An alpha ionone composition and a method for preparing the same

Abstract

The application provides an alpha ionone composition and a preparation method thereof, the alpha ionone composition comprising ionone and isomers, and 0.0001-0.01wt% of impurity A; wherein the structure of the impurity A is shown as formula 1. The application controls the generation of the key impurity A by limiting the content of the pseudo-ionone pre-isomer impurity in the reaction raw material, the method is simple to operate, a typical violet flower fragrance product can be obtained, the product has better fragrance quality than market competitors, and the product is applied to high-end cosmetics and daily-use cosmetics.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to an α-ionone composition and its preparation method. Background Technology

[0002] Alpha-ionone is a traditional synthetic fragrance that plays an irreplaceable role in flavor formulation. Because it blends well with a wide range of floral and woody fragrances, it can be used as a blending agent, modifier, and base fragrance ingredient. Current synthetic methods primarily use pseudoionone as a raw material, undergoing an acid-catalyzed cyclization reaction to obtain the alpha-ionone product.

[0003] Currently, all industrially commercialized methods for synthesizing α-ionone use acid as a catalyst. Extensive research has been conducted on the cyclization reaction itself, as evidenced by Chinese Patent CN1508113, US Patent US4565894, and Chinese Patent CN106278853A. Although α-ionone prepared using existing technologies can achieve a certain level of purity, the aroma of α-ionone produced by different manufacturers varies considerably. The top notes of violet flower fragrance often have a ripe fruity odor, affecting the overall aroma and leading to substandard α-ionone fragrance products.

[0004] In view of this problem, it is of great significance to provide an α-ionone with stable aroma and its preparation method. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide an α-ionone composition and its preparation method.

[0006] Through experimental research, the inventors of this application discovered a key impurity, A, that affects the floral aroma of α-ionone. This impurity emits a ripe fruity aroma, masking the top notes of the violet fragrance and reducing product quality. Reducing this impurity to a certain concentration can eliminate its off-flavor. However, unfortunately, this impurity has a boiling point close to that of the product, and conventional distillation requires a negative pressure <10 Pa and more than 75 platens for separation. These conditions are too stringent, resulting in high energy consumption and low yield. Currently, the content of impurity A in α-ionone is typically between 0.1-3 wt%.

[0007] Through further research, the inventors discovered that impurity A was obtained from the cyclization reaction of the pre-isomer impurity of the pseudoionone raw material. Therefore, the present invention proposes an ideal measure to reduce the pre-isomer impurity to the target content by pre-treating the raw material pseudoionone before the reaction.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides an α-ionone composition comprising ionone and its isomer, and impurity A in an amount of 0.0001-0.01 wt%, such as 0.0001 wt%, 0.0005 wt%, 0.001 wt%, 0.002 wt%, 0.003 wt%, 0.004 wt%, 0.005 wt%, 0.006 wt%, 0.007 wt%, 0.008 wt%, 0.009 wt%, 0.01 wt%, etc.; wherein the structure of impurity A is as shown in Formula 1:

[0010]

[0011] Structural characterization, NMR data: H1NMR (400HZ CDCl3) δ 1.25 (6H,s), 1.29 (2H,t), 1.96 (2H,m), 2.21 (3H,s), 2.24 (3H,s), 5.43 (1H,t), 6.22 (1H,d), 6.33 (1H,d), 16.77 (1H,s).

[0012] In the α-ionone composition of the present invention, ionone and isomers include α-ionone and isomers such as β-ionone and γ-ionone, wherein the proportion of α-ionone is maintained at 70-90 wt%.

[0013] Secondly, the present invention provides a method for preparing the α-ionone composition, which can be prepared from crude α-ionone by any conventional separation method disclosed in the art, or prepared from pseudo-ionone as a raw material by the following cyclization method, without any particular requirement in the present invention.

[0014] In one specific example, the present invention provides a method for preparing the α-ionone composition, wherein the method involves mixing pseudoionone with a solvent and then, under the action of an acid catalyst, obtaining the α-ionone composition through a cyclization reaction; wherein the content of pseudoionone pre-isomer impurities in the pseudoionone is controlled to be ≤0.01wt%, for example, 0.01wt%, 0.009wt%, 0.008wt%, 0.007wt%, 0.005wt%, 0.003wt%, 0.001wt%, 0.0005wt%, 0.0001wt%, etc.

[0015] Currently, the purity of commercially available pseudoionone raw materials is generally greater than 90%, and the content of pre-isomer impurities is less than 10 wt%. The structures of pseudoionone and its pre-isomer are as follows:

[0016]

[0017] The pseudoionone pre-isomer impurity can also participate in acid-catalyzed cyclization reactions, generating impurity A with a fruity aroma. Its boiling point is close to that of the main product, ionone, and its isomers, making it difficult to separate by conventional distillation. Patent CN113548952 proposes reducing the content of the pseudoionone pre-isomer impurity by controlling the reaction, but this still does not reach the control range required by this invention. Therefore, this invention provides a method for pretreatment based on the principle of pseudoionone.

[0018] In this invention, if the content of the pseudoionone pre-isomer impurity in the pseudoionone raw material is >0.01wt%, the pseudoionone pre-isomer can be converted into pseudoionone by a metal-catalyzed isomerization reaction; this method can make the content of the pre-isomer impurity ≤0.01wt%.

[0019] Specifically, the pseudoionone raw material that can be used for isomerization conversion has a pre-isomer impurity content >0.01%, which can be 0.1%, 0.5%, 0.6%, 0.8%, 1.1%, 1.5%, 1.8%, 2.0%, 2.5%, 3.0%, 3.5%, 4.5%, 5.5%, 6.5%, 7.0%, 9.5%, etc. Generally, the impurity content of commercially available pseudoionone is <10%.

[0020] The isomerization reaction proposed in this invention is a metal-catalyzed isomerization reaction transposition, which can be carried out in a fixed-bed reactor. The metal catalyst used is one or more of Pt-Rh / Al2O3, Pt-Ru / Al2O3, Pt-Ir / Al2O3, Pt-Pd / Al2O3, Pt-Ni / Al2O3, and Pt-Co / Al2O3.

[0021] The isomerization reaction is carried out at a temperature of 30-60℃, such as 30℃, 35℃, 40℃, 45℃, 50℃, 60℃, etc., preferably 50-60℃; the residence time is 10-300min, such as 10min, 20min, 30min, 50min, 60min, 90min, 100min, 150min, 210min, 220min, 250min, 300min, etc., preferably 60-150min.

[0022] Preferably, the isomerization reaction is carried out in an inert atmosphere, which is selected from nitrogen, argon, and helium.

[0023] This heterogeneous process is simple to operate, can be carried out continuously, and the material system does not contain toxic or reactive metal impurities. It has an operating cycle of >1 year and is suitable for industrial application.

[0024] It should be noted that the above-described method disclosed in this invention is only used as an example to illustrate one of the catalytic conversion methods used to achieve the pseudoionone with low pre-isomer impurity content (≤0.01wt%) as described in this invention. The source of the pseudoionone raw material described in this invention should not be limited by the steps and parameters in the above method.

[0025] The α-ionone composition described above is prepared by mixing pseudo-ionone with a solvent and then performing a cyclization reaction using an acid as a catalyst. This method is known in the art. The relevant operations and process conditions in the preparation method of this invention, as well as the apparatus used, can all be carried out using conventional methods in the art, and there are no particular limitations. Those skilled in the art can optimize the process based on existing technology and known processes according to actual needs. Specifically, for example, the conditions listed in the following embodiments of this invention can be used:

[0026] In this invention, the solvent is one or a combination of several of the following: benzene, toluene, xylene, cumene, tetrahydrofuran, chloroform, diethyl ether, anisole, and n-hexane.

[0027] Preferably, the mass ratio of the pseudoionone to the solvent is 1:0.1-5, such as 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, etc., and more preferably 1:0.5-2.

[0028] In this invention, the acid catalyst includes one or more of phosphoric acid, sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid;

[0029] Preferably, the amount of acid catalyst used is 0.1-1 times the mass of pseudoionone, for example, 0.1 times, 0.2 times, 0.3 times, 0.5 times, 0.8 times, 1 times, etc.; specifically, the acid catalyst can be prepared as a 20-99 wt% aqueous solution for use.

[0030] In this invention, the cyclization reaction is carried out at a temperature of 40-90℃, such as 50℃, 55℃, 60℃, 75℃, 80℃, 90℃, etc., preferably 50-80℃; the reaction time is 1-12h, such as 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 11h, 12h, etc., preferably 4-8h;

[0031] Preferably, at the start of the reaction, the pseudoionone and solvent can be spread at the bottom in a certain proportion. After the reaction temperature is reached, the acid catalyst can be added dropwise for 1-2 hours. The dropwise time is not included in the total reaction time. Of course, all raw materials can also be added in a conventional one-pot method.

[0032] In this invention, after the cyclization reaction is completed, post-processing processes such as washing and distillation are also included. These are all conventional operations in the field and are not particularly required by this invention. For example, in some specific examples, the post-processing method used is: the cyclization reaction solution is washed with water, desolventized, and distilled to obtain α-ionone.

[0033] The α-ionone composition prepared by the method of the present invention has an α-ionone content maintained at 70-90 wt%, such as 70%, 75%, 80%, 85%, 90%, etc.; the content of impurity A is 0.0001-0.01 wt%, and the remainder is isomers such as β-ionone and γ-ionone.

[0034] Compared with the prior art, the positive effects of the technical solution of this invention are as follows:

[0035] This invention first identifies a key impurity A that affects the floral scent of α-ionone, and controls the formation of impurity A by limiting the content of the pre-isomer impurity of pseudoionone in the reaction raw materials. This method is simple to operate and can produce products with a typical violet floral scent. The aroma quality of the product is superior to that of competing products on the market, and the product can be used in high-end cosmetics and daily cosmetics. Detailed Implementation

[0036] The present invention will be further described below with reference to specific embodiments. These embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention or the method of implementing the present invention.

[0037] The main raw material sources in the embodiments and comparative examples of this invention are as follows; unless otherwise specified, all other raw materials were obtained through ordinary commercial channels:

[0038] Metal-supported catalyst: Aladdin Reagents Co., Ltd.

[0039] Phosphoric acid: Aladdin Reagents Company;

[0040] Pseudoionone: Maclean's Reagent Company (purity >90%, proisomer content <10%).

[0041] The performance test parameters and corresponding test methods used in the various embodiments of the present invention are as follows:

[0042] Aroma evaluation: scored by three experienced perfumers according to GB / T 14454.2-2008;

[0043] The purity of the product was determined using a gas chromatograph. The specific analytical conditions were as follows: instrument: Agilent GC 8890; column: Agilent DB-5; column oven temperature: 80℃; injection port temperature: 300℃; detector temperature: 310℃; split ratio: 10:1; carrier gas flow rate: 1 mL / min; temperature program: hold at 80℃ for 0 min, increase to 200℃ at a rate of 8℃ / min, hold for 5 min, continue to increase to 300℃ at a rate of 30℃ / min, and hold for 7 min.

[0044] Example 1

[0045] 1) Pretreatment of pseudoionone raw materials

[0046] Pt-Rh / Al2O3 was packed into a fixed bed, and pseudoionone (content 95%, pre-isomer content 3wt%) was introduced into the fixed bed for isomerization reaction under a nitrogen atmosphere. The reaction temperature was 60℃, and the residence time was maintained at 50 min. A sample was taken at the outlet for gas phase analysis. The pseudoionone content was 98wt%, and the pre-isomer content was 0.008wt%.

[0047] 2) Preparation of α-ionone composition

[0048] Take 500g of the pseudoionone treated in step 1) and 400g of n-hexane solvent. Premix the two in a glass reactor equipped with a mechanical stirrer and heat to 80℃. Take 150g of 70wt% phosphoric acid aqueous solution and inject it into the reactor using a metering pump. Set the flow rate and add it dropwise for 1 hour. After the addition is complete, continue the cyclization reaction at the temperature for 3 hours. After terminating the reaction, let it stand for 1 hour, separate the acid phase, wash it twice with pure water, remove the solvent by distillation, and then perform vacuum distillation. Collect the fraction at 140℃ / 200PaA to obtain the α-ionone composition. Gas chromatography analysis showed that the α-ionone content was 80wt%, the total ketone content (including α-ionone and isomers such as β-ionone and γ-ionone) was 98wt%, and the impurity A content was 0.007wt%.

[0049] Sensory evaluation of aroma: Typical violet fragrance, free of impurities, pure aroma (39.5 points).

[0050] Example 2

[0051] 1) Pretreatment of pseudoionone raw materials

[0052] Pt-Ru / Al2O3 was packed into a fixed bed, and pseudoionone (content 94.6 wt%, pre-isomer content 3.2 wt%) was introduced into the fixed bed for isomerization reaction under a nitrogen atmosphere. The reaction temperature was 55℃, and the residence time was maintained at 80 min. A sample was taken at the outlet for gas phase analysis. The pseudoionone content was 98 wt%, and the pre-isomer content was 0.007 wt%.

[0053] 2) Preparation of α-ionone composition

[0054] Take 1000g of the pseudoionone treated in step 1) and 600g of diethyl ether solvent. Premix the two in a glass reactor equipped with a mechanical stirrer and heat to 70℃. Take 400g of 30wt% sulfuric acid aqueous solution and inject it into the reactor using a metering pump. Set the flow rate and add it dropwise for 1 hour. After the addition is complete, continue the cyclization reaction at the temperature for 4 hours. After terminating the reaction, let it stand for 1 hour, separate the acid phase, wash it twice with pure water, remove the solvent by distillation, and then perform vacuum distillation. Collect the fraction at 130℃ / 150PaA to obtain the α-ionone composition. Gas chromatography analysis showed that the α-ionone content was 77wt%, the total ketone content (including α-ionone and isomers such as β-ionone and γ-ionone) was 97.5wt%, and the impurity A content was 0.005wt%.

[0055] Sensory evaluation of aroma: Typical violet fragrance, free of impurities, pure aroma (39.1 points).

[0056] Example 3

[0057] 1) Pretreatment of pseudoionone raw materials

[0058] Pt-Ir / Al2O3 was packed into a fixed bed, and pseudoionone (content 94.5 wt%, pre-isomer content 3 wt%) was introduced into the fixed bed for isomerization reaction under a nitrogen atmosphere. The reaction temperature was 50℃, and the residence time was maintained at 100 min. A sample was taken at the outlet for gas phase analysis. The pseudoionone content was 98 wt%, and the pre-isomer content was 0.009 wt%.

[0059] 2) Preparation of α-ionone composition

[0060] Take 800g of the pseudoionone treated in step 1) and 800g of xylene solvent. Premix them in a glass reactor equipped with a mechanical stirrer and heat to 65℃. Take 200g of 50wt% p-toluenesulfonic acid aqueous solution and inject it into the reactor using a metering pump. Set the flow rate and add it dropwise for 1 hour. After the addition is complete, continue the cyclization reaction at the temperature for 5 hours. After terminating the reaction, let it stand for 1 hour, separate the acid phase, wash it twice with pure water, remove the solvent by distillation, and then perform vacuum distillation. Collect the fraction at 130℃ / 150PaA to obtain the α-ionone composition. Gas chromatography analysis showed that the α-ionone content was 85wt%, the total ketone content (including α-ionone and isomers such as β-ionone and γ-ionone) was 98wt%, and the impurity A content was 0.008wt%.

[0061] Sensory evaluation of aroma: Typical violet fragrance, free of impurities, pure aroma (39.6 points).

[0062] Example 4

[0063] 1) Pretreatment of pseudoionone raw materials

[0064] Pt-Ni / Al2O3 was packed into a fixed bed, and pseudoionone (content 95wt%, pre-isomer content 3wt%) was introduced into the fixed bed for isomerization reaction under a nitrogen atmosphere. The reaction temperature was 60℃, and the residence time was maintained at 120min. A sample was taken at the outlet for gas phase analysis. The pseudoionone content was 98wt%, and the pre-isomer content was 0.005wt%.

[0065] 2) Preparation of α-ionone composition

[0066] Take 800g of the pseudoionone treated in step 1) and 1000g of diethyl ether solvent. Premix the two in a glass reactor equipped with a mechanical stirrer and heat to 80℃. Take 300g of 30wt% hydrochloric acid aqueous solution and inject it into the reactor using a metering pump. Set the flow rate and add it dropwise for 1 hour. After the addition is complete, continue the cyclization reaction at the temperature for 6 hours. After terminating the reaction, let it stand for 1 hour, separate the acid phase, wash it twice with pure water, remove the solvent by distillation, and then perform vacuum distillation. Collect the fraction at 135℃ / 180PaA to obtain the α-ionone composition. Gas chromatography analysis showed that the α-ionone content was 83wt%, the total ketone content (including α-ionone and isomers such as β-ionone and γ-ionone) was 98wt%, and the impurity A content was 0.003wt%.

[0067] Sensory evaluation of aroma: Typical violet fragrance, free of impurities, pure aroma (39.5 points).

[0068] Comparative Example 1

[0069] Referring to step 2 in Example 1, the difference is that the pseudoionone (content 95wt%, pre-isomer content 3wt%) is not pretreated and directly participates in the cyclization reaction to obtain the α-ionone composition. Gas chromatography analysis shows that the α-ionone content is 79wt%, the total ketone content (including α-ionone and isomers such as β-ionone and γ-ionone) is 95wt%, and the impurity A content is 2.4wt%.

[0070] Aroma sensory evaluation: The top notes of the aroma are mixed with ripe fruit, the floral notes are weak, and the aroma is acceptable (28.5 points).

[0071] Comparative Example 2

[0072] The α-ionone composition (pre-isomer content 2.4 wt%) prepared using Comparative Example 1 was separated by conventional distillation, reducing the content of impurity A in the composition to 0.02 wt%.

[0073] Aroma sensory evaluation: Excellent violet fragrance, slightly off-putting, the aroma is acceptable (35.5 points).

Claims

1. A method for preparing an α-ionone composition, characterized in that, The α-ionone composition is prepared by mixing pseudoionone with a solvent and then undergoing a cyclization reaction under the action of an acid catalyst; wherein the content of the pseudoionone pre-isomer impurity in the pseudoionone is controlled to be ≤0.01wt%; the structure of the pseudoionone pre-isomer impurity is shown in Formula 2: （2）； The α-ionone composition comprises ionone and its isomer, and impurity A in an amount of 0.0001-0.01 wt%; wherein the structure of impurity A is shown in Formula 1: （1）。 2. The preparation method according to claim 1, characterized in that, The solvent is one or a combination of several of the following: benzene, toluene, xylene, cumene, tetrahydrofuran, chloroform, diethyl ether, anisole, and n-hexane.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the pseudoionone to the solvent is 1:0.1-5.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the pseudoionone to the solvent is 1:0.5-2.

5. The preparation method according to claim 1, characterized in that, The acid catalyst includes one or more of phosphoric acid, sulfuric acid, hydrochloric acid, and p-toluenesulfonic acid.

6. The preparation method according to claim 1, characterized in that, The amount of acid catalyst used is 0.1-1 times the mass of pseudoionone.

7. The preparation method according to claim 1, characterized in that, The cyclization reaction is carried out at a temperature of 40-90℃ for 1-12 hours.

8. The preparation method according to claim 7, characterized in that, The cyclization reaction is carried out at a temperature of 50-80℃ for 4-8 hours.

9. A pretreatment method for pseudoionone raw materials, characterized in that, The impurities of pseudoionone preisomers are converted into pseudoionones through a metal-catalyzed isomerization reaction. The content of the pre-isomer impurity is ≤0.01wt%; The structure of the pseudoionone preisomer impurity is shown in Formula 2: （2）。 10. The method according to claim 9, characterized in that, The pseudoionone feedstock, which can be used for isomerization reaction conversion, wherein the content of pre-isomer impurities is >0.01wt%.

11. The method according to claim 9, characterized in that, The isomerization reaction is a metal-catalyzed isomerization reaction.

12. The method according to claim 11, characterized in that, The reaction is carried out in a fixed-bed reactor.

13. The method according to claim 11, characterized in that, The metal catalyst used in the reaction is one or more of Pt-Rh / Al2O3, Pt-Ru / Al2O3, Pt-Ir / Al2O3, Pt-Pd / Al2O3, Pt-Ni / Al2O3, and Pt-Co / Al2O3.

14. The method according to claim 9, characterized in that, The isomerization reaction is carried out at a temperature of 30-60℃ for a time of 10-300 min.

15. The method according to claim 14, characterized in that, The isomerization reaction is carried out at a temperature of 50-60℃ for a time of 60-150 min.

16. The method according to claim 9, characterized in that, The isomerization reaction is carried out in an inert atmosphere, which is selected from nitrogen, argon, and helium.

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