II and the organic phase II. Transfer the organic phase II to a distillation column, adjust the vacuum degree to -0.088 MPa to -0.1 MPa, and perform fractional distillation at a temperature of 85 - 90 °C to collect the fractions and obtain the finished product of leaf alcohol.

[0023] Further, in step S1.1, the particle size of the nano-Fe3O4 is 100 - 200 nm.

[0024] Further, in step S1.2, the ultrasonic frequency of the ultrasonic disperser is 20 - 40 kHz.

[0025] Further, in step S1.2, the method of washing the solid product with ether is to completely immerse the solid product in ether, and then magnetically stir for 4 - 4.5 hours under the conditions of 80 - 85 °C and a stirring speed of 500 - 600 rpmm.

[0026] Further, the container in step S2.1 is a reaction kettle equipped with a condensation device, a thermometer, an electric stirrer, and a water separator.

[0027] Further, in step S3.1, the mass fraction of the NaOH solution is 50 - 60%.

[0028] Further, in step S3.3, the method of adjusting the pH of the remaining solution is to add an aqueous sulfuric acid solution with a mass fraction of 10 - 15%.

[0029] The beneficial effects are as follows: 1. In the present invention, leaf alcohol is first esterified with acetic acid, and then washed with clear water and sodium carbonate solution. The clear water can effectively remove some water-soluble impurities and acidic by-products, while the sodium carbonate solution can not only neutralize the remaining acidic substances, but also promote the hydrolysis of siloxane impurities in the initial leaf alcohol, which are then taken away by the aqueous phase. Subsequently, alcoholysis occurs among the organic phase I, pure water, and ethanol under the action of a supported basic catalyst to generate leaf alcohol. The silicyl ether impurities are hydrolyzed in a high-temperature strong base environment, and the generated hydrolysis products are dissolved in the waste liquid and removed. The enal impurities with a boiling point lower than that of leaf alcohol are removed by azeotropic distillation with ethanol. In summary, it can effectively reduce the impurities in the finished product of leaf alcohol, making the prepared finished product of leaf alcohol have high purity and pure aroma.

[0030] 2. The present invention prepares a magnetic methylsulfonic acid catalyst. The covalent interaction mode among its components and the existence of the magnetic core-shell endow the magnetic methylsulfonic acid catalyst with good stability and easy separation performance. During the process of catalyzing the reaction of esterifying geraniol with acetic acid, the PDA-modified Fe3O4 support structure of the magnetic methylsulfonic acid catalyst provides a small particle size and a large specific surface area, enabling the magnetic methylsulfonic acid catalyst to be more uniformly dispersed in the esterification system. At the same time, it increases the active sites of the catalytic reaction, thereby improving the catalytic efficiency of the esterification reaction and avoiding the waste caused by incomplete esterification of geraniol.

[0031] 3. The present invention first combines polyvinylpyrrolidone powder and 1,4-diazabicyclo[2.2.2]octane, and then immerses them in a NaOH solution and stirs to prepare a supported basic catalyst. Among them, 1,4-diazabicyclo[2.2.2]octane is an organic base with medium-strength basicity. It can act as a Lewis base to form hydrogen bonds with proton donors (such as acidic hydrogen atoms) or coordinate with metal ions, while NaOH is a strong base that can effectively remove protons from reactants to generate corresponding anion intermediates. When the supported basic catalyst is used for alcoholysis catalysis, 1,4-diazabicyclo[2.2.2]octane can help NaOH more effectively activate the reactants and enhance the effect of NaOH through complexation. The two work together to improve the rate and efficiency of the overall reaction and avoid the waste of geraniol. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a process flow chart of the method for purifying the aroma of geraniol adopted in the embodiments of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1

[0035] A method for purifying the aroma of geraniol, as Figure 1 shown, includes the following steps:

[0036] S1: Preparation of magnetic methylsulfonic acid catalyst

[0037] S1.1: Mix nano-Fe3O4 with a particle size of 100 nm and Tris-HCl solution with a pH of 8 in a mass ratio of 1:120 in a container and stir evenly. Then add dopamine hydrochloride with a mass twice that of nano-Fe3O4 and stir for 8 hours, followed by filtration to obtain a PDA-modified Fe3O4 carrier.

[0038] S1.2: Mix 3 parts by weight of methanesulfonic acid and 80 parts by weight of toluene in a container and stir evenly. Then add 6 parts by weight of the PDA-modified Fe3O4 carrier, place it in an ultrasonic disperser, ultrasonicate at an ultrasonic frequency of 20 kHz for 15 minutes, then heat up to 105 °C, keep the temperature and carry out condensation reflux at a stirring speed of 650 rpm for 12 hours. Then apply a magnetic field to separate the product to obtain a solid product. Immerse the solid product completely in ether, then under the conditions of 80 °C and 500 rpm, stir magnetically for 4 hours, and then collect it with a magnet to obtain a methanesulfonic acid magnetic catalyst.

[0039] S2: Esterification of leaf alcohol

[0040] S2.1: Add 4 parts by weight of leaf alcohol and 0.2 parts by weight of the methanesulfonic acid magnetic catalyst to a reaction kettle equipped with a condensation device, a thermometer, an electric stirrer and a water separator. Then add 3 parts by weight of glacial acetic acid under stirring, and control the stirring speed at 400 rpm. After the glacial acetic acid is completely added, heat and reflux at a temperature of 80 °C, and at the same time separate the water generated by the reaction through the water separator. Take samples of the mixture in the reaction kettle every 3 minutes and conduct GC detection. When the leaf alcohol peak < 0.5%, end the reaction to obtain an esterification mixture.

[0041] S2.2: Let the esterification mixture stand and cool down, then recover the methanesulfonic acid magnetic catalyst with a magnet to obtain an esterification solution. Wash the esterification solution once with water, then wash it with a 10% (mass fraction) Na2CO3 solution until the pH is 10, stir for 1 hour, then let it stand and separate into layers. Use a separatory funnel to separate the aqueous phase I and the organic phase I. Transfer the aqueous phase I to the sewage treatment station, and transfer the organic phase I to the crude product tank for storage and standby.

[0042] S3: Alcoholysis and fractionation of the esterification solution

[0043] S3.1: Mix 1 part by weight of polyvinylpyrrolidone powder with 40 parts by weight of N,N-dimethylformamide in a container until homogeneous. Then add 0.6 part by weight of 1,4-diazabicyclo[2.2.2]octane, and heat to 75 °C with continuous stirring for 20 hours. Filter to obtain a solid reactant. Wash the solid reactant twice with ethanol, place it in a vacuum oven, dry at 60 °C, then grind it evenly and immerse it in a 50% by mass NaOH solution. Stir for 18 hours, wash with water and then filter, and then place it in a vacuum box to dry at 60 °C to obtain a supported basic catalyst;

[0044] S3.2: Place the organic phase I, pure water and ethanol in an alcoholysis kettle at a mass ratio of 1:0.6:0.3, then add 16 wt% of the supported basic catalyst and stir evenly. Heat to 120 °C for reflux for 3 hours, and then fractionally distill to recover ethanol under atmospheric pressure. Wait for the alcoholysis kettle to cool to 30 °C to obtain an alcoholysis solution;

[0045] S3.3: Let the alcoholysis solution stand for liquid separation and then perform suction filtration. Discharge the waste liquid obtained by suction filtration. Add a 10% by mass sulfuric acid aqueous solution to adjust the pH of the remaining solution to 7, then perform suction filtration again to obtain an aqueous phase II and an organic phase II. Transfer the organic phase II to a distillation column, adjust the vacuum degree to -0.088 MPa, and distill at 85 °C to collect the fractions to obtain the finished product leaf alcohol.

[0046] Example 2

[0047] A method for purifying the aroma of leaf alcohol, as Figure 1 shown, includes the following steps:

[0048] S1: Preparation of methylsulfonic acid magnetic catalyst

[0049] S1.1: Mix nano-Fe3O4 with a particle size of 100 nm and a Tris-HCl solution with a pH of 8 in a container at a mass ratio of 1:150 and stir evenly. Then add dopamine hydrochloride with a mass three times that of nano-Fe3O4, stir for 8 hours and then filter to obtain a PDA-modified Fe3O4 support;

[0050] S1.2: Mix 4 parts by weight of methanesulfonic acid and 100 parts by weight of toluene in a container and stir well. Then add 8 parts by weight of the PDA-modified Fe3O4 support, place it in an ultrasonic disperser, and ultrasonicate at an ultrasonic frequency of 20 kHz for 15 minutes. Then heat it to 105 °C, maintain the temperature, and carry out condensation reflux at a stirring speed of 650 rpm for 12 hours. Then apply a magnetic field to separate the product to obtain a solid product. Immerse the solid product completely in ether, and then carry out magnetic stirring at 80 °C and a stirring speed of 500 rpm for 4 hours. Then collect it with a magnet to obtain the methanesulfonic acid magnetic catalyst.

[0051] S2: Esterification of leaf alcohol

[0052] S2.1: Add 5 parts by weight of leaf alcohol and 0.3 parts by weight of the methanesulfonic acid magnetic catalyst to a reaction kettle equipped with a condensation device, a thermometer, an electric stirrer, and a water separator. Then add 4 parts by weight of glacial acetic acid under stirring, and control the stirring speed at 400 rpm. After the glacial acetic acid is completely added, heat and reflux at 80 °C, and at the same time separate the water generated by the reaction through the water separator. Take samples of the mixture in the reaction kettle every 3 minutes and conduct GC detection. When the leaf alcohol peak < 0.5%, end the reaction to obtain an esterification mixture.

[0053] S2.2: After the esterification mixture is allowed to stand and cool down, recover the methanesulfonic acid magnetic catalyst with a magnet to obtain an esterification solution. Wash the esterification solution once with water, and then wash it with a 10% (mass fraction) Na2CO3 solution until the pH is 10. Stir for 1 hour and then let it stand for separation. Use a separating funnel to separate the aqueous phase I and the organic phase I. Transfer the aqueous phase I to the sewage treatment station, and transfer the organic phase I to the crude product tank for storage and standby.

[0054] S3: Alcoholysis and fractional distillation of the esterification solution

[0055] S3.1: Mix 1 part by weight of polyvinylpyrrolidone powder and 50 parts by weight of N,N-dimethylformamide in a container and stir well. Then add 0.8 parts by weight of 1,4-diazabicyclo[2.2.2]octane, and then heat to 75 °C and stir continuously for 20 hours. Filter to obtain a solid reactant. Wash the solid reactant twice with ethanol, then place it in a vacuum oven and dry at 60 °C. Then grind it evenly and immerse it in a 50% (mass fraction) NaOH solution, stir for 18 hours, wash it with water and then filter, and then place it in a vacuum box and dry at 60 °C to obtain a supported basic catalyst.

[0056] S3.2: Place the organic phase I, pure water, and ethanol in an alcoholysis reactor at a mass ratio of 1:0.8:0.4. Then add a 18 wt% supported basic catalyst and stir evenly. Raise the temperature to 120 °C for reflux for 3 hours, and then fractionally distill and recover ethanol under atmospheric pressure. Wait for the alcoholysis reactor to cool down to 30 °C to obtain an alcoholysis solution;

[0057] S3.3: After allowing the alcoholysis solution to stand for liquid separation, perform suction filtration. Discharge the waste liquid obtained from the suction filtration. Add a 10% sulfuric acid aqueous solution to adjust the pH of the remaining solution to 7, and then perform suction filtration again to obtain the aqueous phase II and the organic phase II. Transfer the organic phase II to a distillation column, adjust the vacuum degree to -0.088 MPa, and perform fractional distillation at a temperature of 85 °C. Collect the fractions to obtain the finished product of leaf alcohol.

[0058] Example 3

[0059] A method for purifying the aroma of leaf alcohol, as Figure 1 shown, includes the following steps:

[0060] S1: Preparation of methylsulfonic acid magnetic catalyst

[0061] S1.1: Mix nano-Fe3O4 with a particle size of 200 nm and a Tris-HCl solution with a pH of 8.5 in a container at a mass ratio of 1:120 and stir evenly. Then add dopamine hydrochloride with a mass twice that of nano-Fe3O4 and stir for 10 hours, followed by filtration to obtain a PDA-modified Fe3O4 support;

[0062] S1.2: Mix 3 parts by weight of methylsulfonic acid and 80 parts by weight of toluene in a container and stir evenly. Then add 6 parts by weight of the PDA-modified Fe3O4 support, place it in an ultrasonic disperser, ultrasonically disperse it at an ultrasonic frequency of 40 kHz for 20 minutes, then raise the temperature to 110 °C, maintain the temperature, and perform condensation reflux at a stirring speed of 800 rpm for 15 hours. Then apply a magnetic field to separate the product to obtain a solid product. Immerse the solid product completely in ether, and then perform magnetic stirring at 85 °C and 600 rpmm for 4.5 hours, and then collect it with a magnet to obtain the methylsulfonic acid magnetic catalyst.

[0063] S2: Esterification of leaf alcohol

[0064] S2.1: Add 4 parts by weight of leaf alcohol and 0.2 parts by weight of methylsulfonic acid magnetic catalyst into a reaction kettle equipped with a condensing device, a thermometer, an electric stirrer and a water separator. Then add 3 parts by weight of glacial acetic acid under stirring, and control the stirring speed at 500 rpm. After the glacial acetic acid is completely added, heat and reflux at a temperature of 90 °C, and at the same time separate the water generated by the reaction through the water separator. Take samples of the mixture in the reaction kettle every 5 minutes and conduct GC detection. When the peak of leaf alcohol < 0.5%, end the reaction to obtain an esterification mixture;

[0065] S2.2: After the esterification mixture is allowed to stand and cool down, recover the methylsulfonic acid magnetic catalyst through a magnet to obtain an esterification solution. Wash the esterification solution once with clear water, and then wash it with a 15% (by mass) Na2CO3 solution until the pH reaches 10.5. Stir for 1.5 hours and then let it stand and separate layers. Use a separatory funnel to separate the aqueous phase I and the organic phase I. Transfer the aqueous phase I to the sewage treatment station, and transfer the organic phase I to a crude product tank for storage and standby.

[0066] S3: Alcoholysis and fractionation of the esterification solution

[0067] S3.1: Place 1 part by weight of polyvinylpyrrolidone powder and 40 parts by weight of N,N-dimethylformamide in a container and mix evenly. Then add 0.6 parts by weight of 1,4-diazabicyclo[2.2.2]octane, and then heat to 80 °C and stir continuously for 24 hours. Filter to obtain a solid reactant. Wash the solid reactant 3 times with ethanol, then place it in a vacuum oven and dry at a temperature of 65 °C. Then grind it evenly and immerse it in a 60% (by mass) NaOH solution. Stir for 20 hours, wash with water and then filter, and then place it in a vacuum box and dry at a temperature of 65 °C to obtain a supported basic catalyst;

[0068] S3.2: Place the organic phase I, pure water and ethanol in an alcoholysis kettle according to a mass ratio of 1:0.6:0.3, and then add 16 wt% of the supported basic catalyst and stir evenly. Heat and reflux at a temperature of 130 °C for 4 hours, and then fractionate under normal pressure to recover ethanol. Wait for the alcoholysis kettle to cool down to 40 °C to obtain an alcoholysis solution;

[0069] S3.3: After the alcoholysis solution is allowed to stand and separated by liquid, perform suction filtration. Discharge the waste liquid obtained by suction filtration. Add a 15% (by mass) sulfuric acid aqueous solution to adjust the pH of the remaining solution to 7, and then perform suction filtration again to obtain the aqueous phase II and the organic phase II. Transfer the organic phase II to a rectification column, adjust the vacuum degree to -0.01 MPa, and fractionate at a temperature of 90 °C to collect the fractions to obtain the finished product of leaf alcohol.

[0070] Comparative Example 1

[0071] Compared with Example 1, the difference in Comparative Example 1 is that in Comparative Example 1, the leaf alcohol in step S2.1 is first washed 5 times with pure water, and then fractionated 5 times in a distillation column with a vacuum degree of -0.088 MPa and a temperature of 85 °C to obtain the finished leaf alcohol.

[0072] Comparative Example 2

[0073] Compared with Example 1, the difference in Comparative Example 2 is that in Comparative Example 2, step S1 is removed, and the subsequent methylsulfonic acid magnetic catalyst is replaced with methylsulfonic acid, and the remaining steps are the same as those in Example 1.

[0074] Comparative Example 3

[0075] Compared with Example 1, the difference in Comparative Example 3 is that in Comparative Example 3, step S3.1 is removed, and the subsequent supported basic catalyst is replaced with sodium hydroxide, and the remaining steps are the same as those in Example 1.

[0076] Experiment 1: Take 30 g of leaf alcohol from the same batch, and then divide it into 6 equal parts. The purity of each part of leaf alcohol is measured by gas chromatography-mass spectrometry. Then, each part is used to prepare the finished leaf alcohol through the processes of Examples 1-3 and Comparative Examples 1-3. After weighing, the purity of the finished leaf alcohol prepared in Examples 1-3 and Comparative Examples 1-3 is measured by gas chromatography-mass spectrometry. The mass of the active ingredient = mass × purity. Calculate and record the data, and make a table as shown in Table 1. It can be seen that the purity of the finished leaf alcohol prepared in Examples 1-3 is greater than that in Comparative Example 1, and it can be seen that the mass of the active ingredient of the finished leaf alcohol prepared in Examples 1-3 is greater than that of the finished leaf alcohol prepared in Comparative Examples 2 and 3. It can be proved that the process of the examples makes the prepared finished leaf alcohol have high purity and pure aroma. At the same time, it can be proved that the preparation of the methylsulfonic acid magnetic catalyst and the supported basic catalyst can improve the reaction efficiency, thereby well reducing the loss of leaf alcohol during the treatment process.

[0077] Table 1: Mass, purity and mass of active ingredient of finished leaf alcohol

[0078] Mass of finished product leaf alcohol / g Purity / % Mass of active ingredient / g Initial leaf alcohol 5 95.5 4.78 Example 1 4.73 99.6 4.71 Example 2 4.76 99.3 4.73 Example 3 4.71 99.5 4.69 Comparative Example 1 4.24 97.4 4.13 Comparative Example 2 4.55 99.1 4.51 Comparative Example 3 4.62 98.9 4.57

[0079] The above embodiments are only illustrative of the principles and effects of the present invention, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A method for purifying the aroma of leaf alcohol, characterized in that, It includes the following steps: S1: Preparation of methylsulfonic acid magnetic catalyst Mix nano-Fe3O4 and Tris-HCl solution evenly, then add dopamine hydrochloride, stir and filter to obtain PDA-modified Fe3O4 support. Mix methylsulfonic acid and toluene evenly and add the PDA-modified Fe3O4 support, perform ultrasonic treatment and then carry out condensation reflux, then use magnetic field to separate the product, obtain the solid product and wash it with ether, and obtain the methylsulfonic acid magnetic catalyst after separation and collection; S2: Esterification of leaf alcohol Add leaf alcohol and methylsulfonic acid magnetic catalyst into a container, add glacial acetic acid under stirring, then carry out heating reflux and water separation, take samples regularly for GC detection, end the reaction when the leaf alcohol peak < 0.5%, obtain the esterification mixture. After the esterification mixture stands and cools down, recover the methylsulfonic acid magnetic catalyst to obtain the esterification solution. The esterification solution is washed successively with water and Na2CO3 solution, stirred and then allowed to stand for stratification to separate the aqueous phase I and the organic phase I. The aqueous phase I is transferred to the sewage treatment station, and the organic phase I is transferred to the crude product tank for storage and standby; S3: Alcoholysis and fractionation of the esterification solution Mix polyvinylpyrrolidone powder and N,N-dimethylformamide in a container evenly, then add 1,4-diazabicyclo[2.2.2]octane, filter after heating and stirring to obtain the solid reactant. Wash, dry and grind the solid reactant evenly, then immerse it in NaOH solution and stir, wash, filter and dry to obtain the supported basic catalyst. Mix the organic phase I, pure water and ethanol, add the supported basic catalyst, stir and then carry out heating reflux, recover ethanol at atmospheric pressure. After the alcoholysis kettle cools down, obtain the alcoholysis solution. The alcoholysis solution is allowed to stand for liquid separation and then filtered by suction, discharge the waste liquid and adjust the pH of the remaining solution, then filter by suction again to obtain the aqueous phase II and the organic phase II. Fractionate the organic phase II to obtain the finished leaf alcohol.

2. The aroma purification method of leaf alcohol according to claim 1, characterized in that, The preparation of the methylsulfonic acid magnetic catalyst in step S1 includes the following steps: S1.1: Mix nano-Fe3O4 and Tris-HCl solution with a pH of 8-8.5 in a mass ratio of 1:(120-150) in a container and stir evenly, then add dopamine hydrochloride with a mass 2-3 times that of nano-Fe3O4, stir for 8-10 hours and then filter to obtain the PDA-modified Fe3O4 support; S1.2: Mix 3-4 parts by weight of methylsulfonic acid and 80-100 parts by weight of toluene in a container and stir evenly, then add 6-8 parts by weight of the PDA-modified Fe3O4 support, place it in an ultrasonic disperser and ultrasonicate for 15-20 minutes, then heat up to 105-110 °C, keep the temperature and carry out condensation reflux at a stirring speed of 650-800 rpm for 12-15 hours, then apply a magnetic field to separate the product to obtain the solid product. Wash the solid product with ether and then adsorb and collect it with a magnet to obtain the methylsulfonic acid magnetic catalyst.

3. A method for purifying the aroma of leaf alcohol according to claim 1, characterized in that, The esterification of leaf alcohol in step S2 includes the following steps: S2.1: Add 4 - 5 parts by weight of leaf alcohol and 0.2 - 0.3 parts by weight of methylsulfonic acid magnetic catalyst into a container, then add 3 - 4 parts by weight of glacial acetic acid under stirring, control the stirring speed at 400 - 500 rpm. After the glacial acetic acid is completely added, heat and reflux at a temperature of 80 - 90 °C, and at the same time separate the water generated by the reaction through a water separator. Take samples of the mixture in the reaction kettle every 3 - 5 minutes and conduct GC detection. When the peak of leaf alcohol < 0.5%, end the reaction to obtain an esterification mixture; S2.2: After the esterification mixture is allowed to stand and cool down, recover the methylsulfonic acid magnetic catalyst through a magnet to obtain an esterification solution. Wash the esterification solution once with clear water, then wash it with a Na2CO3 solution with a mass fraction of 10 - 15% until the pH is 10 - 10.

5. Stir for 1 - 1.5 hours and then let it stand for stratification. Use a separatory funnel to separate the aqueous phase I and the organic phase I. Transfer the aqueous phase I to the sewage treatment station, and transfer the organic phase I to the crude product tank for storage and standby.

4. A method for purifying the aroma of leaf alcohol according to claim 1, characterized in that, Step S3 Alcoholysis and fractionation of the esterification solution, including the following steps: S3.1: Place 1 - 2 parts by weight of polyvinylpyrrolidone powder and 40 - 50 parts by weight of N,N - dimethylformamide in a container and mix evenly. Then add 0.6 - 0.8 parts by weight of 1,4 - diazabicyclo[2.2.2]octane, and then heat to 75 - 80 °C and continuously stir for 20 - 24 hours. Filter to obtain a solid reactant. Wash the solid reactant 2 - 3 times with ethanol, then place it in a vacuum oven and dry at a temperature of 60 - 65 °C. Then grind it evenly and immerse it in NaOH solution, stir for 18 - 20 hours, wash it with water and then filter, and then place it in a vacuum box and dry at a temperature of 60 - 65 °C to obtain a supported basic catalyst; S3.2: Place the organic phase I, pure water and ethanol in an alcoholysis kettle according to a mass ratio of 1:(0.6 - 0.8):(0.3 - 0.4), then add 16 - 18 wt% of the supported basic catalyst and stir evenly. Heat and reflux at a temperature of 120 - 130 °C for 3 - 4 hours, and then fractionate under normal pressure to recover ethanol. Wait for the alcoholysis kettle to cool down to 30 - 40 °C to obtain an alcoholysis solution; S3.3: After the alcoholysis solution is allowed to stand and separated by liquid, conduct suction filtration. Discharge the waste liquid obtained by suction filtration, adjust the pH of the remaining solution to 7, and then conduct suction filtration again to obtain the aqueous phase II and the organic phase II. Transfer the organic phase II to a distillation column, adjust the vacuum degree to - 0.088 MPa to - 0.1 MPa, and conduct fractionation at a temperature of 85 - 90 °C to collect the fractions to obtain the finished product of leaf alcohol.

5. A method for purifying the aroma of leaf alcohol according to claim 2, characterized in that, In step S1.1, the particle size of the nano - Fe3O4 is 100 - 200 nm.

6. A method for purifying the aroma of leaf alcohol according to claim 2, characterized in that, In step S1.2, the ultrasonic frequency of the ultrasonic disperser is 20 - 40 kHz.

7. A method for purifying the aroma of leaf alcohol according to claim 2, characterized in that, In step S1.2, the way to wash the solid product with ether is to completely immerse the solid product in ether, and then under the conditions of 80 - 85 °C and a stirring speed of 500 - 600 rpmm, conduct magnetic stirring for 4 - 4.5 hours.

8. A method for purifying the aroma of leaf alcohol according to claim 3, characterized in that, The container in step S2.1 is a reaction kettle equipped with a condensation device, a thermometer, an electric stirrer and a water separator.

9. A method for purifying the aroma of leaf alcohol according to claim 4, characterized in that, In step S3.1, the mass fraction of the NaOH solution is 50-60%.

10. A method for purifying the aroma of leaf alcohol according to claim 4, characterized in that, In step S3.3, the pH of the remaining solution is adjusted by adding an aqueous sulfuric acid solution with a mass fraction of 10-15%.

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