A preparation method of pseudoisomethyl ionone

Abstract

The invention discloses a preparation method of pseudo-isomethyl ionone. The present invention adds a mixed solution of butanone, an organic solvent and a catalyst at the reactor inlet, citral is added in batches, the reaction temperature is 0-30°C, the total reaction time is 5 hours, acid is added and neutralized after the reaction, and butanone and the organic solvent are recovered by means of a stirred tank combined distillation tower. When the desolvation starting stage or the cumulative amount of the top extraction is 65-85% of the total amount of butanone and organic solvent added before the reaction, a quantitative polar cosolvent is added to the tower bottom, and then desolvation is carried out. It is then washed with water and phase-separated, and finally a pseudo-isomethyl ionone product is obtained by vacuum distillation. Compared with the solvent recovered by distillation, the product yield can be increased by 5-8% when the solvent obtained by the method is applied mechanically, and the isomer ratio is between 65-68%.

Description

Technical Field

[0001] The invention belongs to the field of spices and fine chemicals, and particularly relates to a preparation method of isomethyl ionone. Background Art

[0002] Isomethyl ionone is an important synthetic fragrance with unique aroma quality. It has a sweet aroma and the beautiful aroma of violet and iris. It has good stability and can be well blended with many floral and woody spices. Therefore, it has a wide range of uses in flavor formulation.

[0003] Isomethyl ionone is a pale yellow to yellow liquid, typically synthesized in a two-step reaction. First, citral and butanone undergo condensation under an alkaline catalyst to form the intermediate pseudoisomethyl ionone. Then, pseudoisomethyl ionone undergoes a cyclization reaction under acidic conditions to obtain isomethyl ionone. Isomethyl ionone is a mixture of multiple isomers, the primary synthesized forms being α-methyl ionone, β-methyl ionone, α-isomethyl ionone, and β-isomethyl ionone. α-isomethyl ionone has the best aroma, being 2-3 times stronger than the others and possessing the most pronounced violet-iris aroma. Currently, α-isomethyl ionone typically accounts for between 60% and 70% of isomethyl ionone products on the market. Therefore, obtaining the appropriate ratio of pseudoisomethyl ionone in the production process is crucial, generally requiring an isomer ratio of at least 65%.

[0004] Since the aldehyde-ketone molar ratio is relatively high during the reaction and a large amount of solvent is used, in order to improve the utilization rate of butanone and solvent and reduce energy consumption, it is generally necessary to recycle them. The commonly used method for recovering the solvent is atmospheric distillation, in which the distilled solvent is reused. At the same time, the product pseudo-isomethyl ionone is heat-sensitive and is very likely to undergo transformation and deterioration at high temperatures. Patent CN1394841A increases the frequency of gas-liquid exchange and reduces the heat-sensitive loss caused by direct heating of the material by adding a plasticizer during the pseudo-isomethyl ionone fractionation process. However, the distillation method is used to recover the solvent, and the impurity content brought out is usually relatively high. When the solvent is reused, the product isomer ratio cannot be guaranteed; at the same time, the solvent is reduced during the distillation process, and there is a risk of salt precipitation, which promotes the deterioration of pseudo-isomethyl ionone and puts forward higher requirements for the selection of industrial equipment. Patent CN 106748696 A discloses a method for preparing methylionone and its intermediates. PEG is used as an organic solvent, and the base catalyst is recycled through extraction to achieve a high yield. However, the use of PEG as a phase transfer catalyst significantly affects the aroma of the final product.

[0005] In summary, the current preparation methods of pseudo-isomethyl ionone still have problems such as low main reaction yield and how to reasonably control the isomer ratio of the product. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing pseudo-isomethyl ionone. Compared with the previously disclosed method for preparing pseudo-isomethyl ionone, the method has a similar isomer ratio and yield in the first reaction, but can ensure that a higher reaction selectivity and a suitable isomer ratio are obtained when the solvent is recycled. At the same time, when the solvent is recovered, the precipitation of salts is avoided, which would cause a decrease in the separation yield of the product.

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0008] A method for preparing pseudo-isomethyl ionone comprises the following steps: adding a mixed solution of a solvent and a catalyst to a reactor inlet, adding citral for reaction, adding acid for neutralization after the reaction, adding a cosolvent when recovering butanone and an organic solvent, and then performing desolventization; optionally, the solvent removed by the desolventization is reused; the cosolvent is added at the beginning of the desolventization or when the cumulative amount of butanone and organic solvent extracted from the tower top is 65-85% of the total amount of butanone and organic solvent added before the reaction; and the content of light components with boiling points between butanone and citral in the solvent removed during the desolventization process is less than 1wt%.

[0009] The commonly used method of reclaiming solvent is atmospheric distillation at present, but in the still process, due to the steaming of solvent, the salt generated by neutralization reaction can be separated out, which can promote product deterioration at high temperature, and light components such as butanone dimer and water can enter the mechanical solvent, after reacting, the activity of the methyl group of butanone is enhanced, generating false positive methyl ionone, affecting the isomer ratio of the main reaction. Therefore, when reusing solvent, quantitative cosolvents such as dimethyl sulfoxide (DMSO) and ethylene glycol are added to the kettle liquid, by increasing the solubility of light components such as butanone dimer and water in cosolvent, increasing the relative volatility of light components and butanone and solvent, is conducive to the recovery of solvent. Simultaneously, the cosolvent added has certain solubility for salt, can prevent salt from separating out in the rectification process, and affects the yield of product.

[0010] The light component of the present invention refers to a substance with a boiling point between butanone and citral, with a boiling point of 79.6-228° C. at normal pressure. Using the gas chromatography analysis method in the embodiment, the peak position of the organic phase is between 2.829-9.021 min, and the moisture content is measured by a moisture meter, including butanone dimer and water.

[0011] In the present invention, the molar ratio of citral to butanone is 1:9-15, preferably 1:9-10.

[0012] In the present invention, the solvent is one or more C1-C8 alcohols, preferably one or more of methanol, ethanol, and n-propanol, more preferably methanol and / or ethanol; preferably, the mass ratio of the solvent to butanone is 0.8-3:1, more preferably 1.2-1.5:1.

[0013] In the present invention, the catalyst is one or more of NaOH, KOH, and LiOH, preferably KOH and / or NaOH; preferably, the molar ratio of the catalyst to citral is 0.4-1:1, more preferably 0.6-0.68:1.

[0014] In the present invention, the cosolvent is a polar solvent that can partially dissolve salts and has a boiling point between butanone and the product, such as alcohols, amides, sulfoxides, etc., including dimethyl sulfoxide, dimethylformamide and / or ethylene glycol. Preferably, the cosolvent is dimethyl sulfoxide and / or ethylene glycol; preferably, the amount of cosolvent added is 25-80% of the total mass of the initial reaction solution, and the reflux ratio is 1-10. The addition of the cosolvent has two main functions: first, it increases the relative volatility of the light component and butanone and the organic solvent, which is beneficial for the separation of the light component and the organic solvent, reduces the light component content of the solvent, thereby promoting the main reaction to obtain a suitable isomer ratio and improving the selectivity of the reaction; second, during the desolventizing process, adding some cosolvent can avoid the precipitation of salt in the bottom of the tower, which causes the product to deteriorate and causes a decrease in the separation yield. Then, the reaction is washed with water, separated into phases, and subjected to vacuum distillation to obtain the pseudo-isomethyl ionone product.

[0015] In the present invention, the method adopts a tubular reactor, and preferably the tubular reactor is provided with feed ports with nozzles at different positions.

[0016] In the present invention, the citral is added in batches.

[0017] In the present invention, the reaction temperature is 0-30° C., and the total reaction time is 4-6 h.

[0018] In the present invention, the neutralization is to neutralize to pH=6.5-7.

[0019] In the present invention, the method adopts a distillation tower plus a kettle method to recover butanone and an organic solvent.

[0020] Another object of the present invention is to provide a pseudo-isomethyl ionone product.

[0021] A pseudoisomethyl ionone is prepared by adopting the above preparation method.

[0022] Compared with the prior art, the isomer ratio and yield obtained in the first reaction of the present invention are not much different. The main difference lies in the solvent application process. The beneficial effects of the present invention are:

[0023] Compared with the traditional method of recovering solvent by distillation, the present invention adopts a method of combining a stirred tank with a distillation tower, and adds a quantitative co-solvent to the tower bottom when desolventization begins or the cumulative amount extracted from the tower top is 65-85% of the total amount of butanone and organic solvent added before the reaction.

[0024] (1) The light component content in the butanone and organic solvent removed from the top of the tower can be guaranteed to be within 1 wt%, which promotes the main reaction to obtain a suitable isomer ratio during the application process, that is, between 64-68%, and at the same time improves the selectivity of the reaction during the application process.

[0025] (2) During the solvent removal process, adding a co-solvent can avoid salt precipitation in the tower bottom due to solvent removal, which reduces the separation yield of the reaction and affects the selection of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a device used in the present invention, wherein 1 is a tubular reactor, 2 is a neutralization kettle, 3 is a desolventizing tower, 4 is a water washing kettle, 5 is a lightness removal tower, and 6 is a scraper evaporator. DETAILED DESCRIPTION

[0027] For a better understanding of the present invention, the present invention is further described below by way of examples. However, these examples are merely explanations of the present invention and do not limit the scope of protection of the present invention.

[0028] raw material:

[0029] Citral: purity 95%, GC; butanone: 99.5%, GC; methanol: 99.8%; potassium hydroxide: 95%; concentrated sulfuric acid: 98%; hydrochloric acid: 30%; ethylene glycol: 99%; dimethyl sulfoxide 99.9%. All the above raw materials were purchased from Aladdin Company.

[0030] Equipment and instruments:

[0031] Analytical instrument: Agilent gas chromatograph, chromatographic column: HP-INNOWAX, analysis method is area normalization method; Karl Fischer titrator (volume method): measure the water content in the recovered solvent

[0032] Main equipment: horizontal tubular reactor, diameter 0.7m, length 3m (opening scheme A: feed nozzles with nozzles are opened downward at 1 / 4 and 1 / 2 of the tube length; opening scheme B: feed nozzles with nozzles are opened downward at 1 / 3 and 2 / 3 of the tube length), with a jacket outside the tube;

[0033] Desolventizing tower, bottom diameter 1.2m, height 1.7m; tower diameter 0.2m, packing 4m, packing type M452Y;

[0034] Neutralization kettle: diameter 1m, height 1.2m;

[0035] Water washing kettle: diameter 1.2m, height 1.7m;

[0036] Lightness removal tower: tower diameter 0.2m, filler 4m, filler type M452Y;

[0037] Scraper evaporator: evaporation area 1m 2 .

[0038] Example 1

[0039] The reaction was carried out in a tubular reactor A. Under nitrogen atmosphere, the feed was continuously fed from the reactor inlet at a rate of 97 kg / h at normal pressure. The feed was a mixture of butanone, methanol, and potassium hydroxide (corresponding to a mass ratio of 19:28.5:1). Citral was divided into three equal streams at a rate of 8 kg / h and fed at the reactor inlet, 1 / 4, and 1 / 2 of the length. Figure 1 As shown. The front-end reaction temperature is controlled at 0°C, and the temperature is raised to 30°C at 3 / 4 of the tube length. The total reaction time is 5 hours. After the reaction is completed, the reaction solution is transferred to the neutralization kettle, and 8.93kg of concentrated sulfuric acid is added to neutralize it to pH = 7. The neutralized reaction solution is transferred to the desolventizing tower, and 134kg of ethylene glycol is added to the tower kettle as a co-solvent for intermittent distillation. The operating pressure is 40kPaA, the initial reflux ratio is 1, the tower kettle temperature is 50°C, and when the cumulative flow rate of the top extraction is 400kg, the tower kettle temperature is raised to 67°C, the reflux ratio is adjusted to 8, and when the cumulative amount of the top extraction is 454kg, the tower kettle temperature is raised to 130°C, the butanone content in the tower kettle is reduced to 0.2wt%, the methanol content is reduced to 30ppm, and no salt is precipitated in the tower kettle. The light component content in the recovered solvent is 0.42%. The remaining 200 kg of bottom liquid was then transferred to a water washing kettle for washing once with an amount of water equal to the mass of the oil phase, i.e., 200 kg. After stirring for 10 minutes, the mixture was allowed to stand for phase separation. After standing, 58.5 kg of crude oil product was obtained. The crude oil product was subjected to vacuum distillation at a top pressure of 0.35 kPaA, a reflux ratio of 5, and a bottom temperature of 143°C. Finally, a scraper was used for weight removal at a pressure of 0.24 kPaA and a temperature of 110°C to obtain a product with a purity of 98%. The proportion of pseudoisomethylionone in the total ketones, i.e., the isomer ratio, was 67.5%. The citral conversion rate, calculated as citral, was 99.7%, and the product yield was 95.5%.

[0040] Example 2

[0041] The reaction was carried out in a tubular reactor B. Under nitrogen atmosphere, the feed was continuously fed from the reactor inlet at a rate of 97 kg / h at normal pressure. The feed was a mixture of butanone, methanol, and potassium hydroxide (corresponding to a mass ratio of 19:28.5:1). Citral was divided into three streams at a rate of 9 kg / h and fed at the reactor inlet, 1 / 3, and 2 / 3 of the length. Figure 1The reaction temperature at the front end was controlled at 10°C, then raised to 30°C at 3 / 4 of the tube length. The total reaction time was 5 hours. After the reaction, the reaction liquid was transferred to a neutralization kettle and neutralized to pH 7 by adding 8.93 kg of concentrated sulfuric acid. The neutralized reaction liquid was transferred to a desolventizing tower for intermittent distillation at an operating pressure of 40 kPaA, a bottom temperature of 45°C, and a reflux ratio of 1. When the cumulative flow rate of overhead extraction reached 400 kg, the bottom temperature was raised to 50°C. 270 kg of ethylene glycol was added to the bottom as a cosolvent. When the cumulative flow rate of overhead extraction reached 450 kg, the bottom temperature was raised to 140°C. The butanone content in the bottom dropped to 0.4%, and the methanol content was 0.02%. The light component content of the recovered solvent was 0.65%. 340 kg of the bottom liquid was then transferred to a water washing kettle for water washing. The water volume was 340 kg. After stirring for 10 minutes, the mixture was allowed to stand for phase separation. After standing, 66 kg of crude oil product was obtained. The crude oil layer product was subjected to vacuum distillation at a top pressure of 0.35 kPaA, a reflux ratio of 5, and a bottom temperature of 143°C. Finally, a scraper was used for weight removal at a pressure of 0.24 kPaA and a temperature of 110°C to obtain a product with a purity of 98%. The proportion of pseudoisomethylionone in the total ketones, i.e., the isomer ratio, was 67%. The citral conversion, calculated as citral, was 99.8%, and the product yield was 95.2%.

[0042] Example 3

[0043] The reaction was carried out in a tubular reactor A. Under nitrogen atmosphere, the feed was continuously fed from the reactor inlet at a rate of 97 kg / h at normal pressure. The feed was a mixture of butanone, methanol, and potassium hydroxide (corresponding to a mass ratio of 19:28.5:1). Citral was divided into three equal streams at a rate of 8 kg / h and fed at the reactor inlet, 1 / 4, and 1 / 2 of the length. Figure 1As shown. The front-end reaction temperature was controlled at 10°C, and the temperature was raised to 30°C at 3 / 4 of the tube length. The total reaction time was 5 hours. After the reaction was completed, the reaction liquid was transferred to a neutralization kettle and neutralized to pH 6.8 by adding 30% dilute hydrochloric acid solution dropwise. The neutralized reaction liquid was transferred to a desolventizing tower for intermittent distillation. The tower bottom temperature was 45°C, the operating pressure was 40kPaA, the initial reflux ratio was 1, and when the cumulative amount of overhead production reached 310kg, the tower bottom temperature was raised to 50°C. 430kg of dimethyl sulfoxide was added to the tower bottom, and the reflux ratio was increased to 8. When the cumulative amount of overhead production reached 448kg, the tower bottom temperature was raised to 130°C, and the light component content was 0.25%. The methanol content in the tower bottom was reduced to 0.2%, and no butanone was detected. The tower bottom liquid was then transferred to a water washing kettle for water washing. The water volume was 500kg, and the water was stirred for 10 minutes and then allowed to stand for phase separation. After standing, 62kg of crude oil product was obtained. The crude oil layer product was subjected to vacuum distillation at a top pressure of 0.35 kPaA, a reflux ratio of 5, and a bottom temperature of 143°C. Finally, a scraper was used for weight removal at a pressure of 0.24 kPaA and a temperature of 110°C to obtain a product with a purity of 97%. The proportion of pseudoisomethylionone to total ketones, i.e., the isomer ratio, was 67.5%. The citral conversion, calculated as citral, was 99.6%, and the product yield was 94.9%.

[0044] Example 4

[0045] The reaction was carried out in a tubular reactor A. Under nitrogen atmosphere, the feed was continuously fed from the reactor inlet at a rate of 95.33 kg / h at normal pressure. The feed was a mixture of butanone, ethanol, and sodium hydroxide (corresponding to a mass ratio of 27.7:33.2:1). Citral was divided into three equal streams at a rate of 9 kg / h and fed at the reactor inlet, 1 / 4, and 1 / 2 of the length. Figure 1As shown. The front-end reaction temperature is controlled at 0°C, and the temperature is raised to 30°C at 3 / 4 of the tube length. The total reaction time is 5 hours. After the reaction is completed, the reaction solution is transferred to the neutralization kettle, and 9.62kg of concentrated sulfuric acid is added to neutralize it to pH = 6.5. The neutralized reaction solution is transferred to the desolventizing tower, and 213.3kg of ethylene glycol is added to the tower kettle as a co-solvent for intermittent distillation. The operating pressure is 40kPaA, the initial reflux ratio is 1, the tower kettle temperature is 60°C, and when the cumulative flow rate of the top extraction is 290kg, the tower kettle temperature is raised to 67°C, the reflux ratio is adjusted to 10, and when the cumulative amount of the top extraction is 447kg, the tower kettle temperature is raised to 150°C, the ethanol content in the tower kettle is reduced to 0.2wt%, the methanol content is reduced to 10ppm, and no salt is precipitated in the tower kettle. The light component content in the recovered solvent is 0.89%. The remaining bottoms liquid was then transferred to a water washing kettle for washing with 300 kg of water. After stirring for 10 minutes and allowing the mixture to stand for phase separation, 65.75 kg of crude oil product was obtained. The crude oil product was subjected to vacuum distillation at a top pressure of 0.35 kPaA, a reflux ratio of 5, and a bottom temperature of 143°C. Finally, a scraper was used for weight removal at a pressure of 0.24 kPaA and a temperature of 110°C to obtain a product with a purity of 98.5%. The proportion of pseudoisomethylionone to total ketones, i.e., the isomer ratio, was 67.8%. The citral conversion rate, calculated as citral, was 99.5%, and the product yield was 95.1%.

[0046] Examples 5-11

[0047] Take the solvent used in Example 1, add methanol to a total of 285 kg, add butanone to 190 kg, repeat the steps of Example 1, and recycle for 7 times. The product results obtained in each recycle are as follows:

[0048] Serial number Citral conversion rate Product yield Heterogeneous ratio Example 5 - Application for the first time 99.6％ 95％ 66.2％ Example 6 - Apply for the second time 99.4％ 94.8％ 66％ Example 7 - Apply for the third time 99.5％ 95.1％ 66.3％ Example 8 - Application for the 4th time 99.3％ 94.7％ 66.2％ Example 9 - Apply for the 5th time 99.5％ 95.2％ 66％ Example 10 - Application for the 6th time 99.5％ 95％ 65.8％ Example 11 - Application for the 7th time 99.4％ 94.9％ 66.1％

[0049] Comparative Example 1

[0050] The reaction was carried out in a tubular reactor A. Under nitrogen atmosphere, the feed was continuously fed from the reactor inlet at a rate of 97 kg / h at normal pressure. The feed was a mixture of butanone, methanol, and potassium hydroxide (corresponding to a mass ratio of 19:28.5:1). Citral was divided into three equal streams at a rate of 8 kg / h and fed at the reactor inlet, 1 / 4, and 1 / 2 of the length. Figure 1As shown. The front-end reaction temperature is controlled at 10°C, and the temperature is raised to 30°C at 3 / 4 of the tube length. The total reaction time is 5 hours. After the reaction is completed, the reaction liquid is transferred to the neutralization kettle and 8.93kg of concentrated sulfuric acid is added to neutralize it to pH = 7. The neutralized reaction liquid is transferred to the desolventizing tower for distillation. The operating pressure is 40kPaA and the initial tower bottom temperature is 50°C. When the methanol content in the tower bottom drops to 0.2%, the butanone content in the tower bottom is 0.3%, the tower bottom temperature rises to 136°C, and the cumulative flow rate of solvent used in the tower top is 460kg, of which the light component content is 1.7%. Salt precipitates in the tower bottom. The tower bottom liquid is then transferred to the water washing kettle for water washing, and the water washing amount is 80kg. It is allowed to stand for phase separation. After standing, 57kg of crude oil product is obtained. The crude oil layer product was subjected to vacuum distillation at a top pressure of 0.35 kPaA, a reflux ratio of 5, and a bottom temperature of 148°C. Finally, a scraper was used for weight removal at a pressure of 0.24 kPaA and a temperature of 110°C to obtain a product with a purity of 98%. The proportion of pseudoisomethylionone to total ketones, i.e., the isomer ratio, was 66.5%. The citral conversion, calculated as citral, was 99.5%, and the final product yield was 94.8%.

[0051] Take the recovered solvent obtained in Comparative Example 1, add methanol to a total amount of 285 kg, add butanone to 190 kg, repeat the operating steps of Comparative Example 1, and cycle it three times. The product results are as follows:

[0052] Serial number Citral conversion rate Product yield Heterogeneous ratio Apply for the first time 99.3％ 93％ 64.3％ Apply for the second time 99.2％ 91％ 63.2％ Apply for the third time 99.4％ 88％ 61.5％

Claims

1. A method for preparing pseudoisomethyl ionone, characterized in that: The method comprises adding a mixed solution of butanone, a solvent and a catalyst to the inlet of a reactor, adding citral to react, adding acid to neutralize after the reaction is completed, recovering butanone and an organic solvent, adding a cosolvent, and then performing desolventizing. Optionally, the solvent removed by the desolvation is reused; wherein, at the beginning of the desolventizing stage, or when the cumulative amount of the top extraction is 65-85% of the total amount of butanone and organic solvent added before the reaction, a cosolvent is added; The content of light components in the solvent removed during the desolventizing process, whose boiling point is between that of butanone and citral, is less than 1 wt %; Wherein, the cosolvent is a polar solvent that can partially dissolve salt and has a boiling point between butanone and the product, and the cosolvent is one or more of alcohol, amide, and sulfoxide; The method adopts a distillation tower plus kettle method to recover butanone and organic solvent.

2. The preparation method according to claim 1, characterized in that The molar ratio of citral to butanone is 1:9-15; and / or, the solvent is one or more of C1-C8 alcohols; And / or, the catalyst is an alkali metal compound.

3. The preparation method according to claim 1 or 2, characterized in that The molar ratio of citral to butanone is 1:9-10; and / or, the solvent is one or more of methanol, ethanol, and n-propanol; The mass ratio of solvent to butanone is 0.8-3:1; And / or, the catalyst is an alkali metal hydroxide, selected from one or more of NaOH, KOH, and LiOH; The molar ratio of catalyst to citral is 0.4-1:1; and / or, the cosolvent is dimethyl sulfoxide and / or ethylene glycol; The amount of co-solvent added is 25-80% of the total mass of the initial reaction solution, and the reflux ratio is 1-10.

4. The preparation method according to claim 3, characterized in that The solvent is methanol and / or ethanol; The mass ratio of solvent to butanone is 1.2-1.5:1; And / or, the catalyst is KOH and / or NaOH; The molar ratio of the catalyst to citral is 0.6-0.68:

1.

5. The preparation method according to claim 1 or 2, characterized in that The method employs a tubular reactor.

6. The preparation method according to claim 5, characterized in that The method adopts a tubular reactor with feed ports with nozzles at different positions.

7. The preparation method according to claim 1 or 2, characterized in that The reaction temperature is 0-30°C and the total reaction time is 4-6h; And / or, the neutralization is to neutralize to pH=6.5-7; And / or, the adding of citral is performed in batches.

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