Refining method of ethanolamine hydrochloride

Abstract

The invention relates to the technical field of fine chemical engineering, in particular to a refining method of ethanolamine hydrochloride. The refining method of ethanolamine hydrochloride comprises the following steps: carrying out a salt forming reaction on an aqueous solution of ethanolamine and hydrochloric acid under a low-oxygen condition (the oxygen concentration is 0-1.0% VOL) at a first temperature (20-90 DEG C), and concentrating the prepared reaction solution under a low-pressure condition (the vacuum degree is-0.06 to-0.12 MPa) at a second temperature (60-120 DEG C); adding a first organic solvent into the concentrated reaction liquid, mixing, and crystallizing to obtain an ethanolamine hydrochloride crude product; then decolorizing and recrystallizing in a second organic solvent to prepare ethanolamine hydrochloride; the first organic solvent and the second organic solvent are poor solvents of water-soluble ethanolamine hydrochloride. According to the refining method of the ethanolamine hydrochloride, the ethanolamine hydrochloride with ultra-high purity and extremely low water content can be prepared.

Description

Technical Field

[0001] This application relates to the field of fine chemical technology, and in particular to a method for purifying ethanolamine hydrochloride. Background Technology

[0002] Ethanolamine hydrochloride is a widely used organic amine salt with the molecular formula CH2(OH)CH2NH2·HCl. It is commonly used as an anionic surfactant and is also one of the raw materials for the synthesis of taurine and piperazine products. Ethanolamine hydrochloride is mainly prepared by the salt-forming reaction of ethanolamine and hydrochloric acid, and its chemical reaction formula is: CH2OHCH2NH2 + HCl → CH2OHCH2NH2·HCl.

[0003] Currently, most commercially available ethanolamine hydrochloride is industrial-grade, with a purity of around 95%. While laboratory-grade ethanolamine hydrochloride has higher purity, it is more expensive. Research suggests this is related to the properties and practical applications of ethanolamine hydrochloride—it is highly hygroscopic, and the crude product often contains high levels of moisture; organic amines themselves have reducing properties, making them prone to oxidation and impurities during production; furthermore, ethanolamine hydrochloride is a chlorine-containing product, which is highly corrosive to equipment, resulting in high production costs. These factors lead to high refining costs for ethanolamine hydrochloride; therefore, no refining methods for ethanolamine hydrochloride have been reported to date.

[0004] Ethanolamine hydrochloride is a key raw material for important chemical intermediates such as N,N-dimethylethanolamine, 2-chloroethylamine hydrochloride, ethyleneimine, and thiazolidin-2-thione. Using refined ethanolamine hydrochloride helps reduce moisture content, improves weighing accuracy, lowers impurity levels, reduces side reactions, and yields higher-quality chemical intermediates. Ethanolamine hydrochloride is also used to prepare taurine, a commonly used food fortifier with various health benefits. Using refined ethanolamine hydrochloride helps control impurity levels, meeting the impurity limits stipulated in food regulations.

[0005] Therefore, it is necessary to develop a purification method for ethanolamine hydrochloride to obtain ethanolamine hydrochloride with higher purity and lower water content. Summary of the Invention

[0006] Based on this, one or more embodiments of this application provide a method for purifying high-purity, low-water-content ethanolamine hydrochloride.

[0007] The technical solution of this application includes the following:

[0008] A method for purifying ethanolamine hydrochloride includes the following steps:

[0009] An aqueous solution of ethanolamine and hydrochloric acid is subjected to a salt-forming reaction under a first low-oxygen condition and at a first temperature to obtain a reaction solution; the first low-oxygen condition refers to an oxygen concentration of 0~1.0%VOL; the first temperature is 20~90 °C.

[0010] The reaction solution is concentrated under low-pressure conditions at a second temperature; the low-pressure conditions refer to a vacuum degree of -0.06 to -0.12 MPa; the second temperature is 60 to 120 °C.

[0011] Add the first organic solvent to the concentrated reaction solution and mix. Crystallize to obtain crude ethanolamine hydrochloride.

[0012] The crude ethanolamine hydrochloride was dissolved in a second organic solvent for decolorization and recrystallization to obtain ethanolamine hydrochloride;

[0013] The first organic solvent and the second organic solvent are solvents that are soluble in water but do not dissolve the ethanolamine hydrochloride.

[0014] In some embodiments, the first organic solvent and the second organic solvent each independently comprise one or more of methanol, ethanol, isopropanol, acetone, ethyl acetate, ethylene glycol, propylene glycol, glycerol, diethyl ether, acetonitrile, and tetrahydrofuran.

[0015] In some embodiments, the step of preparing a reaction solution by subjecting an aqueous solution of ethanolamine and hydrochloric acid to a salt-forming reaction under a first low-oxygen condition and at a first temperature includes:

[0016] Ethanolamine is loaded into a reaction vessel, and after the air inside the reaction vessel is replaced with nitrogen, nitrogen is continuously introduced into its inlet at a first rate of 1~60 L / min.

[0017] The reaction vessel is heated until its internal temperature reaches the first temperature and then kept at that temperature. An aqueous solution of hydrochloric acid is then added dropwise to the reaction vessel at a second rate to react with the ethanolamine to form a salt, thereby obtaining the reaction solution. The second rate is 0.5~20 mL / min.

[0018] Further, the aqueous solution of hydrochloric acid has a mass concentration of 5-38%; and / or,

[0019] The molar ratio of hydrochloric acid to ethanolamine in the aqueous solution of hydrochloric acid is (1.001~2):1.

[0020] In some embodiments, in the step of concentrating the reaction solution under low pressure and at a second temperature, the weight of water evaporated from the reaction solution is 20-80% of the total weight of the reaction solution.

[0021] In some embodiments, the step of adding a first organic solvent to the concentrated reaction solution, mixing, and crystallizing to obtain crude ethanolamine hydrochloride includes:

[0022] After adding the first organic solvent to the reaction solution at the third temperature and mixing, the mixture is cooled to the fourth temperature to crystallize.

[0023] The third temperature is 60~120 °C; the fourth temperature is -20~-30 °C.

[0024] Furthermore, the volume ratio of the first organic solvent to the ethanolamine is (5~100):1.

[0025] In some embodiments, the step of decolorizing and recrystallizing the crude ethanolamine hydrochloride in a second organic solvent to obtain ethanolamine hydrochloride includes:

[0026] The crude ethanolamine hydrochloride was mixed with the second organic solvent, and then heated and stirred to the fifth temperature under the second low-oxygen condition. Activated carbon was added, and the mixture was stirred for 10-60 min. After filtration, the filtrate was cooled to the sixth temperature to crystallize, and the crystals were collected.

[0027] The crystals were dried under reduced pressure to obtain the ethanolamine hydrochloride.

[0028] The second low-oxygen condition refers to an oxygen concentration of 0~1.0%VOL, the fifth temperature is 50~120 °C, and the sixth temperature is -20~-30 °C.

[0029] Furthermore, the conditions for vacuum drying include: a temperature of 40~120 °C, a time of 6~24 h, and a vacuum degree of -0.06~-0.12 MPa.

[0030] In some embodiments, the mass ratio of the second organic solvent to the crude ethanolamine hydrochloride is (0.1~100):1; and / or,

[0031] The mass ratio of the activated carbon to the crude ethanolamine hydrochloride is (0.0001-0.01):1.

[0032] The purification method for ethanolamine hydrochloride in this application significantly reduces the oxygen content in the system by maintaining low oxygen conditions during the salt formation reaction stage and low pressure during the concentration stage, thereby preventing the oxidation of organic amines and reducing the generation of oxidizing impurities. After the salt formation reaction is completed, the reaction solution is concentrated to remove some of the water, and then a water-soluble first organic solvent is added. This first organic solvent is added at high temperature, which can dissolve unreacted ethanolamine and other impurities, achieving a good impurity removal effect. At the same time, this first organic solvent is a poor solvent for ethanolamine hydrochloride, which can gradually crystallize out in the mixture of the first organic solvent and water, resulting in better-dispersible particles and a crude product with higher purity and fewer impurities. The water in the crude product can be dried and removed more quickly under the entrainment of the first organic solvent, reducing process costs and water content. Further recrystallization and decolorization are carried out using a second organic solvent to further improve the purity of the crude product and further reduce the water content. The above refining method can significantly reduce the impurity content, including unreacted raw materials, reaction byproducts, and metallic impurities such as arsenic, cadmium, and lead, and can significantly reduce the water content, obtaining high-purity, low-water-content ethanolamine hydrochloride.

[0033] In the purification method of ethanolamine hydrochloride of this application, the integrated process of salt formation reaction, concentration, crystallization, recrystallization and decolorization effectively reduces the formation of by-products in the reaction process, and makes it easier to remove unreacted raw materials and other impurities. By controlling the crystallization process of ethanolamine hydrochloride, particles with fewer impurities, high purity and low water content are obtained. Detailed Implementation

[0034] The present application is further described below with reference to embodiments and examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Furthermore, it should be understood that after reading the teachings of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the protection scope of the appended claims.

[0035] Unless otherwise defined, 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 application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0036] the term

[0037] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0038] The term "and / or" as used herein includes any one of two or more related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations encompass any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," or "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0039] In this document, terms such as "preferred," "better," and "more preferred" are merely descriptions of implementation methods or examples that achieve better results, and should be understood as not constituting a limitation on the scope of protection of this application.

[0040] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0041] In this application, the terms "first," "second," "third," "fourth," "fifth," and "sixth," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," "fifth," and "sixth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0042] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0043] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, optional numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0044] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0045] In this application, weight can be a well-known unit of mass in the chemical or food industry, such as μg, mg, g, or kg.

[0046] In this application, unless otherwise specified, the terms "size", "particle size", and "diameter" generally refer to average values.

[0047] In this application, VOL is a physical unit used to describe volume, representing the volume percentage of a specific gas. For example, an oxygen concentration of 0.1%VOL means that the volume percentage of oxygen is 0.1%. In this application, when "approximately" is added before the oxygen concentration value, the oxygen concentration can fluctuate around that value, typically within ±10%, and more specifically within ±5%. For example, "oxygen concentration approximately 0.5%VOL" means that the oxygen concentration can fluctuate around 0.5%VOL.

[0048] One or more embodiments of this application provide a method for purifying ethanolamine hydrochloride, comprising the following steps:

[0049] An aqueous solution of ethanolamine and hydrochloric acid is subjected to a salt-forming reaction under a first low-oxygen condition and at a first temperature to obtain a reaction solution; the first low-oxygen condition refers to an oxygen concentration of 0~1.0%VOL; the first temperature is 20~90 °C.

[0050] The reaction solution is concentrated under low-pressure conditions at a second temperature; the low-pressure conditions refer to a vacuum degree of -0.06 to -0.12 MPa; the second temperature is 60 to 120 °C.

[0051] The concentrated reaction solution was mixed with the first organic solvent, and crystallization was carried out to obtain crude ethanolamine hydrochloride.

[0052] The crude ethanolamine hydrochloride was dissolved in a second organic solvent for decolorization and recrystallization to obtain ethanolamine hydrochloride;

[0053] The first and second organic solvents are solvents that are soluble in water but do not dissolve ethanolamine hydrochloride.

[0054] In some embodiments, the oxygen concentration of the first hypoxia condition can be 0 to 1.0% VOL, more specifically 0 to 0.5% VOL, for example 0, 0.1% VOL, 0.2% VOL, 0.3% VOL, 0.4% VOL, 0.5% VOL, 0.6% VOL, 0.7% VOL, 0.8% VOL, 0.9% VOL, 1.0% VOL, etc.

[0055] In some embodiments, the first temperature can be 20~90 °C, and more particularly 50~70 °C, for example 20 °C, 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, etc.

[0056] In some embodiments, the vacuum degree under low pressure conditions can be -0.06 to -0.12 MPa, and more specifically -0.09 to -0.11 MPa, for example -0.06 MPa, -0.07 MPa, -0.08 MPa, -0.09 MPa, -0.10 MPa, -0.11 MPa, -0.12 MPa, etc.

[0057] In some embodiments, the second temperature can be 60~120 °C, more specifically 80~100 °C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, etc.

[0058] The purification method for ethanolamine hydrochloride in this application significantly reduces the oxygen content in the system by maintaining low oxygen conditions during the salt-forming reaction stage and low pressure during the concentration stage, thus preventing the oxidation of organic amines and reducing the generation of oxidizing impurities. After the salt-forming reaction, the reaction solution is concentrated to remove a portion of the water, and then a portion of a water-soluble first organic solvent is added. This first organic solvent is added at high temperature, which can dissolve unreacted ethanolamine and other organic impurities, achieving a good impurity removal effect. At the same time, this first organic solvent is a poor solvent for ethanolamine hydrochloride, allowing ethanolamine hydrochloride to gradually crystallize and precipitate in the mixture of the first organic solvent and water, resulting in better-dispersible particles and a crude product with higher purity and fewer impurities.

[0059] In some embodiments, the purity of the crude ethanolamine hydrochloride is ≥99%. Further, the content of any single metal impurity in the crude ethanolamine hydrochloride is ≤25 ppm for As, ≤20 ppm for Cd, and ≤20 ppm for Pb. Further, the UV absorbance value (A290) of the crude ethanolamine hydrochloride is... 290 ≤0.1.

[0060] The crude ethanolamine hydrochloride refining method of this application allows for faster drying and removal of moisture in the crude product under the entrainment of a first organic solvent, reducing process costs and moisture content. Further recrystallization and decolorization using a second organic solvent further improve the purity of the crude product and reduce the moisture content. The above refining method can significantly reduce the impurity content, including unreacted raw materials, reaction byproducts, and metallic impurities such as arsenic, cadmium, and lead, and can significantly reduce the water content, resulting in high-purity, low-water-content ethanolamine hydrochloride.

[0061] In some embodiments, the purity of the refined ethanolamine hydrochloride product is ≥99%, and the moisture content is ≤500 ppm. Further, the content of any single metal impurity in the refined ethanolamine hydrochloride product is ≤3 ppm for As, ≤3 ppm for Cd, and ≤3 ppm for Pb. Further, the UV absorbance value (A290) of the crude ethanolamine hydrochloride product is... 290 ≤0.05.

[0062] In some preferred embodiments, the purity of the refined ethanolamine hydrochloride product is ≥99.9%, and the moisture content is ≤300ppm. Further, the content of any single metal impurity in the refined ethanolamine hydrochloride product is ≤3ppm for As, ≤2ppm for Cd, and ≤2ppm for Pb. Further, the UV absorbance value (A2) of the crude ethanolamine hydrochloride product is... 290 ≤0.03.

[0063] In some embodiments, the first organic solvent and the second organic solvent each independently comprise one or more of methanol, ethanol, isopropanol, acetone, ethyl acetate, ethylene glycol, propylene glycol, glycerol, diethyl ether, acetonitrile, and tetrahydrofuran.

[0064] In some preferred embodiments, the first organic solvent and the second organic solvent are independently selected from methanol, acetone or glycerol, respectively.

[0065] In some embodiments, the step of preparing a reaction solution by subjecting an aqueous solution of ethanolamine and hydrochloric acid to a salt-forming reaction under a first low-oxygen condition and at a first temperature includes:

[0066] Ethanolamine is loaded into a reaction vessel, and after the air inside the reaction vessel is replaced with nitrogen, nitrogen is continuously introduced into its inlet at a first rate of 1~60 L / min.

[0067] The reaction vessel is heated until the internal temperature reaches the first temperature and then kept at that temperature. An aqueous solution of hydrochloric acid is then added dropwise to the reaction vessel at a second rate to react with ethanolamine to form a salt, thus obtaining a reaction solution. The second rate is 0.5~20 mL / min.

[0068] The reactor used in this application has a unidirectional inlet and outlet, and the gas inside the reactor can be discharged from the outlet.

[0069] In some embodiments, ethanolamine is loaded into a reaction vessel, and after the air inside the reaction vessel is replaced with nitrogen, nitrogen is continuously introduced into its inlet at a first rate, which can maintain the oxygen concentration inside the reaction vessel at 0~1.0%VOL.

[0070] Optionally, the first rate can be 1 to 60 L / min. For example, the first rate can be 1 L / min, 5 L / min, 10 L / min, 20 L / min, 30 L / min, 40 L / min, 50 L / min, 60 L / min, etc.

[0071] In some embodiments, the step of adding an aqueous solution of hydrochloric acid dropwise to a reaction vessel at a second rate to carry out a salt-forming reaction with ethanolamine includes:

[0072] At the first temperature, an aqueous solution of hydrochloric acid is added dropwise to the reactor at a second rate. After the addition is complete, the reaction continues at the first temperature for 0.5 to 8 hours.

[0073] The time taken to complete the dripping is related to the dripping speed. In some embodiments, the time taken to complete the dripping is about 20 to 30 hours, for example, 20 hours, 22 hours, 25 hours, 28 hours, 30 hours, etc.

[0074] After the addition is complete, the reaction can continue for 0.5 to 8 hours, for example, 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0075] In some embodiments, the mass concentration of the hydrochloric acid aqueous solution is 5-38%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 38%, etc. In this embodiment, the appropriate mass concentration of the hydrochloric acid aqueous solution, when added dropwise at a second rate for the salt formation reaction, can reduce the inclusion of impurities and obtain a crude product with higher purity.

[0076] In some embodiments, the molar ratio of hydrochloric acid to ethanolamine in the aqueous solution of hydrochloric acid is (1.001~2):1, for example 1.001:1, 1.1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, etc. An excess of hydrochloric acid relative to ethanolamine promotes the formation of ethanolamine hydrochloride, and the excess hydrochloric acid can be removed in subsequent purification steps.

[0077] In some embodiments, in the step of concentrating the reaction solution under low pressure at a second temperature, it is not necessary to evaporate the reaction solution to be completely anhydrous, because the subsequently added first organic solvent can effectively reduce the solubility of ethanolamine hydrochloride in water and promote the precipitation of ethanolamine hydrochloride at an appropriate rate.

[0078] In some embodiments, in the step of concentrating the reaction solution under low pressure and at a second temperature, the weight of water evaporated from the reaction solution is 20-80% of the total weight of the reaction solution. Evaporating an appropriate amount of water allows the first organic solvent to better dissolve unreacted ethanolamine and other impurities upon addition, while ethanolamine hydrochloride can gradually crystallize out at a suitable rate in the mixture of the first organic solvent and water, reducing impurity inclusions. In some embodiments, the step of adding the first organic solvent to the concentrated reaction solution, mixing, crystallizing, and obtaining crude ethanolamine hydrochloride includes:

[0079] After adding the first organic solvent to the reaction solution at the third temperature and mixing, the mixture is cooled to the fourth temperature to crystallize.

[0080] The third temperature is 60~120 °C; the fourth temperature is -20~-30 °C. For example, the third temperature can be 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, etc.; the fourth temperature can be -20 °C, -21°C, -22°C, -23°C, -24°C, -25°C, -26°C, -27°C, -28°C, -29°C, -30°C, etc.

[0081] The first organic solvent can better dissolve unreacted ethanolamine and other impurities at the third temperature. Then, crystallization is carried out at the fourth temperature, which can better control the crystal precipitation rate, reduce impurity inclusions, and further reduce the solubility of ethanolamine hydrochloride, thereby increasing the yield.

[0082] Furthermore, the volume ratio of the first organic solvent to ethanolamine is (5~100):1. For example, the volume ratio of the first organic solvent to ethanolamine can be 5:1, 10:1, 30:1, 50:1, 80:1, 100:1, etc.

[0083] In some embodiments, the step of decolorizing and recrystallizing crude ethanolamine hydrochloride in a second organic solvent to obtain ethanolamine hydrochloride includes:

[0084] After mixing crude ethanolamine hydrochloride with a second organic solvent, the mixture is heated and stirred to a fifth temperature under a second low-oxygen condition. Activated carbon is added and stirred for 10-60 min. The mixture is then filtered, and the filtrate is cooled to a sixth temperature to crystallize. The crystals are collected.

[0085] The crystals were dried under reduced pressure to obtain ethanolamine hydrochloride;

[0086] The second low-oxygen condition refers to an oxygen concentration of 0~1.0% VOL, the fifth temperature is 50~120 °C, and the sixth temperature is -20~-30 °C.

[0087] After obtaining the crude product using the refining method of this application, the water content and the content of various impurities can be further reduced by the above-mentioned decolorization and recrystallization, thereby further improving the purity of ethanolamine hydrochloride and further reducing the water content.

[0088] Since the second organic solvent is soluble in water but not in ethanolamine hydrochloride, mixing crude ethanolamine hydrochloride with the second organic solvent and heating and stirring at the fifth temperature under the second low-oxygen condition can dissolve particles with high water content or high impurity content in the crude ethanolamine hydrochloride, while the purer and more crystalline portions remain unaffected. Subsequently added activated carbon can adsorb and decolorize the various impurities dissolved in the system. After sufficient adsorption by stirring for 10-60 minutes, crystallization occurs at the sixth temperature, resulting in high-purity ethanolamine hydrochloride with low water content.

[0089] Furthermore, the conditions for vacuum drying include: a temperature of 40–120 °C, a time of 6–24 h, and a vacuum degree of -0.06–-0.12 MPa. Under these conditions, ethanolamine hydrochloride will not decompose to produce byproducts, and the moisture on the particle surface can be thoroughly dried, further reducing the water content of ethanolamine hydrochloride.

[0090] In some embodiments, the mass ratio of the second organic solvent to the crude ethanolamine hydrochloride is (0.1~100):1, for example 0.1:1, 10:1, 20:1, 50:1, 80:1, 100:1, etc.

[0091] In some embodiments, the mass ratio of activated carbon to crude ethanolamine hydrochloride is (0.0001~0.01):1, for example 0.0001:1, 0.0005:1, 0.001:1, 0.005:1, 0.01:1, etc.

[0092] The following are some specific examples.

[0093] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0094] The raw materials and reagents involved in the following specific embodiments can be obtained commercially or prepared by those skilled in the art using known methods.

[0095] I. Preparation of purified ethanolamine hydrochloride

[0096] Example 1

[0097] This embodiment provides a method for purifying the ethanolamine hydrochloride of this application, comprising the following steps:

[0098] (1) Take 5 kg of ethanolamine and put it into a 20 L pressure reactor. After replacing the air in the reactor with nitrogen, continuously introduce nitrogen into the inlet at a rate of 30 L / min (first rate) to maintain an oxygen concentration of about 0.5% VOL (first low oxygen condition). Turn on the steam until the internal temperature of the reactor reaches 60°C (first temperature) and then start the heat preservation. Add 22.38 kg of 20% hydrochloric acid aqueous solution to the reactor at a rate of 10 mL / min (second rate). After the addition is completed in about 22 hours, continue stirring the reaction for 4 hours.

[0099] (2) The reaction solution was transferred to a low-temperature concentration evaporator and concentrated at 90°C (second temperature) under a vacuum of -0.10MPa (low pressure conditions) to remove water from the reaction solution. After the weight of the removed water reached 13 kg, the pressure of the low-temperature concentration evaporator was adjusted to atmospheric pressure, the heat was turned off to stop the concentration, and 600 L of methanol (first organic solvent) was added into the tank while it was hot (temperature about 60°C) and mixed. The mixture was cooled to room temperature, crystallized, and collected. The crystals were washed with a small amount of methanol and dried under reduced pressure at 80 °C and -0.09 mPa to obtain crude ethanolamine hydrochloride.

[0100] (3) Mix 1 kg of crude ethanolamine hydrochloride with 10 kg of methanol (second organic solvent), stir and heat the mixture to 70°C under low oxygen conditions, add 1 g of activated carbon to keep warm and continue stirring for 30 min until the ethanolamine hydrochloride is completely dissolved, filter while hot, cool to 10°C, crystallize, and collect the crystals; dry the crystals under reduced pressure at 80°C for 16 h to obtain refined ethanolamine hydrochloride, which appears as a white crystalline powder.

[0101] Example 2

[0102] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that of Example 1, except that the first temperature is reduced to 30°C. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0103] Example 3

[0104] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that of Example 1, except that the low-temperature concentration temperature is 110°C. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0105] Example 4

[0106] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that of Example 1, except that the vacuum degree is -0.06 MPa. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0107] Example 5

[0108] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that the first and second organic solvents are acetone. All other operations, preparation parameters, and reaction raw materials and their amounts are the same as in Example 1.

[0109] Example 6

[0110] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that the first and second organic solvents are glycerol. All other operations, preparation parameters, and reaction raw materials and their amounts are the same as in Example 1.

[0111] Example 7

[0112] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that in Example 1, except that the nitrogen gas introduction rate is adjusted to 60 L / min. -1 The salt formation reaction was completed when the oxygen concentration was measured to be 0.0% VOL. All other operations, preparation parameters, and reactants and their quantities were the same as in Example 1.

[0113] Example 8

[0114] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that in Example 1, except that the dropping rate of the hydrochloric acid aqueous solution is adjusted to 20 mL / min. -1 The remaining operations, preparation parameters, and reaction materials and their amounts are the same as in Example 1.

[0115] Example 9

[0116] This embodiment provides a purification method for the ethanolamine hydrochloride of this application, which adopts a purification method similar to that of Example 1, except that the portion of water removed is 10% of the total weight of the reaction solution. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0117] Comparative Example 1

[0118] This comparative example provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that the first temperature is reduced to 10°C. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that nitrogen gas is not introduced throughout the process. All other operations, preparation parameters, and reaction raw materials and their amounts are the same as in Example 1.

[0121] Comparative Example 3

[0122] This comparative example provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that the low-temperature concentration temperature is 150°C. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0123] Comparative Example 4

[0124] This comparative example provides a purification method for the ethanolamine hydrochloride of this application, employing a purification method similar to that of Example 1, except that the vacuum degree is -0.02 MPa. All other operations, preparation parameters, and reactants and their amounts are the same as in Example 1.

[0125] II. Purity Determination of Crude and Refined Ethanolamine Hydrochloride Products

[0126] Table 1. Purity determination of crude ethanolamine hydrochloride (purity unit: wt%; moisture unit: ppm; A) 290 UV absorbance at 290 nm; As, Cd, and Pb content (ppm); Yield (crude product yield, %)

[0127]

[0128] Table 2 Purity determination of refined ethanolamine hydrochloride products (purity unit: wt%; moisture unit: wt%); A 290(UV absorbance at 290nm; As, Cd, Pb content in ppm)

[0129]

[0130] As can be seen from Tables 1 and 2, the purity of the crude ethanolamine hydrochloride product in the embodiments of this application can reach over 99.0%, with a water content ≤1.5%. 290 The purity of ethanolamine hydrochloride was further improved by refining to ≤0.1, and the water content was reduced to ≤300 ppm, while the content of single metal impurities such as arsenic, cadmium, and lead was reduced to ≤4 ppm. The purity of crude ethanolamine hydrochloride in Comparative Examples 1 to 4 was lower than that in the examples, with higher water content. After further refining, the purity could not be improved to the requirements of refined products, and the content of single metal impurities such as arsenic, cadmium, and lead was also higher.

[0131] All references to this application are incorporated herein by reference as if each document were individually incorporated herein by reference. Unless they conflict with the purpose and / or technical solution of this application, all cited references are incorporated herein by reference in their entirety and for all purposes. When references are cited in this application, the definitions of relevant technical features, terms, nouns, phrases, etc., are also incorporated herein by reference. Examples and preferred embodiments of the cited technical features may also be incorporated herein by reference, but only to the extent that they enable the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, this application shall prevail or modifications shall be made adaptably to the description in this application.

[0132] The technical features of the above-described embodiments and examples can be combined in any suitable manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0133] The embodiments described above merely illustrate several implementation methods of this application and should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Furthermore, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the protection scope of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A method for purifying ethanolamine hydrochloride, characterized in that, Includes the following steps: An aqueous solution of ethanolamine and hydrochloric acid is subjected to a salt-forming reaction under a first low-oxygen condition and at a first temperature to obtain a reaction solution; the first low-oxygen condition refers to an oxygen concentration of 0~1.0%VOL; the first temperature is 20~90 °C. The reaction solution is concentrated under low-pressure conditions at a second temperature; the low-pressure conditions refer to a vacuum degree of -0.06 to -0.12 MPa; the second temperature is 60 to 120 °C. Add the first organic solvent to the concentrated reaction solution and mix. Crystallize to obtain crude ethanolamine hydrochloride. The crude ethanolamine hydrochloride was dissolved in a second organic solvent for decolorization and recrystallization to obtain ethanolamine hydrochloride; The first organic solvent and the second organic solvent are solvents that are soluble in water but do not dissolve the ethanolamine hydrochloride.

2. The refining method according to claim 1, characterized in that, The first organic solvent and the second organic solvent each independently comprise one or more of methanol, ethanol, isopropanol, acetone, ethyl acetate, ethylene glycol, propylene glycol, glycerol, diethyl ether, acetonitrile, and tetrahydrofuran.

3. The refining method according to claim 1, characterized in that, The steps for preparing the reaction solution by carrying out a salt-forming reaction of an aqueous solution of ethanolamine and hydrochloric acid under a first low-oxygen condition and at a first temperature include: Ethanolamine is loaded into a reaction vessel, and after the air inside the reaction vessel is replaced with nitrogen, nitrogen is continuously introduced into its inlet at a first rate of 1~60 L / min. The reaction vessel is heated until its internal temperature reaches the first temperature and then kept at that temperature. An aqueous solution of hydrochloric acid is then added dropwise to the reaction vessel at a second rate to react with the ethanolamine to form a salt, thereby obtaining the reaction solution. The second rate is 0.5~20 mL / min.

4. The refining method according to claim 3, characterized in that, The aqueous solution of hydrochloric acid has a mass concentration of 5-38%; and / or, The molar ratio of hydrochloric acid to ethanolamine in the aqueous solution of hydrochloric acid is (1.001~2):

1.

5. The refining method according to any one of claims 1 to 4, characterized in that, In the step of concentrating the reaction solution under low pressure and at a second temperature, the weight of water evaporated from the reaction solution is 20-80% of the total weight of the reaction solution.

6. The refining method according to any one of claims 1 to 4, characterized in that, The steps of adding a first organic solvent to the concentrated reaction solution, mixing, crystallizing, and obtaining crude ethanolamine hydrochloride include: After adding the first organic solvent to the reaction solution at the third temperature and mixing, the mixture is cooled to the fourth temperature to crystallize. The third temperature is 60~120 °C; the fourth temperature is -20~-30 °C.

7. The refining method according to claim 6, characterized in that, The volume ratio of the first organic solvent to the ethanolamine is (5~100):

1.

8. The refining method according to any one of claims 1 to 4, characterized in that, The step of decolorizing and recrystallizing the crude ethanolamine hydrochloride in a second organic solvent to obtain ethanolamine hydrochloride includes: After mixing the crude ethanolamine hydrochloride with the second organic solvent, the mixture is heated and stirred to the fifth temperature under the second low-oxygen condition. Activated carbon is added, and the mixture is stirred for 10-60 min. The mixture is then filtered, and the filtrate is cooled to the sixth temperature to crystallize. The crystals are collected. The crystals were dried under reduced pressure to obtain the ethanolamine hydrochloride. The second low-oxygen condition refers to an oxygen concentration of 0~1.0%VOL, the fifth temperature is 50~120 °C, and the sixth temperature is -20~-30 °C.

9. The refining method according to claim 8, characterized in that, The conditions for vacuum drying include: a temperature of 40~120 °C, a time of 6~24 h, and a vacuum degree of -0.06~-0.12 MPa.

10. The refining method according to claim 8, characterized in that, The mass ratio of the second organic solvent to the crude ethanolamine hydrochloride is (0.1~100):1; and / or, The mass ratio of the activated carbon to the crude ethanolamine hydrochloride is (0.0001-0.01):1.

Images