Isomethyl ionone and preparation method thereof

Abstract

The invention discloses a preparation method of iso-methyl ionone. According to the method disclosed by the invention, residual citral methylal in pseudo-iso-methyl ionone is decomposed to generate citral in a cyclization process, and is oxidized into C10 acid by air in a refining process, and the C10 acid enters an iso-methyl ionone product, so that the effects of regulating the odor of the product and improving the odor stability of the product are achieved.

Description

Technical Field

[0001] The invention relates to a production method of isomethyl ionone, and belongs to the technical field of chemical industry. Technical Background

[0002] Isomethyl ionone is a traditional synthetic fragrance, which is prepared by condensation and cyclization with citral and butanone as raw materials. Since the methylene and methyl groups next to the keto carbonyl of butanone have little difference in reactivity, the pseudo-isomethyl ionone obtained by the condensation reaction is mostly a mixture of pseudo-normal-methyl ionone and pseudo-isomethyl ionone, and the content of pseudo-isomethyl ionone configuration in the mixture is generally 60-70%.

[0003] After cyclization, pseudo-isomethyl ionone can obtain 6 main isomers, among which α-isomethyl ionone has the best smell and a good floral aroma, while β and γ configurations tend to have a woody aroma and a sweet taste.

[0004]

[0005] Other residual impurities in pseudo-isomethyl ionone, such as citral methylal, will also decompose under acidic conditions to produce methanol and citral. The specific production pathways are as follows:

[0006]

[0007] Citral has a lemon smell, and the ppm level citral has a strong smell. In view of the problems existing in production, such as the removal of ppm level impurities, the use of refining methods often causes a certain proportion of products to enter the waste liquid, resulting in product waste; if not removed, the smell of the product will be impure and storage instability due to the fluctuation of the ppm level citral content. In production, distillation is generally used to remove trace citral and other light impurities.

[0008] Since the boiling points of the various configuration isomers of isomethyl ionone are very close, in order to maximize the yield, the commercially available isomethyl ionone products are all mixtures, among which the content of α-isomethyl configuration in the mainstream products is generally above 60%. Due to the particularity of the composition of isomethyl ionone products, isomethyl ionone has unique characteristics in terms of smell, which is generally described as having a sweet aroma, a violet flower aroma, and a combination of woody and honey wax aromas, an elegant aroma of iris, a slight amber aroma, and an osmanthus and acacia-like scent.

[0009] Due to the particularity of the composition of isomethyl ionone products and the fact that it is used multiple times in small quantities after opening the package in downstream applications, the stability of the odor of isomethyl ionone becomes particularly important. The industry generally adds citric acid below 40ppm to the finished product before packaging to ensure the stability of the odor during use. However, since citric acid has a strong sour taste, the amount added is small, and it is solid, it is difficult to add. Adding more can easily mask the original aroma and sweetness of the product, giving the product a distinct sour taste. Adding less will result in insufficient sweetness, and the floral aroma will be dry and not soft enough, so the accuracy of citric acid addition is required to be high. Summary of the invention

[0010] The object of the present invention is to provide a method for preparing isomethyl ionone, by which the separation efficiency can be effectively improved, the loss in the separation process can be reduced, and the influence of the accuracy of citric acid addition on the product odor in the existing production process can be avoided. The method has the advantages of simple operation, high product yield, stable odor, etc., and is suitable for industrial application.

[0011] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0012] A method for preparing isomethyl ionone comprises: subjecting a cyclization raw material pseudoisomethyl ionone containing citral methylal to cyclization reaction and refining to obtain isomethyl ionone, wherein the citral methylal is decomposed to generate citral during the acid-catalyzed cyclization reaction, and then is oxidized to C10 acid in contact with air during the refining process and enters into the product; wherein the content of citral methylal in the cyclization raw material pseudoisomethyl ionone is 0.001-0.1wt%, preferably 0.001-0.01wt%.

[0013] As a preferred technical solution, in the pseudo-isomethyl ionone of the cyclization raw material, the content of pseudo-isomethyl ionone is 60-70wt%, preferably 65-70%, the content of pseudo-normal methyl ionone is 29-39.8wt%, the content of citral methylal is 0.001-0.1wt%, preferably 0.001-0.01%, and the rest are other pseudo-isomethyl ionone isomers. The content of citral methylal can be adjusted to below 1000ppm by rectification, or can be controlled by adjusting the citral drop speed, drop reaction temperature, aging temperature and time coupling in the condensation reaction process, for example, the drop speed of citral is controlled at 1.2-6.1g / min, the reaction temperature after drop addition is preferably 20-28°C, the duration is 80-160min, and then the temperature is raised to 35-40°C at a speed of 0.1-0.3°C / min for 20-60min.

[0014] In the present invention, the catalyst for the cyclization reaction is an acidic catalyst, preferably at least one of sulfuric acid, phosphoric acid, fluorosulfonic acid, and methanesulfonic acid, more preferably 80-95% sulfuric acid, 60-85% phosphoric acid;

[0015] In the present invention, the solvent for the cyclization reaction is aromatic hydrocarbons or alkanes, preferably C6-C10 aromatic hydrocarbons or alkanes, more preferably toluene, m-xylene, octane, or heptane;

[0016] In the present invention, the mass ratio of cyclization raw material: solvent: catalyst is 1:0.5-1.5:0.1-0.5;

[0017] The conditions of the cyclization reaction are: the reaction temperature is 40-100°C, preferably 50-80°C; the reaction pressure is 0-0.5MPa, preferably 0.01-0.1MPa.

[0018] The citral methylal in the cyclization raw material is decomposed to generate citral during the acid-catalyzed cyclization reaction.

[0019] In the present invention, the refining includes solvent removal and distillation operations, wherein the solvent removal conditions are: vacuum degree 1-3KPa, operating temperature 110-140°C; the distillation conditions are: vacuum degree 0.1-1KPa, operating temperature 120-170°C, tower plate number 0-10, and reflux ratio 0.1-1.

[0020] In the present invention, the amount of air added in the distillation process is 0.1-10%, preferably 0.5-1%, of the volume percentage of the gas phase space in the distillation tower. By introducing a certain amount of air, citral is oxidized to C10 acid and enters the isomethyl ionone product.

[0021] The present invention further provides an isomethyl ionone product, which preferably contains 10-860 ppm, more preferably 10-86 ppm of C10 acid; the C10 acid is obtained by oxidation of citral.

[0022] The isomethyl ionone product of the present invention has a rounded floral fragrance, a sweet / sweet-and-sour smell, and has good smell stability.

[0023] The beneficial effects of the present invention are:

[0024] Compared with the prior art, the present invention controls the content of citral methylal in the cyclization raw material pseudoisomethyl ionone, decomposes it into citral through a cyclization reaction, and then oxidizes it into C10 acid through a separation process to enter the isomethyl ionone product, which also plays the role of adding citric acid in the existing production process. However, because the sour taste of C10 acid is obviously weaker than that of citric acid, the present invention avoids the problem of product odor deviation caused by insufficient accuracy of citric acid addition, and the product has good odor stability. At the same time, it overcomes the problem of product loss caused by removal of trace citral. DETAILED DESCRIPTION

[0025] The present invention is further described in detail with reference to the following examples, but the scope of the present invention is not limited to these examples.

[0026] Gas chromatography analysis conditions of the product: Agilent gas chromatograph, RTX-WAX column, 50°C for 5 min; 10°C / min to 80°C, for 5 min; 10°C / min to 100°C, for 5 min; 10°C / min to 160°C, for 15 min.

[0027] The sources of the reagents in the following examples are shown in Table 1:

[0028] Table 1

[0029]

[0030]

[0031] Unless otherwise specified, other reagents used in the following examples are commercially available.

[0032] Preparation Example 1

[0033] 900 g of butanone and 900 g of methanol were added to the reactor, replaced with nitrogen and pressurized to 0.3 MPa, stirred and mixed, and the temperature was maintained at 25°C. 24 g of potassium hydroxide was added, and stirring was continued for 60 min. 304 g of citral was added dropwise, and the dropping time was 120 min (the dropping speed was 2.53 g / min). After the dropping was completed, 25°C was maintained to continue the reaction for 150 min, and the operating temperature was increased to 40°C at a rate of 0.2°C / min, and the reaction was continued for 30 min. The conversion rate of citral in the reactant was 99.8% in the gas phase monitoring. The reaction was completed, neutralized with acetic acid, methanol and unreacted butanone were removed, and the pseudo-isomethyl ionone was washed with water and distilled to obtain pseudo-isomethyl ionone, which was composed of 98.5% of total ketones (of which pseudo-isomethyl ionone accounted for 67.2% and pseudo-normal methyl ionone accounted for 31.3%), 32 ppm of citral formal, and the others were pseudo-isomethyl ionone isomers.

[0034] Preparation Example 2

[0035] The citral addition time in the preparation example 1 was adjusted to 100 min (the dropping speed was 3.04 g / min), the temperature during the dropping was 23° C., and the reaction was continued for 120 min at 23° C. after the dropping was completed. The operating temperature was increased to 38° C. at a rate of 0.25° C. / min, and the reaction was continued for 40 min. The other conditions remained unchanged, and the composition of the obtained pseudoisomethylionone was 98.6% of total ketones (of which pseudoisomethylionone accounted for 67.3% and pseudo-normal-methylionone accounted for 31.3%), citral formalin 54 ppm, and the rest were pseudoisomethylionone isomers.

[0036] Preparation Example 3

[0037] The citral addition time in the preparation example 1 was adjusted to 60 min (the dropping speed was 5.06 g / min), the dropping temperature was 26° C., and the reaction was continued for 90 min at 26° C. After the dropping was completed, the operating temperature was increased to 39° C. at a rate of 0.3° C. / min, and the reaction was continued for 50 min. The other conditions remained unchanged, and the composition of the obtained pseudoisomethylionone was 98.5% of total ketones (of which pseudoisomethylionone accounted for 67.3% and pseudo-normal-methylionone accounted for 31.2%), citral formalin 79 ppm, and the rest were pseudoisomethylionone isomers.

[0038] Preparation Example 4

[0039] Referring to the synthesis method of pseudo-isomethyl ionone in the document "Synthesis Research of Flavor Ionone Series Compounds", 113.1g of 90% KOH was dissolved in 1172.5g of methanol, and 868.4g of butanone was added. After mixing, 304g of citral was added dropwise at 15°C. After the addition was completed, the temperature was raised to 40°C and kept warm for 2.5h. Acetic acid was neutralized, methanol and unreacted butanone were removed, and the mixture was washed with water. The citral methylal content in the crude product was 1470ppm by gas phase detection. The crude product was treated by distillation to remove unreacted citral and part of citral methylal, and the composition of pseudo-isomethyl ionone was 98.3% of total ketones (of which pseudo-isomethyl ionone accounted for 67.1% and pseudo-normal methyl ionone accounted for 31.2%), citral methylal 761ppm, and the rest were pseudo-isomethyl ionone isomers.

[0040] Embodiment 1

[0041] 300g of m-xylene and 100g of phosphoric acid were added to a 1000mL reactor, the temperature was raised to 65°C, the operating pressure was 0.01MPa, and 300g of raw material pseudoisomethylionone (of which pseudoisomethylionone accounted for 67.3%, pseudo-n-methylionone accounted for 31.2%, citral formalin content was 79ppm, and the rest were other pseudoisomethylionone isomers) was added dropwise. The conversion rate of pseudoisomethylionone was 99.9% when monitored by gas phase. The reaction was stopped and the phosphoric acid was separated by standing. The oil phase was washed with water, and the meta-xylene was removed from the washed oil phase under the conditions of 2000 Pa and 123°C, and then the oil phase was refined under the conditions of 300 Pa, 135°C, 5 plates, 0.4 reflux ratio and 0.5% air introduction. 296.7 g of isomethyl ionone product was obtained at the top of the tower, wherein the α-isomethyl ionone content was 62.7%, and the C10 acid content was 67.4 ppm. The odor of the product was described as rounded floral fragrance and sweet. The product was stored at room temperature for 2 months without any change in odor.

[0042] Embodiment 2

[0043] Add 450g of m-xylene and 70g of phosphoric acid into a 1000mL reactor, heat to 75°C, operate at 0.1MPa, and dropwise add 300g of raw material pseudoisomethylionone (of which pseudoisomethylionone accounts for 67.2%, pseudo-n-methylionone accounts for 31.3%, citral formalin content is 32ppm, and the rest is other pseudoisomethylionone isomers). The conversion rate of pseudoisomethylionone is 99.8% when monitored by gas phase. Stop the reaction, let stand and separate the phosphoric acid phase. After the oil phase was washed with water, the meta-xylene was removed from the washed oil phase under the conditions of 1500Pa and 134°C, and then the oil phase was refined under the conditions of 200Pa, 127°C, 2 plates, 0.8 reflux ratio and 0.2% air intake. 296.5g of isomethyl ionone product was obtained at the top of the tower, wherein the α-isomethyl ionone content was 62.3%, the C10 acid content was 27.3ppm, and the product odor was described as a round floral fragrance and sweet; the product was stored at room temperature for 2 months, and the odor did not change.

[0044] Embodiment 3

[0045] Add 180g of m-xylene and 140g of phosphoric acid into a 1000mL reactor, heat to 55°C, operate at 0.05MPa, and dropwise add 300g of raw material pseudoisomethylionone (of which pseudoisomethylionone accounts for 67.3%, pseudo-n-methylionone accounts for 31.3%, citral formalin content is 54ppm, and the rest is other pseudoisomethylionone isomers). The conversion rate of pseudoisomethylionone is monitored by gas phase and is >99.9%. Stop the reaction, let stand and separate the phosphoric acid. The oil phase was washed with water, and the meta-xylene was removed from the washed oil phase under the conditions of 2000Pa and 123°C, and then the oil phase was refined under the conditions of 500Pa, 153°C, 8 plates, 0.2 reflux ratio and 0.8% air introduction. 296.7g of isomethyl ionone product was obtained at the top of the tower, wherein the content of α-isomethyl ionone was 63.1%, and the content of C10 acid was 46.1ppm. The odor of the product was described as rounded floral fragrance and sweet. The product was stored at room temperature for 2 months without any change in odor.

[0046] Embodiment 4

[0047] Add 260g of m-xylene and 120g of phosphoric acid into a 1000mL reactor, heat to 55°C, operate at 0.08MPa, and dropwise add 300g of raw material pseudoisomethylionone (of which pseudoisomethylionone accounts for 67.1%, pseudo-n-methylionone accounts for 31.2%, citral formalin content is 761ppm, and the rest is other pseudoisomethylionone isomers). The conversion rate of pseudoisomethylionone is monitored by gas phase>99.9%, stop the reaction, let stand and separate the phosphoric acid phase. After the oil phase was washed with water, the meta-xylene was removed from the washed oil phase under the conditions of 2150Pa and 126°C, and then the oil phase was refined under the conditions of 400Pa, 151°C, 8 plates, 0.3 reflux ratio and 1.5% air intake. 296.6g of isomethyl ionone product was obtained at the top of the tower, wherein the content of α-isomethyl ionone was 63.1%, and the content of C10 acid was 644.8ppm. The odor of the product was described as a round floral fragrance with a sweet and sour taste. The product was stored at room temperature for 2 months without any change in odor.

[0048] Comparative Example 1

[0049] The raw material composition is: 300g of pseudo-isomethyl ionone (of which pseudo-isomethyl ionone accounts for 66.8%, pseudo-normal methyl ionone accounts for 31.2%, citral formal content is 1300ppm, and the rest are other pseudo-isomethyl ionone isomers), and the remaining operations are the same as in Example 3. 296.1g of isomethyl ionone product is obtained at the top of the tower, wherein the α-isomethyl ionone content is 62.9%, the C10 acid content is 1110ppm, and the product odor is described as a rounded floral fragrance, sweet and sour; after being stored at room temperature for 2 months, the product odor is described as a rounded floral fragrance, with a lighter sweetness and sourness.

[0050] Comparative Example 2

[0051] The air introduction operation during refining was omitted, and the remaining operations were the same as in Example 3. 296.1 g of isomethyl ionone product was obtained at the top of the tower, wherein the α-isomethyl ionone content was 63.2%, the citral content was 41.5 ppm, and the product odor was described as a mixed floral scent with a lighter lemon flavor; after storage at room temperature for 2 months, the product odor was described as having a mixed floral scent with a heavier impurity.

[0052] Comparative Example 3

[0053] During the distillation process of the comparative example, 5 g of light components (including 0.25% citral and 99.75% α-isomethyl ionone) were removed, and the remaining operations were the same as those of the comparative example 2. 291.3 g of isomethyl ionone product was obtained from the top of the tower, wherein the α-isomethyl ionone content was 61.3% and the citral content was 0.5 ppm. The product odor was described as having a flowery fragrance, being relatively dry, and having a relatively light sweetness. After being stored at room temperature for 2 months, the product odor was described as having a relatively light flowery fragrance, being dry, and having a miscellaneous gas.

[0054] Comparative Example 4

[0055] 25 ppm of citric acid was added to the product in Comparative Example 3, and the product odor was described as a rounded floral fragrance and sweet. After being stored at room temperature for 2 months, the product odor did not change significantly.

[0056] Comparative Example 5

[0057] 50 ppm of citric acid was added to the product in Comparative Example 3, and the product odor was described as weak floral and sour. After being stored at room temperature for 2 months, the product odor was described as having a lighter floral aroma, a stronger sour taste, and no sweetness.

Claims

1. An isomethyl ionone composition, characterized in that Contains 10-860 ppm, preferably 10-86 ppm, of C10 acid, which is obtained by oxidation of citral.

2. A method for preparing isomethyl ionone, comprising: The cyclization raw material pseudoisomethyl ionone containing citral methylal is subjected to cyclization reaction and refining to obtain isomethyl ionone, wherein the citral methylal is decomposed to generate citral during the acid-catalyzed cyclization reaction, and then oxidized to C10 acid during the refining process and enters the product; wherein the content of citral methylal in the cyclization raw material pseudoisomethyl ionone is 0.001-0.1wt%, preferably 0.001-0.01wt%.

3. The method according to claim 2, characterized in that: In the cyclization reaction, the mass ratio of cyclization raw material: solvent: catalyst is 1:0.5-1.5:0.1-0.

5.

4. The method according to claim 2 or 3, characterized in that: In the cyclization raw material pseudo-isomethyl ionone, the content of pseudo-isomethyl ionone is 60-70wt%, and the content of pseudo-normal methyl ionone is 29-39.8wt%.

5. The method according to any one of claims 2 to 4, characterized in that: The catalyst for the cyclization reaction is an acidic catalyst, preferably at least one of sulfuric acid, phosphoric acid, fluorosulfonic acid, and methanesulfonic acid, more preferably 80-95% sulfuric acid, 60-85% phosphoric acid; and / or: The solvent for the cyclization reaction is at least one of aromatic hydrocarbons and alkanes.

6. The method according to any one of claims 2 to 5, characterized in that: The conditions of the cyclization reaction are: reaction temperature of 40-100° C. and reaction pressure of 0-0.5 MPa.

7. The method according to any one of claims 2 to 6, characterized in that: The refining includes solvent removal and distillation.

8. The method according to claim 7, characterized in that: The solvent removal conditions are: vacuum degree 1-3KPa, operating temperature 110-140℃.

9. The method according to claim 7, characterized in that: The distillation conditions are: vacuum degree 0.1-1KPa, operating temperature 120-170°C, number of plates 0-10, and reflux ratio 0.1-1.

10. The method according to any one of claims 7 to 9, characterized in that: A certain amount of air is introduced during the distillation process, and the amount of air added is 0.1-10% of the volume percentage of the gas phase space of the distillation tower, preferably 0.5-1%.

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