Decoloring and fragrance-keeping method for synthesizing linalool

Abstract

The invention relates to the technical field of linalool synthesis, in particular to a decoloring and aroma-keeping method for synthesizing linalool, which comprises the following specific steps: S1, cracking generation: heating beta-pinene to high temperature, and cracking the beta-pinene to generate myrcene; s2, rapid cooling: rapidly cooling the split product myrcene to avoid side reaction; s3, crude sample generation: in the presence of an acid catalyst, myrcene reacts with water to generate linalool, the reaction temperature is 40-80 DEG C, and the reaction time is 4-12 hours; s4, neutralizing the crude sample: after the reaction is finished, neutralizing residual acid by using a sodium bicarbonate solution, and separating an organic phase by using a separating funnel; s5, washing the crude sample: washing the organic layer to be neutral, and removing water-soluble impurities at the same time; s6, purifying the crude sample: adding anhydrous sodium sulfate to dry an organic layer. According to the decoloring and fragrance-keeping method used in the invention, the synthesized linalool is easy to decolor and natural in fragrance, can easily meet the standards of food additives and spice supplies, and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of linalool synthesis, and particularly to a method for decolorizing and preserving the fragrance of synthesized linalool. Background Art

[0002] Synthetic linalool is a terpene alcohol compound artificially synthesized by chemical methods and has the same chemical structure as natural linalool (present in plants such as rosewood and lavender). As an organic compound with a unique chemical structure and properties, it exhibits extensive application value in industrial production and scientific research due to its excellent physical and chemical characteristics. Its unique aromatic odor makes it play a crucial role in the fragrance and cosmetics industries.

[0003] In the common process of synthesizing linalool in the prior art, problems such as difficult decolorization and unstable chromaticity are sometimes encountered. "Difficult decolorization" usually means that certain impurities in the crude product are difficult to remove by conventional methods (such as activated carbon adsorption, distillation, ion exchange, etc.), resulting in a darker color of the product. And "unstable chromaticity" means that the color of its finished product changes (such as turning yellow or getting darker) during storage or use, and a colorless or light-colored product cannot be obtained through simple treatment. These problems will seriously affect the quality of the product. The color change will directly affect the appearance of perfumes and cosmetics (such as a clear liquid becoming turbid or yellowing), reducing consumer acceptance. At the same time, oxidation products may be accompanied by peculiar odors (such as rancid odor), destroying the original fresh floral fragrance characteristics of linalool, which will lead to non-compliance or even violation of regulations whether used in daily chemicals or food additives.

[0004] Therefore, according to the above related technologies, there is an urgent need to develop a method for decolorizing and preserving the fragrance of synthesized linalool. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for decolorizing and preserving the fragrance of synthesized linalool to solve the problems of difficult decolorization, unstable chromaticity, and poor aroma quality in the prior art.

[0006] Based on the above purpose, the present invention provides a method for decolorizing and preserving the fragrance of synthesized linalool:

[0007] S1. Pyrolysis generation: Heat β-pinene to a high temperature to pyrolyze it into myrcene;

[0008] S2. Rapid cooling: Rapidly cool the pyrolysis product myrcene to avoid side reactions;

[0009] S3. Crude sample generation: In the presence of an acidic catalyst, myrcene reacts with water to generate linalool. The reaction temperature is 40 - 80°C, and the reaction time is 4 - 12 hours;

[0010] S4. Neutralize the crude sample: After the reaction is completed, neutralize the residual acid with sodium bicarbonate solution and separate the organic phase using a separatory funnel.

[0011] S5. Wash the crude sample: Wash the organic layer with water until it is neutral, and remove water-soluble impurities at the same time.

[0012] S6. Purify the crude sample: Add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear.

[0013] S7. Obtain the crude product: Remove the solvent by vacuum distillation using a rotary evaporator to obtain the crude product.

[0014] S8. Fractionate the crude product: Distill at a low pressure (10 - 20 mmHg) and collect the linalool fraction.

[0015] S9. Confirm the crude product: Confirm the main component by gas chromatography - mass spectrometry, and then obtain the crude linalool.

[0016] S10. Rectify the crude product: Add 1000 g of crude linalool and 50 g of composite decolorizing agent (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1) to the glass rectification column with a round-bottom flask in sequence, and use an electromagnetic heating mantle to heat and stir to make the material temperature reach 95 - 105 °C.

[0017] S11. Low-vacuum treatment: Maintain at 95 - 105 °C, and apply a low-vacuum state to the solution, and heat and reflux for 1 - 4 hours.

[0018] S12. Obtain the finished product: Switch to a high-vacuum system and rectify to obtain linalool under the conditions of a vacuum degree of 100 - 300 Pa and a temperature of 100 - 145 °C.

[0019] S13. Closed observation: Detect the chromaticity of linalool under the condition of closed storage at room temperature for 30 days.

[0020] Preferably, the weight ratio of the synthesized crude linalool to the composite decolorizing agent in S10 is 100:5.

[0021] Preferably, the composite decolorizing agent in S10 is a solution, and the composition of the solution is the sum of the weights of the three main materials dissolved in 10 times the amount of water.

[0022] Preferably, the water-washing step in S5 needs to be repeated 3 times with distilled water, and the amount of water each time is 1 / 5 of the volume of the organic phase. After water-washing, it is also necessary to let it stand until the two phases are clearly separated.

[0023] Preferably, in S7, the solution needs to be poured into the rotary flask inside the rotary evaporator, and the volume of the solution does not exceed 2 / 3 of the volume of the flask.

[0024] Preferably, in S4, ethyl acetate is used as the solvent for separating the organic phase using a separatory funnel, and the volume of ethyl acetate is 5 / 12 of the volume of the solution.

[0025] Preferably, the low vacuum state in S11 is 4000-8000 Pa.

[0026] Preferably, the high temperature in S1 specifically refers to 500-600°C.

[0027] Beneficial effects of the present invention:

[0028] The present invention uses a quasi-solution mixture of thiourea dioxide, sodium hydroxide and activated carbon powder as a composite decolorizing agent, adopts a one-pot method to react, and the reaction is simple to operate, has no danger, and does not damage the product. The thiourea dioxide in the composite decolorizing agent can remove coloring substances in the crude product, the sodium hydroxide can enhance its reducibility, and the activated carbon can remove impurities and odors, so that the distillation product is colorless and has an aroma that meets the requirements, and is more convenient to be applied in the fields of food additives, cosmetics, etc.

[0029] Under the action of the composite decolorizing agent mentioned in the present application, linalool can be distilled to obtain linalool distillate with a chromaticity of Y-1.5 after distillation. Not only does the chromaticity meet the production requirements, Y-1.5 indicates that the product is colorless and transparent or only slightly yellow, and even some color-sensitive formulas can be used. Moreover, the aroma is soft, and after being added to other commodities, additional aroma can be added to the commodities. Even if it is stored in a closed state at room temperature for 30 days, it does not change color, is convenient for transportation and storage, is suitable for large-scale procurement by factories, and can be widely used in food additives, cosmetics and other fields. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0031] The sources of some raw materials used in the present invention are as follows:

[0032] The crude synthetic linalool used in the following comparative examples and embodiments is synthesized by a specific chemical process of our factory, has a purity of 91%, is a brown clear oil, and has a distinct linalool lily of the valley aroma characteristic.

[0033] The synthesis of crude linalool requires preparation of β-pinene, acidic catalyst (phosphoric acid), purified water, sodium bicarbonate solution and anhydrous sodium sulfate.

[0034] Among them, β-pinene was provided by Jiangxi Xinsen Natural Vegetable Oil Co., Ltd., the acidic catalyst (phosphoric acid) came from Jiangsu Chengxing Phosphorus Chemical Industry Co., Ltd., the sodium bicarbonate solution was purchased from the baking soda factory of Shandong Haihua Co., Ltd., and anhydrous copper sulfate was purchased from Taixing Smelter Co., Ltd. (formerly Taixing Smelter).

[0035] Example 1: A method for decolorizing and preserving the fragrance of synthetic linalool, comprising the following steps:

[0036] S1. Pyrolysis generation: Heat β-pinene to a high temperature (500 °C) to pyrolyze it into myrcene;

[0037] S2. Rapid cooling: Rapidly cool the pyrolysis product myrcene to avoid side reactions;

[0038] S3. Crude sample generation: In the presence of an acidic catalyst, myrcene reacts with water to form linalool, and it is necessary to ensure that the reaction temperature is 50 °C and the reaction time is 4 hours;

[0039] S4. Neutralize the crude sample: After the reaction, neutralize the residual acid with a sodium bicarbonate solution and separate the organic phase using a separatory funnel;

[0040] S5. Wash the crude sample: Wash the organic layer until it is neutral and remove water-soluble impurities at the same time;

[0041] S6. Purify the crude sample: Add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear;

[0042] S7. Obtain the crude product: Remove the solvent by vacuum distillation using a rotary evaporator to obtain the crude product;

[0043] S8. Crude product fractionation: Distill at a low pressure and collect the linalool fraction (boiling point about 198 - 200 °C);

[0044] S9. Confirm the crude product: Confirm the main component by gas chromatography-mass spectrometry (GC-MS / MS) to finally obtain the crude linalool product.

[0045] S10. Crude product rectification: Add 1000 g of crude linalool product and 50 g of composite decolorizing agent (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving the weight in 10 times water) into a glass rectification column with a round-bottom flask in sequence, and use an electromagnetic heating mantle to heat and stir to make the material temperature reach 95 °C;

[0046] S11. Low vacuum treatment: Maintain at 95 °C and apply a low vacuum (4000 Pa) state to the solution, and heat and reflux for 1 hour;

[0047] S12. Obtain the finished product: Switch to a high-vacuum system and rectify at a vacuum degree of 100 Pa and a temperature of 100 °C to obtain approximately 850 g of linalool (linalool content: 98%). At this time, the color of the distillate is Y - 1.5, and the aroma of the distillate is gentle.

[0048] S13. Closed observation: Under the condition of closed storage at room temperature for 30 days, the linalool did not change color.

[0049] Example 2: A method for decolorizing and preserving the fragrance of synthetic linalool, comprising the following steps:

[0050] S1. Pyrolysis generation: Heat β-pinene to a high temperature (500 °C) to pyrolyze it into myrcene.

[0051] S2. Rapid cooling: Rapidly cool the pyrolysis product myrcene to avoid side reactions.

[0052] S3. Crude sample generation: In the presence of an acidic catalyst, myrcene reacts with water to form linalool. It is necessary to ensure that the reaction temperature is 50 °C and the reaction time is 4 hours.

[0053] S4. Neutralize the crude sample: After the reaction, neutralize the residual acid with a sodium bicarbonate solution and separate the organic phase using a separatory funnel.

[0054] S5. Wash the crude sample: Wash the organic layer until it is neutral, and at the same time remove water-soluble impurities.

[0055] S6. Purify the crude sample: Add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear.

[0056] S7. Obtain the crude product: Remove the solvent by vacuum distillation using a rotary evaporator to obtain the crude product.

[0057] S8. Crude product fractionation: Distill at a low pressure and collect the linalool fraction.

[0058] S9. Confirm the crude product: Confirm the main component by gas chromatography-mass spectrometry (GC-MS / MS) to finally obtain the crude linalool product.

[0059] S10. Rectify the crude product: Add 1000 g of crude linalool and 50 g of a composite decolorizing agent (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:1:1, a standard solution prepared by dissolving it in 10 times its weight of water) into a glass rectification column with a round-bottom flask in sequence, and use an electromagnetic heating mantle to heat and stir to make the material temperature reach 95 °C.

[0060] S11. Low-vacuum treatment: Maintain at 95 °C and apply a low vacuum (4000 Pa) to the solution, and heat and reflux for 1 hour.

[0061] S12. Obtain the finished product: Switch to a high-vacuum system and rectify to obtain approximately 850 g of linalool (linalool content: 98%) under the conditions of a vacuum degree of 100 Pa and a temperature of 100 °C. At this time, the colority of the distillate is Y-1.5, and the aroma of the distillate is gentle.

[0062] S13. Closed observation: Under the condition of closed storage at room temperature for 30 days, the linalool did not change color.

[0063] Example 3: A method for decolorizing and preserving the fragrance of synthetic linalool, comprising the following steps:

[0064] S1. Pyrolysis generation: Heat β-pinene to a high temperature (500 °C) to pyrolyze it to generate myrcene.

[0065] S2. Rapid cooling: Rapidly cool the pyrolysis product myrcene to avoid side reactions.

[0066] S3. Generation of crude sample: In the presence of an acidic catalyst, myrcene reacts with water to generate linalool, and it is necessary to ensure that the reaction temperature is 50 °C and the reaction time is 4 hours.

[0067] S4. Neutralize the crude sample: After the reaction, neutralize the residual acid with a sodium bicarbonate solution and separate the organic phase using a separating funnel.

[0068] S5. Wash the crude sample: Wash the organic layer until it is neutral and remove water-soluble impurities at the same time.

[0069] S6. Purify the crude sample: Add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear.

[0070] S7. Obtain the crude product: Remove the solvent by vacuum distillation using a rotary evaporator to obtain the crude product.

[0071] S8. Crude product fractionation: Distill at a low pressure and collect the linalool fraction (boiling point is about 198 - 200 °C).

[0072] S9. Confirm the crude product: Confirm the main component by gas chromatography-mass spectrometry (GC-MS / MS) to finally obtain the crude linalool product.

[0073] S10. Rectify the crude product: Add 1000 g of crude linalool and 50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:1:2, a standard solution prepared by dissolving it in 10 times its weight of water) into a glass rectifying column with a round-bottom flask in sequence, and use an electromagnetic heating mantle to heat and stir to make the material temperature reach 95 °C.

[0074] S11. Low-vacuum treatment: Maintain at 95 °C and apply a low vacuum (4000 Pa) state to the solution, and heat and reflux for 1 hour.

[0075] S12. Obtain the finished product: Switch to a high-vacuum system and rectify to obtain about 850 g of linalool (linalool content: 98%) at a vacuum degree of 100 Pa and a temperature of 100 °C. At this time, the color degree of the distillate is Y-1.5, and the aroma of the distillate is gentle;

[0076] S13. Closed observation: Under the condition of closed storage at room temperature for 30 days, the linalool did not change color.

[0077] Example 4: A method for decolorizing and preserving the fragrance of synthetic linalool, comprising the following steps:

[0078] S1. Pyrolysis generation: Heat β-pinene to a high temperature (500 °C) to pyrolyze it into myrcene;

[0079] S2. Rapid cooling: Rapidly cool the pyrolysis product myrcene to avoid side reactions;

[0080] S3. Generation of crude sample: In the presence of an acidic catalyst, myrcene reacts with water to generate linalool, and it is necessary to ensure that the reaction temperature is 50 °C and the reaction time is 4 hours;

[0081] S4. Neutralize the crude sample: After the reaction, neutralize the residual acid with a sodium bicarbonate solution and separate the organic phase using a separating funnel;

[0082] S5. Wash the crude sample: Wash the organic layer until it is neutral and remove water-soluble impurities at the same time;

[0083] S6. Purify the crude sample: Add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear;

[0084] S7. Obtain the crude product: Remove the solvent by vacuum distillation using a rotary evaporator to obtain the crude product;

[0085] S8. Crude product fractionation: Distill at a low pressure and collect the linalool fraction (boiling point about 198-200 °C);

[0086] S9. Confirm the crude product: Confirm the main component by gas chromatography-mass spectrometry (GC-MS / MS) to finally obtain the crude linalool product.

[0087] S10. Rectify the crude product: Add 1000 g of crude linalool and 50 g of a composite decolorizing agent (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving the weight in 10 times the amount of water) into a glass rectification column with a round-bottom flask in sequence, and use an electromagnetic heating jacket to heat and stir to make the material temperature reach 100 °C;

[0088] S11. Low-vacuum treatment: Maintain at 100 °C and apply a low vacuum (4000 Pa) to the solution, and heat and reflux for 1 hour;

[0089] S12. Obtain the finished product: Switch to a high-vacuum system and rectify to obtain approximately 850 g of linalool (linalool content: 98%) under the conditions of a vacuum degree of 100 Pa and a temperature of 100 °C. At this time, the color degree of the distillate is Y - 1.5, and the aroma of the distillate is gentle.

[0090] S13. Closed observation: Under the condition of closed storage at room temperature for 30 days, the linalool did not change color.

[0091] Comparative example 1:

[0092] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)" is replaced with "50 g of mixed decolorizer (granular activated carbon, diatomaceous earth = 2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)", and the rest of the steps are the same.

[0093] Comparative example 2:

[0094] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)" is replaced with "50 g of mixed decolorizer (aluminum oxide, activated clay = 3:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)", and the rest of the steps are the same.

[0095] Comparative example 3:

[0096] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)" is replaced with "50 g of mixed decolorizer (activated clay, molecular sieve = 2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)", and the rest of the steps are the same.

[0097] Comparative example 4:

[0098] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)" is replaced with "triethylene glycol reagent with a content of 99%", and the rest of the steps are the same.

[0099] Comparative example 5:

[0100] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving its weight in 10 times the amount of water)" is replaced with "boric acid crystal powder with a content of 99%", and the rest of the steps are the same.

[0101] Comparative example 6:

[0102] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving it in 10 times its weight of water)" is replaced with "acrylic carboxylic acid resin", and the rest of the steps are the same.

[0103] Comparative Example 7:

[0104] This comparative example is the same as Example 1 except that "50 g of composite decolorizer (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1, a standard solution prepared by dissolving it in 10 times its weight of water)" is replaced with "activated silica gel of 100 mesh", and the rest of the steps are the same.

[0105] Performance test:

[0106] Chromaticity detection:

[0107] ASTM E313-05 is a method for visually rating the yellowness or whiteness of white, near-white or colorless samples under sunlight, and can be used to evaluate white textiles, coatings, plastics, etc. Its definition of near white is: a color that meets [Munsell value greater than 8.3 (luminous reflectance factor light reflectance coefficient Y = 63)] and [Munsell hue B not exceeding 0.5, hue Y not exceeding 0.8, other hues not exceeding 0.3]. It indicates that the ideal diffuser is preferred white.

[0108] Experimental procedure:

[0109] 1. Instrument preparation and preheating

[0110] Environmental inspection: Ensure that the laboratory temperature is stable (22 °C), the humidity is below 85%, and avoid strong magnetic fields and direct light interference;

[0111] Turn on the machine and preheat: Connect the power supply and turn on the machine, preheat for 25 minutes, and open the cuvette dark box cover during preheating to avoid fatigue of the phototube.

[0112] 2. Calibration and parameter setting

[0113] Wavelength calibration: Use a praseodymium-neodymium filter to check the wavelength accuracy and adjust it to the target wavelength (235 nm);

[0114] Transmittance calibration: Put in a blank solution (distilled water) and adjust the transmittance T = 100%, absorbance A = 0;

[0115] Sensitivity setting: Fix the sensitivity gear ("1" gear) to ensure that the absorbance reading is 0.4.

[0116] 3. Sample measurement

[0117] Cuvette operation: Use quartz cuvettes (ultraviolet region), hold the frosted glass surface by hand, and avoid contaminating the light-transmitting surface;

[0118] The sample concentration needs to be diluted to an absorbance of 0.4 and measured in the order from dilute to concentrated.

[0119] Measurement steps:

[0120] Fill the blank solution and the sample solution into cuvettes respectively and place them in the sample cell rack;

[0121] Pull the lever to make the sample enter the optical path and record the absorbance A or transmittance T;

[0122] For high-precision measurement, repeat 3 times and take the average value.

[0123] Odor detection:

[0124] 1. Sample pretreatment

[0125] Extraction and enrichment: Enrich volatile components by methods such as dynamic headspace (DHS), solvent-assisted flavor evaporation (SAFE), or solid-phase microextraction (SPME). Specifically, use dynamic headspace DHS to purge the headspace of linalool samples with nitrogen, trap aroma compounds into a Tenax tube, and then perform thermal desorption and concentration;

[0126] Purification and concentration: Use cold trap focusing (liquid nitrogen cooling) to improve sensitivity and ensure effective enrichment of trace compounds (ppb level);

[0127] 2. Instrument parameter settings

[0128] Gas chromatography (GC): Select a polar column (DB-WAX) chromatographic column, with an initial temperature of 40 °C, hold for 2 minutes, increase to 200 °C at a rate of 2 °C / min, use helium as the carrier gas, and adjust the flow rate to 1 mL / min;

[0129] Mass spectrometry (MS): Use electron impact (EI) mode, adjust the temperature to 230 °C, adjust the scanning range to m / z 35, the scanning rate is 1 time / second, then set the split ratio of the sniffing interface to 1.5:1, part of the effluent enters the sniffing port, and the rest enters the mass spectrometer;

[0130] 3. Separation and detection

[0131] GC separation: After the sample is separated by the chromatographic column, it is split to the sniffing instrument and the mass spectrometer through a microfluidic device;

[0132] Sniffing detection: Sniffers record the odor characteristics and intensity in real time and mark the corresponding retention time. Sniffers need to be specially trained before formal work. When making records, unified descriptive vocabulary should be used to reduce subjective deviation. For example, the standard of ISO 5492 is adopted for description. ISO 5492 is the standard of sensory analysis terms issued by the International Organization for Standardization (ISO), with the full name of "Sensory analysis—Vocabulary". This standard systematically defines the key terms in the field of sensory evaluation, aiming to unify the professional expressions of sensory science research worldwide.

[0133] Table 1 Summary of experimental data in Examples 1 - 3 and Comparative Examples 1 - 8

[0134]

[0135]

[0136] Data analysis:

[0137] As can be seen from Table 1, the treatment method and several related examples in the present invention have better chromaticity stability and more appropriate odor.

[0138] Under the action of composite decolorizing agents with different weight ratios, the linalool distillate obtained after rectification of linalool has a chromaticity of Y - 1.5, a soft aroma, and does not change color even when stored sealed at room temperature for 30 days. It can be widely used in fields such as food additives and cosmetics;

[0139] In Comparative Example 1, a mixed decolorizing agent of granular activated carbon and diatomite is used to replace the composite decolorizing agent in the example. Although the granular activated carbon can adsorb some pigments, its adsorption capacity for impurities with boiling points close to linalool (such as eucalyptol and camphor) is limited. Granular activated carbon mainly adsorbs non - polar pigments (such as polycyclic aromatic hydrocarbons). The adsorption of substances by activated carbon mainly depends on pore size and surface chemical properties, but its non - polar characteristics may lead to uneven adsorption efficiency of some polar or non - polar components in linalool, affecting the separation effect. Especially in high - concentration or complex - component systems, activated carbon may adsorb both impurities and target products, reducing the rectification purity. And diatomite adsorbs polar impurities (such as metal ions and colloids). When the two are mixed, the removal efficiency of key impurities (such as aldehydes and ketones) may decrease by 10 - 30% due to competition for adsorption sites. And diatomite naturally contains trace acidic components (such as SiO 2 -Al 2 O 3 ) and may catalyze the isomerization of linalool (to form α - terpineol) or oxidation (to form linalool oxides) under high - temperature rectification (>90°C), affecting the aroma purity. It may be due to the above reasons that the aroma of the final product has a "wood" smell;

[0140] In Comparative Example 2, a mixed decolorizing agent of alumina and activated clay was used to replace the composite decolorizing agent in the example. Linalool is a thermosensitive compound and is prone to isomerization or decomposition at high temperatures (such as generating terpene by-products). When alumina and activated clay are used as adsorbents or catalyst carriers, relatively high temperatures may be required (such as activation or regeneration conditions), resulting in thermal degradation of linalool, reducing the product purity and yield. Moreover, the adsorption-desorption process of the adsorbent may prolong the residence time of the material at high temperatures, exacerbating thermal decomposition. At the same time, activated clay usually contains acidic sites (such as H + ), and alumina (especially acidic or basic types) may synergistically catalyze the isomerization of linalool (such as conversion to α-terpineol) or dehydration reaction (generating terpene by-products), resulting in a decrease in product purity. At the same time, alumina (especially γ-Al 2 O 3 ) will synergistically catalyze the isomerization of linalool through its surface acidic sites. The porous structure and high specific surface area of γ-Al 2 O 3 will also enhance the adsorption capacity of the reactants, and the high temperature during the rectification process will exacerbate the catalytic activity of the acidic sites, thus possibly triggering the occurrence of dehydration phenomena. It may be due to the above reasons that the chromaticity of the final product does not meet the requirements;

[0141] In Comparative Example 3, a mixed decolorizing agent of molecular sieve and activated clay was used to replace the composite decolorizing agent in the example. First of all, the molecular sieve selectively adsorbs small molecules through uniform pore sizes, while activated clay mainly adsorbs polar macromolecules (such as pigments and colloids). When the two are mixed, competitive adsorption may occur for linalool (molecular weight 154.25, medium polarity), resulting in partial adsorption of the target product and reducing the yield. Secondly, the molecular sieve has a very strong adsorption capacity for water (about 20% - 25% of its own weight), while the adsorption capacity of activated clay for organic matter is relatively low (usually <10%). After mixing, the overall efficiency may decrease due to inconsistent saturation rates of the adsorbents. Finally, the acidic sites (H + ) of activated clay may catalyze the isomerization of linalool (generating α-terpineol) or dehydration (generating terpene by-products) at high temperatures (>80°C). At the same time, the microporous structure of the molecular sieve (such as pore size) may limit the diffusion of linalool molecules, prolong its residence time in the acidic environment, exacerbate side reactions, and increase the content of by-products by 5 - 15%, resulting in non-compliance with the chromaticity requirements. In addition to these problems, due to the large density difference between activated clay (particle size 1 - 50μm) and molecular sieve (particle size 1 - 3mm), the two are prone to stratification after mixing, so the flow pattern in the rectification tower is uneven, and even the distributor may be blocked, resulting in an impact on the rectification efficiency;

[0142] In Comparative Example 4, triethylene glycol was used as the decolorizing agent, and the color of the distillate after rectification was Y-1.5. Although the decolorization effect was achieved, the stability was poor. First, it might be because triethylene glycol underwent oxidation or thermal cracking at high temperatures, generating by-products such as ethylene glycol and diethylene glycol, which contaminated linalool and led to a decrease in product purity (the typical impurity content increased by 0.5–2%). Linalool is a heat-sensitive substance, while triethylene glycol has a relatively high boiling point (about 285°C). If the rectification temperature was not properly controlled (such as approaching the boiling point of triethylene glycol), it might cause local overheating of linalool, triggering decomposition or isomerization (such as generating α-terpineol or geraniol). Second, triethylene glycol and linalool might form a non-ideal azeotropic mixture during rectification, resulting in a decrease in the relative volatility in the rectification column and a 20–40% decrease in separation efficiency. Finally, triethylene glycol and linalool have similar polarities, and trace amounts of triethylene glycol might remain after rectification (especially in the high-boiling point section), affecting the purity of linalool (such as causing abnormal odor or decreased transparency). After tracking, observing, and detecting, the product after rectification using triethylene glycol as the decolorizing agent changed color on the fifth day of storage at room temperature in a closed container, with the color becoming Y-2, and the aroma did not meet the requirements, being dull and having a gelatinized smell. These adverse results might be caused by the combination of the above multiple theoretical speculations;

[0143] In Comparative Example 5, boric acid was used as the decolorizing agent, and the color of the distillate after rectification was Y-1.5, and the aroma met the requirements, but the color stability was also poor. First, boric acid (H 3 BO 3 ) might undergo an esterification reaction with linalool (a terpene alcohol containing a hydroxyl group) under high-temperature or acidic conditions, generating linalool borate. Such by-products not only reduced the purity of the target product but also might change the odor and chemical stability of linalool. Second, it might be because boric acid released weak acidity (pH≈5) at high temperatures, which might catalyze the isomerization of linalool (such as generating α-terpineol) or dehydration reaction (generating terpene by-products), resulting in a decrease in the purity of the target product (the typical by-product content increased by 5–15%). Third, boric acid would dehydrate to form boric anhydride (B 2 O 3 ) and release water vapor at high temperatures (>170°C). This process might cause local overheating of linalool, exacerbating the heat-sensitive decomposition or oxidation reaction. Finally, the allyl hydroxyl group in linalool might undergo intramolecular cyclization under the action of boric acid, generating impurities such as eucalyptol and destroying its natural floral fragrance characteristics. After long-term tracking, observing, and detecting, the finished product changed color on the eighth day under storage at room temperature in a closed container, with the color becoming Y-2. These adverse results might be caused by the combination of the above multiple theoretical speculations;

[0144] In Comparative Example 6, the acrylic carboxylic resin is a weakly acidic cation resin. First, the carboxylic acid groups (-COOH) of the acrylic resin may undergo an esterification reaction with the hydroxyl groups (-OH) of linalool under high temperature or acidic conditions, generating by-products such as linalool acrylate, reducing the purity of the target product and changing its aroma characteristics. Second, the acrylic carboxylic resin may adsorb linalool molecules through hydrogen bonds or van der Waals forces, resulting in a yield loss of 5–15% during the rectification process, especially more significant for high-purity crude products (>90%). Moreover, the acidic sites on the resin surface (such as sulfonic acid groups) may catalyze the isomerization of linalool (generating α-terpineol) or dehydration (generating terpene by-products), causing the content of by-products to increase by 3–8%. Third, if relatively deteriorated resin is used, it may also release Fe 3+ , Ca 2+ and other metal ions, forming complexes with linalool and leading to an increase in chromaticity. Finally, the heat resistance of acrylic resin is usually lower than 120 °C (some cross-linked resins can withstand up to 150 °C), while the rectification of linalool often requires a relatively high temperature. Long-term high-temperature operation is likely to cause swelling or degradation of the resin skeleton, releasing oligomers to contaminate the product. These adverse results may be caused by the combination of the above-mentioned multiple theoretical speculations;

[0145] In Comparative Example 7, silica gel is a porous polar adsorbent. Through the polar interaction between the surface hydroxyl groups and impurities, it selectively adsorbs colored substances, thereby improving the color and purity of linalool. Before rectifying linalool, it is necessary to activate the silica gel first to remove the adsorbed water and restore its adsorption activity. Moreover, the pore size of the silica gel applied to rectify linalool also needs to be controlled under the condition that it does not affect its filtration efficiency. Nevertheless, the adsorption capacity of silica gel for non-polar pigments is weak, the decolorization effect is not as good as that of activated carbon, and the decolorization ability for dark or complex pigments is also insufficient. The finally detected chromaticity is relatively high. This unqualified result may be caused by the combination of the above-mentioned multiple theoretical speculations.

[0146] From the above multiple comparative examples, it can be known that: using the composite in this application as a decolorizing agent for synthesizing crude linalool, the obtained product has good chromaticity stability, the aroma meets the requirements, and the economic benefit is higher, having a broader market space.

[0147] Those of ordinary skill in the art should understand that: the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0148] This invention is intended to cover all such alternatives, modifications, and variations that fall within the broad scope of the appended claims. Accordingly, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A method for decolorizing and preserving fragrance of synthetic linalool, characterized in that: The specific steps include: S1. Cracking: heating β-pinene to a high temperature to crack it to generate myrcene; S2. Rapid cooling: Rapidly cooling the cleavage product myrcene to avoid side reactions; S3. Crude sample generation: In the presence of an acidic catalyst, myrcene reacts with water to generate linalool at a temperature of 40-80°C and a reaction time of 4-12 hours; S4. Neutralization of the crude sample: After the reaction is completed, the residual acid is neutralized with sodium bicarbonate solution, and the organic phase is separated using a separatory funnel; S5. Wash the crude sample with water: wash the organic layer with water until it is neutral and remove water-soluble impurities; S6. Purify the crude sample: add anhydrous sodium sulfate to dry the organic layer and let it stand until the solution is clear; S7. Obtaining a crude product: removing the solvent by reduced pressure distillation on a rotary evaporator to obtain a crude product; S8. Crude product fraction: distilled under low pressure (10-20 mmHg), collecting linalool fraction; S9. Confirm the crude product: confirm the main component by chromatography-mass spectrometry, and then obtain the crude linalool. S10 crude product distillation: 1000g of crude linalool and 50g of composite decolorizing agent (thiourea dioxide, activated carbon powder, sodium hydroxide = 3:2:1) were sequentially added to a glass distillation tower with a round-bottom flask, and heated and stirred with an electromagnetic heating jacket to a material temperature of 95-105°C; S11. Low vacuum treatment: maintaining 95-105°C, applying a low vacuum state to the solution, and heating under reflux for 1-4 hours; S12. Obtaining the finished product: Switching to a high vacuum system, distilling linalool at a vacuum degree of 100-300 Pa and a temperature of 100-145 ° C; S13. Closed observation: Store in closed condition at room temperature for 30 days and test the color of linalool.

2. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: The weight ratio of the crude synthetic linalool to the composite decolorizing agent in S10 is 100:

5.

3. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: The composite decolorizing agent in S10 is a solution, and the composition of the solution is the weight of the three main materials plus 10 times the weight of water dissolved.

4. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: The water washing step in S5 needs to be repeated 3 times with distilled water, and the amount of water each time is 1 / 5 of the volume of the organic phase. After the water washing, it is necessary to stand until the two phases are clearly separated.

5. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: In S7, the solution needs to be poured into the rotary flask inside the rotary evaporator, and the volume of the solution does not exceed 2 / 3 of the volume of the flask.

6. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: In S4, ethyl acetate is selected as the solvent for separating the organic phase using a separatory funnel, and the volume of ethyl acetate is 5 / 12 of the volume of the solution.

7. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: The low vacuum state in S11 is 4000-8000 Pa.

8. The method for decolorizing and preserving the fragrance of synthetic linalool according to claim 1, characterized in that: The high temperature in S1 specifically refers to 500-600°C.

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