A method for purifying cinnamaldehyde by low-temperature melt crystallization

Abstract

This invention discloses a method for purifying cinnamaldehyde through low-temperature melt crystallization, aiming to provide an environmentally friendly purification method that solves the problems of easy degradation and difficulty in achieving the required purity of cinnamaldehyde, a heat-sensitive substance, in traditional purification processes. The method includes the following steps: S1. Adding crude cinnamon oil to a crystallizer and cooling it at -30℃ to 35℃ for 15 to 20 minutes; S2. Adding 0.1g of cinnamaldehyde seed crystals to the cinnamon oil in the crystallizer; S3. Stirring slowly for one minute, then waiting for 30 to 40 minutes until the cinnamon oil... All crystals are obtained as crude cinnamon oil. The ambient temperature is then adjusted to -26℃ to -25℃. S4. The crude cinnamon oil is subjected to a sweating process, with a heating rate of 1.9~2.1℃ / h and a sweating temperature range of -25℃ to -21℃. S5. The sweating liquid is extracted, and the remaining crystals are melted and recrystallized. S6. Steps S3-S4 are repeated, increasing the temperature range by 0.4~0.6℃ each time sweating occurs, until the cinnamaldehyde content in the final crystals meets the national standard. (Separation technology field)

Description

Technical Field

[0001] This invention relates to a method for low-temperature melt crystallization, and more specifically, to a method for purifying cinnamaldehyde from cinnamon oil, thus relating to the field of separation technology. Background Technology

[0002] Cinnamaldehyde is an aromatic aldehyde naturally found in the bark of plants such as cinnamon, and can also be synthesized through the aldol condensation reaction of benzaldehyde and acetaldehyde. Its chemical formula is crude crystal C9H8O, and it is a pale yellow oily liquid at room temperature with a strong cinnamon aroma. As a typical difficult-to-separate heat-sensitive compound, it readily polymerizes or degrades at high temperatures, and its boiling point is very close to that of structurally similar byproducts such as benzaldehyde and cinnamyl acetate. Cinnamon, a unique natural spice resource in southern my country, has essential oils rich in natural cinnamaldehyde with antibacterial activity, showing broad application prospects in food preservation, pharmaceuticals, and daily chemical fragrances.

[0003] To address the aforementioned issues, the industry currently primarily employs methods such as distillation, molecular distillation, and coupling techniques. However, existing methods still have significant limitations. From a technical perspective, while traditional distillation processes are mature, they are complex to operate. Initial vacuum distillation can achieve a cinnamaldehyde content of 90%–95%, but subsequent molecular distillation purification is required to achieve a cinnamaldehyde purity of over 98%. Molecular distillation requires extremely high vacuum levels and has high equipment costs.

[0004] Melt crystallization technology requires no solvents, consumes less energy, operates under mild conditions, and can effectively prevent the degradation of heat-sensitive substances. It provides high-purity cinnamaldehyde products for food flavorings, pharmaceutical intermediates, antibacterial and preservation materials, and has strong practical value.

[0005] Therefore, developing an environmentally friendly and low-cost method for cinnamaldehyde purification is of great significance for promoting the industrial production of cinnamaldehyde and expanding its market application. Summary of the Invention

[0006] The purpose of this invention is to overcome the high cost problem of the prior art and provide an environmentally friendly purification method to solve the problems of easy degradation and difficulty in achieving the required purity of cinnamaldehyde as a heat-sensitive substance in traditional purification processes. This method reduces equipment investment and energy consumption while ensuring that the purity of the product meets the application requirements.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for purifying cinnamaldehyde by low-temperature melt crystallization comprises the following steps:

[0009] S1. Add crude cinnamon oil to a crystallizer and cool at -32℃~32℃ for 15~20 minutes;

[0010] S2. Add cinnamaldehyde seed crystals to the cinnamon oil in the crystallizer;

[0011] S3. Stir slowly for one minute, then wait 30 to 40 minutes until all the cinnamon oil crystallizes into crude cinnamon oil. Then adjust the ambient temperature to -26℃ to -25℃.

[0012] S4. Begin sweating of the crude crystalline cinnamon oil. The heating rate during sweating is 1.9~2.1℃ / h, and the sweating temperature range is -25℃ to -21℃.

[0013] S5. Extract the sweating liquid and recrystallize the remaining crystallized crude cinnamon oil after melting the crystals;

[0014] S6. Recycle steps S3-S4, increasing the temperature range by 0.4~0.6℃ for each sweating episode, until the cinnamaldehyde content in the final crystals reaches the national standard.

[0015] Furthermore, in the above-mentioned method for purifying cinnamaldehyde by low-temperature melt crystallization, the crude cinnamon oil is cinnamon oil with a purity greater than 85%.

[0016] Furthermore, in the above-mentioned method for purifying cinnamaldehyde by low-temperature melting crystallization, the method for preparing the seed crystals is as follows: 1g of cinnamaldehyde analytical standard is added to a glass tube and placed in an environment of -40℃ to -50℃, waiting for crystal formation.

[0017] Furthermore, in the above-mentioned method for purifying cinnamaldehyde by low-temperature melt crystallization, the mass ratio of crude cinnamon oil to cinnamaldehyde seed crystals is 100:1.

[0018] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages:

[0019] 1. This invention uses a low-temperature melt crystallization process to purify cinnamaldehyde. The entire process does not require the addition of additional organic solvents, nor does it require the high temperature and high vacuum conditions required by traditional distillation processes. It does not introduce foreign impurities into the product and avoids the degradation or polymerization of heat-sensitive cinnamaldehyde during high-temperature treatment. This ensures the safety of the product as a natural fragrance and effectively improves the product yield.

[0020] 2. This invention has low equipment requirements, does not require the high vacuum configuration needed for molecular distillation, has lower equipment investment costs, and can gradually increase purity through gradual heating during the sweating cycle. The overall energy consumption is also lower than that of traditional multi-step purification processes, resulting in lower production costs and making it more suitable for large-scale industrial production.

[0021] 3. The purity of cinnamaldehyde obtained by the present invention can stably meet the national standard requirements. The product can be directly applied to fields with high purity requirements such as food preservation, pharmaceuticals and health products, and daily chemical fragrances. It has strong applicability. At the same time, the entire production process has no difficult-to-treat solvent waste liquid and low emissions of waste gas, wastewater, and solid waste, which meets the current production requirements of green chemical industry. Attached Figure Description

[0022] Figure 1 The gas chromatographic standard curve of cinnamaldehyde tested in the examples uses the internal standard method, with benzyl alcohol as the internal standard. The horizontal axis represents the concentration ratio of cinnamaldehyde to benzyl alcohol, and the vertical axis represents the peak area ratio of cinnamaldehyde to benzaldehyde.

[0023] Figure 2 The image shows the gas chromatograms of the sample and internal standard in Example 1. Detailed Implementation

[0024] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0025] Example 1

[0026] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0027] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0028] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -22℃, and the temperature rise rate during sweating will be 2℃ / h.

[0029] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0030] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0031] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -21.5℃. The heating rate during sweating is 2℃ / h.

[0032] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0033] S8. Continue until the sweating temperature reaches -11℃. At this point, the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde. Refer to the gas chromatographic standard curve of cinnamaldehyde obtained in the example. Figure 1 The internal standard method was used for quantitative analysis, and benzyl alcohol was selected as the internal standard. The horizontal axis represents the concentration ratio of cinnamaldehyde to benzyl alcohol, and the vertical axis represents the peak area ratio of cinnamaldehyde to benzyl alcohol.

[0034] The gas chromatograms of the sample to be tested and the internal standard in Example 1 are shown in Table 1. The purity and yield of the purified cinnamaldehyde are shown in Table 1.

[0035] Example 2

[0036] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0037] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0038] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -21℃, and the temperature rise rate during sweating will be 2℃ / h.

[0039] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0040] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0041] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -20.5℃. The heating rate during sweating is 2℃ / h.

[0042] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0043] S8. Continue until the sweating temperature reaches -11℃. At this point, the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0044] Example 3

[0045] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0046] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0047] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -20℃, and the temperature rise rate during sweating will be 2℃ / h.

[0048] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0049] S5. Melt the coarse crystal C and recrystallize it (Note: Do not melt it all; leave a small amount of crystal for recrystallization).

[0050] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -19.5℃. The heating rate during sweating is 2℃ / h.

[0051] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0052] S8. Continue until the sweating temperature reaches -11℃. At this point, the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0053] Example 4

[0054] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0055] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0056] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -19℃, and the temperature rise rate during sweating will be 2℃ / h.

[0057] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0058] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0059] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -18.5℃. The heating rate during sweating is 2℃ / h.

[0060] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0061] S8. Continue until the sweating temperature reaches -11℃. At this point, the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0062] Example 5

[0063] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0064] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0065] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -22℃, and the temperature rise rate during sweating will be 4℃ / h.

[0066] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0067] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0068] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -21.5℃. The heating rate during sweating is 2℃ / h.

[0069] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0070] S8. Continue until the sweating temperature reaches -11℃, at which point the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0071] Example 6

[0072] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0073] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0074] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -21℃, and the temperature rise rate during sweating will be 4℃ / h.

[0075] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0076] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0077] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -20.5℃. The heating rate during sweating is 2℃ / h.

[0078] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0079] S8. Continue until the sweating temperature reaches -11℃, at which point the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0080] Example 7

[0081] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0082] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0083] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -20℃, and the temperature rise rate during sweating will be 4℃ / h.

[0084] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0085] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0086] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -19.5℃. The heating rate during sweating is 2℃ / h.

[0087] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0088] S8. Continue until the sweating temperature reaches -11℃, at which point the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde.

[0089] Example 8

[0090] S1. Add 10.0g of crude cinnamon oil (cinnamaldehyde content of 88.36%) to a crystallizer and cool at -30℃ for 15min to obtain cinnamon oil A;

[0091] S2. Add 0.1g of cinnamaldehyde seed crystals to cinnamon oil A and stir slowly for 1 minute.

[0092] S3. After waiting for 30 minutes, cinnamon oil A will be completely crystallized. Then, the crystallization temperature will be adjusted to -26℃, and sweating will begin from -26℃. The sweating temperature will be -19℃, and the temperature rise rate during sweating will be 4℃ / h.

[0093] S4. After the sweating is finished, use a syringe to extract the sweat liquid B. The remaining crystals are coarse crystals C.

[0094] S5. After melting the coarse crystal C, recrystallize it, leaving about 1 / 10 of the total volume of crystals, and then recrystallize it.

[0095] S6. After recrystallization, adjust the temperature to -25.5℃, start sweating from this temperature, and continue sweating until -18.5℃. The heating rate during sweating is 2℃ / h.

[0096] S7. Repeat the recrystallization-sweating process, increasing the temperature by 0.5℃ each time.

[0097] S8. Continue until the sweating temperature reaches -11℃, at which point the cinnamaldehyde meets the national standard (content ≥98%). Refer to Table 1 for the purity and yield of the purified cinnamaldehyde. Refer to Table 1 for the purity and yield of cinnamaldehyde obtained in Examples 1-8.

[0098] Preparation method of seed crystals described in Examples 1-8: Take 1g of cinnamaldehyde analytical standard and add it into a glass tube, place it at -45℃, and wait for 8 minutes for crystal formation.

[0099] The cinnamaldehyde analytical standard was purchased from Leyan's trans-cinnamaldehyde.

[0100] Table 1

[0101] Example 1 -22 2 99.59 39 Example 2 -21 2 99.16 37 Example 3 -20 2 98.53 32 Example 4 -19 2 98.06 32 Example 5 -22 4 98.95 35 Example 6 -21 4 98.44 32 Example 7 -20 4 98.09 31 Example 8 -19 4 97.72 30

[0102] As can be seen from the data in Table 1, the low-temperature melt crystallization purification method of this application achieves a purity of 99.59% and a yield of 39% for cinnamaldehyde when the sweating heating rate is 2℃ / h and the initial sweating temperature is -22℃. This method demonstrates the best overall performance and can consistently meet the purity requirements of the national standard. Furthermore, it can be seen that under the same initial sweating temperature, a slower heating rate is more conducive to improving the purity and yield of the final product. This is because a slower heating rate allows impurities to be more fully excreted with the sweat, while reducing the loss of cinnamaldehyde crystals.

Claims

1. A method for purifying cinnamaldehyde by low-temperature melt crystallization, characterized in that, The steps are as follows: S1. Add crude cinnamon oil to a crystallizer and cool at -30℃~35℃ for 15~20 minutes; S2. Add cinnamaldehyde seed crystals to the cinnamon oil in the crystallizer; S3. Stir slowly for one minute, then wait 30 to 40 minutes until all the cinnamon oil crystallizes into crude cinnamon oil. Then adjust the ambient temperature to -26℃ to -25℃. S4. Begin sweating of the crude crystalline cinnamon oil. The heating rate during sweating is 1.9~2.1℃ / h, and the sweating temperature range is from -25℃ to -21℃. S5. Extract the sweating liquid and recrystallize the remaining crystallized crude cinnamon oil after melting the crystals; S6. Recycle steps S3-S4, increasing the temperature range by 0.4~0.6℃ for each sweating episode, until the cinnamaldehyde content in the final crystals reaches the national standard.

2. The method for purifying cinnamaldehyde by low-temperature melt crystallization according to claim 1, characterized in that, The crude cinnamon oil is cinnamon oil with a purity greater than 85%.

3. The method for purifying cinnamaldehyde by low-temperature melt crystallization according to claim 1, characterized in that, The method for preparing the seed crystals is as follows: 1g of cinnamaldehyde analytical standard is added to a glass tube and placed in an environment of -40℃ to -50℃ for 5-10 minutes to allow crystal formation.

4. The method for purifying cinnamaldehyde by low-temperature melt crystallization according to claim 1, characterized in that, The mass ratio of crude cinnamon oil to cinnamaldehyde seed crystals is 100:1.

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