Cinnamaldehyde segmented temperature control preparation method based on styrene and paraformaldehyde

Abstract

The invention discloses a cinnamyl aldehyde segmented temperature control preparation method based on styrene and paraformaldehyde, and relates to the technical field of cinnamyl aldehyde processing.According to the cinnamyl aldehyde segmented temperature control preparation method based on styrene and paraformaldehyde, styrene and paraformaldehyde are adopted as raw materials and are low in price and easy to obtain; compared with a cinnamyl alcohol oxidation method, the raw material cost can be reduced by more than 40%; through segmented temperature control integrated reaction, the steps of washing for multiple times, column chromatography purification and the like are omitted, the single-batch production period is shortened to be within 8 hours, and equipment investment and energy consumption are reduced; segmented temperature control reduces side reactions, short-path distillation purification is combined, the product purity can reach 90% or above, and the yield is increased to 70% or above; by adding hydroquinone and regulating and controlling the temperature, the reaction system is prevented from being sticky, and the industrial amplification feasibility is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cinnamaldehyde processing, and particularly relates to a cinnamaldehyde preparation method based on styrene and paraformaldehyde. BACKGROUND

[0002] The existing cinnamaldehyde preparation method based on styrene and paraformaldehyde still has the following disadvantages in actual use:

[0003] Cinnamaldehyde is an unsaturated aldehyde compound with a conjugated structure, and its chemical name is 3-phenylpropenal. It is a colorless to light yellow liquid at room temperature and has a unique cinnamomum aromatic. Its molecular structure contains active groups such as aldehyde group and carbon-carbon double bond. It is not only an important perfume raw material, widely used in food, cosmetics, daily perfume and other fields, but also has important application value in the fields of pharmaceutical intermediates synthesis, agricultural preservatives and other fields due to its antibacterial, antioxidant and other biological activities.

[0004] At present, the preparation methods of cinnamaldehyde mainly include the following types:

[0005] Cinnamyl alcohol oxidation method: this method takes cinnamyl alcohol as raw material, and generates cinnamaldehyde under the action of oxidizing agent (such as potassium permanganate, potassium dichromate, etc.). The advantage of this method is that the reaction selectivity is high, and the product purity is easy to control. However, the core problem is that the raw material cost is high - cinnamyl alcohol usually needs to be extracted from natural cinnamomum oil or prepared by multi-step synthesis, resulting in that the raw material procurement cost accounts for more than 60% of the production cost, and the use of oxidizing agent will produce a large amount of wastewater containing heavy metals, which further increases the subsequent environmental protection treatment cost; aldol condensation method: this method takes benzaldehyde and acetaldehyde as raw materials, and generates cinnamaldehyde under the action of alkaline catalyst (such as sodium hydroxide). After dehydration, cinnamaldehyde is generated. This method is relatively easy to obtain raw materials, but the preparation process is complicated: the raw material ratio (usually the molar ratio of benzaldehyde to acetaldehyde is 1:1.2-1.5) and the reaction pH value (8-10) need to be strictly controlled, and the intermediate needs to go through multiple water washing, neutralization, extraction and other steps, and the single batch production cycle is as long as 8-10 hours. Moreover, polymeric by-products are easily generated during the reaction process, and high-purity products can be obtained only through multiple column chromatography purification, which not only increases the solvent consumption and equipment investment, but also leads to low yield (usually only 50%-60%), further increasing the production cost.

[0006] Other synthesis methods: such as natural product extraction method, which depends on natural resources such as cinnamomum bark, is greatly affected by factors such as raw material origin and harvesting season, and has unstable yield and low extraction rate (usually less than 3%); although some chemical synthesis methods attempt to use low-cost raw materials, due to the complex reaction mechanism (which needs multi-step catalytic conversion) or the need for high temperature and high pressure, the equipment investment and energy consumption cost are high, which is difficult to realize industrial application.

[0007] In summary, the existing cinnamaldehyde preparation methods generally have problems of high raw material cost, complicated process, long production cycle, etc., which leads to high industrial production cost of cinnamaldehyde and restricts its large-scale promotion in the middle and low-end application fields. SUMMARY

[0008] The purpose of the present application is to provide a cinnamaldehyde preparation method based on styrene and paraformaldehyde with segmented temperature control, in order to solve the above problems.

[0009] In order to achieve the above purpose, the present application provides the following technical solution: a cinnamaldehyde preparation method based on styrene and paraformaldehyde with segmented temperature control, comprising the following steps:

[0010] S1, raw material pretreatment: grinding 12 grams of paraformaldehyde to a particle diameter of less than 100 microns, taking 20 milliliters of analytical pure styrene, distilling under reduced pressure at 60-70℃ and 10 millimeters of mercury pressure to remove the polymerization inhibitor, then adding 0.1 grams of hydroquinone, and adding the pretreated paraformaldehyde and styrene into a flask;

[0011] S2, initial stage of reaction: adding acetic acid as a solvent into the flask, slowly adding concentrated sulfuric acid after fully dissolving, controlling the reaction temperature at 0-5℃, and continuously reacting at low temperature for 1 hour, then slowly heating to 25℃, and stirring for 2 hours with a magnetic stirrer;

[0012] S3, deepening stage of reaction: heating the reaction container to 40-50℃, and continuously reacting for 3-4 hours;

[0013] S4, quenching and separation: using sodium bicarbonate solution to quench the reactants to neutralize the concentrated sulfuric acid, using diethyl ether to extract the aqueous phase, and combining the organic phases;

[0014] S5, purification: drying the organic phase with anhydrous sodium sulfate, distilling to remove diethyl ether and acetic acid to obtain a crude product, collecting colorless to light yellow cinnamaldehyde fraction through short path distillation, and then refining to obtain a pure product;

[0015] S6, detection: calculating the yield and estimating the purity of the refined product.

[0016] Further, the mass-volume ratio of styrene to paraformaldehyde in step S1 corresponds to a raw material molar ratio of 1:1.5-2.

[0017] Further, the amount of acetic acid used in step S2 is an effective amount that allows complete dissolution of styrene and paraformaldehyde.

[0018] Further, the addition rate of concentrated sulfuric acid in step S2 is a slow addition rate that avoids the reaction temperature exceeding 5℃.

[0019] Further, the amount of concentrated sulfuric acid added in step S2 is 5-10% of the total mass of styrene and paraformaldehyde.

[0020] Further, a reaction control step is further included, wherein if the solution becomes obviously thick during the reaction, less than 0.1 gram of hydroquinone is added and the temperature is lowered.

[0021] Further, the concentration of the sodium bicarbonate solution in step S4 is an effective concentration capable of neutralizing the concentrated sulfuric acid in the system, and the amount added is determined according to the pH value of the system reaching 6-7.

[0022] Further, the operating conditions of the short path distillation in step S5 are as follows: vacuum degree 0.1-10 mmHg, distillation temperature 120-150 DEG C.

[0023] Further, the rectification in step S5 is vacuum rectification, and the operating pressure is 5-20 mmHg, and the temperature for collecting the distillate is 130-160 DEG C.

[0024] Further, the amount of anhydrous sodium sulfate used in step S5 is 1 / 5-1 / 3 of the volume of the organic phase, and the drying time is 2-4 hours.

[0025] Compared with the prior art, the cinnamaldehyde preparation method based on styrene and paraformaldehyde provided by the present application has the following beneficial effects:

[0026] The cinnamaldehyde preparation method based on styrene and paraformaldehyde, by using styrene and paraformaldehyde as raw materials, which are low in price and easy to obtain, can reduce the raw material cost by more than 40% compared with the oxidation method of cinnamic alcohol; by using the integrated reaction of segmented temperature control, the steps of multiple water washing and column chromatography purification are omitted, and the single batch production cycle is shortened to 8 hours, thereby reducing the equipment investment and energy consumption; the segmented temperature control reduces the side reactions, and in combination with the short path distillation purification, the purity of the product can reach more than 90%, and the yield is increased to more than 70%; by adding hydroquinone and temperature control, the reaction system is prevented from being thick, and the industrialization amplification is feasible. DETAILED DESCRIPTION

[0027] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below.

[0028] The cinnamaldehyde preparation method based on styrene and paraformaldehyde includes the following steps:

[0029] S1, raw material pretreatment:

[0030] ① 12 grams of paraformaldehyde are ground in an agate mortar, sieved through a 150 mesh standard sieve, and paraformaldehyde particles with a particle diameter of less than 100 microns are obtained;

[0031] ② Take 20 milliliters of analytical pure styrene into the vacuum distillation device, set the distillation temperature to 60-70℃, the distillation pressure to 10 mmHg, and perform vacuum distillation for 1.5-2 hours to remove the polymerization inhibitor;

[0032] ③ Add 0.1 grams of hydroquinone to the distilled styrene and stir for 10-15 minutes to completely dissolve it;

[0033] ④ Add the paraformaldehyde treated in step ① and the styrene solution obtained in step ③ into a 500 milliliter three-necked flask in sequence, and place a magnetic stirrer in the flask.

[0034] S2, initial stage of reaction:

[0035] ① Add acetic acid as a solvent into the three-necked flask, the amount of acetic acid added being 1.5-2 times the volume of styrene, start the magnetic stirrer (set the speed to 300-400 rpm), and stir for 20-30 minutes until the raw materials are completely dissolved;

[0036] ② Slowly add concentrated sulfuric acid into the flask through a constant pressure dropping funnel, the amount of concentrated sulfuric acid added being 5%-10% of the total mass of styrene and paraformaldehyde, and the dropping speed being controlled at 1-2 drops per second, while controlling the reaction temperature at 0-5℃ through an ice bath;

[0037] ③ Continue stirring at 0-5℃ for 1 hour, and record the reaction temperature every 15 minutes during this period;

[0038] ④ Turn off the ice bath, slowly warm up to 25℃ through a water bath (the warming rate is controlled at 1-2℃ / min), and continue stirring at 300-400 rpm for 2 hours.

[0039] S3, deepening stage of reaction:

[0040] ① Increase the water bath temperature to 40-50℃ (the warming rate is 2-3℃ / min), maintain this temperature and stirring speed of 300-400 rpm for 3-4 hours, and observe the solution state every 30 minutes during this period;

[0041] ② If the solution becomes obviously thick during the reaction (the stirring resistance increases obviously), immediately add 0.05-0.1 grams of hydroquinone into the system, lower the reaction temperature to 25℃ and maintain for 30 minutes, and then restore it to 40-50℃ to continue the reaction.

[0042] S4, quenching and separation:

[0043] ① Take a sodium bicarbonate solution with a mass concentration of 5%-10%, slowly add it into the reaction container under stirring (the dropping speed is 3-5 drops per second), until the pH value of the system reaches 6-7, stop dropping and continue stirring for 10 minutes;

[0044] ②Transfer the mixed solution to a separatory funnel, add an equal volume of diethyl ether to the mixed solution, and shake and extract 3 times (each time for 1-2 minutes, and let stand for 15-20 minutes for layering);

[0045] ③Collect the organic phase obtained in each extraction, and combine and place in a 250-mL conical flask.

[0046] S5, Purification:

[0047] ①Add anhydrous sodium sulfate to the combined organic phase, and the amount of anhydrous sodium sulfate is 1 / 5-1 / 3 of the volume of the organic phase, and seal and place on a magnetic stirrer for stirring at 200 rpm for 2-4 hours for drying;

[0048] ②Filter the dried organic phase through a Buchner funnel covered with filter paper to remove the anhydrous sodium sulfate;

[0049] ③Add the filtrate to a rotary evaporator, set the water bath temperature to 35-40°C, the vacuum degree to 50-100 mmHg, and distill for 30-45 minutes to remove diethyl ether and acetic acid to obtain the crude cinnamaldehyde product;

[0050] ④Add the crude product to a short-path distillation device, set the vacuum degree to 0.1-10 mmHg, and the distillation temperature to 120-150°C, and collect the colorless to light yellow fraction;

[0051] ⑤Add the fraction obtained by short-path distillation to a rectification device, set the rectification pressure to 5-20 mmHg, and the reflux ratio to 3:1, and collect the fraction at 130-160°C to obtain the pure cinnamaldehyde product.

[0052] S6, Detection:

[0053] ①Calculate the yield by weight method: weigh the mass of the pure cinnamaldehyde product after rectification, and calculate according to the formula "yield = (actual yield / theoretical yield) x 100%";

[0054] ②Detect the purity by gas chromatograph, use HP-5 capillary column (30 m x 0.32 mm x 0.25 μm) for chromatographic column, column temperature program is initial temperature 80°C for 2 minutes, temperature rising at 10°C / min to 200°C for 5 minutes, carrier gas is nitrogen (flow rate 1.0 mL / min), sample size 1 μL, and estimate the purity according to the main peak area ratio.

[0055] The mass-volume ratio of styrene to paraformaldehyde in step S1 corresponds to a raw material molar ratio of 1:1.5-2.

[0056] The amount of acetic acid in step S2 is an effective amount to completely dissolve styrene and paraformaldehyde.

[0057] The adding rate of concentrated sulfuric acid in step S2 is a slow adding rate to avoid the reaction temperature exceeding 5℃.

[0058] The adding amount of concentrated sulfuric acid in step S2 is 5%-10% of the total mass of styrene and paraformaldehyde.

[0059] The reaction regulating step is also included: if the solution is obviously thickened during the reaction, less than 0.1 gram of hydroquinone is added and the temperature is lowered.

[0060] The concentration of sodium bicarbonate solution in step S4 is an effective concentration to neutralize the concentrated sulfuric acid in the system, and the adding amount is determined according to the pH value of the system reaching 6-7.

[0061] The operating conditions of short path distillation in step S5 are: vacuum degree 0.1-10 mmHg, distillation temperature 120-150℃.

[0062] The rectification in step S5 is vacuum rectification, and the operating pressure is 5-20 mmHg, and the collection fraction temperature is 130-160℃.

[0063] The amount of anhydrous sodium sulfate in step S5 is 1 / 5-1 / 3 of the volume of the organic phase, and the drying time is 2-4 hours.

[0064] Example 1

[0065] The raw material ratio is: styrene 20 mL (0.17 mol), paraformaldehyde 12 g (0.4 mol, molar ratio 1:2.35), acetic acid 30 mL, concentrated sulfuric acid 2.0 g.

[0066] The reaction conditions are: low temperature stage 0-5℃ for 1 hour, temperature raised to 25℃ for 2 hours, and 45℃ for 3.5 hours.

[0067] The post-treatment is performed according to the above steps, and finally 15.8 g of pure cinnamaldehyde is obtained.

[0068] Results: yield 72%, GC purity 91%, product is a light yellow transparent liquid with typical cinnamaldehyde aroma.

[0069] Example 2

[0070] The raw material ratio is: styrene 20 mL, paraformaldehyde 9 g (0.3 mol, molar ratio 1:1.76), acetic acid 25 mL, concentrated sulfuric acid 1.8 g.

[0071] The reaction conditions are the same as in Example 1, but the reaction time at 45℃ is extended to 4 hours.

[0072] The post-treatment is the same as in Example 1, and 14.2 g of pure cinnamaldehyde is obtained.

[0073] Result: yield 69%, GC purity 90%, product is colorless transparent liquid.

[0074] Example 3

[0075] Raw material ratio: styrene 20 mL, polyformaldehyde 10.5 g (0.35 mol, molar ratio 1:2.06), acetic acid 35 mL, concentrated sulfuric acid 2.2 g.

[0076] Reaction condition: the low temperature stage is prolonged to 1.5 hours, and the rest is the same as example 1.

[0077] Post-processing: the same as example 1, and 16.1 g of pure cinnamaldehyde is obtained.

[0078] Result: yield 73%, GC purity 92%, product is light yellow transparent liquid.

[0079] Comparison of key process parameters

[0080] Example Styrene: paraformaldehyde (molar ratio) Amount of concentrated sulfuric acid (g) Yield (%) Purity (%) 1 1:2.35 2.0 72 91 2 1:1.76 1.8 69 90 3 1.2.06 2.2 73 92

[0081] Conclusion: through segmented temperature control and optimization of raw material ratio, efficient preparation of cinnamaldehyde can be realized, and the yield and purity are better than those of the traditional method; the ratio and condition of example 3 are the best.

[0082] The above only describes some exemplary embodiments of the present application by way of illustration, and it is needless to say that the described embodiments can be modified in various ways without departing from the spirit and scope of the present application for those skilled in the art. Therefore, the above description is illustrative in nature and should not be understood as limiting the scope of protection of the claims of the present application.

Claims

1. A segmented temperature-controlled preparation method for cinnamaldehyde based on styrene and paraformaldehyde, characterized in that, Includes the following steps: S1. Raw material pretreatment: Grind 12 g of paraformaldehyde until the particle diameter is less than 100 micrometers. Take 20 ml of analytical grade styrene and distill it under reduced pressure at 60-70℃ and 10 mmHg to remove the polymerization inhibitor. Then add 0.1 g of hydroquinone. Add the pretreated paraformaldehyde and styrene to a flask. S2. Initial stage of reaction: Add acetic acid to the flask as a solvent. After it is fully dissolved, slowly add concentrated sulfuric acid and control the reaction temperature at 0-5℃. Continue the low temperature reaction for 1 hour, then slowly raise the temperature to 25℃ and stir with a magnetic stir bar for 2 hours. S3, Reaction Deepening Stage: Heat the reaction vessel to 40-50℃ and continue the reaction for 3-4 hours; S4. Quenching and Separation: The reactants are quenched with sodium bicarbonate solution to neutralize concentrated sulfuric acid, the aqueous phase is extracted with diethyl ether, and the organic phases are combined. S5. Purification: The organic phase is dried with anhydrous sodium sulfate, and the diethyl ether and acetic acid are removed by distillation to obtain the crude product. The crude product is collected by short-path distillation to collect the colorless to pale yellow cinnamaldehyde fraction, and then purified by distillation to obtain the pure product. S6. Detection: Calculate the yield and estimate the purity of the product after distillation.

2. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The mass-volume ratio of styrene to paraformaldehyde in step S1 corresponds to a raw material molar ratio of 1:1.5-2.

3. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The amount of acetic acid used in step S2 is the effective amount required to completely dissolve styrene and paraformaldehyde.

4. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The concentrated sulfuric acid added in step S2 is added at a slow rate to avoid the reaction temperature from exceeding 5°C.

5. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The amount of concentrated sulfuric acid added in step S2 is 5%-10% of the total mass of styrene and paraformaldehyde.

6. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, It also includes reaction control steps: if the solution becomes significantly thicker during the reaction, add less than 0.1 grams of hydroquinone and cool down.

7. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The concentration of the sodium bicarbonate solution mentioned in step S4 is an effective concentration that can neutralize the concentrated sulfuric acid in the system, and the amount added is based on the system pH value reaching 6-7.

8. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The operating conditions for short-path distillation in step S5 are: vacuum degree 0.1-10 mmHg, distillation temperature 120-150℃.

9. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The distillation described in step S5 is vacuum distillation, with an operating pressure of 5-20 mmHg and a collection temperature of 130-160℃.

10. The method for segmented temperature-controlled preparation of cinnamaldehyde based on styrene and paraformaldehyde according to claim 1, characterized in that, The amount of anhydrous sodium sulfate used in step S5 is 1 / 5 to 1 / 3 of the volume of the organic phase, and the drying time is 2 to 4 hours.