Method for resource utilization of chloroacetic acid method glycine production wastewater

Abstract

The present application relates to wastewater treatment and environmental protection technical field, specifically relates to a kind of chloroacetic acid method glycine production wastewater resource utilization method, after glycine production wastewater is evaporated pretreatment, solid-liquid separation, esterification reaction, oil-water separation etc., resource recycling glycine in glycine production wastewater and ammonium chloride;Through the invention, the problem of glycine production wastewater is reasonably solved, which not only reduces environmental pollution, but also realizes resource recycling, improves its industrial value, and also eliminates the generation of new "three wastes", is a clean production process in line with the development direction of green chemistry, and has broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment and environmental protection technology, specifically to a method for the resource utilization of wastewater from glycine production via the chloroacetic acid process. Background Technology

[0002] Glycine, also known as aminoacetic acid, is the simplest α-amino acid. It has a wide range of applications, serving as an important raw material in pharmaceuticals, pesticides, organic synthesis, and biochemical research, and is also a crucial intermediate in organic synthesis. Currently, domestic glycine production mainly employs the chloroacetic acid ammonolysis process. In this process, hexamethylenetetramine is used as a catalyst, and excess ammonia reacts with chloroacetic acid to obtain a mixture of glycine and ammonium chloride. After alcohol precipitation, centrifugation, and drying, the glycine product is obtained. The methanol mother liquor obtained from centrifugation contains water, ammonium chloride, glycine, hexamethylenetetramine, and a small amount of liquid ammonia. Methanol wastewater generated during intermediate synthesis, glycine synthesis, and recrystallization of glycine and ammonium chloride is combined with the methanol mother liquor and subjected to distillation to recover methanol, yielding glycine wastewater. This wastewater contains high concentrations of ammonium chloride, unprecipitated glycine, and the catalyst hexamethylenetetramine. Currently, the lower-quality ammonium chloride product is obtained primarily through double-effect evaporation, concentration, and cooling. The high-value-added glycine is not being utilized effectively, wasting resources, polluting the environment, and increasing production costs.

[0003] Patents CN108658374A and CN116143240A disclose a method for cleaning and treating wastewater from glycine production. The method involves adjusting the ammonium chloride mother liquor with hydrochloric acid, directly reusing the primary and secondary evaporation condensates in the glycine production process, and allowing the flash evaporation condensate to enter a low-temperature evaporation system. The evaporated liquid undergoes membrane treatment and biochemical treatment before being discharged, and the remaining residue is returned to the glycine production process. While this method involves membrane and biochemical treatment, the membrane treatment efficiency is low, and it suffers from high investment costs and high treatment expenses.

[0004] Patent CN111943321 A discloses a method for recycling wastewater from glycine production. The method is characterized by using a ceramic membrane to remove suspended solids, colloids, and impurities from the wastewater; using a multi-stage nanofiltration system to separate and concentrate the catalyst hexamethylenetetramine for reuse; and using an ammonia removal membrane system to deeply remove high-concentration ammonia nitrogen before subjecting the effluent to biochemical treatment.

[0005] Patent CN116022982A discloses a method for treating glycine production wastewater, mainly involving the recovery of hexamethylenetetramine (HMT) from the wastewater using GMA-modified diatomaceous earth. The method involves distilling the glycine production wastewater to obtain a mother liquor; mixing the mother liquor with GMA-modified diatomaceous earth, filtering, and obtaining a filtrate and a filter residue; washing the filter residue with ether to recover and reuse HMT; and using double-effect evaporation of the filtrate to recover solid ammonium chloride. However, this method primarily focuses on the recovery and reuse of the hexamethylenetetramine catalyst, neglecting the recovery and reuse of glycine from the wastewater, resulting in resource waste.

[0006] Patent CN103303942A discloses a method and equipment for recovering ammonium chloride from glycine mother liquor. The method primarily involves separating 90%–93% methanol from the glycine mother liquor after alcohol precipitation and centrifugation using a packed distillation column. The remaining liquid from the distillation column is then concentrated in a two-stage countercurrent evaporator (110℃ and 85℃) under vacuum (-0.04 MPa to -0.07 MPa). The concentrated liquid is then continuously cooled and crystallized. Finally, the crystallized liquid is thickened and centrifuged to obtain ammonium chloride. This process generates evaporation condensate and final waste liquid. However, this method merely re-concentrates the wastewater after methanol recovery under vacuum, resulting in low-quality ammonium chloride. High-value-added products such as glycine are not treated, and the environmental problems caused by the evaporation condensate and waste liquid remain.

[0007] Patent CN107573252A discloses a method for wastewater recovery and utilization in the chloroacetic acid process for glycine production. It aims to comprehensively recover and utilize the solvent water and hexamethylenetetramine added during the traditional chloroacetic acid ammoniation process for glycine production, thereby solving the problems of seamless wastewater treatment and reducing hexamethylenetetramine consumption. It primarily targets the wastewater after glycine extraction, utilizing the hexamethylenetetramine catalyst to reduce hexamethylenetetramine consumption. However, in the methanol extraction and crystallization process for glycine, complete extraction is not achieved, and some glycine dissolves in the wastewater. The recovery and utilization of glycine from the wastewater is not addressed, which is significantly different from the main problem solved by this patent. Summary of the Invention

[0008] To address the aforementioned problems, this invention discloses a method for the resource utilization of wastewater from glycine production using the chloroacetic acid process. In this method, glycine in the wastewater is utilized as a resource, ammonium chloride is effectively recovered, and urotropine is enriched and recovered using other methods, thereby saving resources and reducing environmental pollution.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] First, the glycine production wastewater undergoes pretreatment via evaporation, solid-liquid separation, esterification reaction, and oil-water separation to recover glycine and ammonium chloride from the wastewater in a resource-based manner. The method includes the following steps:

[0011] (1) Evaporation pretreatment: Glycine wastewater is evaporated to obtain condensate with high ammonia nitrogen and high COD content, which is then reused in the glycine production system;

[0012] (2) Solid-liquid separation: The material in the bottom of the tower after evaporation pretreatment is cooled and separated into solid and liquid to obtain filtrate, and ammonium chloride is recovered;

[0013] (3) Esterification reaction: The above filtrate is esterified with methyl tert-butyl ether in the presence of a catalyst to obtain an esterification reaction solution;

[0014] (4) Oil-water separation: The esterification reaction solution is separated into crude glycine tert-butyl ester and ammonium chloride aqueous solution. The ammonium chloride aqueous solution is recycled to step (1). After hexamethylenetetramine is enriched by recycling, it is discharged and recycled.

[0015] The further improvement is that the evaporation pretreatment in step (1) is carried out under vacuum conditions.

[0016] A further improvement is that the molar ratio of methyl tert-butyl ether in step (3) to glycine in the filtrate of step (2) is 1 to 1.2:1, preferably 1.1:1; wherein when the molar ratio is greater than 1.2:1, the product does not increase significantly.

[0017] The further improvement is that the catalyst in step (3) is an H-type cation exchange resin.

[0018] The further improvement is that the esterification reaction temperature in step (3) is 20℃~50℃.

[0019] The further improvement is that the esterification reaction time in step (3) is 2h to 6h.

[0020] Generally, the evaporation pretreatment conditions are an absolute pressure of 10 kPa to 12 kPa.

[0021] A further improvement is that the amount of condensate generated by the evaporation pretreatment is 45% to 50% of the total amount of input materials.

[0022] A further improvement is that the cooling refers to a temperature drop to 20-25℃.

[0023] A further improvement is that the cyclic enrichment of urotropine refers to the urotropine reaching a saturation concentration.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1) Glycine in the wastewater from glycine production is utilized as a resource, ammonium chloride is effectively recovered, and hexamethylenetetramine is enriched and recovered using other methods; thus saving resources and reducing environmental pollution.

[0026] 2) Evaporation pretreatment is carried out under vacuum conditions, which helps to reduce the decomposition of ammonium chloride and lower the ammonia nitrogen content in the condensate;

[0027] 3) The condensate produced by the evaporation pretreatment can be directly reused in the glycine production system as makeup water, realizing a closed-loop circulation and reducing wastewater treatment costs;

[0028] 4) Reusing ammonium chloride aqueous solution can improve the recovery rate of ammonium chloride, and unreacted glycine can participate in the esterification reaction again, reducing resource waste.

[0029] 5) The esterification reaction conditions are mild, the catalyst can be recycled, and the energy consumption and cost are low;

[0030] 6) Glycine tert-butyl ester is a high-value-added fine chemical with significant economic benefits;

[0031] 7) The process and equipment are simple and easy to operate. It will not generate new "three wastes". The process is green, environmentally friendly, safe and reliable. It belongs to the green and clean production process, which can further promote the good operation of the glycine production system. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the process of resource utilization in this invention. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0034] The main components of the glycine production wastewater used in the following examples are as follows:

[0035] The mass concentrations of glycine, hexamethylenetetramine, ammonium chloride, acetic acid, methanol, formaldehyde, ammonia, and water were 5.05%, 2.73%, 20.92%, 0.36%, 0.22%, 0.11%, 0.12%, 69.87%, and 0.62%, respectively.

[0036] Example 1

[0037] 1000g of glycine production wastewater was evaporated under a vacuum pressure of 12kPa to obtain 493.1g of evaporated condensate and 500.3g of solid-liquid mixture in the bottom of the tower. After the bottom material was cooled to 20℃ under stirring, solid-liquid separation was performed to obtain 323.8g of filtrate and 175.2g of crude ammonium chloride filter cake.

[0038] 70g of methyl tert-butyl ether and 6g of H-type cation exchange resin were added to the esterification reactor. Stirring and heating were started. Then, the above filtrate was slowly added dropwise to the esterification reactor to carry out the esterification reaction. After the reaction was completed, the H-type cation exchange resin was separated first, and then oil-water separation was performed to obtain 301.6g of aqueous ammonium chloride solution and 91.3g of crude glycine tert-butyl ester in the oil phase. The oil phase was quantitatively analyzed by liquid chromatography, and the content of glycine tert-butyl ester was 28.5%.

[0039] Example 2

[0040] 1000g of glycine production wastewater was evaporated under a vacuum pressure of 10kPa to obtain 470.9g of evaporated condensate and 521.4g of solid-liquid mixture in the bottom of the tower. After the bottom material was cooled to 25℃ under stirring, solid-liquid separation was performed to obtain 351.7g of filtrate and 168.8g of crude ammonium chloride filter cake.

[0041] 70g of methyl tert-butyl ether and 10g of H-type cation exchange resin were added to an esterification reactor. Stirring and heating were initiated, and the filtrate was then slowly added dropwise to the reactor for esterification. After the reaction was complete, the H-type cation exchange resin was separated first, followed by oil-water separation to obtain 317.8g of aqueous ammonium chloride solution and 102.4g of crude glycine tert-butyl ester in the oil phase. Quantitative analysis of the oil phase using liquid chromatography revealed a glycine tert-butyl ester content of 29.6%.

[0042] Example 3

[0043] 1000g of glycine production wastewater was evaporated under a vacuum pressure of 10kPa to obtain 444.7g of evaporated condensate and 547.5g of solid-liquid mixture in the bottom of the tower. After the bottom material was cooled to 23℃ under stirring, solid-liquid separation was performed to obtain 389.5g of filtrate and 156.6g of crude ammonium chloride filter cake.

[0044] 60g of methyl tert-butyl ether and 10g of H-type cation exchange resin were added to an esterification reactor. Stirring and heating were initiated, and the filtrate was then slowly added dropwise to the reactor for esterification. After the reaction was complete, the H-type cation exchange resin was separated first, followed by oil-water separation to obtain 356.3g of aqueous ammonium chloride solution and 92.3g of crude glycine tert-butyl ester in the oil phase. Quantitative analysis of the oil phase using liquid chromatography revealed a glycine tert-butyl ester content of 29.1%.

[0045] Example 4

[0046] 700g of glycine production wastewater was mixed with 300g of ammonium chloride aqueous solution obtained in Example 1 and evaporated under a vacuum pressure of 10kPa to obtain 441.4g of evaporated condensate and 549.3g of solid-liquid mixture in the bottom of the tower. After the bottom material was naturally cooled to 21°C under stirring, solid-liquid separation was performed to obtain 402.7g of filtrate and 145.2g of crude ammonium chloride filter cake.

[0047] 100g of methyl tert-butyl ether and 10g of H-type cation exchange resin were added to an esterification reactor. Stirring and heating were initiated, and the filtrate was then slowly added dropwise to the reactor for esterification. After the reaction was complete, the H-type cation exchange resin was separated first, followed by oil-water separation to obtain 376.7g of aqueous ammonium chloride solution and 124.5g of crude glycine tert-butyl ester in the oil phase. Quantitative analysis of the oil phase using liquid chromatography revealed a glycine tert-butyl ester content of 32.1%.

[0048] Example 5

[0049] 700g of glycine production wastewater was mixed with 300g of ammonium chloride aqueous solution obtained in Example 4 and evaporated under a vacuum pressure of 12kPa to obtain 438.2g of evaporated condensate and 552.6g of solid-liquid mixture in the bottom of the tower. After the bottom material was cooled to 22°C under stirring, solid-liquid separation was performed to obtain 407.8g of filtrate and 143.4g of crude ammonium chloride filter cake.

[0050] 100g of methyl tert-butyl ether and 10g of H-type cation exchange resin were added to an esterification reactor. Stirring and heating were initiated, and the filtrate was then slowly added dropwise to the reactor for esterification. After the reaction was complete, the H-type cation exchange resin was separated first, followed by oil-water separation to obtain 378.4g of aqueous ammonium chloride solution and 127.3g of crude glycine tert-butyl ester in the oil phase. Quantitative analysis of the oil phase using liquid chromatography revealed a glycine tert-butyl ester content of 32.0%.

[0051] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for resource utilization of wastewater from glycine production via the chloroacetic acid process, characterized in that: After undergoing evaporation pretreatment, solid-liquid separation, esterification reaction, and oil-water separation, glycine and ammonium chloride in the glycine production wastewater are recovered in a resource-based manner. The method package specifically includes the following steps: Step (1) Evaporation pretreatment: Glycine wastewater is evaporated to obtain condensate with high ammonia nitrogen and high COD content, which is then reused in the glycine production system; Step (2) Solid-liquid separation: After the pre-evaporation material in the tower is cooled and separated into solid and liquid, filtrate is obtained and ammonium chloride is recovered; Step (3) Esterification reaction: The above filtrate is esterified with methyl tert-butyl ether in the presence of a catalyst to obtain an esterification reaction solution; Step (4) Oil-water separation: The esterification reaction solution is separated into crude glycine tert-butyl ester and ammonium chloride aqueous solution, and the ammonium chloride aqueous solution is recycled to step (1); after hexamethylenetetramine is recycled and enriched, it is discharged and recycled. In step (3), the molar ratio of methyl tert-butyl ether to glycine in the filtrate of step (2) is 1 to 1.2:1, and the catalyst is H-type cation exchange resin; In step (3), the esterification reaction temperature is 20℃~50℃; the esterification reaction time is 2h~6h.

2. The method for resource utilization of wastewater from glycine production via the chloroacetic acid process according to claim 1, characterized in that: The evaporation pretreatment in step (1) is carried out under vacuum conditions; the vacuum pressure in step (1) is 10 kPa to 12 kPa.

3. The method for resource utilization of glycine production wastewater according to claim 1, characterized in that: The amount of condensate generated by evaporation in step (1) is 45% to 50% of the total amount of materials input.

4. The method for resource utilization of glycine production wastewater according to claim 1, characterized in that: In step (2), cooling refers to reducing the temperature to 20-25℃.

5. The method for resource utilization of glycine production wastewater according to claim 1, characterized in that: In step (4), the cyclic enrichment of urotropine refers to the urotropine reaching a saturation concentration.

6. The method for resource utilization of glycine production wastewater according to claim 1, characterized in that: In step (3), the molar ratio of methyl tert-butyl ether to glycine in the filtrate of step (2) is 1.1:1.

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