CN109134287B - Purification method of byproduct sodium chloride in betaine or betaine hydrochloride production - Google Patents
Purification method of byproduct sodium chloride in betaine or betaine hydrochloride production Download PDFInfo
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- C07C227/04—Formation of amino groups in compounds containing carboxyl groups
- C07C227/06—Formation of amino groups in compounds containing carboxyl groups by addition or substitution reactions, without increasing the number of carbon atoms in the carbon skeleton of the acid
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- C01D3/00—Halides of sodium, potassium or alkali metals in general
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Abstract
The invention relates to a method for separating and purifying byproduct sodium chloride in the production process of betaine/betaine hydrochloride, which comprises the working procedures of pretreatment of reaction mother liquor, primary separation of betaine and sodium chloride crude products, secondary purification and separation, combined purification of betaine, combined purification of sodium chloride, refining and the like. The method is suitable for industrial large-scale separation and purification, does not need the procedures of electrodialysis and the like, and has higher economical efficiency and environmental protection. The purified sodium chloride can reach the feed grade standard, the recycling of byproducts is realized, the treatment method is simple, and no secondary pollution is generated.
Description
Technical Field
The invention relates to the technical field of separation and purification, in particular to a method for purifying a byproduct sodium chloride produced in a chemical product production process, and particularly relates to a method for efficiently separating and purifying the byproduct sodium chloride in a betaine/betaine hydrochloride production process.
Background
Betaine is also known as trimethylglycine, trimethylglycine and the like, is a novel well-known non-toxic, harmless and pollution-free multifunctional additive, and is widely applied to the fields of food medicine, daily chemical industry and the like. The betaine is usually chemically synthesized, because the betaine is extracted from roots, stems, leaves and fruits of natural plants in nature by an extraction process comprising an ion method and a polyethylene-divinyl resin chromatographic separation method, and is high in cost and difficult to produce on a large scale. Betaine is very soluble in water and is slightly more soluble in methanol than ethanol. The betaine hydrochloride is also called betaine hydrochloride, is a high-efficiency, high-quality, economic and widely applied to food-calling and growth-promoting nutritional additive for livestock, poultry and aquaculture.
In the chemical synthesis method of betaine or hydrochloride thereof in the field, chloroacetic acid, sodium hydroxide and trimethylamine are generally used as raw materials for neutralization and amination reaction, the production process route of the betaine/betaine hydrochloride is generally called as a sodium method production process, specifically, chloroacetic acid and sodium hydroxide are adopted for reaction to generate sodium chloroacetate, the sodium chloroacetate and trimethylamine react to obtain a mixed finished solution of the betaine and sodium chloride, and the mixed finished solution of the betaine and the sodium chloride is obtained after high-temperature salt filtration. Adding concentrated hydrochloric acid into the betaine finished solution at a certain temperature, filtering at a high temperature, cooling, and filtering to obtain betaine hydrochloride. For example, CN101255118 discloses a method for synthesizing betaine hydrochloride by using a chemical method, which comprises the following steps: firstly, adding chloroacetic acid solution into a reaction kettle, then introducing liquid trimethylamine gas into the chloroacetic acid solution, keeping the temperature below 30 ℃, fully stirring, then heating to 40-45 ℃, fully stirring, and then cooling to below 30 ℃; secondly, adding sodium hydroxide into the reaction kettle, fully stirring to ensure that the pH value of the solution is 5-8, concentrating, purifying and crystallizing by a conventional method to obtain betaine, and adding hydrochloric acid into the betaine to obtain betaine hydrochloride.
The chloroacetic acid and the sodium chloroacetate are subjected to hydrolysis, polymerization and other reactions under the strong alkaline condition to generate a large amount of sodium chloride by-products. According to the production process, a certain amount of betaine, free ammonia, chloroacetic acid/sodium chloroacetate, sodium glycolate and the like are adhered to the surfaces of the sodium chloride particles as byproducts, and the sodium chloride particles are usually discarded or used as industrial materials due to the difficulty in separation, so that the waste of sodium chloride resources is caused and the environment is polluted. Generally, sodium chloride, which is a byproduct in the chemical preparation of betaine or betaine hydrochloride, accounts for about half of the content of betaine, and since both betaine and sodium chloride are easily soluble in water and difficult to separate, the obtained betaine product contains high content of sodium chloride residues, and sodium chloride crystals also contain a large amount of impurities such as betaine and the like. The current prior art does not overcome these drawbacks well.
The related art for the preparation of betaine or its hydrochloride and the isolation of the product in the prior art can be exemplified as follows.
CN101323581 provides a method for synthesizing betaine and betaine hydrochloride. The method comprises the following steps: selecting strong-base anion resin as a carrier, and processing the carrier into a hydroxyl type; eluting with chloroacetic acid solution; circularly eluting with trimethylamine solution; washing with distilled water, mixing the washing solution with the circulating eluent, vacuum distilling to viscous, and vacuum distilling to obtain powdery or platelet-shaped white betaine; dissolving the aqueous betaine with ethanol, and vacuum distilling to obtain anhydrous betaine; adding hydrochloric acid into the vacuum distilled sticky matter, stirring, and vacuum distilling to obtain powdery or flake white betaine hydrochloride.
CN10178696 discloses a method for preparing betaine hydrochloride, which takes chloroacetic acid, trimethylamine and a water removal agent as raw materials, and the raw materials react in an organic solvent to generate the betaine hydrochloride. The specific process steps are as follows: putting an organic solvent into a reaction kettle, starting stirring, then adding chloroacetic acid and a water removing agent, introducing trimethylamine at a certain temperature for reaction, and cooling, crystallizing, centrifuging, cleaning and drying after the reaction to obtain the betaine hydrochloride.
CN101863784 discloses a method for preparing and extracting betaine and betaine hydrochloride. The preparation and extraction method of the betaine comprises the following steps: firstly, carrying out neutralization reaction on sodium hydroxide solution and chloroacetic acid, introducing liquid trimethylamine into a reaction kettle when the temperature of the solution is reduced to 20-60 ℃, and stirring to fully react; drying to remove water; anhydrous methanol is used as an extracting agent to extract high-purity betaine crystals by means of crystallization treatment and the like. The preparation and extraction method of the betaine hydrochloride comprises the following steps: directly adopts liquid-liquid reaction to prepare a crude product of the betaine hydrochloride, and dries the crude product to remove water to obtain a pure product of the betaine hydrochloride.
CN 106938975A discloses a process for the preparation of betaine and betaine hydrochloride. Mixing and stirring light calcium carbonate and chloroacetic acid aqueous solution to perform neutralization reaction; filtering the reaction solution, introducing liquid trimethylamine, and stirring to fully perform amination reaction; and concentrating the amination solution, and then carrying out spray drying to obtain the betaine. Or after the amination solution is concentrated, hydrochloric acid is added for reaction, and then the betaine hydrochloride is obtained through crystallization.
In the preparation method in the prior art, the post-treatment adopts means such as ion exchange resin and the like, so that the separation effect is good, but the speed is low, the industrial requirement of large-scale treatment cannot be met, the cost is high, and a large amount of wastewater is discharged when the resin is regenerated; when a simple concentration and crystallization method is adopted, although the post-treatment step is simple, the separation effect is poor, the efficiency is low, the purity of the obtained betaine is not high, and a byproduct sodium chloride is usually abandoned, so that the requirement of green process production is not met.
Therefore, the prior art lacks a green and efficient separation and purification method which is used for producing the byproduct sodium chloride with high purity and no discharge in the betaine/betaine hydrochloride production process on an industrial scale.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: provides a method for separating and purifying sodium chloride which is a byproduct in the production process of betaine/betaine hydrochloride with high purity.
The method can effectively separate the betaine and the sodium chloride in the mixed product obtained by preparing the betaine by a chloroacetic acid and trimethylamine chemical method, wherein the purification purity of the sodium chloride can reach more than 99 percent, and the obtained high-purity sodium chloride only contains low-content betaine residues and can be directly used for feed-grade sodium chloride; therefore, the recycling of the sodium chloride byproduct containing high-content impurities is realized, the used solvent can be recycled, secondary pollution cannot be caused in the treatment process, and meanwhile, the obtained betaine has high purity and is beneficial to further obtaining high-purity betaine hydrochloride; the method has the advantages of simple separation process, low energy consumption, high atom utilization rate and no byproduct and three-waste pollutant discharge.
The method for producing and preparing the betaine/betaine hydrochloride is prepared by a chemical method well known in the field, namely chloroacetic acid and trimethylamine are used as reaction raw materials; specifically, the method comprises the following steps: chloroacetic acid and sodium hydroxide are subjected to neutralization reaction to obtain sodium chloroacetate, and then the sodium chloroacetate and trimethylamine are subjected to amination reaction to obtain a mixture containing betaine and sodium chloride. Betaine hydrochloride is prepared by further reacting betaine solution with equimolar hydrochloric acid.
The method for separating and purifying the byproduct sodium chloride in the production process of the betaine/betaine hydrochloride comprises the working procedures of pretreatment of reaction mother liquor, primary separation of crude products of the betaine and the sodium chloride, secondary purification and separation, combined purification of the betaine and the sodium chloride, refining and the like, and mainly comprises the following steps:
step S1: concentrating or vacuum distilling the reaction mixture containing betaine, sodium chloride and a small amount of trimethylamine under reduced pressure to obtain betaine-sodium chloride crystallization mother liquor; primarily evaporating and concentrating the crystallization mother liquor, adding a small amount of isopropanol to obtain a sodium chloride mixed crystal crude product, and washing with anhydrous ethanol at 60-70 ℃ to remove impurities to obtain a sodium chloride primary-screened crude product;
step S2: concentrating and crystallizing the mother liquor after the separation of the sodium chloride mixed crystal crude product to obtain a betaine-sodium chloride crude product, and dissolving and separating sodium chloride solid in the crude product by using a separation solvent 1 to obtain a sodium chloride crystal product 1;
step S3: adding the primary screened crude product of sodium chloride into a separation solvent 2, heating and stirring, filtering and separating solid while the crude product is hot, washing with absolute ethyl alcohol and drying to obtain a sodium chloride crystal product 2;
step S4: and combining the sodium chloride crystal product 1 and the sodium chloride crystal product 2, washing or leaching with anhydrous methanol, then boiling and washing the materials with anhydrous ethanol for 5-10min, carrying out suction filtration while the materials are hot, and recrystallizing and refining.
Wherein, the separation solvent is a mixed alcohol solvent of absolute methanol and absolute ethanol which is prepared according to a certain proportion.
Specifically, the steps of the present invention specifically include the following processes:
step S1 is specifically as follows:
(1) after the reaction for preparing betaine by taking chloroacetic acid and trimethylamine as raw materials is finished, concentrating the product mixed solution, namely the reaction mixture containing the betaine, sodium chloride and a small amount of trimethylamine under reduced pressure or distilling the reaction mixture in vacuum until solid is separated out, removing the trimethylamine and part of water and other components, and obtaining the betaine-sodium chloride crystallization mother solution.
(2) Preheating the mother liquor in a preheater to 90-100 ℃, then carrying out evaporation concentration in an industrial evaporation crystallizer, wherein the evaporation temperature is 95-100 ℃, stopping evaporation concentration when the residual volume of the mother liquor is 50-70% of the volume of the mother liquor during preheating, cooling to 50-60 ℃, and adding 5-10% of isopropanol to obtain a sodium chloride mixed crystal crude product and the residual mother liquor. Filtering and separating out a precipitated crystal crude product, wherein the crystal crude product mainly contains sodium chloride and a small amount of betaine; the filtrate obtained was a concentrated mother liquor containing a major part of betaine and a minor amount of sodium chloride (not more than 40 wt% of the total amount of sodium chloride).
Wherein, preferably, the concentration degree of the evaporative crystallization is 50 to 60% of the preheating volume.
Optionally, the content of sodium chloride in the filtrate is detected by chromatography, and the amount of isopropanol is adjusted to control the content of sodium chloride in the filtrate to be not more than 10%, preferably not more than 8%.
(3) Adding the obtained mixed crystal crude product into 60-70 ℃ absolute ethyl alcohol, stirring and washing for 2-3 times to remove the doped betaine, filtering and drying the solid to obtain a sodium chloride crude product, wherein the content of sodium chloride is more than 95%; then, the washing solution containing betaine is combined into the above concentrated mother liquor filtrate to obtain betaine filtrate 1 containing a small amount of sodium chloride.
Optionally, the crude sodium chloride can be further washed with absolute ethyl alcohol to further remove trace impurities such as betaine, sodium chloroacetate and the like adhered to the surface.
Step S2 is specifically as follows:
(1) continuously evaporating and crystallizing the betaine filtrate 1 containing sodium chloride in the step in an evaporation crystallizer and recovering an ethanol solvent, stopping evaporating and crystallizing when the volume of the filtrate is 10-20%, filtering, transferring the concentrated filtrate to a cooling crystallization kettle for cooling and crystallizing at 0-5 ℃ until all solids are completely separated out, filtering, combining the solids obtained by filtering twice, and drying at 150-180 ℃ to obtain a betaine-sodium chloride mixed crystal crude product taking betaine as a main component; alternatively, the remaining crystallization mother liquor may be combined into the next batch of reaction mixture starting material or betaine filtrate 1 for further recycling separation.
(2) Mixing absolute ethyl alcohol and absolute methyl alcohol according to a certain proportion to prepare a separation solvent 1, wherein the mass ratio of the mixed crystal crude product to the separation solvent is 1: 2-3, adding a separation solvent, continuously adding deionized water accounting for 1-2% (v/v) of the total volume of the separation solvent to increase the polarity of the solution, heating to 60-65 ℃, fully stirring and mixing for 5-15min until the betaine is completely dissolved, centrifuging or performing suction filtration when the residual solid is not continuously dissolved, separating insoluble solid, washing the obtained solid with absolute ethyl alcohol for 2-3 times to remove the betaine solution attached to the solid, and combining the washed ethyl alcohol into the filtrate; and drying the obtained solid to obtain a sodium chloride crystal product 1.
Wherein, the volume ratio of the absolute ethyl alcohol in the separation solvent is 50-90%, preferably 70-90%;
(3) concentrating the filtrate containing betaine by rotary evaporation, recovering the solvent, crystallizing the concentrated solution at a low temperature of 0-4 ℃ when the crystals begin to precipitate at an evaporation temperature of 45-50 ℃, filtering and drying to obtain betaine crystals 1, combining the crystallized mother liquor with the recovered solvent, distilling and recovering the mixed alcohol solvent containing anhydrous methanol and anhydrous ethanol components to obtain a separation solvent 2 with higher ethanol content, and recovering the concentrated residual mother liquor after the solvent is recovered for later use.
Step S3 is specifically as follows:
(1) adding the crude sodium chloride obtained in the step (S1) into the recovered separation solvent 2 with the mass of 1-2 times, heating to the temperature of 60-65 ℃ while stirring, and fully stirring and mixing for 10-15 min; then the solid is separated by filtration while the solution is hot, and the solid product is washed with anhydrous ethanol and dried to obtain a sodium chloride crystal product 2.
(2) And (3) combining an ethanol washing solution into the filtrate, adding the concentrated residual mother liquor obtained after the solvent is recovered in the step S2, carrying out evaporation concentration by using a condensing rotary evaporator and the like, recovering the solvent for recycling, stopping concentration after most of solid is separated out from the obtained concentrated solution, cooling and crystallizing at 0-5 ℃, filtering to obtain a betaine crystal 2, drying the obtained crystal, and combining the dried crystal with the obtained betaine crystal 1 to obtain a total betaine crystal product, wherein the purity can reach more than 98%.
Preferably, the obtained betaine crystals can be recrystallized and purified for 1-2 times, so that a refined betaine crystal product with the purity of more than 99% is obtained, the residue burning rate is lower than 0.3%, and the melting range is 226.7-227.6 ℃.
Step S4 is specifically as follows:
(1) mixing the sodium chloride crystal product 1 prepared in the step with the sodium chloride crystal product 2, washing or leaching the mixture for 1 to 2 times by using 0.5 to 1 time of anhydrous methanol with the mass of 55 to 60 ℃, recovering the methanol, and drying sodium chloride solid at the temperature of 180 ℃;
(2) adding 2-3 times of anhydrous ethanol into the dried sodium chloride solid, heating to 75-78 ℃, stirring, boiling and washing the sodium chloride material for 5-10min, carrying out suction filtration while the sodium chloride is hot, drying the obtained sodium chloride solid, and recovering an ethanol solvent, wherein the content of sodium chloride in the obtained solid is more than 99%;
(3) dissolving the washed and dried sodium chloride with deionized water of which the mass is 3-5 times that of the sodium chloride, stirring and heating the solution to 80-90 ℃, fully stirring the solution until the solution is completely dissolved, and carrying out vacuum evaporation and concentration until solids are separated out to obtain saturated liquid;
(4) and (2) continuing to evaporate and concentrate the saturated solution to 20-30% of the volume of the saturated solution, stopping evaporation and concentration, cooling to room temperature, crystallizing at the low temperature of 0-4 ℃, filtering, continuing to evaporate and crystallize filtrate until solid is completely separated out, and drying the obtained crystal to obtain refined white sodium chloride crystals, wherein the content of betaine is not more than 0.4%, recrystallization is not required, and the white sodium chloride crystals can be directly used for feed.
The purity of the sodium chloride crystal obtained by the method is not lower than 99.0 percent after refining, and the purification yield reaches more than 90 percent.
Compared with the prior art, the invention has at least the following beneficial effects:
1. compared with the direct alcohol solvent extraction crystallization method, the method for purifying the sodium chloride byproduct has the characteristics of high yield, high product purity and low impurity content; in step S2, a separation solvent mainly comprising absolute ethanol is creatively used, and methanol with higher polarity and higher betaine solubility and deionized water with stronger polarity in 1-2% by volume are used as auxiliary materials; experiments prove that the separation solvent is the best separation and dissolution combination and has the best effect. Among them, tests prove that sodium chloride is hardly soluble in ethanol solvent with purity of more than 96%, and the existence of low content of water in the separation solvent can further promote the dissolution of betaine and enable the betaine to enter filtrate more effectively compared with anhydrous ethanol solvent, so that the purity and the yield are higher.
2. In the mixed crystal purification steps S2-S3, a gradient separation solvent method is adopted, namely, ethanol washing liquid is merged to gradually increase the ethanol content in the separation solvent, so that the ethanol washing liquid can be recycled on one hand, and on the other hand, the toxic methanol content can be gradually reduced on the basis of ensuring the high solubility of betaine; deep separation of betaine and sodium chloride can be more effectively realized.
3. Compared with various conventional methods such as a vacuum distillation method, an ion exchange method, membrane separation and the like, the method has lower cost and is suitable for industrial large-scale treatment, and the obtained betaine can reach the purity of more than 98% without recrystallization; the purity of the refined betaine after recrystallization can reach more than 99 percent, and the content of sodium chloride is not higher than 0.3 percent. The purity of the obtained sodium chloride crystal is more than or equal to 99.0 percent, the purification yield is more than or equal to 90 percent, and the high-efficiency separation of the betaine product and the high-purity recovery of the sodium chloride are realized.
4. The purification method has the advantages of simple and convenient process, low production cost, easy operation, no solvent waste, environmental friendliness and the like, the obtained sodium chloride containing trace betaine can be directly used in the livestock breeding industry, and compared with pure sodium chloride, the purification method has beneficial betaine additive effect and economic value.
5. The method not only solves the environmental pollution of the byproduct salt, but also fully utilizes resources, the solvent used in the treatment process can be recycled, and the filtrate can be recycled, so that the method has no waste water and gas emission, no secondary pollution and low treatment process cost.
Detailed Description
The present invention is described in detail below with reference to specific preparation examples and examples, but the use and purpose of these exemplary embodiments are merely to illustrate the present invention, and do not constitute any limitation to the actual scope of the present invention in any form, and the scope of the present invention is not limited thereto.
The following detailed description of preferred embodiments of the invention and the examples included therein will make it easier to understand the context of the invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.
Example 1
(1) After the betaine preparation reaction is finished, 1.28kg of reaction mixture containing betaine, sodium chloride and a small amount of trimethylamine is decompressed and concentrated until crystals are separated out, and components such as trimethylamine, water and the like are removed to obtain betaine-sodium chloride crystallization mother liquor; preheating the mother liquor in a preheater to 90 ℃, then carrying out evaporation concentration in an evaporation crystallizer, wherein the evaporation temperature is 98 ℃, the evaporation concentration is stopped when the volume of the mother liquor is about half of the volume, cooling to 50 ℃, adding 10% of isopropanol by volume, continuing crystallization to obtain sodium chloride coarse crystals and residual mother liquor, and filtering and separating solids. Washing the obtained solid with 180ml of 60 ℃ absolute ethyl alcohol, filtering, washing the solid with 120ml of 60 ℃ absolute ethyl alcohol, filtering, and drying the obtained solid to obtain about 121g of crude sodium chloride product, wherein the content of sodium chloride is 96.3% by ion chromatography; then, the ethanol washing solution containing betaine is combined into the residual mother liquor filtrate to obtain betaine filtrate 1.
(2) Continuously evaporating and crystallizing the betaine filtrate 1 in a rotary evaporation crystallizer, recovering ethanol and isopropanol solvent, stopping evaporating and crystallizing when the volume of the filtrate is about 10%, filtering, transferring the concentrated filtrate to a cooling crystallization kettle, cooling and crystallizing at 5 ℃ until solids are completely separated out, filtering, combining the solids obtained by filtering twice, and drying at 150 ℃ to obtain 381g of a betaine-sodium chloride mixed crystal crude product with betaine as a main component; the remaining mother liquor is combined into the next batch of the reaction mixture starting material in step (1) or betaine filtrate 1 for further separation.
(3) Mixing absolute ethyl alcohol and absolute methyl alcohol according to the volume ratio of 7:3 to serve as a separation solvent, adding the mixed crystal crude product into 850ml of the separation solvent, adding 15ml of deionized water to increase the polarity of the solution, heating to 62-63 ℃, fully stirring and mixing for 10min, performing suction filtration while hot, separating insoluble solid sodium chloride, washing for 2 times by using the absolute ethyl alcohol to remove attached betaine, and combining the washed ethyl alcohol into filtrate; and drying the obtained solid to obtain a sodium chloride crystal product 1.
Evaporating the filtrate containing betaine at 50 deg.C under reduced pressure, concentrating, recovering separation solvent, crystallizing at 0-4 deg.C until crystals precipitate, filtering, drying to obtain betaine crystals 1, mixing the crystallized mother liquor with the recovered solvent, distilling to recover mixed alcohol solvent containing anhydrous methanol and anhydrous ethanol as separation solvent 2; and recovering the solvent to obtain the betaine crystallization mother liquor for later use.
(4) Adding the crude sodium chloride obtained in the step (1) into 155g of the separation solvent 2, heating to the temperature of 60 ℃ while stirring, and fully stirring and mixing for 10 min; then solid sodium chloride is separated by filtration while the solution is hot, and the solid product is washed by absolute ethyl alcohol and dried to obtain a sodium chloride crystal product 2. And (3) combining an ethanol washing solution into the filtrate, adding the concentrated solution of the betaine crystallization mother liquor after the solvent is recovered, evaporating and concentrating by adopting a condensing rotary evaporator, recovering the solvent for recycling, stopping concentrating after the obtained concentrated solution begins to precipitate solids, cooling at 0 ℃ for crystallization, filtering to obtain betaine crystals 2, combining the betaine crystals 2 with the obtained betaine crystals 1, and drying to obtain 338.7g of total betaine products, wherein the melting range is 226.7-227.6 ℃, and the HPLC purity is 98.6%.
(5) Mixing the sodium chloride crystal product 1 prepared in the step with the sodium chloride crystal product 2, washing with 0.5 times of anhydrous methanol at 55 ℃, recovering the methanol, and drying the obtained sodium chloride solid at 180 ℃; adding the dried sodium chloride solid into 2 times of anhydrous ethanol, heating to 75 ℃, stirring, boiling and washing the sodium chloride material for 5min, carrying out suction filtration while the sodium chloride material is hot, drying the obtained sodium chloride solid, and recovering the ethanol solvent.
(6) Dissolving the washed and dried sodium chloride by using deionized water with the mass of 4 times, heating to 90 ℃, fully stirring until the sodium chloride is completely dissolved, and carrying out vacuum evaporation concentration until solids are separated out to obtain saturated liquid; and (3) continuing to evaporate and concentrate the saturated solution to about 30% of the volume of the saturated solution, stopping evaporating and concentrating, crystallizing at the low temperature of 0 ℃, filtering, continuing to evaporate and crystallize the filtrate until the solid is completely separated out, combining the solid and drying to obtain 159.6g of refined sodium chloride crystals, wherein the purity is 99.4% by HPLC (high performance liquid chromatography), the content of betaine is 0.32%, and the purification yield is 91.4%.
Example 2
(1) Distilling 132.7kg of reaction mixture containing betaine, sodium chloride and a small amount of trimethylamine in a reduced pressure distillation tower, wherein the tower top temperature is 65 ℃, the tower bottom temperature is 95 ℃, and removing components such as trimethylamine, water and the like to obtain betaine-sodium chloride crystallization mother liquor; preheating the mother liquor in a preheater to 95 ℃, then carrying out evaporation concentration in an industrial evaporation crystallizer, wherein the evaporation temperature is 95 ℃, the evaporation concentration is stopped when the volume of the mother liquor is about half of the volume, cooling to 50 ℃, adding 5% of isopropanol by volume, continuing crystallization to obtain sodium chloride coarse crystals and the residual mother liquor, and filtering to separate solids. Washing the obtained solid with 18L of anhydrous ethanol at 60 ℃, filtering, and drying to obtain a sodium chloride crude product; then, the ethanol washing solution containing betaine is combined into the residual mother liquor filtrate to obtain betaine filtrate 1.
(2) Crystallizing the betaine filtrate 1 in an evaporative crystallizer, recovering ethanol and isopropanol solvent, filtering to obtain solid, transferring the crystallized mother liquor to a cooling crystallization kettle, cooling and crystallizing at 0 ℃, filtering, combining the solid obtained by two-time filtration, and drying to obtain 40.2kg of a crude product of the betaine-sodium chloride mixed crystal.
(3) Mixing absolute ethyl alcohol and absolute methyl alcohol according to the volume ratio of 8:2 to serve as a separation solvent, adding the mixed crystal crude product into 82L of the separation solvent, adding 1.2L of deionized water, heating to 65 ℃, stirring for 10min, performing suction filtration to separate insoluble solid sodium chloride while the mixed crystal crude product is hot, washing with the absolute ethyl alcohol to remove attached betaine, and combining the washed ethyl alcohol into a filtrate; drying and drying the obtained sodium chloride solid to obtain a sodium chloride crystal product 1. Distilling the filtrate containing betaine under reduced pressure, recovering separation solvent, crystallizing the concentrated solution after crystal precipitation at 0-4 deg.C, filtering, drying solid to obtain betaine crystal 1, mixing the crystallization mother liquor with the recovered solvent, distilling to recover mixed alcohol solvent containing anhydrous methanol and anhydrous ethanol as separation solvent 2; and recovering the solvent to obtain the betaine crystallization mother liquor for later use.
(4) Adding the crude sodium chloride obtained in the step (1) into 16Kg of the separation solvent 2, heating to the temperature of 60 ℃ while stirring, and stirring and mixing for 10 min; then solid sodium chloride is separated by filtration while the solution is hot, washed by absolute ethyl alcohol and dried to obtain a sodium chloride crystal product 2. And (3) combining an ethanol washing solution into the filtrate, adding the concentrated solution of the betaine crystallization mother liquor after the solvent is recovered, evaporating and concentrating the mixed solution, recovering the solvent, stopping concentrating after the obtained concentrated solution begins to separate out solids, cooling to crystallize at 0 ℃, filtering to obtain betaine crystals 2, combining the betaine crystals 2 with the obtained betaine crystals 1, and drying to obtain 35.3kg of total betaine products with the HPLC purity of 98.1%.
(5) Mixing the sodium chloride crystal product 1 prepared in the step with the sodium chloride crystal product 2, washing with 0.5 times of anhydrous methanol at 55 ℃, recovering the methanol, and drying the obtained sodium chloride solid at 180 ℃; adding the dried sodium chloride solid into 2 times of anhydrous ethanol, heating to 75 ℃, stirring, boiling and washing the sodium chloride material for 5min, carrying out suction filtration while the sodium chloride material is hot, drying the obtained sodium chloride solid, and recovering the ethanol solvent;
(6) dissolving washed and dried sodium chloride with 82.6Kg of deionized water, heating to 90 ℃, fully stirring to be completely dissolved, carrying out vacuum evaporation concentration until the concentrated solution is about 25L, stopping evaporation concentration, crystallizing at the low temperature of 0 ℃, filtering, continuously evaporating and crystallizing filtrate until sodium chloride solid is completely separated out, combining the solids and drying to obtain 16.8Kg of sodium chloride crystals with the purity of 99.1%, wherein the content of betaine is 0.38% by HPLC (high performance liquid chromatography), and the purification yield is 90.8%.
Comparative example 1
Comparative example 1 was conducted in the same manner as in example 1 except that the betaine-sodium chloride mixed crystal obtained by direct evaporative crystallization was used in place of steps (1) to (2) (i.e., the reaction product mixture was directly evaporated and concentrated to obtain a betaine-sodium chloride mixed crystal product without the step of pre-separating sodium chloride), whereby a sodium chloride crystal having a betaine content of 2.86% was obtained.
Comparative example 2
Comparative example 2 was conducted in the same manner as in example 1 except that the separation solvent was replaced with an equal amount of absolute ethanol and no deionized water was added, to obtain sodium chloride crystals having a betaine content of 1.17%.
Comparative example 3
Comparative example 3 was conducted in the same manner as in example 1 except that no step (5) was included (i.e., no methanol rinse-ethanol rinse operation of the sodium chloride crystal product was performed, but the combined sodium chloride product was directly recrystallized), to obtain sodium chloride crystals having a betaine content of 1.68%.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (5)
1. A separation and purification method of byproduct sodium chloride in the production process of betaine/betaine hydrochloride comprises the working procedures of reaction liquid pre-separation treatment, separation of mixed crystal crude products of betaine and sodium chloride, secondary purification and separation, combination and purification of betaine, and combination, purification and refining of sodium chloride;
the method is characterized by comprising the following steps:
step S1: concentrating or vacuum distilling the reaction mixture containing betaine, sodium chloride and a small amount of trimethylamine under reduced pressure to obtain betaine-sodium chloride crystallization mother liquor; primarily evaporating and concentrating the crystallization mother liquor, adding a small amount of isopropanol to obtain a sodium chloride mixed crystal crude product, and washing with anhydrous ethanol at 60-70 ℃ to remove impurities to obtain a sodium chloride primary-screened crude product;
step S2: concentrating and crystallizing the mother liquor after the separation of the sodium chloride mixed crystal crude product to obtain a betaine-sodium chloride crude product, and dissolving and separating sodium chloride solid in the crude product by using a separation solvent 1 to obtain a sodium chloride crystal product 1;
step S3: adding the primary screened crude product of sodium chloride into a separation solvent 2, heating and stirring, filtering and separating solid while the crude product is hot, washing with absolute ethyl alcohol and drying to obtain a sodium chloride crystal product 2;
step S4: mixing the sodium chloride crystal product 1 and the sodium chloride crystal product 2, washing or leaching with anhydrous methanol, boiling and washing the materials with anhydrous ethanol for 5-10min, performing suction filtration while hot, and recrystallizing and refining the obtained sodium chloride;
the specific process of step S1 is as follows:
(1) after the chemical method for preparing betaine by taking chloroacetic acid and trimethylamine as raw materials finishes reaction, carrying out reduced pressure concentration or vacuum distillation on a product mixed solution, namely a reaction mixture containing the betaine, sodium chloride and a small amount of trimethylamine, until solid is separated out, removing the trimethylamine and part of water components, and obtaining a betaine-sodium chloride crystallization mother solution;
(2) preheating the mother liquor in a preheater to 90-100 ℃, then carrying out evaporation concentration in an evaporation crystallizer, wherein the evaporation temperature is 95-100 ℃, stopping concentration when the residual volume of the mother liquor is 50-70% of the volume of the mother liquor during preheating, cooling to 50-60 ℃, and adding 5-10% of isopropanol to obtain a sodium chloride mixed crystal crude product and the residual mother liquor;
(3) filtering and separating out a precipitated solid crude product, wherein the solid crude product mainly contains sodium chloride and a small amount of betaine impurities; adding the obtained mixed crystal crude product into anhydrous ethanol at the temperature of 60-70 ℃, stirring and washing for 2-3 times to remove the doped betaine organic components, filtering and drying the solid to obtain a sodium chloride crude product; mixing the washing solution containing betaine with the above filtrate to obtain betaine filtrate 1;
the specific process of step S2 is as follows:
(1) continuously evaporating and crystallizing the betaine filtrate 1 in the step S1 in an evaporation crystallizer and recovering an ethanol solvent, stopping evaporating and crystallizing when the volume of the filtrate is 10-20%, filtering, transferring the concentrated filtrate to a cooling crystallization kettle for cooling and crystallizing at 0-5 ℃ until all solids are completely separated out, filtering, combining the solids obtained by two-time filtration, and drying at 150 ℃ and 180 ℃ to obtain a crude product of the betaine-sodium chloride mixed crystal;
(2) mixing absolute ethyl alcohol and absolute methyl alcohol according to a certain volume ratio to prepare a separation solvent 1, wherein the mass ratio of the mixed crystal crude product to the separation solvent is 1: 2-3, adding a separation solvent 1, adding deionized water accounting for 1-2% of the total volume of the separation solvent to increase the polarity of the solution, heating to 60-65 ℃, fully stirring and mixing for 5-15min, separating insoluble solids, washing the obtained solids for 2-3 times by using absolute ethyl alcohol to remove attached betaine solution, and combining the washed ethyl alcohol into the filtrate; drying the obtained solid to obtain a sodium chloride crystal product 1;
(3) evaporating and concentrating the filtrate containing betaine in the step (2) and recovering the solvent, wherein the evaporation temperature is 45-50 ℃, crystallizing the concentrated solution at the low temperature of 0-4 ℃ when crystals are separated out, filtering and drying to obtain betaine crystals 1, combining the crystallization mother liquor and the recovered solvent, and recovering a mixed alcohol solvent containing methanol and an ethanol component as a separation solvent 2 for later use.
2. The method of claim 1, wherein the extent of evaporative crystallization is controlled to provide a residual concentrate volume of 50-60% of the volume of the pre-heating.
3. The method of claim 1, wherein the volume ratio of the absolute ethanol in the separation solvent 1 is 50-90%.
4. The method according to claim 1, wherein the step S3 is specifically performed as follows:
(1) adding the primary screened crude sodium chloride product obtained in the step (S1) into a separation solvent 2 with the mass of 1-2 times, heating to the temperature of 60-65 ℃ while stirring, and fully stirring and mixing for 10-15 min; then solid is filtered and separated while the solution is hot, and the solid product is washed by absolute ethyl alcohol and dried to obtain a sodium chloride crystal product 2;
(2) mixing the ethanol washing solution with the filtrate, evaporating for concentration, recovering solvent for cyclic utilization, stopping concentration after large semisolid is separated out from the obtained concentrated solution, cooling at 0-5 deg.C for crystallization, filtering to obtain betaine crystal 2, mixing with the obtained betaine crystal 1, and drying to obtain total betaine product.
5. The method according to claim 1, wherein the step S4 is specifically performed as follows:
(1) mixing the sodium chloride crystal product 1 prepared in the above steps with the sodium chloride crystal product 2, washing or leaching with anhydrous methanol at 55-60 ℃ for 1-2 times, recovering methanol, and drying to obtain sodium chloride solid;
(2) adding the dried sodium chloride solid into absolute ethyl alcohol, heating to 75-78 ℃, stirring, boiling and washing the sodium chloride material for 5-10min, carrying out suction filtration while the sodium chloride material is hot, drying the obtained sodium chloride solid, and recovering an ethanol solvent;
(3) dissolving the washed and dried sodium chloride with deionized water of which the mass is 3-5 times that of the sodium chloride, stirring and heating the solution to 80-90 ℃, fully stirring the solution until the solution is completely dissolved, and carrying out vacuum evaporation and concentration until solid is separated out to obtain saturated liquid;
(4) and (3) continuing to evaporate and concentrate the saturated liquid to 20-30% of the volume of the saturated liquid, stopping evaporating and concentrating, cooling to room temperature, crystallizing at the low temperature of 0-4 ℃, filtering, continuing to evaporate and crystallize the filtrate until solid is completely separated out, and drying the obtained crystals to obtain refined feed-grade sodium chloride crystals, wherein the content of betaine is not more than 0.4%.
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| CN112174843B (en) * | 2020-10-10 | 2022-07-01 | 衢州学院 | Preparation method for low-ignition residue betaine hydrochloride and co-production sodium fluosilicate |
| CN114835157B (en) * | 2022-04-20 | 2023-07-04 | 柳州华锡有色设计研究院有限责任公司 | Method for reducing chloride ion content in sodium stannate production process |
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