Preparation method of linalool

Abstract

The invention relates to the technical field of chemical engineering, and discloses a preparation method of linalool. According to the preparation method, a proper amount of auxiliaries containing Zn, Co and Fe elements are added into dehydrolinalool serving as a reaction raw material, so that the catalyst can break through the catalytic characteristic of the catalyst in the hydrogenation reaction process, the hydrogenation degree of the raw material is regulated and controlled, a certain amount of by-products dihydrolinalool and cyclodehydrolinalool capable of regulating and controlling fragrance are generated, and through testing of a professional fragrance evaluator, the effect is remarkable. The linalool product prepared by the invention is more fragrant, and the product quality is improved. Meanwhile, before the hydrogenation reaction liquid is rectified and refined, the reaction liquid is washed with an alkali solution to be subjected to deacidification treatment, so that the linalool can be inhibited from being dehydrated in the rectification process, and the product purity and the qualified product yield are improved.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and in particular to a method for preparing linalool. Background Art

[0002] Linalool is an important fragrance variety, and the purity of its aroma is the most important indicator for evaluating the quality of linalool. The aroma of linalool obtained by different processes varies greatly. Linalool with poor aroma can only be used in the detergent industry, while linalool with better aroma can be used in high value-added fields such as perfume and fragrance. Therefore, producing more competitive linalool products has become a common goal pursued in this field.

[0003] At present, the production process of linalool mainly adopts the intermittent reactor process, which uses dehydrolinalool as raw material, Pd / CaCO3 as catalyst, and is obtained by reacting with hydrogen. The intermittent reactor process not only has low production efficiency, but also the raw materials will be converted into linalool and dihydrolinalool with a high content under the action of the catalyst. In order to adjust the aroma of the product, it is also necessary to artificially add other spices to the product during post-processing to adjust the aroma, resulting in complex process, high cost, and unstable aroma of each batch of products. Therefore, how to directly generate an appropriate amount of adjustable aroma byproducts during the hydrogenation reaction of dehydrolinalool is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0004] In view of this, the present application provides a method for preparing linalool to solve the problem that the existing process requires additional adjustment of the product aroma, resulting in a complex process and unstable aroma of each batch of products.

[0005] According to an embodiment of the present application, a method for preparing linalool is provided, comprising the following steps:

[0006] S1, mixing dehydrolinalool and an auxiliary agent uniformly to form a raw material mixture;

[0007] The auxiliary agent comprises a compound containing at least one of the elements Zn, Co and Fe, and the mass ratio of the auxiliary agent to the dehydrolinalool is 0.001%-0.005%;

[0008] S2. Under the action of a catalyst, the raw material mixture reacts with hydrogen in a solvent, and a reaction liquid is obtained after the reaction is completed;

[0009] S3, washing the reaction solution with an alkaline solution, collecting an organic phase, performing a rectification treatment on the organic phase, and collecting a distillation tower top fraction.

[0010] It should be noted that the linalool production process in the prior art usually pursues high purity of linalool to avoid the short fragrance retention time, light fragrance and single aftertaste of linalool products. However, the present application found that the fragrance of linalool products is not the result of the action of a single substance, but is jointly affected by the purity of the main product and the content of key impurities. If the purity of linalool in the linalool product is very high, the content of key impurities such as dihydrolinalool is relatively small, which will cause the fragrance of the linalool product to be dull, and other spices need to be added to adjust the fragrance.

[0011] To this end, the present application proposes a method for preparing linalool, by adding a certain amount of auxiliary agents containing Zn, Co, and Fe elements to the reaction raw material dehydrolinalool, the metal elements in these auxiliary agents can be strongly combined with the active sites on the catalyst, inhibiting the partial activity of the catalyst, so that the catalyst breaks through its catalytic characteristics during the hydrogenation reaction, regulating the degree of hydrogenation of the raw materials, and generating a certain amount of byproducts dihydrolinalool and cyclodehydrolinalool (structural formula shown below) that can regulate the aroma. After testing by professional perfumers, the linalool product prepared by the present application has a more transparent aroma, which improves the product quality. If the auxiliary agent content is too high, it will affect the catalyst activity, resulting in the raw material conversion rate and product yield failing to meet the requirements. On the contrary, if the auxiliary agent content is too low, a certain amount of dihydrolinalool and cyclodehydrolinalool byproducts cannot be generated, affecting the product aroma.

[0012]

[0013] Cyclodehydrolinalool structure

[0014] At the same time, the present application has found that in the separation and refining process of linalool products, due to the high boiling point of linalool itself, the temperature of the tower bottom is still very high even under low pressure, and the auxiliary agent containing elements such as Zn, Co, and Fe is Lewis acid, which will catalyze the dehydration reaction of linalool at high temperature (the dehydration side reaction is shown in the following formula), and the dehydration byproduct has a similar boiling point to linalool and is not easy to separate, resulting in the product purity not meeting the standard, and the qualified product yield is only 20%-30%. In view of this, the present application washes the reaction solution with an alkaline solution before rectifying and refining the hydrogenation reaction solution for deacidification treatment, which can inhibit the dehydration of linalool during the rectification process, thereby improving the product purity and the qualified product yield.

[0015]

[0016] In some optional embodiments, the mass ratio of the auxiliary agent to the dehydrolinalool is 0.002%-0.004%. The amount of the auxiliary agent within this range can better balance the catalyst activity and the content of byproducts (dihydrolinalool and cyclodehydrolinalool).

[0017] In some optional embodiments, the auxiliary agent includes at least one of phosphate or acetate of Zn, Co, and Fe elements. The present application has found that phosphate or acetate of Zn, Co, and Fe elements has good solubility in the reaction solvent and can be evenly dispersed in the reaction system, so as to better strongly bind to the catalyst active site, so that only a small amount of auxiliary agent is needed to achieve the effect of suppressing the activity of the catalyst part. Exemplary, the auxiliary agent includes at least one of zinc phosphate, ferric phosphate, ferrous phosphate, cobalt phosphate, zinc acetate, ferrous acetate, ferrous acetate, or cobalt acetate.

[0018] Furthermore, in order to solve the problem of low production efficiency caused by the intermittent reactor process in the existing linalool production process, in some optional embodiments, S2 is carried out in a fluidized bed reactor, comprising the following steps: loading the catalyst and the solvent into the fluidized bed reactor, sealing it, and continuously introducing hydrogen into the fluidized bed reactor to ensure that the catalyst is in a fluidized state; thereafter, slowly pumping the raw material mixture into the fluidized bed reactor for reaction, controlling the reaction temperature to 40°C-120°C, and the reaction pressure to 1MPa-5MPa.

[0019] The present application adopts a fluidized bed reactor for hydrogenation reaction, which can ensure the continuous progress of the reaction and improve production efficiency. Controlling the reaction temperature and pressure within the above range can ensure the smooth progress of the reaction, while improving the purity of linalool, obtaining a certain amount of by-products dihydrolinalool and cyclodehydrolinalool, and improving the aroma of the product.

[0020] Furthermore, by controlling the reaction temperature to 50°C-100°C and the reaction pressure to 2MPa-4MPa, the aroma of the linalool product can be better ensured so that it can be applied in high-end fields.

[0021] In some optional embodiments, the feed rate of the raw material mixture is 1 mL / min-5 mL / min. Controlling the raw materials to enter the reactor slowly can ensure that the raw materials are completely converted in the reactor, avoid raw material residue, and also avoid violent heat release of the reaction and prevent the reaction from overheating.

[0022] It is understandable that in order to ensure that the reaction raw material dehydrolinalool can fully contact with hydrogen and promote the hydrogenation reaction, it is also necessary to reasonably control the amount of solvent. In some optional embodiments, the mass ratio of the solvent to the dehydrolinalool is 0.5-3:1, especially 0.5-1.5:1, on the one hand, it can ensure the smooth progress of the hydrogenation reaction, and on the other hand, it can also dilute the reaction system to avoid the violent heat release of the hydrogenation reaction, and prevent the reactor from causing safety accidents due to the failure to remove heat in time.

[0023] Exemplarily, the solvent includes pure water, at least one of aliphatic alkanes, aromatic hydrocarbons, ethers, and alcohols that do not react with dehydrolinalool, for example, at least one of ethanol, methanol, n-heptane, or toluene.

[0024] The amount of catalyst used has a great influence on the hydrogenation effect. The present application has found that when the mass ratio of the catalyst to the dehydrolinalool is 0.005-0.03:1, especially 0.01-0.02:1, the raw material conversion can be ensured to be complete, and the accumulation of raw materials in the reaction solution can be avoided, thereby affecting the purity and aroma of the linalool product.

[0025] Exemplarily, the catalyst includes at least one of Ni / SiO2, Ni / Al2O3, and Pd / CaCO3, thereby partially hydrogenating dehydrolinalool to linalool. It is understood that in the representation of the catalyst, the substance before the " / " represents the catalyst active component, and the substance after the " / " represents the catalyst carrier.

[0026] In some optional embodiments, the alkaline solution is an aqueous solution of an alkali metal hydroxide, and the content of the alkali metal hydroxide is 3%-10% based on the mass of the alkaline solution, thereby adjusting the acid sites of the catalyst and avoiding the dehydration side reaction of the product during the distillation process. Exemplarily, the alkali metal hydroxide includes at least one of NaOH and KOH.

[0027] In some optional embodiments, when the mass ratio of the alkali metal hydroxide to the dehydrolinalool is 0.005-0.025, especially 0.01-0.02, the acid sites of the catalyst can be better adjusted, thereby avoiding excessive dehydration side reaction of the product during the distillation process.

[0028] In some optional embodiments, the alkaline solution undergoes a neutralization reaction with the reaction solution, the reaction temperature is 50°C-90°C, and the reaction time is 10min-50min. In particular, when the reaction temperature is 60°C-80°C and the reaction time is 20min-40min, the acid sites of the catalyst can be better adjusted to avoid excessive dehydration side reactions of the product during the distillation process.

[0029] In some optional embodiments, the bottom temperature of the distillation tower is 130°C-170°C, the top temperature is 80°C-130°C, the pressure in the tower is 10Pa-500Pa absolute pressure, and the number of theoretical plates of the distillation tower is 15-25. In this way, product purification can be achieved, thereby obtaining a qualified linalool product.

[0030] Furthermore, when the bottom temperature of the distillation tower is controlled to be 140°C-160°C, the top temperature is 85°C-110°C, the pressure in the tower is 10Pa-100Pa absolute pressure, and the number of theoretical plates is 15-20, a linalool product with higher purity can be obtained, thereby obtaining a better aroma.

[0031] In some optional embodiments, based on the total mass of the overhead fraction, the overhead fraction comprises linalool with a content of >96%, dihydrolinalool with a content in the range of 0.01%-2%, and cyclodehydrolinalool with a content of ≥2%. Further, the overhead fraction comprises 96.1%-97% linalool, 0.6%-1.2% dihydrolinalool, and 2.1%-2.7% cyclodehydrolinalool.

[0032] In the presence of an appropriate amount of dihydrolinalool and cyclodehydrolinalool, the aroma of the linalool product can be made more penetrating, while also ensuring that the product has a long lasting fragrance, a steady fragrance, and a rich aftertaste, thereby improving the quality of the linalool product. The perfumer's score is higher than 90 points. Therefore, the linalool product prepared in this application can be used in higher-end daily chemical flavors and fragrances such as perfumes.

[0033] The technical solution of this application has the following advantages:

[0034] The preparation method of linalool provided in the present application, by adding an appropriate amount of additives containing Zn, Co, and Fe elements to the reaction raw material dehydrolinalool, can make the catalyst break through its catalytic characteristics during the hydrogenation reaction, regulate the degree of hydrogenation of the raw material, and generate a certain amount of byproducts dihydrolinalool and cyclodehydrolinalool that can regulate the aroma. After testing by professional perfumers, the linalool product prepared in the present application has a more transparent aroma, which improves the product quality. Compared with the later stage of adding additional spices to adjust the aroma, the process of the present application is simpler, the cost is lower, and the batch stability is better. Compared with the linalool with higher purity, the linalool product prepared in the present application has a more transparent aroma, a good fragrance, and a high aroma quality.

[0035] At the same time, before the hydrogenation reaction liquid is distilled and refined, the present application first washes the reaction liquid with an alkaline solution to perform a deacidification treatment, which can inhibit the dehydration of linalool during the distillation process, thereby improving the product purity and the yield of qualified products.

[0036] Additional aspects and advantages of the embodiments of the present application will be described and shown in part in the subsequent description, or explained through the implementation of the embodiments of the present application. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0038] In the following examples and comparative examples, if no specific experimental steps or conditions are specified, the conventional experimental steps or conditions described in the literature in the art can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0039] In the examples and comparative examples of the present application, the reagents used are as follows:

[0040] Hydrogen (purity 99.9%), Dalian Guangming Special Gas Co., Ltd.;

[0041] Zinc phosphate, zinc acetate, iron phosphate, cobalt phosphate, iron acetate, cobalt acetate, Sinopharm Group;

[0042] Pd / CaCO3 catalyst, Jiangsu Xinnok;

[0043] Dehydrolinalool, Haichuan Chemical.

[0044] The gas chromatography test conditions used in this application are as follows:

[0045] Instrument model: Agilent 7890B;

[0046] Chromatographic column: DB-5 (30m×0.25mm×0.25μm);

[0047] Column temperature: starting temperature 80°C, heating to 150°C at 10°C / min, maintaining for 5 min, then heating to 300°C at 20°C / min, maintaining for 10 min;

[0048] Inlet temperature: 200°C;

[0049] FID detector temperature: 300°C;

[0050] Split injection, split ratio 50:1;

[0051] Injection volume: 2.0 μm;

[0052] N2 flow rate: 40ml / min;

[0053] H2 flow rate: 400ml / min.

[0054] Example 1

[0055] The preparation method of linalool provided in this embodiment comprises the following steps:

[0056] 1) Weigh 100 g of dehydrolinalool, add 0.002 g of zinc phosphate thereto, mix well and set aside.

[0057] 2) Add anhydrous ethanol (50g) and Pd / CaCO3 catalyst (2g) to a 50ml micro fluidized bed reactor, seal the reactor cover, pressurize N2 to 3MPa to maintain pressure for leak testing, confirm that the reactor is well sealed, replace with N2 3 times and then replace with H2 3 times, and evacuate the H2 in the reactor. Turn on hydrogen, with a hydrogen flow rate of 5ml / s, so that the catalyst is in a fluidized state, control oil bath heating and kettle cooling, maintain the reaction temperature at 60°C, and the reaction pressure is 2MPa. Then, slowly pump the Zn-containing dehydrolinalool raw material prepared in step 1) into the reactor at a feed rate of 3mL / min, continuously feed and continuously extract.

[0058] 3) The reaction solution obtained in step 2) was washed with a 5 wt % sodium hydroxide aqueous solution (40 g) at 70° C. for 30 min, and the organic phase was collected and sent to a vacuum distillation tower (theoretical plate number is 17), the bottom temperature of the distillation tower was controlled to be 150° C., the top temperature of the tower was 100° C., and the pressure in the tower was 50 Pa absolute pressure to remove organic solvents, water and other impurities, and the top of the tower with a purity of linalool greater than 96% was extracted as a qualified product.

[0059] After testing, the product contains 96.8wt% of linalool, 2.2wt% of cyclodehydrolinalool and 0.3wt% of dihydrolinalool.

[0060] Example 2

[0061] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc phosphate added was 0.004 g.

[0062] Example 3

[0063] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc phosphate added was 0.005 g.

[0064] Example 4

[0065] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc phosphate added was 0.001 g.

[0066] Example 5

[0067] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc acetate added was 0.003 g.

[0068] Example 6

[0069] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of iron phosphate added was 0.004 g.

[0070] Example 7

[0071] Linalool was prepared according to the method of Example 1, except that the amount of cobalt acetate added in step 1) was 0.002 g.

[0072] Example 8

[0073] Linalool was prepared according to the method of Example 1, except that the amount of catalyst used in step 2) was 1 g.

[0074] Example 9

[0075] Linalool was prepared according to the method of Example 1, except that 3 g of Ni / Al2O3 catalyst was used in step 2).

[0076] Example 10

[0077] Linalool was prepared according to the method of Example 1, except that 0.5 g of Ni / Al2O3 catalyst was used in step 2).

[0078] Embodiment 11

[0079] Linalool was prepared according to the method of Example 1, except that in step 2), the reaction temperature was 40° C. and the reaction pressure was 5 MPa.

[0080] Example 12

[0081] Linalool was prepared according to the method of Example 1, except that in step 2), the reaction temperature was 100° C. and the reaction pressure was 3 MPa.

[0082] Embodiment 13

[0083] Linalool was prepared according to the method of Example 1, except that in step 2), the reaction temperature was 120° C. and the reaction pressure was 2 MPa.

[0084] Embodiment 14

[0085] Linalool was prepared according to the method of Example 1, except that in step 3), 50 g of a 5 wt % sodium hydroxide aqueous solution was used to wash the reaction solution.

[0086] Embodiment 15

[0087] Linalool was prepared according to the method of Example 1, except that in step 3), 30 g of a 10 wt % sodium hydroxide aqueous solution was used to wash the reaction solution.

[0088] Example 16

[0089] Linalool was prepared according to the method of Example 1, except that in step 3), the bottom temperature of the distillation tower was 140° C., the top temperature was 85° C., and the pressure in the tower was 10 Pa absolute pressure.

[0090] Embodiment 17

[0091] Linalool was prepared according to the method of Example 1, except that in step 3), the bottom temperature of the distillation tower was 160° C., the top temperature was 110° C., and the pressure in the tower was 100 Pa absolute pressure.

[0092] Comparative Example 1

[0093] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc phosphate added was 0.0005 g.

[0094] Comparative Example 2

[0095] Linalool was prepared according to the method of Example 1, except that in step 1), the amount of zinc phosphate added was 0.01 g.

[0096] Comparative Example 3

[0097] Linalool was prepared according to the method of Example 1, except that step 1) was omitted and dehydrolinalool was directly hydrogenated and refined.

[0098] Comparative Example 4

[0099] Linalool was prepared according to the method of Example 1, except that the alkaline solution washing process in step 3) was omitted, and the reaction solution obtained in step 2) was directly purified.

[0100] Comparative Example 5

[0101] 1) Add anhydrous ethanol (50g), Pd / CaCO3 catalyst (2g) and zinc phosphate (0.002g) to a 50ml micro fluidized bed reactor, seal the reactor cover, pressurize N2 to 3MPa to maintain pressure and test for leaks, confirm that the reactor is well sealed, replace with N2 3 times and then replace with H2 3 times, and evacuate the H2 in the reactor. Turn on hydrogen, with a hydrogen flow rate of 5ml / s, so that the catalyst is in a fluidized state, control oil bath heating and reactor cooling, maintain the reaction temperature at 60°C, and the reaction pressure at 2MPa. Then, slowly pump dehydrolinalool raw material (100g) into the reactor at a feed rate of 3mL / min, continuously feed and continuously extract.

[0102] 2) The reaction solution obtained in step 1) was washed with a 5 wt % sodium hydroxide aqueous solution (40 g) at 70° C. for 30 min, and the organic phase was collected and sent to a vacuum distillation tower (theoretical plate number is 17), the bottom temperature of the distillation tower was controlled to be 150° C., the top temperature of the tower was 100° C., and the pressure in the tower was 50 Pa absolute pressure to remove organic solvents, water and other impurities, and the top of the tower with a purity of linalool greater than 96% was extracted as a qualified product.

[0103] Comparative Example 6

[0104] 1) Add 200 g of n-hexane, 2 g of Pd / CaCO3 catalyst, and 0.002 g of zinc phosphate to the autoclave, seal the autoclave, and replace with nitrogen 6 times. Replace with synthesis gas containing carbon monoxide and hydrogen in a volume ratio of 1:1 6 times, turn on the stirring paddle, maintain the synthesis gas pressure (absolute pressure) at 1.0 MPa, and maintain the temperature in the reactor at 30°C for 12 hours. Stop stirring and vent the gas, and obtain a partial hydrogenation catalyst after filtering.

[0105] 2) Add anhydrous ethanol (50g) and the partial hydrogenation catalyst (2g) obtained in step 1) to a 50ml microfluidized bed reactor, seal the reactor cover, pressurize N2 to 3MPa to maintain pressure for leak testing, confirm that the reactor is well sealed, replace with N2 3 times and then replace with H2 3 times, and evacuate the H2 in the reactor. Turn on hydrogen, with a hydrogen flow rate of 5ml / s, so that the catalyst is in a fluidized state, control oil bath heating and kettle cooling, maintain the reaction temperature at 60°C, and the reaction pressure is 2MPa. Then, slowly pump dehydrolinalool raw material (100g) into the reactor at a feed rate of 3mL / min, continuously feed, and continuously extract.

[0106] 3) The reaction solution obtained in step 2) was washed with a 5 wt % sodium hydroxide aqueous solution (40 g) at 70° C. for 30 min, and the organic phase was collected and sent to a vacuum distillation tower (theoretical plate number is 17), the bottom temperature of the distillation tower was controlled to be 150° C., the top temperature of the tower was 100° C., and the pressure in the tower was 50 Pa absolute pressure to remove organic solvents, water and other impurities, and the top of the tower with a purity of linalool greater than 96% was extracted as a qualified product.

[0107] The linalool products obtained in Examples 1-17 and Comparative Examples 1-6 were subjected to GC detection, and the contents of the components were shown in Table 1.

[0108] Table 1 Linalool product composition

[0109]

[0110]

[0111] As can be seen from Table 1, the linalool product prepared in the present application includes linalool with a content of >96%, dihydrolinalool with a content in the range of 0.3-1.6%, and cyclodehydrolinalool with a content of ≥2%.

[0112] Compared with Example 1, the amount of auxiliary agent used in Comparative Example 1 is too small, resulting in too high content of dihydrolinalool, a product of over-hydrogenation, and correspondingly reduced content of linalool, while the content of cyclization product cyclodehydrolinalool is also too low. Similar rules also appear in Comparative Examples 3 and 5.

[0113] Compared with Example 1, the amount of auxiliary agent used in Comparative Example 2 is too much, which excessively suppresses the catalyst activity, resulting in low raw material conversion rate, correspondingly low linalool yield, and the content of over-hydrogenation product dihydrolinalool is also low, and the content of cyclization product cyclodehydrolinalool is slightly increased. In Comparative Example 4, the alkali washing step is omitted, which makes it difficult to suppress the dehydration of linalool during the distillation process, thereby causing the linalool content to decrease and the content of cyclodehydrolinalool to increase. In Comparative Example 6, the catalyst is partially deactivated in advance, so that no auxiliary agent is added during the hydrogenation reaction, which results in the reaction being unable to generate cyclodehydrolinalool.

[0114] The linalool products obtained in Examples 1-17 and Comparative Examples 1-6 were evaluated by 4 internal perfumers and 6 external perfumers from five dimensions: aroma intensity, odor complexity, aroma characteristics, aroma persistence, and sensory evaluation. The specific evaluation criteria are as follows:

[0115] 1. Aroma intensity (out of 20 points)

[0116] Intense (18-20 points): The aroma is very strong and attracts attention quickly and strongly, and can be clearly perceived even at a distance.

[0117] Moderate (12-17 points): The aroma intensity is moderate, neither too strong nor too weak, and can be perceived continuously and steadily.

[0118] Faint (6-11 points): The aroma is relatively faint and requires close proximity to be clearly perceived, or may be difficult to detect in some cases.

[0119] 2. Odor complexity (out of 20 points)

[0120] Highly complex (18-20 points): The aroma is composed of a variety of different odor components, each of which can be clearly distinguished and well balanced and coordinated with each other.

[0121] Medium complexity (12-17 points): The aroma is composed of several different odor components, but they are not as clearly distinguished as highly complex ones, and have a certain sense of hierarchy.

[0122] Simple (6-11 points): The aroma is mainly composed of a single or a few odor components, lacking complexity and layering.

[0123] 3. Aroma characteristics (out of 20 points)

[0124] Unique and Distinctive (18-20 points): The aroma has very unique characteristics and can be easily identified and distinguished from other aromas, making it recognizable.

[0125] General Characteristics (12-17 points): The aroma has some characteristics, but it is not as prominent as a unique and distinctive aroma. It can be recognized but may lack some uniqueness.

[0126] Unobvious (6-11 points): The aroma characteristics are not obvious, difficult to distinguish from other aromas, and lack recognition.

[0127] 4. Fragrance persistence (full score 20 points)

[0128] Long lasting (18-20 points): The aroma lasts very long in the air or in the human senses and can still be perceived even after a period of time.

[0129] Medium persistence (12-17 points): The aroma lasts for a moderate period of time and can be perceived for a certain period of time, but not as long as long persistence.

[0130] Short lasting (6-11 points): The aroma lasts for a short time, dissipates quickly, and is difficult to maintain for a long time.

[0131] 5. Sensory evaluation (full score 20 points)

[0132] Excellent (18-20 points): The aroma gives people a very pleasant feeling and can cause a strong positive emotional response. It is a leader in sensory experience.

[0133] Good (12-17 points): The aroma gives people a good feeling and can evoke a positive emotional response, but it may not be as profound as excellent.

[0134] Average (6-11 points): The aroma gives a general feeling and may not cause any special emotional response, or may cause some negative feelings.

[0135] Using the above criteria, the evaluator can score each dimension according to the actual performance of the aroma, and classify it into the corresponding grade according to the score. The total score is the sum of the scores of the five dimensions, with a full score of 100. After scoring the aroma quality, the average value is taken as the final score of the linalool product. The results are shown in Table 2.

[0136] Table 2 Evaluation of aroma of linalool products

[0137]

[0138]

[0139] According to Table 2, compared with Comparative Examples 1-6, the product scores of Examples 1-17 are all above 90 points, especially the product scores of multiple examples such as Example 1 are higher than 95 points. This shows that the method of the present application can obtain a linalool product with a more transparent aroma, better fragrance type and higher aroma quality, which can be used in the field of higher-end daily chemical flavors and fragrances such as perfumes.

[0140] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A method for preparing linalool, characterized in that, The steps include: S1, mixing dehydrolinalool and an auxiliary agent uniformly to form a raw material mixture; The auxiliary agent comprises a compound containing at least one of the elements Zn, Co and Fe, and the mass ratio of the auxiliary agent to the dehydrolinalool is 0.001%-0.005%; S2. Under the action of a catalyst, the raw material mixture reacts with hydrogen in a solvent, and a reaction liquid is obtained after the reaction is completed; S3, washing the reaction solution with an alkaline solution, collecting an organic phase, performing a rectification treatment on the organic phase, and collecting a distillation tower top fraction.

2. The method for preparing linalool according to claim 1, wherein The mass ratio of the auxiliary agent to the dehydrolinalool is 0.002%-0.004%; And / or, the auxiliary agent includes at least one of phosphates or acetates of Zn, Co, and Fe, preferably at least one of zinc phosphate, ferric phosphate, ferrous phosphate, cobalt phosphate, zinc acetate, ferric acetate, ferrous acetate, or cobalt acetate.

3. The preparation method of linalool according to claim 1, characterized in that, S2 is carried out in a fluidized bed reactor and comprises the following steps: The catalyst and the solvent are loaded into a fluidized bed reactor, which is sealed, and hydrogen is continuously introduced into the fluidized bed reactor to ensure that the catalyst is in a fluidized state; thereafter, the raw material mixture is slowly pumped into the fluidized bed reactor for reaction, and the reaction temperature is controlled to be 40°C-120°C and the reaction pressure is controlled to be 1MPa-5MPa.

4. The method for preparing linalool according to claim 3, wherein The reaction temperature is 50°C-100°C, and the reaction pressure is 2MPa-4MPa; And / or, the feed rate of the raw material mixture is 1 mL / min-5 mL / min.

5. The method for preparing linalool according to claim 1 or 3, characterized in that, The mass ratio of the solvent to the dehydrolinalool is 0.5-3:1, preferably 0.5-1.5:1; And / or, the solvent comprises pure water, at least one of aliphatic alkanes, aromatic hydrocarbons, ethers, and alcohols that do not react with dehydrolinalool, preferably at least one of ethanol, methanol, n-heptane, or toluene.

6. The method for preparing linalool according to claim 1 or 3, characterized in that, The mass ratio of the catalyst to the dehydrolinalool is 0.005-0.03:1, preferably 0.01-0.02:1; And / or, the catalyst includes at least one of Ni / SiO2, Ni / Al2O3, and Pd / CaCO3.

7. The method for preparing linalool according to claim 1, wherein The alkaline solution is an aqueous solution of alkali metal hydroxide, and the content of the alkali metal hydroxide is 3%-10% based on the mass of the alkaline solution; And / or, the alkali metal hydroxide includes at least one of NaOH and KOH; And / or, the mass ratio of the alkali metal hydroxide to the dehydrolinalool is 0.005-0.025, preferably 0.01-0.

02.

8. The method for preparing linalool according to claim 1 or 7, characterized in that, The alkaline solution reacts with the reaction solution to undergo a neutralization reaction at a temperature of 50°C to 90°C and a reaction time of 10min to 50min; Preferably, the reaction temperature is 60°C-80°C, and the reaction time is 20min-40min.

9. The method for preparing linalool according to claim 1, wherein The bottom temperature of the distillation tower is 130°C-170°C, the top temperature is 80°C-130°C, the pressure in the tower is 10Pa-500Pa absolute pressure, and the number of theoretical plates of the distillation tower is 15-25; Preferably, the bottom temperature of the distillation tower is 140°C-160°C, the top temperature is 85°C-110°C, the pressure in the tower is 10Pa-100Pa absolute pressure, and the number of theoretical plates is 15-20.

10. The method for preparing linalool according to claim 1, 2, 3, 4, 7 or 9, characterized in that: Based on the total mass of the tower top fraction, the tower top fraction comprises linalool having a content of >96%, dihydrolinalool having a content in the range of 0.01%-2%, and cyclodehydrolinalool having a content of ≥2%; Preferably, the overhead fraction comprises 96.1%-97% of linalool, 0.6%-1.2% of dihydrolinalool and 2.1%-2.7% of cyclodehydrolinalool.

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