An ethylenediamine derivative composition, a chelating agent and a method for preparing the same

Abstract

The present application provides a kind of ethylenediamine derivative composition, chelating agent and preparation method thereof, the composition includes ethylenediaminetetraacetic acid tetrasodium / potassium and the compound shown in formula (1);Formula (1);The compound of formula (1) R1, R2 And R3 Selected from H or CH2COONa or CH2COOK;The average molar ratio of amino hydrogen atom substituted by carboxymethyl in the composition is 97.0-99.5% based on the total ethylenediamine skeleton structure mole number.The composition shows excellent chelating speed to metal ions, and is conducive to industrial production.

Description

Technical Field

[0001] This invention relates to the field of chelating agent synthesis technology, specifically to an ethylenediamine-derived composition, a chelating agent, and a method for preparing the same. Background Technology

[0002] Tetrasodium ethylenediaminetetraacetate (EDTA-4Na) is the most widely used and in-demand core product among aminopolycarboxylic acid chelating agents. With its excellent metal ion complexing ability and acid-base stability, it is widely used in water treatment, daily chemical washing, industrial cleaning, food, medicine, papermaking, textiles, rubber additives and other fields. It is an indispensable key additive in modern fine chemical and clean production.

[0003] Currently, the mainstream industrial process for preparing tetrasodium ethylenediaminetetraacetate is based on the sodium cyanide-formaldehyde method, supplemented by the chloroacetic acid method, hydrogen cyanide method, hydroxyacetonitrile method, and iminodiacetonitrile derivatization method. Each of these processes has obvious limitations, which restrict high-quality, continuous, and green production.

[0004] The commonly used sodium cyanide-formaldehyde process in the industry uses ethylenediamine, liquid alkali, sodium cyanide, and formaldehyde as raw materials. The reaction is carried out stepwise in a reactor under controlled temperature, with reduced pressure to remove byproduct ammonia. Post-processing yields a tetrasodium EDTA condensate. While this process is mature and the equipment is simple, it has significant drawbacks: low ammonia removal efficiency leading to side reactions; small gas-liquid mass transfer area in the reactor; ammonia accumulation within the system; and the easy formation of impurities such as trisodium triacetate (NTA.3Na) with formaldehyde and sodium cyanide. In conventional processes, the NTA.3Na content reaches 0.2%–1.0%, consuming raw materials and reducing product quality, thus limiting its application in high-end fields.

[0005] To improve process defects, existing technologies attempt optimization and improvement: For example, CN105646254B uses a supergravity reactor to achieve continuous reaction, improve mixing and mass transfer efficiency, and shorten reaction time. However, rapid mixing of formaldehyde and sodium cyanide can easily trigger side reactions, and the impurities of trisodium triacetate are still too high, resulting in limited improvement in product purity. CN113444006B introduces a thin-film evaporator for online ammonia removal, increases the gas-liquid contact area, and rapidly removes ammonia. Side reactions are significantly reduced, and the yield is increased to over 96%. The trisodium triacetate impurity is reduced to 300–700 ppm, but the raw material consumption is still high.

[0006] In summary, existing technologies for producing tetrasodium ethylenediaminetetraacetate generally suffer from problems such as high feed ratios, incomplete deammoniation, and high levels of byproducts, failing to simultaneously meet the industrial demands for high yields, low impurities, and green safety. Therefore, developing a new process for preparing ethylenediaminetetraacetate with efficient deammoniation, low side reactions, and low nitrogen and sulfur content (as opposed to trisodium triacetate) has become a key direction for technological upgrading and the supply of high-end products in the industry. Furthermore, as a chelating agent, the industry often requires a more stable chelating force for metal ions in water, while neglecting the chelation rate of metal ions. Summary of the Invention

[0007] The purpose of this invention is to provide an ethylenediamine-derived composition that can enhance the chelation rate of metal ions by sodium / potassium ethylenediaminetetraacetate.

[0008] Another objective of this invention is to provide a chelating agent that has high effective content in both liquid and solid products, low addition amount in downstream applications, and fast chelation rate for metal ions.

[0009] Another object of the present invention is to provide a method for preparing the chelating agent, which has the advantages of low side reactions and low content of residual cyanide and trisodium triacetate in the product.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides an ethylenediamine-derived composition comprising tetrasodium ethylenediaminetetraacetate and / or tetrapotassium ethylenediaminetetraacetate, and a compound of formula (1);

[0012] Equation (1);

[0013] Among them, R1, R2 and R3 are selected from H or CH2COONa or CH2COOK;

[0014] In the composition, based on the molar number of amino hydrogen atoms in the total ethylenediamine skeleton structure, the average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups is 97.0-99.5%, including but not limited to 97.5%, 97.8%, 98%, 98.2%, 98.5%, 98.7%, 99%, 99.2%, or any combination thereof.

[0015] In their research, the inventors discovered that when the average molar percentage of amino hydrogen atoms substituted with carboxymethyl groups in the ethylenediamine-derived composition is 97.0-99.5%, it exhibits excellent metal chelation rate and chelation ability. When the average molar percentage of amino hydrogen atoms substituted is below 97.0% or above 99.5%, the chelation rate and ability decrease. The compound represented by formula (1) contained in the ethylenediamine-derived composition can be a single compound or multiple compounds corresponding to different substituents.

[0016] As a preferred embodiment, the composition comprises 0.05-10%, preferably 0.08-9.75% of the compound of formula (1) by weight of the total composition, including but not limited to 0.07%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or any combination thereof. The composition does not contain water.

[0017] In the composition of this invention, based on the molar number of amino hydrogen atoms in the total ethylenediamine skeleton, the average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups is calculated as follows:

[0018]

[0019] Equation (1)

[0020] In equation (1):

[0021] W1 is the mass fraction of tetrasodium ethylenediaminetetraacetate / potassium in the composition;

[0022] W2 is the mass fraction of trisodium ethylenediaminetriacetate / potassium in the composition;

[0023] W3 represents the mass fraction of disodium ethylenediaminediacetate / potassium in the composition;

[0024] W4 represents the mass fraction of sodium / potassium ethylenediamine monoacetate in the composition;

[0025] W5 represents the mass fraction of ethylenediamine in the composition;

[0026] M1 is the molar mass of tetrasodium ethylenediaminetetraacetate / potassium in the composition;

[0027] M2 is the molar mass of trisodium ethylenediaminetriacetate / potassium in the composition;

[0028] M3 is the molar mass of disodium ethylenediaminediacetic acid / potassium in the composition;

[0029] M4 is the molar mass of sodium / potassium ethylenediamine monoacetate in the composition;

[0030] M5 is the molar mass of ethylenediamine in the composition.

[0031] In this invention, the mass fractions of tetrasodium / potassium ethylenediaminetetraacetate, trisodium / potassium ethylenediaminetriacetate, disodium / potassium ethylenediaminediaacetate, and monosodium / potassium ethylenediaminemonacetate can be analyzed and tested by liquid chromatography, and the mass fraction of ethylenediamine can be analyzed and tested by gas chromatography.

[0032] In a second aspect, the present invention provides a chelating agent comprising 38-45% by mass of an aqueous solution of the above-mentioned ethylenediamine derivative composition, or 82-92% by mass of an ethylenediamine derivative composition containing water of crystallization.

[0033] Thirdly, the present invention provides a method for preparing the chelating agent, comprising the following steps:

[0034] 1) Reaction process: Cyanide, ethylenediamine, formaldehyde and alkali are reacted in water to obtain a reaction solution;

[0035] 2) Separation process: The reaction solution from step 1) is separated and purified to obtain the chelating agent.

[0036] Preferably, the content of dissolved ammonia during the reaction is controlled to be less than or equal to 0.15 wt%.

[0037] In this invention, step 1) of the reaction of cyanide, ethylenediamine, formaldehyde, and alkali is carried out in water. Specifically, ethylenediamine and alkali are first mixed, and then cyanide and formaldehyde are added dropwise simultaneously in a certain proportion, controlling the temperature at 90-110℃, preferably 98-105℃, including but not limited to 92℃, 95℃, 97℃, 100℃, 102℃, 104℃, 106℃, 108℃, or any combination thereof. After the addition is completed, the reaction residence time is 1-3 hours, including but not limited to 1.2 hours, 1.5 hours, 1.8 hours, 2 hours, 2.2 hours, 2.5 hours, 2.7 hours, 2.9 hours, or any combination thereof, to prepare an aqueous solution containing the above composition.

[0038] Preferably, the cyanide salt is sodium cyanide and / or potassium cyanide.

[0039] Preferably, in step 1), the molar ratio of ethylenediamine:cyanide:formaldehyde:alkali is 1.0:(4.0-4.50):(4.0-4.50):(0.2-0.8), more preferably 1.0:(4.05-4.50):(4.03-4.50):(0.2-0.8), including but not limited to 1:4.1:4.0:0.3, 1:4.15:4.15:0.4, 1:4.2:4.2:0.5, and 1:4.25:4.3. 0.6, 1:4.3:4.3:0.7, 1:4.4:4.4:0.8, 1:4.5:4.5:0.2, 1:4.1:4.5:0.3, 1:4.2:4.4:0.4, 1:4.3:4.1:0.4, 1:4.4:4.1:0.6, 1:4.05:4.03:0.7, 1:4.05:4.03:0.8, 1:4.05:4.03:0.2, or a range consisting of any two of these.

[0040] In this invention, the raw material alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate.

[0041] In step 1) of this invention, the hydrolysis of nitrile or cyanide groups generates ammonia gas. This ammonia gas consumes the raw material cyanide salt and formaldehyde, further generating the undesirable impurity trisodium triacetate / potassium. Researchers have found that controlling the dissolved ammonia content during the reaction to less than or equal to 0.15% can effectively control the formation of the impurity trisodium triacetate / potassium.

[0042] In this invention, in order to quickly remove the ammonia gas generated during the reaction process, reduce the consumption of raw materials and the generation of impurities, and thus more accurately control the substitution rate of amino hydrogen atoms of carboxymethyl groups in the raw material ethylenediamine according to the feed ratio, the preferred control method is to maintain the reaction system under a slight negative pressure and introduce a small amount of stripping nitrogen gas.

[0043] Preferably, the reaction pressure is controlled within the range of -1 to -10 kPaG. This includes, but is not limited to, ranges of -2 kPaG, -2.5 kPaG, -3 kPaG, -3.5 kPaG, -4.0 kPaG, -5 kPaG, -26 kPaG, -7 kPaG, -8 kPaG, -9 kPaG, or any combination thereof. Too low a pressure will prevent the rapid removal of the generated ammonia, while too high a pressure will lead to the large-scale volatilization of water and ethylenediamine in the system, and the reaction temperature cannot be maintained.

[0044] Preferably, the amount of nitrogen introduced per hour during the reaction is 50-200 times the total liquid volume, including but not limited to 60, 70, 80, 90, 100, 120, 140, 150, 160, 180, 190 times, or any combination thereof, calculated based on standard volume. More preferably, nitrogen is introduced after the ratio of raw material cyanide and formaldehyde reaches 50%, preferably at an hourly nitrogen volume of 80-120 times the total liquid volume.

[0045] If necessary, the reaction products obtained from the reaction process can be concentrated. A small amount of solvent water and residual ammonia can be removed using a known evaporator such as a distillation column, controlling the separation pressure at -60 to -80 kPaG and the separation temperature at 60-80°C, to obtain a 38-45% (w / w) aqueous solution of the composition.

[0046] Alternatively, the reaction products obtained from the reaction process can be further concentrated as needed. A large amount of solvent water and residual ammonia are removed using a known evaporator such as an MVR, controlling the separation pressure at -60 to -90 kPaG and the separation temperature at 60-100°C, so that the composition is supersaturated in water. The supersaturated solution is then further crystallized using a known batch crystallizer. The crystals are then further agitated in a centrifuge to obtain a wet product of the composition.

[0047] Additionally, the wet product of the above composition can be dried as needed, using known drying equipment such as a rotary drum dryer with hot air temperature of 120-150°C, to further remove moisture and obtain a composition containing 82-92% by mass of water of crystallization.

[0048] In this invention, the chelation time of the aqueous solution of the ethylenediamine derivative composition for metal ions, especially calcium ions, is shortened by more than 10% compared with the corresponding tetrasodium / potassium ethylenediaminetetraacetate solution, meaning that the chelation rate of the same amount of calcium ions is faster.

[0049] In this invention, all components in the ethylenediamine-derived composition are converted to ethylenediaminetetraacetic acid tetrasodium tetrahydrate, and the chelation value of ethylenediaminetetraacetic acid tetrasodium tetrahydrate meets the standard of ≥220 mg CaCO3 / g.

[0050] The chelating agent of this invention is mainly used in industrial cleaning and water treatment.

[0051] The technical solution provided by this invention has the following beneficial effects:

[0052] The ethylenediamine-derived composition of the present invention, due to the presence of a certain amount of unsubstituted ethylenediamine derivative, accelerates the chelation rate of the composition for metal ions, especially calcium, copper and magnesium ions, in an oil-water system, and the chelation value for metal ions does not change significantly.

[0053] By using the preparation method described in this invention, the content of nitrogen trisodium triacetate / potassium in the chelating agent can be controlled to ≤1.0% by controlling the reaction and separation process conditions. Detailed Implementation

[0054] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the listed embodiments, and should also include any other known modifications within the scope of the claims of the present invention.

[0055] Raw material source:

[0056] Ethylenediamine, Inokai, 99%

[0057] Sodium hydroxide, Aladdin, 99%

[0058] Formaldehyde aqueous solution, Inokai, 36.5%

[0059] Analysis method:

[0060] The method for determining the content of tetrasodium, trisodium, disodium, monosodium, and trisodium triacetate of ethylenediamine derivatives was as follows: liquid chromatography with external standard method. The instrument was an Agilent 1260, with an Agilent Poroshell 120EC-C18 column (4µm, 150×4.6mm). The mobile phase was: cation pair reagent (copper acetate solution): acetonitrile = 90:10. The flow rate was 1mL / min, the detection wavelength was 290nm, the injection volume was 20μL, and the column temperature was 40℃.

[0061] The method for determining ethylenediamine content was gas chromatography using the external standard method. The instrument used was an Agilent 7890 gas chromatogram with an HP-VOC column and an FID detector. The injection port temperature was 150℃, and the detector temperature was 260℃. The carrier gas was nitrogen (10 mL / min), with a split ratio of 10:1. The injection volume was 10 μL. The initial column temperature was 50℃ for 2 minutes, then increased to 80℃ at a rate of 5℃ / min, and finally increased to 250℃ at a rate of 15℃ / min, holding for 10 minutes.

[0062] Ammonia content test method: Refer to industry standard HJ535-2009 "Determination of ammonia nitrogen in water quality by Nessler's reagent spectrophotometric method".

[0063] The test method for calcium carbonate chelation value is the calcium acetate complexation potentiometric titration method. The test method used is as follows: An automatic potentiometric titrator (Metrohm 905Titrando) equipped with a platinum composite electrode was used. A sample with an absolute content of 0.5 g of the ethylenediamine derivative composition (calculated based on liquid chromatography and gas chromatography) was dissolved in 50 ml of water, followed by the addition of 20 ml of ammonia-ammonium chloride buffer solution (pH=10). The solution temperature was stabilized at 23℃. Titration was performed using a prepared 0.1 mol / L calcium acetate standard solution, and the chelation value X (mgCaCO3 / g) was calculated using the following formula:

[0064]

[0065] Equation (2)

[0066] In equation (2):

[0067] c represents the concentration (mol / L) of the calcium acetate standard solution;

[0068] V is the volume (L) of calcium acetate consumed in the titration.

[0069] m is the absolute mass (g) of the ethylenediamine derivative composition;

[0070] M1 is the molar mass of calcium acetate;

[0071] M2 is the molar mass of tetrasodium ethylenediaminetetraacetate tetrahydrate;

[0072] M3 is the molar mass of tetrasodium / potassium ethylenediaminetetraacetate.

[0073] Chelation time: The time required to titrate 0.5 g of ethylenediamine-derived composition to the endpoint was determined by the calcium acetate complexation potentiometric titration method.

[0074] Example 1

[0075] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 90 °C. The negative pressure system was turned on to maintain the system pressure at -10 kPaG. 130.67 g of 30 wt% sodium cyanide solution (0.80 mol) and 65.8 g of 36.5 wt% formaldehyde solution (0.80 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 40 L / h after 1.5 h. The addition was completed after 3 h. A sample was taken and the ammonia content was tested to be 0.12 wt%. The mixture was then kept at the same temperature for another 3 h.

[0076] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and samples were taken. The content of the ethylenediamine derivative composition was tested by liquid chromatography and gas chromatography using external standard methods. The result was 38.0 wt%, with the remainder being water. The content of tetrasodium ethylenediaminetetraacetate was 35.54 wt%, trisodium ethylenediaminetriacetate was 1.98 wt%, disodium ethylenediaminediaacetate was 0.40 wt%, monosodium ethylenediaminemonacetate was 0.07%, and the content of ethylenediamine was 0.01%. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 97.0%, and the NTA·3Na content was 0.5%.

[0077] The calcium carbonate chelation value of the aqueous solution of the composition was tested and found to be 225 mg CaCO3 / g, with a chelation time of 160 s.

[0078] Example 2

[0079] 12.1 g of ethylenediamine (0.2 mol), 4.5 g of potassium hydroxide (0.08 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 98 °C. The negative pressure system was turned on to maintain the system pressure at -5 kPaG. 176.8 g of 30 wt% potassium cyanide solution (0.816 mol) and 66.4 g of 36.5 wt% formaldehyde solution (0.808 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 20 L / h after 1.5 h. The addition was completed after 3 h. A sample was taken and the ammonia content was tested to be 0.13 wt%. The mixture was then kept at the same temperature for another 3 h.

[0080] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and the contents of the ethylenediamine derivative composition were tested by liquid chromatography and gas chromatography using external standard methods. The content was 45.0 wt%, of which the tetrapotassium ethylenediaminetetraacetate (EDTA) content was 42.71 wt%, the tripotassium ethylenediaminetriacetate (EDTA) content was 1.92 wt%, the dipotassium ethylenediaminediaacetate (EDTA) content was 0.31 wt%, the monopotassium ethylenediaminemonacetate (EDTA) content was 0.06%, and ethylenediamine was not detected. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 97.8%, and the NTA.3K content was 0.6%.

[0081] The calcium carbonate chelation value of the aqueous solution of the composition was tested and found to be 223 mg CaCO3 / g, with a chelation time of 167 s.

[0082] Example 3

[0083] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 95 °C. The negative pressure system was turned on to maintain the system pressure at -2 kPaG. 140.5 g of 30 wt% sodium cyanide solution (0.86 mol) and 70.7 g of 36.5 wt% formaldehyde solution (0.86 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 16 L / h after 1.5 h. The addition was completed after 3 h. A sample was taken and the ammonia content was tested to be 0.13 wt%. The mixture was then kept at the same temperature for another 2 h.

[0084] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and samples were taken. The content of the ethylenediamine derivative composition was tested by liquid chromatography and gas chromatography using external standard methods. The content was 40.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 38.46 wt%, the content of trisodium ethylenediaminetriacetate was 1.40 wt%, the content of disodium ethylenediaminediaacetate was 0.10 wt%, the content of monosodium ethylenediaminemonacetate was 0.04%, and ethylenediamine was not detected. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 98.5%, and the NTA·3Na content was 0.7%.

[0085] The calcium carbonate chelation value of the aqueous solution of the composition was tested, and the result was 230 mg CaCO3 / g with a chelation time of 157 s.

[0086] Example 4

[0087] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 110 °C. The negative pressure system was turned on to maintain the system pressure at -1 kPaG. 134.6 g of 30 wt% sodium cyanide solution (0.824 mol) and 67.1 g of 36.5 wt% formaldehyde solution (0.816 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 10 L / h after 1.5 h. The addition was completed after 3 h. A sample was taken and the ammonia content was tested to be 0.13 wt%. The mixture was then kept at the same temperature for another 1 h.

[0088] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. After some water was distilled off and crystals appeared, the crystals of the composition were separated in a centrifuge and then dried in an oven at 100°C for 2 hours. The obtained sample was tested by liquid chromatography and gas chromatography with external standard method. The content of the ethylenediamine derivative composition was 82.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 79.89 wt%, the content of trisodium ethylenediaminetriacetate was 1.90 wt%, the content of disodium ethylenediaminediaacetate was 0.16 wt%, the content of monosodium ethylenediaminemonacetate was 0.05%, and ethylenediamine was not detected. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 99.0%, and the NTA·3Na content was 0.6%.

[0089] The calcium carbonate chelation value of the crystals of this composition was tested, and the result was 227 mg CaCO3 / g with a chelation time of 165 s.

[0090] Example 5

[0091] 12.1 g of ethylenediamine (0.2 mol), 6.4 g of sodium hydroxide (0.16 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 100 °C. The negative pressure system was turned on to maintain the system pressure at -5 kPaG. 134.6 g of 30 wt% sodium cyanide solution (0.83 mol) and 67.1 g of 36.5 wt% formaldehyde solution (0.82 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 20 L / h after 1.5 h. The addition was completed after 3 h. A sample was taken and the ammonia content was tested to be 0.12 wt%. The mixture was then kept at the same temperature for another 2 h.

[0092] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. After some water was distilled off and crystals appeared, the crystals of the composition were separated in a centrifuge and then dried in an oven at 100°C for 4 hours. The obtained sample was tested by liquid chromatography and gas chromatography with external standard method. The content of the ethylenediamine derivative composition was 92.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 90.53 wt%, the content of trisodium ethylenediaminetriacetate was 1.41 wt%, the content of disodium ethylenediaminediaacetate was 0.06 wt%, and monosodium ethylenediaminemonacetate and ethylenediamine were not detected. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 99.5%, and the NTA.3Na content was 0.8%.

[0093] The calcium carbonate chelation value of the crystals of this composition was tested, and the result was 227 mg CaCO3 / g with a chelation time of 170 s.

[0094] Comparative Example 1

[0095] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 95 °C with a system pressure of 0 kPaG. 140.5 g of 30 wt% sodium cyanide solution (0.86 mol) and 70.7 g of 36.5 wt% formaldehyde solution (0.86 mol) were added dropwise to the reaction flask. The addition was stopped after 3 hours. A sample was taken and the ammonia content was tested to be 0.31 wt%. The mixture was then kept at the same temperature for another 2 hours.

[0096] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and samples were taken. The content of the ethylenediamine derivative composition was determined by liquid chromatography and gas chromatography with external standard method to be 40.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 36.63 wt%, the content of trisodium ethylenediaminetriacetate was 2.56 wt%, the content of disodium ethylenediaminediaacetate was 0.68 wt%, the content of monosodium ethylenediaminemonacetate was 0.11%, and the content of ethylenediamine was 0.02%. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 96.0%, and the NTA·3Na content was 1.6%.

[0097] The calcium carbonate chelation value of the aqueous solution of the composition was tested and found to be 210 mg CaCO3 / g with a chelation time of 185 s.

[0098] Comparative Example 2

[0099] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 95 °C. 140.5 g of 30 wt% sodium cyanide solution (0.86 mol) and 70.7 g of 36.5 wt% formaldehyde solution (0.86 mol) were added dropwise to the reaction flask. Nitrogen gas was introduced at a flow rate of 200 L / h to maintain a slight positive pressure of approximately 3 kPaG in the system. The addition was stopped after 3 hours. A sample was taken and the ammonia content was tested to be 0.26 wt%. The mixture was then kept at the temperature for another 2 hours.

[0100] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and samples were taken. The content of the ethylenediamine derivative composition was tested by liquid chromatography and gas chromatography with external standard method. The content was 40.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 39.77 wt%, the content of trisodium ethylenediaminetriacetate was 0.2 wt%, the content of disodium ethylenediaminediaacetate was 0.03 wt%, and the content of monosodium ethylenediamine monoacetate and ethylenediamine were not detected. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 99.8%, and the NTA.3Na content was 1.2%.

[0101] The calcium carbonate chelation value of the aqueous solution of the composition was tested and found to be 219 mg CaCO3 / g, with a chelation time of 190 s.

[0102] Comparative Example 3

[0103] 12.1 g of ethylenediamine (0.2 mol), 1.6 g of sodium hydroxide (0.04 mol), and 100 g of water were added to a four-necked flask equipped with a reflux condenser. Stirring was started, and the temperature was raised to 95°C. The negative pressure system was activated to maintain a system pressure of -2 kPaG. 140.5 g of 30 wt% sodium cyanide solution (0.86 mol) and 70.7 g of 36.5 wt% formaldehyde solution (0.86 mol) were added dropwise to the reaction flask. The addition was completed after 3 hours. A sample was taken, and the ammonia content was measured to be 0.28 wt%. The mixture was then kept at this temperature for another 2 hours.

[0104] The obtained reaction solution was subjected to negative pressure distillation at a system pressure of -80 kPaG. Some water was distilled off, and samples were taken. The content of the ethylenediamine derivative composition was determined by liquid chromatography and gas chromatography with external standard method to be 40.0 wt%, of which the content of tetrasodium ethylenediaminetetraacetate was 37.16 wt%, the content of trisodium ethylenediaminetriacetate was 2.13 wt%, the content of disodium ethylenediaminediaacetate was 0.60 wt%, the content of monosodium ethylenediaminemonacetate was 0.10%, and the content of ethylenediamine was 0.01%. The average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups in the composition was calculated to be 96.5%, and the NTA·3Na content was 1.4%.

[0105] The calcium carbonate chelation value of the aqueous solution of the composition was tested and found to be 213 mg CaCO3 / g, with a chelation time of 181 s.

[0106] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. An ethylenediamine-derived composition, characterized in that, The composition comprises tetrasodium / potassium ethylenediaminetetraacetate and the compound shown in formula (1); Formula (1); in the compound of formula (1), R1, R2 and R3 are selected from H or CH2COONa or CH2COOK; In the composition, based on the molar number of amino hydrogen atoms in the entire ethylenediamine skeleton structure, the average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups is 97.0-99.5%.

2. The composition according to claim 1, characterized in that, The composition contains 0.05-10%, preferably 0.08-9.75 wt% of the compound represented by formula (1) based on the total weight of the composition.

3. The composition according to any one of claims 1-2, characterized in that, In the composition described above, based on the molar number of amino hydrogen atoms in the entire ethylenediamine skeleton, the average molar ratio of amino hydrogen atoms replaced by carboxymethyl groups is calculated as follows: Equation (1) In equation (1): W1 is the mass fraction of tetrasodium ethylenediaminetetraacetate / potassium in the composition; W2 is the mass fraction of trisodium ethylenediaminetriacetate / potassium in the composition; W3 represents the mass fraction of disodium ethylenediaminediacetate / potassium in the composition; W4 represents the mass fraction of sodium / potassium ethylenediamine monoacetate in the composition; W5 represents the mass fraction of ethylenediamine in the composition; M1 is the molar mass of tetrasodium ethylenediaminetetraacetate / potassium in the composition; M2 is the molar mass of trisodium ethylenediaminetriacetate / potassium in the composition; M3 is the molar mass of disodium ethylenediaminediacetic acid / potassium in the composition; M4 is the molar mass of sodium / potassium ethylenediamine monoacetate in the composition; M5 is the molar mass of ethylenediamine in the composition.

4. A chelating agent comprising 38-45% by mass of an aqueous solution of the composition according to any one of claims 1-3, or 82-92% by mass of the composition according to any one of claims 1-3, wherein the composition contains water of crystallization.

5. The method for preparing the chelating agent according to claim 4, characterized in that, The method includes: 1) Reaction process: Cyanide, ethylenediamine, formaldehyde and alkali are reacted in water to obtain a reaction solution; 2) Separation process: The reaction solution from step 1) is separated and purified to obtain the chelating agent; Preferably, the content of dissolved ammonia during the reaction is controlled to be less than or equal to 0.15 wt%.

6. The method according to claim 5, characterized in that, The molar ratio of ethylenediamine: cyanide: formaldehyde: alkali mentioned in step 1) is 1.0: (4.0~4.50): (4.0~4.50): (0.2~0.8).

7. The method according to claim 5 or 6, characterized in that, Step 1) The reaction temperature is 90-110℃, preferably 98-105℃.

8. The method according to any one of claims 5-7, characterized in that, In step 1), ethylenediamine and alkali are first mixed in water, then cyanide and formaldehyde are added. After the addition is complete, the reaction is allowed to proceed for 1-3 hours to obtain the reaction solution.

9. The method according to any one of claims 5-8, characterized in that, In step 1), the reaction liquid is stripped with nitrogen under reaction pressure; the reaction pressure is -1 to -10 kPaG. Preferably, the amount of nitrogen introduced per hour during the reaction is 50-200 times the total volume of the liquid. More preferably, nitrogen is introduced after the proportion of raw material cyanide and formaldehyde reaches 50%.

10. The method according to claim 5, characterized in that, In step 2), the reaction solution is concentrated only to obtain an aqueous solution of the composition with a mass percentage of 38-45%. The reaction solution is concentrated, crystallized and dried to obtain a composition containing water of crystallization with a mass percentage of 82-92%.

Images