Process for the preparation of alpha-hexylcinnamaldehyde

Abstract

The application belongs to the technical field of organic synthesis, and specifically discloses a preparation method of alpha-hexyl cinnamic aldehyde; under the protection of nitrogen, tert-butyl alcohol, ethanol and water are used as solvents, potassium hydroxide and PEG-400 are used as catalysts, benzaldehyde is reacted with n-octyl aldehyde at 60 DEG C for 6 hours, and then extraction, acidolysis, solvent recovery, drying, and vacuum distillation are carried out to collect a fraction at 175-176 DEG C to obtain the alpha-hexyl cinnamic aldehyde. The application adds tert-butyl alcohol in the solvent, and due to the steric hindrance effect, the condensation of n-octyl aldehyde and the product alpha-hexyl cinnamic aldehyde itself can be effectively prevented, and the yield of synthesis is effectively improved. Through process adjustment, the water phase in the solvent and the water phase in the acidolysis solution can be recycled and applied, and the discharge of waste water is greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing α-hexylcinnamaldehyde. Background Technology

[0002] α-Hexylcinnamaldehyde, with a sweet, jasmine-like aroma, is widely used in the food and cosmetics industries. Its synthesis method is described in "Practical Synthetic Fragrances" edited by Ding Desheng et al., Shanghai Science and Technology Press, 1991 edition. This method uses potassium hydroxide as a catalyst and ethanol as a solvent to synthesize α-hexylcinnamaldehyde, but the yield is only about 40%. Summary of the Invention

[0003] This invention provides a method for preparing α-hexylcinnamaldehyde, which can improve the yield and allow the aqueous phase in the synthesis process to be recycled, reducing waste liquid discharge.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing α-hexylcinnamaldehyde, comprising the following steps:

[0005] S1. First, mix the catalyst with a mixed solvent containing tert-butanol, ethanol and water, heat it and then add benzaldehyde, followed by the dropwise addition of n-octaldehyde to carry out the reaction.

[0006] S2. After the reaction solution is cooled, it is allowed to stand and separate. The organic phase in the aqueous phase is extracted, the organic phases are combined and acid is added. The organic solvent is recovered during acid hydrolysis.

[0007] S3. After the organic solvent is recovered, the feed solution is cooled and allowed to stand for separation. The organic phase in the aqueous phase is extracted, and the combined organic phases are dried and then distilled under reduced pressure (2 x 10⁻⁶). 3 (Pa), collect the fraction at 175-176℃ to obtain α-hexylcinnamaldehyde.

[0008] Furthermore, S1 is composed of tert-butanol, ethanol, and water in a volume ratio of 1:1~3:2~4; the catalyst is composed of PEG-400 and KOH in a mass ratio of 1:1.3.

[0009] Furthermore, in S1, the mass ratio of benzaldehyde to n-octaldehyde is 1:1.1; the weight ratio of n-octaldehyde to solvent is 1:3~5; and the weight ratio of catalyst to mixed solvent is 1:7~1:9.

[0010] Furthermore, after the solvent and catalyst in S1 are mixed, the mixture is heated to 60°C. The reaction temperature in S1 is 60°C, and the reaction time is 6 hours.

[0011] Furthermore, the extractant in S2 and S3 is diethyl ether; the acid in S2 is dilute sulfuric acid, and dilute sulfuric acid is added during acidolysis to adjust the pH to 2-3.

[0012] Furthermore, the mass concentration of the dilute sulfuric acid is 0.8%.

[0013] Further, in S2, the extractant diethyl ether is recovered between 30-45°C, and ethanol and tert-butanol are recovered between 45-95°C. The recovered tert-butanol and ethanol are combined with the aqueous phase after separation in S2.

[0014] Furthermore, the aqueous phase after separation in S2 is replenished with the corresponding components and then recycled back into S1 as a solvent and catalyst.

[0015] Furthermore, the aqueous phase after separation in S3 is replenished with the corresponding components and then recycled back into the acid solution in S2.

[0016] Furthermore, the organic phase in S3 was dried using molecular sieves, and the distillation was performed under reduced pressure at a pressure of 2 x 10⁻⁶. 3 Pa.

[0017] The present invention has the following beneficial effects:

[0018] 1. The present invention adds tert-butanol to the solvent. Due to its steric hindrance, it can effectively prevent the condensation of n-octanal and the product α-hexylcinnamaldehyde, effectively improving the synthesis yield and bringing significant economic benefits to enterprises.

[0019] 2. In this invention, after the reaction is complete, the aqueous phase is separated first, and then sulfuric acid is added for acid hydrolysis. The separated aqueous phase can be recycled, and the aqueous phase added later for acid hydrolysis can also be recycled, which greatly reduces the discharge of wastewater.

[0020] 3. This invention recovers solvent during acid hydrolysis, thus reducing energy consumption.

[0021] 4. The synthesis method provided by this invention is simple to operate, requires no complicated production equipment, requires little investment, has a high recovery rate, and is suitable for industrial production. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0023] In the following examples, all n-octanal had a purity of 95%, and benzaldehyde had a purity of 99.9%.

[0024] Example 1

[0025] The preparation method of α-hexylcinnamaldehyde includes the following specific steps:

[0026] First, purge the reactor with nitrogen to remove air. Add 5400g of a mixed solvent (tert-butanol, ethanol, and water in a volume ratio of 1:2:3) and 678g of catalyst (PEG-400 and KOH in a mass ratio of 1:1.3). Start stirring. Heat the reactor to 60℃, then add 1166.15g of benzaldehyde. While stirring, add 10mol of n-octanal (1349.68g, added dropwise over 40 minutes). Maintain the temperature at 60℃ and continue stirring for 6 hours. Adjust the temperature of the circulating water to 30℃, stir and cool to below 40℃, then stop stirring, allow to stand, and separate the liquids.

[0027] The aqueous phase is extracted three times with 1 / 2 volume of diethyl ether to obtain aqueous phase A. The extracted organic phases are combined with the above organic phases to obtain organic phase A. 0.8% dilute sulfuric acid is added to organic phase A with stirring until the pH value is 3.

[0028] Heat to approximately 100℃, and collect ether (between 30-45℃) and solvent (tert-butanol, ethanol) (between 45-95℃) separately while stirring; continue stirring and reflux for 30 min, adjust the circulating pump temperature to 30℃, stir and cool to below 40℃, stop stirring, let stand, separate the liquids, extract the aqueous phase three times with ether to obtain aqueous phase B, combine the organic phases to obtain organic phase B, dry organic phase B with molecular sieves, and pressurize under reduced pressure (2x10⁻⁶). 3 Distillation at 175-176℃ yielded 1817.0 g of α-hexylcinnamaldehyde, with a yield of 84% and a purity of 95.2%.

[0029] Example 2

[0030] Same as Example 1, but the amount of n-octanal used is 1 mol, the weight ratio of catalyst to mixed solvent is 1:7; the mixed solvent is tert-butanol, ethanol and water mixed in a volume ratio of 1:1:2, and the weight ratio of n-octanal to mixed solvent is 1:3.

[0031] 166.57 g of α-hexylcinnamaldehyde was obtained, with a yield of 77% and a purity of 95.1%.

[0032] Example 3

[0033] Same as Example 1, but the amount of n-octanal used is 0.5 mol, the weight ratio of catalyst to mixed solvent is 1:9; the mixed solvent is tert-butanol, ethanol and water mixed in a volume ratio of 1:3:4, and the weight ratio of n-octanal to mixed solvent is 1:5.

[0034] 87.61 g of α-hexylcinnamaldehyde was obtained, with a yield of 81.0% and a content of 95.3%.

[0035] Example 4

[0036] Same as in Example 1, the amount of n-octanal used is 20 mol; the weight ratio of catalyst to mixed solvent is 1:8; the mixed solvent is a mixture of tert-butanol, ethanol and water in a volume ratio of 1:2:3; the weight ratio of n-octanal to mixed solvent is 1:4.

[0037] 3625.09 g of α-hexylcinnamaldehyde was obtained, with a yield of 83.79% and a purity of 94.9%.

[0038] Example 5

[0039] Same as in Example 1, the amount of n-octanal used was 0.2 mol, the weight ratio of catalyst to mixed solvent was 1:8; the mixed solvent was a mixture of tert-butanol, ethanol, and water in a volume ratio of 1:2:3; the weight ratio of n-octanal to mixed solvent was 1:4. The yield of α-hexylcinnamaldehyde is shown in Table 1.

[0040] Aqueous phase A and aqueous phase B of this embodiment were recycled. Aqueous phase A was replenished with ethanol, tert-butanol, potassium hydroxide, and PEG-400 to the appropriate concentrations (i.e., satisfying: a mixed solvent to catalyst weight ratio of 8:1; a volume ratio of tert-butanol, ethanol, and water in the mixed solvent of 1:2:3; and a weight ratio of PEG-400 and KOH in the catalyst of 1:1.3), and then recycled. Aqueous phase B was replenished with concentrated sulfuric acid to a sulfuric acid content of 0.8%, and then recycled. The yield results of multiple recycling cycles are shown in Table 1 below.

[0041] Table 1

[0042]

[0043] As can be seen from Table 1, the yield of α-hexylcinnamaldehyde was not affected after the aqueous phase was reused 7 times.

[0044] Comparative Example 1:

[0045] Same as Example 1, but the amount of n-octanal used is 0.1 mol, the weight ratio of catalyst to mixed solvent is 1:8; the mixed solvent is ethanol and water mixed in a volume ratio of 1:1, and the weight ratio of n-octanal to mixed solvent is 1:4.

[0046] 8.70 g of α-hexylcinnamaldehyde was obtained, with a yield of 40.2%.

[0047] Comparative Example 2

[0048] Same as Example 1, but the amount of n-octanal used is 0.1 mol, the weight ratio of catalyst to mixed solvent is 1:8; the mixed solvent is a mixture of isobutanol, ethanol and water in a volume ratio of 1:2:3, and the weight ratio of n-octanal to mixed solvent is 1:4.

[0049] 10.37 g of α-hexylcinnamaldehyde was obtained, with a yield of 47.9%.

[0050] Comparative Example 3

[0051] Same as Example 1, but the amount of n-octanal used is 0.1 mol, the weight ratio of catalyst to mixed solvent is 1:8; the mixed solvent is a mixture of tert-amyl alcohol, ethanol and water in a volume ratio of 1:2:3, and the weight ratio of n-octanal to mixed solvent is 1:4.

[0052] 13.83 g of α-hexylcinnamaldehyde was obtained, with a yield of 63.9%.

[0053] The comparative results show that the yield is significantly reduced when tert-butanol is absent from the reaction system; and the yield is noticeably reduced when tert-butanol is replaced with isobutanol or tert-amyl alcohol, which have sterically hindered effects. This indicates that tert-butanol achieves the best results in this reaction system.

[0054] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing α-hexylcinnamaldehyde, characterized in that, Includes the following steps: S1. First, mix the catalyst with a mixed solvent prepared by tert-butanol, ethanol and water in a volume ratio of 1:1~3:2~4, heat it and add benzaldehyde, and then add n-octaldehyde dropwise to carry out the reaction; the catalyst is a mixture of PEG-400 and KOH in a mass ratio of 1:1.

3. S2. After the reaction solution is cooled, it is allowed to stand and separate. The organic phase in the aqueous phase is extracted, the organic phases are combined and acid is added. The organic solvent is recovered during acid hydrolysis. S3. After the organic solvent is recovered, the liquid is cooled and allowed to stand for separation. The organic phase in the aqueous phase is extracted, and the organic phases are combined, dried, and then distilled under reduced pressure to obtain α-hexylcinnamaldehyde.

2. The preparation method according to claim 1, characterized in that: In S1, the weight ratio of catalyst to mixed solvent is 1:7 to 1:9; the weight ratio of n-octanal to solvent is 1:3 to 5; and the mass ratio of benzaldehyde to n-octanal is 1:1.

1.

3. The preparation method according to any one of claims 1 to 2, characterized in that: After the solvent and catalyst in S1 are mixed, the mixture is heated to 60°C. The reaction temperature in S1 is 60°C and the reaction time is 6 hours.

4. The preparation method according to claim 1, characterized in that: The extractant in S2 and S3 is diethyl ether; the acid in S2 is dilute sulfuric acid, and dilute sulfuric acid is added during acidolysis to adjust the pH to 2-3.

5. The preparation method according to claim 4, characterized in that: The mass concentration of the dilute sulfuric acid is 0.8%.

6. The preparation method according to claim 4, characterized in that: In S2, the extractant diethyl ether is recovered between 30-45℃, and tert-butanol and ethanol are recovered between 45-95℃.

7. The preparation method according to claim 1, characterized in that: The organic phase in S3 was dried using molecular sieves, and the vacuum distillation pressure was 2 x 10⁻⁶. 3 Pa, the fraction collected at 175-176℃ is α-hexylcinnamaldehyde.

Images