A recycling process for cinnamaldehyde production wastewater

Abstract

The invention discloses a recycling process for cinnamaldehyde production wastewater. The process comprises the following steps: filtering the cinnamaldehyde production wastewater after cooling treatment to obtain a first aqueous phase and a first solid phase; performing azeotropic distillation on the first aqueous phase to separate the azeotrope of acetaldehyde, benzaldehyde and water to obtain wastewater containing polyacetaldehyde; adding acid to the wastewater containing polyacetaldehyde to perform acidolysis reaction, then distilling and recovering acetaldehyde, and then filtering the mixture left by distillation to obtain acetaldehyde-free wastewater and scraps; dissolving the first solid phase with a first organic solvent, then adding alkali to perform a first neutralization reaction, separating the liquid after the reaction is completed, and then performing a first acidification on the inorganic layer to obtain benzoic acid, and concentrating the organic layer to obtain scraps. The present invention realizes the comprehensive utilization of useful components in wastewater, reduces emissions and reduces the treatment intensity of the final waste, achieves the transformation of waste into treasure, and comprehensive utilization of resources, significantly improves economic benefits, and greatly enhances the market competitiveness of the cinnamaldehyde project.

Description

Technical Field

[0001] The invention relates to the technical field of cinnamaldehyde production wastewater treatment, in particular to a recycling treatment process of cinnamaldehyde production wastewater. Background Art

[0002] Cinnamaldehyde (3-phenyl-2-propenal), English name: cinnamaldehyde, is an important chemical raw material and a widely used synthetic food flavoring. It can be used to prepare food preservatives, condiments, oral care products, chewing gum, and candy flavors.

[0003] At present, the synthesis of cinnamaldehyde in industry is mostly based on benzaldehyde and acetaldehyde as raw materials, and is synthesized through condensation reaction under catalyst conditions. After the condensation reaction is completed, the target product cinnamaldehyde is often obtained by distillation and rectification after liquid separation. In this process, the aqueous phase obtained contains a large amount of unconverted benzaldehyde, a small amount of cinnamaldehyde and polyacetaldehyde and other by-products. Directly as wastewater, due to the variety of organic matter and complex content, COD concentration is as high as more than 40,000, and wastewater treatment is difficult. If it is directly pre-treated and enters the sewage treatment system, it will cause a greater impact on the sewage treatment system, resulting in the collapse of the sewage treatment system, causing the wastewater treatment to be substandard. At the same time, there are still many useful raw materials, products and by-products in the wastewater, which are directly treated as waste materials, greatly increasing production costs. Summary of the invention

[0004] The purpose of the present invention is to overcome the above technical deficiencies, propose a recycling process for cinnamaldehyde production wastewater, and solve the technical problems of difficulty in treating cinnamaldehyde production wastewater and poor economic benefits in the prior art.

[0005] The present invention provides a recycling process for cinnamaldehyde production wastewater, comprising the following steps:

[0006] The cinnamaldehyde production wastewater is subjected to cooling treatment and then filtered to obtain a first water phase and a first solid phase;

[0007] The first aqueous phase is subjected to azeotropic distillation to separate the azeotrope of acetaldehyde, benzaldehyde and water to obtain wastewater containing polyacetaldehyde;

[0008] Acid is added to the above-mentioned wastewater containing polyacetaldehyde to carry out acid hydrolysis reaction, followed by distillation to recover acetaldehyde, and then the mixture left after distillation is filtered to obtain acetaldehyde-free wastewater and scraps;

[0009] The first solid phase is dissolved in a first organic solvent, and then a base is added to perform a first neutralization reaction. After the reaction is completed, the liquids are separated, and then the inorganic layer is first acidified to obtain benzoic acid, and the organic layer is concentrated to obtain the waste.

[0010] Compared with the prior art, the beneficial effects of the present invention include:

[0011] The present invention realizes the comprehensive utilization of useful components in wastewater, reduces emissions and lowers the treatment intensity of final waste, turns waste into treasure, comprehensively utilizes resources, significantly improves economic benefits, and greatly enhances the market competitiveness of the cinnamaldehyde project. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a process flow chart of an embodiment of a process for recycling and treating cinnamaldehyde production wastewater provided by the present invention;

[0013] Figure 2 The present invention provides a process flow chart of another embodiment of the process for recycling cinnamaldehyde production wastewater. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0015] See also Figure 1 The present invention provides a process for recycling cinnamaldehyde production wastewater, comprising the following steps:

[0016] S1, cinnamaldehyde production wastewater is filtered after cooling treatment to obtain the first aqueous phase and the first solid phase. In this step, the inventor finds according to the analysis of cinnamaldehyde production wastewater components that the cinnamaldehyde production wastewater contains unreacted materials benzaldehyde and acetaldehyde, and first designs and considers the recovery of the above-mentioned materials so that it re-enters the synthesis reaction system to improve the utilization rate of the overall raw materials. First, cinnamaldehyde production wastewater is subjected to cooling treatment, and as the temperature decreases, the solubility of high molecular weight organic matter and benzoic acid etc. is reduced, and it will precipitate, and the first solid phase obtained after filtration contains benzoic acid, organic macromolecules and polymers.

[0017] S2, subjecting the first aqueous phase to azeotropic distillation to separate azeotropes of acetaldehyde, benzaldehyde and water, and obtaining wastewater containing polyacetaldehyde (such as trimeraldehyde, tetrameraldehyde, etc.). In this step, the distilled water containing acetaldehyde and benzaldehyde is returned to the cinnamaldehyde condensation process.

[0018] S3, adding acid to the above-mentioned wastewater containing polyacetaldehyde for acidolysis reaction, then distilling and recovering acetaldehyde, and then filtering the remaining mixture after distillation to obtain acetaldehyde-free wastewater and scraps. In this step, polyacetaldehyde is depolymerized by adding acid and combined with distillation to recover acetaldehyde. The acetaldehyde-free wastewater obtained after filtering the remaining mixture after distillation has little impact on the sewage treatment system. After micro-electrolysis and Fenton treatment, it can enter the sewage treatment system for biochemical treatment, and then it can be directly discharged.

[0019] S4, dissolving the first solid phase with a first organic solvent, then adding alkali to carry out a first neutralization reaction, separating the liquids after the reaction is completed, and then acidifying the inorganic layer to obtain benzoic acid, and concentrating the organic layer to obtain scraps.

[0020] The inventor found through preliminary tests that although each batch of cinnamaldehyde synthesis reaction and product separation post-treatment conditions are different, resulting in differences in the main organic component content of the wastewater produced, its components are basically benzaldehyde, acetaldehyde, cinnamaldehyde, polyacetaldehyde, benzoic acid and other organic polymers, etc., with various components, and partly soluble in water, and partly slightly soluble in water. If separated separately, the cost is too high. Therefore, designing an efficient treatment process, the comprehensive utilization of useful components in wastewater, reducing emissions and reducing the treatment intensity of the final waste are the keys to the entire cinnamaldehyde production. The inventor has developed a treatment process for the comprehensive utilization of cinnamaldehyde wastewater through long-term research and practice, which has achieved turning waste into treasure, comprehensive utilization of resources, and greatly improved the market competitiveness of the cinnamaldehyde project. Therefore, the present invention is proposed.

[0021] In this embodiment, in step S1, during the cooling process, the cinnamaldehyde production wastewater is cooled to -5-0° C. In some specific embodiments of the present invention, the cinnamaldehyde production wastewater is cooled by ice bath cooling.

[0022] In this embodiment, in step S2, the temperature of azeotropic distillation is 50-70°C, preferably 55-65°C.

[0023] In this embodiment, in step S3, during the acidolysis reaction, the first acid used is concentrated sulfuric acid with a mass fraction of 90-98%, and the amount ratio of the wastewater containing polyacetaldehyde to the concentrated sulfuric acid is 1kg: (0.01-0.03)mL; the temperature of the acidolysis reaction is 55-80°C, preferably 55-70°C, and the time of the acidolysis reaction is 4-6h; during the distillation process, the distillation temperature is 50-80°C, preferably 55-75°C.

[0024] In this embodiment, in step S4, the first organic solvent is at least one of ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, and dichloromethane, preferably ethyl acetate; the amount ratio of the first solid phase to the first organic solvent is 0.8-2kg:1L; in the first neutralization reaction process, the present invention does not limit the type of the first base used, and those skilled in the art can select it according to actual conditions, for example, it can be an inorganic base such as sodium hydroxide, potassium hydroxide, and ammonia water. In some specific embodiments of the present invention, the first base is sodium hydroxide. In some more specific embodiments of the present invention, the first alkali is added to the system in the form of an aqueous solution, the mass concentration of the first alkali solution is 10%-30%, and the usage ratio of the first solid phase to the first alkali solution is 1kg: (0.1-0.3)mL; the temperature of the first neutralization reaction is 50-60°C, and the time of the first neutralization reaction is 4-6h; in the first acidification process, the final pH is adjusted to 3-4 to obtain benzoic acid. If the pH is too high, the excess hydrochloric acid increases the cost, and if it is too low, it cannot be completely converted into benzoic acid; the present invention does not limit the type and concentration of the first acid solution used in the acidification process, and those skilled in the art can choose according to actual conditions, for example, it can be an inorganic acid such as hydrochloric acid, sulfuric acid, and nitric acid; in some specific embodiments of the present invention, the first acid solution is hydrochloric acid, and the mass fraction of hydrochloric acid is 15%-20%.

[0025] See also Figure 2 In the present invention, the above-mentioned cinnamaldehyde production wastewater recovery and treatment process further includes the following steps:

[0026] S5, dissolving the above-mentioned scraps with a second organic solvent, then adding alkali to carry out a second neutralization reaction, then adding activated carbon to the neutralized solution for adsorption and decolorization, removing the activated carbon and performing liquid separation to obtain a first oil phase and a second aqueous phase. In this step, the carboxylic acid in the scraps is first converted into a water-soluble salt by an acid-base neutralization reaction to increase the water solubility of the carboxylic acid and significantly reduce the phenomenon of membrane clogging; then the ions and pigments in the solution are removed by adsorption and decolorization with activated carbon; and then the polymer dissolved in ethyl acetate in the cinnamaldehyde waste solution is removed by liquid separation.

[0027] S6, removing the second organic solvent from the first oil phase, then adding an alcohol solvent for beating, filtering to obtain a filter residue and a filtrate, and the filtrate dealcoholization solvent is an oily liquid, and the filter residue is a benzaldehyde acetaldehyde polymer. In this step, a small amount of carboxylic acid substances are still present in the first oil phase. By removing the second organic solvent+alcohol solvent beating, the carboxylic acid substances in the first oil phase can be dissolved in the alcohol solvent, separated from the benzaldehyde acetaldehyde polymer, and the recovery rate of the carboxylic acid is improved.

[0028] S7, adding acid to the second aqueous phase and the oily liquid for a second acidification, then extracting the acidified liquid with a third organic solvent to obtain a second oil phase and a third aqueous phase, desolventizing the second oil phase, then cooling and crystallizing to obtain 5-phenylpent-2-enoic acid. In this step, the main component of the oily liquid is a carboxylic acid substance, which is combined with the second aqueous phase and converted into a carboxylic acid by acidification, and finally 5-phenylpent-2-enoic acid with a purity of ≥98% is obtained by extraction with a third organic solvent, drying and dehydration, removal of the third organic solvent, reduced pressure distillation, and cooling and crystallization; the third aqueous phase can be used for neutralization reaction after desalting.

[0029] In this embodiment, in step S5, before the scraps are fully dissolved in the second organic solvent, the relative content of carboxylic acid in the cinnamaldehyde waste sample can also be detected by liquid chromatography, which is convenient for subsequent testing of the recovery rate of carboxylic acid. In order to improve the dissolution effect, the cinnamaldehyde waste is fully dissolved in the second organic solvent in the form of powder. Further, the cinnamaldehyde waste powder is obtained by fully grinding the cinnamaldehyde waste. The second organic solvent is at least one of ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, and dichloromethane, preferably ethyl acetate; the amount ratio of the scraps to the second organic solvent is 1g: (3-8) mL. If the waste concentration is too high, the system will be more viscous and the reactivity will be reduced; if the waste concentration is too low, the solvent consumption and the number of treatments will increase, and the treatment cost will be increased. In the second neutralization reaction process, the present invention does not limit the type of the second base used, and those skilled in the art can choose according to actual conditions, for example, it can be an inorganic base such as sodium hydroxide, potassium hydroxide, and ammonia water. In some specific embodiments of the present invention, the second base is sodium hydroxide. The present invention uses sodium hydroxide as the second base, with a small amount of addition and cost saving. In some more specific embodiments of the present invention, the second alkali is added to the system in the form of an aqueous solution, and the mass concentration of the second alkali solution is 10%-20%; the ratio of the waste material to the second alkali solution is 1g: (1-3)mL. If the amount of the second alkali added is too little, the carboxylic acid reaction is incomplete, reducing the yield. If the amount of the second alkali added is too much, the processing cost will increase. During the adsorption decolorization process, the amount of activated carbon added is 20%-30% of the mass of the cinnamaldehyde waste; the decolorization temperature is 30-60°C, preferably 30-50°C, and the decolorization time is 20-100min, preferably 80-90min. The inventor found in the experimental process that if the neutralization solution is directly separated, the viscosity of the neutralization solution is too large and the subsequent separation operation cannot be performed; and the inventor screened different decolorization temperatures and decolorization times and found that within this temperature and time range, the carboxylic acid crystals have the highest purity (≥99%). If the temperature is too high, the second organic solvent evaporates too quickly, and if the temperature is too low or the insulation time is too short, the impurity adsorption is insufficient. After the separation process is completed, the organic layer obtained by separation can be extracted with water and the inorganic layers can be combined to improve the recovery rate of 5-phenylpent-2-enoic acid.

[0030] In this embodiment, in step S6, the alcohol solvent may be methanol, ethanol, etc. During the pulping process, in order to improve the recovery rate of the carboxylic acid, the obtained filter residue may be added with ethanol again for repeated pulping, and the filtrate obtained during each pulping process is combined. In some specific embodiments of the present invention, the ratio of the waste material to the alcohol solvent is 1g: (3-10)mL, and the time for each pulping is 4-6h.

[0031] In this embodiment, in step S7, during the second acidification process, the final pH is adjusted to 2-3 to obtain 5-phenylpent-2-enoic acid. If the pH is too high, the excess amount of hydrochloric acid increases the cost, and if it is too low, the carboxylate cannot be completely converted into carboxylic acid. The present invention does not limit the type and concentration of the acid solution used in the acidification process. Those skilled in the art can choose according to actual conditions. For example, it can be an inorganic acid such as hydrochloric acid, sulfuric acid, and nitric acid. In some specific embodiments of the present invention, the acid solution is hydrochloric acid, and the mass fraction of hydrochloric acid is 15%-20%; the third organic solvent is ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, dichloromethane, etc., preferably ethyl acetate; the volume ratio of the acidification solution to the third organic solvent is 1: (0.2-2), and the temperature of cooling crystallization is -5-0°C.

[0032] In the present invention, the second organic solvent, the alcohol solvent and the third organic solvent are removed by vacuum distillation. Further, the temperature of the vacuum distillation is 30-60°C, preferably 30-55°C.

[0033] Example 1

[0034] (1) 15 kg of cinnamaldehyde production wastewater was cooled in an ice bath and then filtered to obtain 14 kg of water phase and 1 kg of solid phase. The relative contents of benzaldehyde and acetaldehyde in the water phase were detected by liquid chromatography. The test results showed that the total content was about 25%;

[0035] (2) subjecting the aqueous phase in (1) to azeotropic distillation at 65° C. to obtain 3 kg of an aqueous solution containing benzaldehyde and acetaldehyde;

[0036] (3) Add 200 mL of concentrated sulfuric acid with a mass concentration of 90% to the wastewater containing polyacetaldehyde remaining from the azeotropic distillation in (2), and perform a reflux depolymerization reaction at 60° C. After 5 hours, distill the reaction solution at 65° C. to obtain 1.1 kg of acetaldehyde aqueous solution, and then filter the remaining mixture to obtain 0.26 kg of macromolecular polymer (waste), and then perform micro-electrolysis, Feton treatment, and biochemical treatment on the remaining aqueous phase to finally obtain 11 kg of dischargeable wastewater, and the amount of wastewater reduced = (15-11) / 15*100% = 26%. The total content of benzaldehyde and acetaldehyde in the dischargeable wastewater is detected by liquid chromatography again, and the result shows that the total content of benzaldehyde and acetaldehyde accounts for about 9.5%, and the recovery rate of benzaldehyde and acetaldehyde = 1-(11*9.5%) / (14*25%)*100% = 70%;

[0037] (4) First, 1L of ethyl acetate was added to the solid phase in (1) to fully dissolve it to form a homogeneous solution, and then 200mL of sodium hydroxide with a mass concentration of 20% was added to neutralize and react at 50°C for 4h. After the reaction was complete, the liquid was separated, and the organic layer was concentrated to obtain 0.15kg of macromolecular polymer (waste), and 250mL of hydrochloric acid solution with a mass concentration of 20% was added to the inorganic layer obtained by separation to adjust the pH to 3-4, and finally 0.64kg of benzoic acid was obtained. The overall utilization rate of wastewater = (3+0.64+1.1+0.15+0.26) / 15*100% = 34%.

[0038] After repeating the process for many times, the recovery rate of benzaldehyde and acetaldehyde in the wastewater is 70-75%, the overall utilization rate of the wastewater is 30-35%, and the amount of wastewater is reduced by 25-30%.

[0039] Example 2

[0040] (1) 15 kg of cinnamaldehyde production wastewater was cooled in an ice bath and then filtered to obtain 14 kg of water phase and 1 kg of solid phase. The relative contents of benzaldehyde and acetaldehyde in the water phase were detected by liquid chromatography. The test results showed that the total content was about 25%;

[0041] (2) subjecting the aqueous phase in (1) to azeotropic distillation at 55° C. to obtain 4 kg of an aqueous solution containing benzaldehyde and acetaldehyde;

[0042] (3) Add 200 mL of concentrated sulfuric acid with a mass concentration of 90% to the wastewater containing polyacetaldehyde remaining from the azeotropic distillation in (2), and perform a reflux depolymerization reaction at 60° C. After 5 hours, distill the reaction solution at 75° C. to obtain 1 kg of acetaldehyde aqueous solution, and then filter the remaining mixture to obtain 0.16 kg of macromolecular polymer (waste), and then perform micro-electrolysis, Feton treatment, and biochemical treatment on the remaining aqueous phase to finally obtain 9 kg of dischargeable wastewater, and the amount of wastewater reduced = (15-9) / 15*100% = 40%. The total content of benzaldehyde and acetaldehyde in the dischargeable wastewater is detected by liquid chromatography again, and the result shows that the total content of benzaldehyde and acetaldehyde is about 9.7%, and the recovery rate of benzaldehyde and acetaldehyde = 1-(9*9.7%) / (14*25%)*100% = 75%;

[0043] (4) First, add 1L of ethyl acetate to fully dissolve the solid phase in (1) to form a homogeneous solution, then add 200mL of 20% sodium hydroxide to neutralize and react at 50°C for 4h. After the reaction is complete, separate the liquids, and then concentrate the organic layer to obtain 0.2kg of macromolecular polymer (waste), and add 250mL of 20% hydrochloric acid solution to the inorganic layer obtained by separation to adjust the pH to 3-4, and finally obtain 0.60kg of benzoic acid. The overall utilization rate of wastewater = (4+0.6+1+0.2+0.16) / 15*100% = 40%.

[0044] After repeating the process several times, the recovery rate of benzaldehyde and acetaldehyde in the wastewater was 75%-80%, the overall utilization rate of the wastewater was 38%-43%, and the amount of wastewater was reduced by 40%-45%.

[0045] Example 3

[0046] (1) 15 kg of cinnamaldehyde production wastewater was cooled in an ice bath and then filtered to obtain 14 kg of water phase and 1 kg of solid phase. The relative contents of benzaldehyde and acetaldehyde in the water phase were detected by liquid chromatography. The test results showed that the total content was about 25%;

[0047] (2) subjecting the aqueous phase in (1) to azeotropic distillation at 55° C. to obtain 4 kg of an aqueous solution containing benzaldehyde and acetaldehyde;

[0048] (3) Add 200 mL of concentrated sulfuric acid with a mass concentration of 90% to the wastewater containing polyacetaldehyde remaining from the azeotropic distillation in (2), and perform a reflux depolymerization reaction at 60° C. After 5 hours, distill the reaction solution at 55° C. to obtain 0.8 kg of acetaldehyde aqueous solution, and then filter the remaining mixture to obtain 0.4 kg of macromolecular polymer (waste), and then perform micro-electrolysis, Feton treatment, and biochemical treatment on the remaining aqueous phase to finally obtain 10 kg of dischargeable wastewater, and the amount of wastewater reduced = (15-10) / 15*100% = 33%. The total content of benzaldehyde and acetaldehyde in the dischargeable wastewater is detected by liquid chromatography again, and the results show that the total content of benzaldehyde and acetaldehyde is about 8.5%, and the recovery rate of benzaldehyde and acetaldehyde = 1-(10*8.5%) / (14*25%)*100% = 76%;

[0049] (4) First, 1L of ethyl acetate was added to the solid phase in (1) to fully dissolve it to form a homogeneous solution, and then 200mL of sodium hydroxide with a mass concentration of 20% was added to neutralize and react at 50°C for 4h. After the reaction was complete, the liquid was separated, and the organic layer was concentrated to obtain 0.2kg of macromolecular polymer (waste), and 250mL of hydrochloric acid solution with a mass concentration of 20% was added to the inorganic layer obtained by separation to adjust the pH to 3-4, and finally 0.62kg of benzoic acid was obtained. The overall utilization rate of wastewater = (4 + 0.62 + 0.8 + 0.2 + 0.4) / 15 * 100% = 40%. The process was repeated many times, and the recovery rate of benzaldehyde and acetaldehyde in wastewater was 75%-80%, the overall utilization rate of wastewater was 38%-43%, and the amount of wastewater was reduced by 30%-35%.

[0050] Example 4

[0051] (1) taking the waste sample obtained in the above example, and detecting the type and relative content of carboxylic acid in the sample by liquid chromatography, the test results show that the type of carboxylic acid contained in the cinnamaldehyde waste is 5-phenylpent-2-enoic acid, and the content is about 35%;

[0052] (2) Take 200 g of the scraps, use 1 L of ethyl acetate to fully dissolve them, then add 400 mL of 20% sodium hydroxide solution and stir them thoroughly, then add 60 g of activated carbon and heat at 50° C. to adsorb and decolorize for 90 min, filter to remove the activated carbon, and separate the liquids to obtain an oil phase and an aqueous phase;

[0053] (3) The oil phase in (2) was distilled under reduced pressure at 50°C to remove ethyl acetate, and then 1L of ethanol was added to pulp for 4 hours, and the first filter residue and the first filtrate were obtained by filtration. 960mL of ethyl acetate was recovered in this stage; the first filter residue was taken, and 1L of ethanol was added to pulp again and filtered to obtain 130g of the second filter residue (benzaldehyde acetaldehyde polymer) and the second filtrate, and the macromolecule removal rate was 65%; the first filtrate and the second filtrate were combined to remove the solvent, and 10g of oily liquid was obtained. 1900mL of ethanol was recovered in this stage;

[0054] (4) The aqueous phase in (2) and the oily liquid in (3) are combined, and 400 mL of a 20% hydrochloric acid solution is added to adjust the pH to 2-3, followed by extraction with 300 mL of ethyl acetate to obtain an oil phase and an aqueous phase; the oil phase is dried to remove water, and vacuum distilled to obtain a light yellow oily liquid, and finally cooled to 0°C to precipitate 60 g of white crystals of 5-phenylpent-2-enoic acid, with a carboxylic acid yield of 30%. 290 mL of ethyl acetate is recovered in this stage; the aqueous phase produced in this process can be used for neutralization reaction after desalination treatment.

[0055] The process was repeated several times, with carboxylic acid yield = 30-35% and macromolecular removal rate 60-65%.

[0056] Example 5

[0057] (1) taking the waste sample obtained in the above example, and detecting the type and relative content of carboxylic acid in the sample by liquid chromatography, the test results show that the type of carboxylic acid contained in the cinnamaldehyde waste is 5-phenylpent-2-enoic acid, and the content is about 35%;

[0058] (2) Take 200 g of the scraps, use 1 L of dichloromethane to fully dissolve them, then add 400 mL of a 20% sodium hydroxide solution and stir them thoroughly, then add 60 g of activated carbon and heat at 30° C. to adsorb and decolorize for 90 min, filter to remove the activated carbon, and separate the liquids to obtain an oil phase and an aqueous phase;

[0059] (3) The oil phase in (2) was distilled under reduced pressure at 50°C to remove dichloromethane, and then 1L of ethanol was added to pulp for 4 hours, and the first filter residue and the first filtrate were obtained by filtration. 900mL of dichloromethane was recovered in this stage; the first filter residue was taken, and 1L of ethanol was added to pulp again and filtered to obtain 125g of the second filter residue (benzaldehyde acetaldehyde polymer) and the second filtrate, and the macromolecule removal rate = 62.5%; the first filtrate and the second filtrate were combined to remove the solvent, and 10g of oily liquid was obtained. 1900mL of ethanol was recovered in this stage;

[0060] (4) The aqueous phase in (2) and the oily liquid in (3) are combined, and 400 mL of 20% hydrochloric acid solution is added to adjust the pH to 2-3, followed by extraction with 300 mL of ethyl acetate to obtain an oil phase and an aqueous phase; the oil phase is dried to remove water, and vacuum distilled to obtain a light yellow oily liquid, and finally cooled to 0°C to precipitate 38 g of white crystals of 5-phenylpent-2-enoic acid, with a carboxylic acid yield of 19%. 290 mL of ethyl acetate is recovered in this stage; the aqueous phase produced in this process can be used for neutralization reaction after desalination treatment.

[0061] After repeating the process several times, the carboxylic acid yield was 15-20% and the macromolecule removal rate was 60-65%, indicating that the use of dichloromethane had a low yield and also had the disadvantages of being highly volatile as a solvent, being unable to be recycled multiple times, being expensive, being environmentally unfriendly and being highly toxic.

[0062] In summary, the present invention also has the following beneficial effects:

[0063] (1) Recovery rate of benzaldehyde and acetaldehyde in wastewater ≥ 70%

[0064] Benzaldehyde and acetaldehyde in the wastewater are the starting materials of cinnamaldehyde. The recovery of these materials has a crucial impact on the production cost of cinnamaldehyde. Through optimization of the wastewater treatment and recycling process, the recovery rate of benzaldehyde and acetaldehyde exceeds 70%, which greatly reduces the production cost of cinnamaldehyde.

[0065] (2) Overall utilization rate of wastewater ≥ 30%

[0066] The wastewater has many components and is relatively complex, but benzaldehyde and acetaldehyde, benzoic acid, and 5-phenylpentenoic acid extracted from the waste can be directly used as the starting materials of cinnamaldehyde after being treated by this process, while benzoic acid is a by-product. At the same time, products such as 5-phenylpentenoic acid extracted from the waste also have high added value. Overall, through the comprehensive evaluation of the process's energy consumption and cost, the wastewater utilization rate exceeds 30%.

[0067] (3) Removal rate of benzoic acid and macromolecules in wastewater ≥ 60%

[0068] The wastewater after distillation and rectification can be reprocessed to effectively separate benzoic acid and recycle macromolecular polymers as solid waste. Through one process, the removal rate of benzoic acid and macromolecular polymers exceeds 60%, which greatly reduces the COD of the wastewater and reduces the pressure of wastewater treatment.

[0069] (4) Wastewater reduction ≥ 25%

[0070] When benzaldehyde and acetaldehyde are condensed to synthesize cinnamaldehyde, water is used as a solvent, and the amount of water used is nearly 20 times the amount of the reactants. If it is directly treated as wastewater, the pressure is very high. Considering that it contains useful materials and products, especially benzaldehyde and acetaldehyde, they form an azeotropic system with water during the distillation recovery process. At the same time, in the process of recovering acetaldehyde, the aqueous solution of acetaldehyde is also obtained, which can be directly recycled. Taking all factors into consideration, the amount of wastewater can be reduced by at least 25%.

[0071] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A process for recycling cinnamaldehyde production wastewater, characterized in that: The following steps are involved: The cinnamaldehyde production wastewater is subjected to cooling treatment and then filtered to obtain a first water phase and a first solid phase; The first aqueous phase is subjected to azeotropic distillation to separate the azeotrope of acetaldehyde, benzaldehyde and water to obtain wastewater containing polyacetaldehyde; Adding acid to the wastewater containing polyacetaldehyde to carry out acid hydrolysis reaction, then distilling to recover acetaldehyde, and then filtering the mixture left after distillation to obtain acetaldehyde-free wastewater and scraps; The first solid phase is dissolved in a first organic solvent, and then a base is added to perform a first neutralization reaction. After the reaction is completed, the liquids are separated, and then the inorganic layer is first acidified to obtain benzoic acid, and the organic layer is concentrated to obtain the waste material; wherein, During the cooling treatment process, the cinnamaldehyde production wastewater is cooled to -5-0°C; During the azeotropic distillation process, the temperature of the azeotropic distillation is 50-70°C.

2. The recycling process of cinnamaldehyde production wastewater according to claim 1, characterized in that: During the acidolysis reaction, the first acid used is concentrated sulfuric acid with a mass fraction of 90-98%, and the dosage ratio of the wastewater containing polyacetaldehyde to the concentrated sulfuric acid is 1kg: (0.01-0.03)mL; the temperature of the acidolysis reaction is 55-80°C, and the time of the acidolysis reaction is 4-6h; during the distillation process, the distillation temperature is 50-80°C.

3. The recycling process of cinnamaldehyde production wastewater according to claim 1, characterized in that: The first organic solvent is at least one of ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, and dichloromethane; the dosage ratio of the first solid phase to the first organic solvent is 0.8-2kg:1L; during the first acidification process, the final pH is adjusted to 3-4.

4. The recycling process of cinnamaldehyde production wastewater according to claim 1, characterized in that: During the first neutralization reaction, the first alkali is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; the first alkali is added to the system in the form of an aqueous solution, the mass concentration of the first alkali solution is 10%-30%, and the dosage ratio of the first solid phase to the first alkali solution is 1kg: (0.1-0.3)mL; the temperature of the first neutralization reaction is 50-60°C, and the time of the first neutralization reaction is 4-6h.

5. The recycling process of cinnamaldehyde production wastewater according to claim 1, characterized in that: The recycling process of cinnamaldehyde production wastewater also includes the following steps: The waste material is dissolved in a second organic solvent, and then an alkali is added to perform a second neutralization reaction, and activated carbon is added to the neutralized solution for adsorption and decolorization, and the activated carbon is removed and the liquid is separated to obtain a first oil phase and a second water phase; The first oil phase is freed from the second organic solvent, and then an alcohol solvent is added to the first oil phase for pulping, and a filter residue and a filtrate are obtained after filtration, and the filtrate is freed from the alcohol solvent to obtain an oily liquid, and the filter residue is a benzaldehyde acetaldehyde polymer; Acid is added to the second aqueous phase and the oily liquid for a second acidification, and then the acidified liquid is extracted with a third organic solvent to obtain a second oil phase and a third aqueous phase. The second oil phase is desolventized and then cooled and crystallized to obtain 5-phenylpent-2-enoic acid.

6. The recycling process of cinnamaldehyde production wastewater according to claim 5, characterized in that: The second organic solvent is at least one of ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, and dichloromethane; the ratio of the waste material to the second organic solvent is 1g: (3-8) mL; during the second neutralization reaction, the second alkali used is at least one of sodium hydroxide, potassium hydroxide, and ammonia water; the second alkali is added to the system in the form of an aqueous solution, and the mass concentration of the second alkali solution is 10%-20%; the ratio of the waste material to the second alkali solution is 1g: (1-3) mL; during the adsorption decolorization process, the amount of activated carbon added is 20%-30% of the mass of the cinnamaldehyde waste; the decolorization temperature is 30-60°C, and the decolorization time is 20-100min.

7. The recycling process of cinnamaldehyde production wastewater according to claim 5, characterized in that: The alcohol solvent is at least one of methanol and ethanol; the usage ratio of the waste material to the alcohol solvent is 1g: (3-10)mL, and the beating time for each time is 4-6h.

8. The process for recycling cinnamaldehyde production wastewater according to claim 5, characterized in that: During the second acidification process, the final pH is adjusted to 2-3; the third organic solvent is at least one of ethyl acetate, methyl tert-butyl ether, diisopropyl ether, methanol, ethanol, and dichloromethane; the volume ratio of the acidification liquid to the third organic solvent is 1: (0.2-2), and the temperature of the cooling crystallization is -5-0°C.

9. The process for recycling cinnamaldehyde production wastewater according to claim 5, characterized in that: The second organic solvent, the alcohol solvent and the third organic solvent are removed by distillation under reduced pressure.

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