Medium trace element liquid iminodisuccinic acid chelate fertilizer and preparation method using temperature difference phase separation method

Abstract

The invention discloses a medium trace element liquid iminodisuccinate chelate fertilizer which is prepared by chelating iminodisuccinate and divalent metal salt corresponding to medium trace elements, crystallizing by a pH temperature difference method, and separating to obtain liquid through nutrient element index regulation. The divalent metal salt is at least one of nitrate containing divalent metal and sulfate containing divalent metal. According to the medium trace element liquid IDS chelated fertilizer, the product quality, stability and applicability are remarkably improved, separated crystals can be effectively recycled, no waste is generated, no secondary pollution is caused, and comprehensive utilization of raw materials and products is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of medium and trace element liquid fertilizers, in particular to a medium and trace element liquid iminodisuccinic acid chelate fertilizer and a method for preparing the liquid iminodisuccinic acid chelate fertilizer by using a temperature difference phase separation method. Background Art

[0002] Liquid fertilizer, as a new form of fertilizer, is becoming increasingly popular among manufacturers and users due to its clear appearance and easy use. Moreover, along with the process of water-fertilizer integration in my country, especially in its promotion and application in the northwest region, the output and production capacity of liquid fertilizer have developed rapidly.

[0003] In terms of the nutrients in fertilizers, liquid fertilizers circulating on the market are mainly composed of macro-elements (fertilizers with element content that meets national standards are called macro-element fertilizers, such as nitrogen-containing urea, urea ammonium nitrate solution, phosphorus and potassium-containing potassium phosphite, potassium dihydrogen phosphate, etc. in liquid form, etc.), while medium-element liquid fertilizers (fertilizers containing only calcium, magnesium and sulfur, such as calcium nitrate solution, magnesium nitrate solution, sulfonated organic acid salts, magnesium sulfate solution, etc.), trace element liquid fertilizers (liquid fertilizers containing trace elements such as copper, iron, zinc, manganese, boron, molybdenum, etc.) and organic water-soluble fertilizers have a very small market share. Among them, liquid fertilizers of large amounts of elements are mainly nitrogen-containing fertilizers, which account for more than 80% of the market share of total liquid fertilizers. Due to the influence of solubility and raw material purity, liquid fertilizers of phosphorus and potassium are only sold in small quantities in the high-end market, and are not widely accepted due to price issues. Among liquid fertilizers of medium and trace elements, zinc and boron are the most numerous, but they basically exist in the form of solid water-soluble fertilizers or as a supplement to nitrogen-containing fertilizers. Solid water-soluble fertilizers need to be dissolved and diluted during use, which also has great limitations on their application.

[0004] Fundamentally speaking, the reason why there are few liquid fertilizers containing medium and trace elements (collectively referred to as medium and trace elements) is based on the solubility and cost of the materials, as well as the restrictions on nutrients in the corresponding national standards. In order to meet the corresponding requirements, various manufacturers began to use a large amount of nitrates containing medium and trace elements. Although liquid fertilizer products have been supplemented to a certain extent, the hidden dangers of nitrates to the soil cannot be ignored.

[0005] With the continuous development of new products and new processes, tetrasodium (tetrapotassium)iminodisuccinate (minodisuccinate Na(K)-salt solution) has received attention in the field of liquid fertilizers. As a new type of chelating agent, the anions of iminodisuccinate (IDS) can form octahedral coordination geometries with metal cations in a wide pH range from weak acid to strong base, and have a strong chelating ability for calcium, magnesium, zinc and other transition metal ions. In particular, the chelating ability for metal elements such as copper, iron, and manganese exceeds that of ordinary chelating agents such as EDTA, and the effect is better when used in combination with other chelating dispersants. Moreover, as a new generation of amino carboxylic acid chelating agent, IDS has the advantages of non-toxic, pollution-free, and easy biodegradation, meeting the direction of green development.

[0006] However, there are indeed great difficulties in the actual application of IDS at present. First of all, in production, to meet solubility, all free acid structures of IDS exist in the form of salts, and the solubility of salts will have a great impact on the appearance and performance of products. Excessive inorganic salts will cause secondary salinization of the soil and harm the growth of crops. Secondly, the main body of IDS existing in the form of sodium salt or potassium salt will lead to a large amount of inorganic salt by-products in the process of chelating metal salts. How to deal with these by-products has become one of the problems restricting its development. Thirdly, as a synthetic product, the conversion rate of IDS is between 75% and 85%, and it is difficult to improve further. Unconverted raw materials such as aspartic acid and maleic acid, as well as fumaric acid produced by the reaction, exist in the system. Based on cost considerations and the limitation that it is difficult to separate iminodisuccinic acid from raw materials and products such as fumaric acid, it will affect the stability of IDS liquid products. As a chelating agent with medium chelating strength, the stability of IDS liquid products needs to be solved, especially the stability of products chelated with transition metals. Therefore, the above problems need to be solved as a whole to develop a truly practical liquid fertilizer based on iminodisuccinic acid chelate salt. Summary of the Invention

[0007] To solve the deficiencies of the above-mentioned prior art, the present invention provides a liquid iminodisuccinic acid chelate fertilizer prepared by a temperature difference phase transfer separation technology, which realizes the effective separation of salts and impurities in the liquid fertilizer of trace metal elements in IDS chelation, can not only significantly improve the stability of liquid IDS chelate fertilizer, but also improve the applicability to meet the requirements of agricultural application, and the separated crystals can be effectively reused without generating waste.

[0008] To achieve the above object, the medium and trace element liquid iminodisuccinic acid chelate fertilizer provided by the present invention is a liquid obtained by chelating iminodisuccinate with a divalent metal salt corresponding to medium and trace elements, followed by crystallization and separation by the pH temperature difference method, and is prepared by adjusting the nutrient element index; the divalent metal salt is at least one of a nitrate containing a divalent metal and a sulfate containing a divalent metal.

[0009] Based on the characteristics of iminodisuccinate chelating trace and medium elements and divalent metal nitrates and sulfates, the present invention utilizes the pH temperature difference crystallization technology to precipitate salts and impurities in IDS in the form of crystals. Most of the precipitated crystals are inorganic salts such as sodium / potassium nitrate and sodium / potassium sulfate (derived from the reaction of iminodisuccinate and nitrate or sulfate, that is, if it is the reaction of tetrasodium iminodisuccinate and nitrate, most of the crystals are inorganic salts of sodium nitrate, and the same applies hereinafter), a small part are organic salts co-crystallized with inorganic salts such as sodium / potassium maleate and sodium / potassium fumarate (derived from the reaction of fumaric acid or maleic acid impurities contained in iminodisuccinate and nitrate or sulfate), and a small amount of iminodisuccinate chelate salts, so as to purify the liquid material, which is helpful for nutrient absorption. Especially based on the removal of fumarate and maleate, the liquid fertilizer can be better absorbed through the protection barrier of the crop after foliar application and entering the crop, and then play its effect. Therefore, the obtained liquid chelate fertilizer of trace and medium elements solves the problems existing in the preparation of existing liquid fertilizers of trace and medium elements, such as high salt content, and impurities affecting stability and effect, and provides a high-quality liquid fertilizer of trace and medium elements suitable for agricultural application for the market.

[0010] The crystals obtained by crystallization can also be reused. The maleate and fumarate contained therein can continue to play a role, such as being used as a stable carbon source for the soil, and together with the remaining iminodisuccinate chelate salts, acting as a soil conditioner or biostimulant in the soil to play an effect, without generating waste and causing secondary pollution.

[0011] As a limitation to the above technical solution, the iminodisuccinate is selected from at least one of tetrasodium iminodisuccinate and tetrapotassium iminodisuccinate.

[0012] As a limitation to the above technical solution, the nitrate containing divalent metal is a nitric acid compound containing at least one divalent metal among calcium, magnesium, copper, iron, zinc, and manganese; the sulfate containing divalent metal is a sulfuric acid compound containing at least one divalent metal among magnesium, copper, iron, zinc, and manganese.

[0013] As a limitation to the above technical solution, the molar ratio of iminodisuccinate to divalent metal salt is 1:1 or 1:2.

[0014] Further limit the types of iminodisuccinate, nitrate / sulfate of divalent metal used, as well as the dosage ratio of the chelating agent to the metal salt, and optimize the quality of the liquid iminodisuccinate chelate fertilizer of trace and medium elements.

[0015] As a limitation to the above technical solution, the operating conditions of the pH temperature difference crystallization are:

[0016] Crystalline nitrate, maintain the pH at 6.0 - 10.0, control the crystallization temperature difference at 39 - 51°C;

[0017] Crystalline sulfate, maintain the pH at 5.0 - 7.5, control the crystallization temperature difference at 44 - 66°C;

[0018] Preferably, it is required to cool the crystallization to below 15°C.

[0019] As a limitation to the above technical solution, for crystalline nitrate, control the crystallization temperature to decrease from 45 - 55°C to 5 ± 1°C; for crystalline sulfate, control the crystallization temperature to decrease from 50 - 70°C to 5 ± 1°C; the crystallization time is above 12h.

[0020] In the pH temperature difference method crystallization process, the control of pH and the limitation of temperature difference will affect the crystallization effect. For pH, being too high will affect the crystallization effect of impurities in iminodisuccinate, and being too low will cause the co - crystallization of the active ingredient iminodisuccinic acid, affecting the yield of liquid fertilizer; for temperature, the temperature difference refers to the difference between the chelation temperature and the crystallization temperature. Only with an appropriate temperature difference and the front - and - back temperatures can the most stable liquid chelated fertilizer product be obtained.

[0021] As a limitation to the above technical solution, during the regulation process of nutrient element indicators, add a protective agent and a stabilizer, and reach the standard requirements of medium and trace element liquid fertilizers through concentration;

[0022] Preferably, the protective agent is selected from substances with antioxidant functions, and further preferably vitamin C and sodium dehydroacetate;

[0023] Preferably, the stabilizer includes at least one of a solubilizer and a precipitant. Further preferably, the solubilizer is an amino acid, and further preferably, the precipitant is an organic acid.

[0024] The liquid obtained after crystallization regulates the nutrient element indicators according to the standard requirements of medium and trace element liquid fertilizers. To optimize the product quality, a protective agent and a stabilizer are added during the nutrient regulation process.

[0025] Meanwhile, the present invention also provides a method for preparing the above - mentioned medium and trace element liquid iminodisuccinic acid chelated fertilizer by the temperature difference phase separation method, including the following preparation steps:

[0026] a. Prepare a chelation solution: Under stirring, add water, liquid product of iminodisuccinate, divalent metal salt (i.e., solid nitrate or / and sulfate of divalent metal), mix evenly until the solid is completely dissolved, and regulate the pH of the solution by adjusting the dosages of iminodisuccinate and divalent metal salt (adjust the dosages within a small range required by the molar ratio of iminodisuccinate to divalent metal salt based on the influence of the water addition amount in the chelation solution and impurities contained in the raw materials to regulate the pH of the solution), to obtain an iminodisuccinic acid chelated metal salt solution;

[0027] b. pH difference method crystallization: Heat the iminodisuccinic acid chelated metal salt solution to the crystallization high temperature, keep it warm for 1 h, then quickly transfer it to the crystallization low temperature environment, control the crystallization time to be no less than 12 h, separate the crystals, and collect the liquid;

[0028] c. Prepare chelated fertilizer: Weigh the liquid after crystallization precipitation quantitatively, add a protective agent and a stabilizer, stir and dissolve them, and then concentrate to obtain a medium and trace element liquid iminodisuccinic acid chelated fertilizer.

[0029] As a limitation to the above technical solution, the solid content of the iminodisuccinic acid chelated metal salt solution prepared in step a is 40 - 45%.

[0030] As a limitation to the above technical solution, during the crystal separation process in step b, keep the separation temperature not higher than 10 °C compared to the crystallization low temperature; or / and; the addition amount of the protective agent in step c is 0.1 - 0.15‰ of the mass of the liquid material, the addition amount of the solubilizer is 25 - 30% of the mass of the protective agent, and the addition amount of the precipitant is 15 - 20% of the mass of the protective agent.

[0031] The change of the separation temperature will directly affect the quality of the chelated fertilizer product. Keep the temperature during the separation operation process not higher than 10 °C compared to the crystallization low temperature to ensure the quality of the chelated fertilizer.

[0032] In summary, after the iminodisuccinate is chelated with the nitrate / sulfate of the divalent metal corresponding to the medium and trace elements in the present invention, the nitrate / sulfate therein is crystallized by the pH difference method, so that the salts and impurities in the liquid fertilizer are effectively separated. The obtained liquid is then adjusted to obtain a liquid chelated fertilizer containing medium and trace elements by controlling the nutrient indexes, significantly improving the quality, stability and application performance of the liquid IDS chelated fertilizer; at the same time, since the protective agent and solubilizer added therein have certain antioxidant and surface activity effects, the absorption and utilization performance of the liquid fertilizer is enhanced, and it can also play a certain role in scavenging free radical oxidation and reducing crop senescence. Meanwhile, the separated crystals can also be prepared into a macronutrient solid suspension fertilizer containing medium and trace elements by adding corresponding nutrients and additives, so as to achieve effective comprehensive reuse, without generating waste to cause secondary pollution, and realizing the comprehensive utilization of raw materials and products. Description of the Drawings

[0033] Figure 1 The zinc content detection result of the iminodisuccinic acid chelated zinc fertilizer in Example 1;

[0034] Figure 2 The state photos of each iminodisuccinic acid chelated fertilizer sample in Examples 1 and 3 and Comparative Examples 1, 2, 3 - 1, and 4 during the detection of concentration stability and storage stability (at room temperature) at 3 days of storage;

[0035] Figure 3 、Photos of the samples of iminodisuccinic acid chelated fertilizers of Examples 1 and 3 at 0 d and after 28 days of storage during the 28-day accelerated storage (54 °C) stability test;

[0036] Figure 4 、Photos of the samples of iminodisuccinic acid chelated fertilizers of Examples 1 and 3 at 0 d and after 28 days of storage during the low-temperature storage (-5 °C) stability test. Detailed implementation manners

[0037] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the scope of protection of the present invention.

[0038] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The raw materials or test materials used in the following embodiments are all typical products purchased on the market unless otherwise specified. For the quantitative tests in the following embodiments, three repeated experiments are set, and the results are averaged.

[0039] The solid content of the following samples was determined by the method of HG / T 3822-2020 Water treatment agent - Polyaspartic acid (salt), the pH was determined by the method of NY / T 1973 Determination of water-insoluble matter content and pH of water-soluble fertilizers, and the metal ion content was determined by the method of NY / T 1974 Determination of copper, iron, manganese, zinc, boron, and molybdenum contents in water-soluble fertilizers.

[0040] Example 1

[0041] A liquid iminodisuccinic acid chelated zinc fertilizer was prepared by the temperature difference phase separation method, and the specific operations were as follows:

[0042] In a 500 mL flask, with stirring started, 36 g of water and 381 g of liquid potassium iminodisuccinate product (the solid content of this liquid potassium iminodisuccinate product was 42.20%, the conversion rate was 85.12%, and the calculated effective content of potassium iminodisuccinate was liquid solid content × conversion rate = 35.92%) were added at one time; 94.5 g of zinc sulfate heptahydrate solid with a purity of 98% was further added; after continuing to stir until the zinc sulfate heptahydrate was completely dissolved, it was heated to boiling and maintained for 15 min, then naturally cooled to the required temperature of 60 °C and kept warm for 1 h. At this time, the pH of the system was measured to be 6.08, the solid content was 41.79%, and the ratio of chelating agent to zinc (in terms of molar ratio, the same below) was 1:1. After the holding time was completed, it was quickly transferred to a low-temperature environment of 4 °C for crystallization.

[0043] After crystallization at 4°C for 15 h, a suction filter flask with heat preservation measures was used to separate the crystals from the liquid under the conditions of 0.1 MPA and an aqueous phase filter membrane; the material temperature was 4°C at the start of suction filtration and 10°C at the end; 402.99 g of liquid was recovered and 108.51 g of crystals were obtained.

[0044] For the obtained zinc-iminodisuccinate chelate liquid, its solid content was measured to be 35.64%, pH was 6.02, and zinc content was 52.70 g / L. Take 200 g of this liquid, add 0.1 g of Vc and 0.03 g of glycine (both are industrial grade with a content of 98%), stir and dissolve, and then concentrate to 120.95 g by multi-effect evaporation (such as a three-stage steam circulation application scheme) to obtain a zinc-iminodisuccinate chelate fertilizer with a zinc content > 100 g / L. After third-party testing, the zinc content was 108.65 g / L, and the test results are as Figure 1 shown, meeting the relevant requirements of the national standard NY1428-2010 for trace element water-soluble fertilizers.

[0045] The obtained crystals were dried and ground with the required nutrients to obtain a macronutrient solid fertilizer that meets the requirements, which was effectively utilized.

[0046] Example 2

[0047] The liquid manganese-iminodisuccinate chelate fertilizer was prepared by the temperature difference phase separation method, and the specific operations were as follows:

[0048] In a 500 mL flask, start stirring and add 76.50 g of water and 443.40 g of the liquid potassium iminodisuccinate product (solid content 42.20%, conversion rate 85.12%) at one time; continue to add 68.0 g of solid manganese sulfate monohydrate with a purity of 99%; continue to stir until the manganese sulfate monohydrate is completely dissolved, then heat to boiling and keep it for 15 min, and then naturally cool to the required temperature of 55°C and keep it warm for 1 h; at this time, the pH of the system was measured to be 7.35, the solid content was 42.00%, and the ratio of chelating agent to manganese was 1:1. After the insulation time was completed, quickly transfer it to a low-temperature environment of 4°C for crystallization.

[0049] After crystallization at 4°C for 18 h, a suction filter flask with heat preservation measures was used to separate the crystals from the liquid under the conditions of 0.1 MPA and an aqueous phase filter membrane; the material temperature was 4°C at the start of suction filtration and 11°C at the end; 449.28 g of liquid was recovered and 138.62 g of crystals were obtained.

[0050] The obtained manganese-iminodisuccinic acid chelate liquid was determined to have a solid content of 35.43%, a pH of 7.57, and a manganese content of 77.21 g / L. Take 200 g of this liquid, add 0.1 g of Vc and 0.03 g of glycine (industrial grade, content 98%), stir and dissolve, and concentrate to 176.40 g to obtain a manganese-iminodisuccinic acid chelate fertilizer with a manganese content > 100 g / L. The laboratory test was 102.58 g / L, meeting the relevant requirements of the national standard NY1428-2010 for trace element water-soluble fertilizers.

[0051] After the obtained crystals are dried and ground with the required nutrients, a macronutrient solid fertilizer that meets the requirements can be obtained and effectively utilized.

[0052] Example 3

[0053] Use the temperature difference phase separation method to prepare liquid zinc-iminodisuccinic acid chelate fertilizer, and the specific operations are as follows:

[0054] In a 500 mL flask, start stirring and add 63.32 g of water and 292.18 g of liquid tetrasodium iminodisuccinate product (the solid content of this tetrasodium iminodisuccinate liquid product is 43.20%, the conversion rate is 84.62%, and the calculated effective content of tetrasodium iminodisuccinate is 35.82%) at one time; continue to add 94.5 g of solid zinc sulfate heptahydrate with a purity of 98%; continue to stir until the zinc sulfate heptahydrate is completely dissolved, then heat to boiling and maintain for 15 min, and then naturally cool to the required temperature of 63 °C and keep warm for 1 h. At this time, the pH of the system is 5.80, the solid content is 41.60%, and the ratio of chelating agent to zinc is 1:1. After the holding time is completed, quickly transfer to a 4 °C low-temperature environment for crystallization.

[0055] After crystallization at 4 °C for 15 h, use a suction filter flask with heat preservation measures to separate the crystals from the liquid under the conditions of 0.1 MPA and an aqueous phase filter membrane; the material temperature at the start of suction filtration is 4 °C and at the end is 10 °C; 334.76 g of liquid is recovered and 115.24 g of crystals are obtained.

[0056] The obtained zinc-iminodisuccinic acid chelate liquid has a solid content of 38.70%, a pH of 6.12, and a zinc content of 54.39 g / L; take 200 g of this liquid, add 0.15 g of sodium dehydroacetate and 0.02 g of citric acid monohydrate (industrial grade, content 99%), stir and dissolve, and concentrate to 114.42 g to obtain a zinc-iminodisuccinic acid chelate fertilizer with a zinc content > 100 g / L. The laboratory test was 101.85 g / L, meeting the relevant requirements of the national standard NY1428-2010 for trace element water-soluble fertilizers.

[0057] Example 4

[0058] Prepare liquid iminodisuccinic acid chelated manganese fertilizer by the temperature difference phase separation method, and the specific operation is as follows:

[0059] In a 500 mL flask, start stirring and add 89.50 g of water and 374.88 g of liquid sodium iminodisuccinate product (solid content 43.20%, conversion rate 84.62%) at one time; continue to add 68.0 g of manganese sulfate monohydrate solid with a purity of 99%; continue stirring until the manganese sulfate monohydrate is completely dissolved, then heat to boiling and maintain for 15 min, and then naturally cool to the required temperature of 58 °C and keep warm for 1 h. At this time, the pH of the system is 7.35, the solid content is 41.83%, and the ratio of chelating agent to manganese is 1:1. After the insulation time is completed, quickly transfer it to a low-temperature environment of 4 °C for crystallization.

[0060] After crystallization at 4 °C for 15 h, use a suction filter bottle with heat preservation measures to separate the crystals from the liquid under the conditions of 0.1 MPA and aqueous phase filter membrane; the material temperature at the start of suction filtration is 4 °C and at the end is 10 °C; 419.25 g of liquid and 113.13 g of crystals are recovered.

[0061] The obtained iminodisuccinic acid chelated manganese liquid has a solid content of 34.14%, pH 7.57, and manganese content of 79.05 g / L; take 200 g of this liquid, add 0.1 g of Vc and 0.03 g of glycine (industrial grade, 98%), stir and dissolve, and then concentrate to 166.24 g to obtain iminodisuccinic acid chelated manganese fertilizer with a manganese content > 100 g / L. Laboratory testing shows it is 101.67 g / L, meeting the relevant requirements of the national standard NY1428-2010 for trace element water-soluble fertilizers.

[0062] Example 5

[0063] Prepare liquid iminodisuccinic acid chelated calcium fertilizer by the temperature difference phase separation method, and the specific operation is as follows:

[0064] In a 500 mL flask, start stirring and add 49.50 g of water and 328.27 g of liquid sodium iminodisuccinate (solid content 43.20%, conversion rate 84.62%) at one time; continue to add 84.0 g of calcium nitrate tetrahydrate solid with a purity of 98%; continue stirring until the calcium nitrate tetrahydrate is completely dissolved, then heat to boiling and maintain for 15 min, and then naturally cool to the required temperature of 50 °C and keep warm for 1 h. At this time, the pH of the system is 6.35, the solid content is 43.35%, and the ratio of chelating agent to calcium is 1:1. After the insulation time is completed, quickly transfer it to a low-temperature environment of 4 °C for crystallization.

[0065] After crystallization at 4°C for 15 h, a suction filter flask with heat preservation measures was used to separate the crystals from the liquid under the conditions of 0.1 MPA and an aqueous phase filter membrane. The material temperature was 4°C at the start of suction filtration and 10°C at the end. 329.62 g of liquid and 132.15 g of crystals were recovered.

[0066] The obtained calcium iminodisuccinate chelate liquid had a solid content of 40.68%, a pH of 6.57, and a calcium content of 62.05 g / L. 200 g of this liquid was taken, 0.1 g of Vc and 0.03 g of glycine (industrial grade, 98%) were added, and after stirring and dissolving, it was concentrated to 134.28 g to obtain a calcium iminodisuccinate chelate fertilizer with a calcium content > 100 g / L. Laboratory testing showed it to be 104.28 g / L, meeting the relevant requirements of the national standard NY1428 - 2010 for trace element water-soluble fertilizers.

[0067] Example 6

[0068] A medium and trace element liquid zinc iminodisuccinate chelate fertilizer was prepared from a mixed salt of sulfate and nitrate using the temperature difference phase separation method, specifically according to the following operations:

[0069] In a 500 mL flask, with stirring started, 63.32 g of water and 292.18 g of a liquid tetrasodium iminodisuccinate product (the solid content of this liquid tetrasodium iminodisuccinate product was 43.20% and the conversion rate was 84.62%) were added all at once. 47.0 g of zinc sulfate heptahydrate solid with a purity of 98% and 49.16 g of zinc nitrate hexahydrate solid with a purity of 98.5% were added continuously. After continuing to stir until completely dissolved, it was heated to boiling and maintained for 15 min, then naturally cooled to the required temperature of 60°C and kept warm for 1 h. At this time, the pH of the system was measured to be 5.79, the solid content was 40.78%, and the ratio of chelating agent to zinc was 1:1. After the insulation time was completed, it was quickly transferred to a low-temperature environment at 4°C for crystallization.

[0070] After crystallization at 4°C for 15 h, a suction filter flask with heat preservation measures was used to separate the crystals from the liquid under the conditions of 0.1 MPA and an aqueous phase filter membrane. The material temperature was 4°C at the start of suction filtration and 10°C at the end. 334.30 g of liquid and 117.36 g of crystals were recovered.

[0071] The obtained zinc iminodisuccinate chelate liquid had a solid content of 38.04%, a pH of 6.08, and a zinc content of 49.87 g / L. 200 g of this liquid was taken, 0.15 g of sodium dehydroacetate and 0.02 g of citric acid monohydrate (industrial grade, content 99%) were added, and after stirring and dissolving, it was concentrated to 114.22 g to obtain a zinc iminodisuccinate chelate fertilizer with a zinc content > 100 g / L. Laboratory testing showed it to be 102.96 g / L, meeting the relevant requirements of the national standard NY1428 - 2010 for trace element water-soluble fertilizers.

[0072] Example 7

[0073] Using the temperature difference phase separation method, liquid zinc iminodisuccinate chelate fertilizer was prepared under different chelation ratio conditions. The materials used, chelation process, crystallization process, and separation operation were the same as those in Example 1. The only difference was the amount of zinc sulfate heptahydrate solid and water used (the amounts of other materials were the same as in Example 1), which were 189.00 g of zinc sulfate heptahydrate and 72 g of water. Before crystallization, the solid content of the system was measured to be 41.56% and the pH was 5.82. At this time, the ratio of the chelating agent to zinc was 1:2.0.

[0074] The crystallization separation operation was the same as that in Example 1; 463.64 g of liquid and 178.36 g of crystals were recovered.

[0075] The obtained liquid zinc iminodisuccinate chelate had a solid content of 38.31% and a pH of 5.76. After concentration, a zinc iminodisuccinate chelate fertilizer with a zinc content of 101.02 g / L was obtained, which met the relevant requirements of the national standard NY1428-2010 for trace element water-soluble fertilizers.

[0076] Comparative Example 1

[0077] Using the temperature difference phase separation method, liquid zinc iminodisuccinate chelate fertilizer was prepared under different chelation ratio conditions. The materials used, chelation process, crystallization process, and separation operation were the same as those in Example 1. The only difference was the amount of zinc sulfate heptahydrate solid and water used (the amounts of other materials were the same as in Example 1), which were 141.75 g and 57.45 g. At this time, the solid content of the system was 43.00% and the pH was 5.73; the ratio of the chelating agent to zinc was 1:1.5.

[0078] The crystallization separation operation was the same as that in Example 1; 390.31 g of liquid and 168.44 g of crystals were recovered. A large amount of crystals appeared during the concentration process of the recovered liquid, and a stable and uniform solution could not be formed, which did not meet the requirements of liquid fertilizer products. In addition, the recovered liquid became turbid after being stored for 3 days, indicating a high impurity content in the product and poor storage stability.

[0079] Comparative Example 2

[0080] Using the temperature difference phase separation method, liquid zinc iminodisuccinate chelate fertilizer was prepared by crystallization at room temperature. The materials used and their amounts, chelation process, and separation operation were the same as those in Example 1. The only difference was the crystallization temperature, that is, after the 60°C heat preservation time was completed, it was quickly transferred to room temperature of 25°C for crystallization for 15 h.

[0081] 455.22 g of recovered liquid and 56.28 g of crystals were obtained; a large amount of crystals appeared during the concentration process of the recovered liquid, and a stable and uniform solution could not be formed, which did not meet the requirements of liquid fertilizer products. In addition, the recovered liquid became turbid after being stored for 3 days and was not resistant to storage.

[0082] Comparative Example 3

[0083] Using the temperature difference phase separation method, liquid zinc iminodisuccinate chelate fertilizer was prepared under different crystallization conditions.

[0084] Comparative Example 3-1: The materials used, their dosages, the chelation process, and the separation operation were the same as those in Example 1; the only difference was the crystallization time, that is, after maintaining the temperature at 60 °C for 1 h, it was quickly transferred to a low-temperature environment at 4 °C for crystallization for 7.5 h.

[0085] 425.74 g of the recovered liquid and 85.76 g of crystals were obtained; during the concentration process of the recovered liquid, a large amount of crystals appeared, and a stable and uniform solution could not be formed, which did not meet the requirements of liquid fertilizer products; in addition, the recovered liquid became turbid after being stored for 3 days and was not resistant to storage.

[0086] Comparative Example 3-2: The materials used, their dosages, the chelation process, and the separation operation were the same as those in Example 1; the only difference was the crystallization temperature difference, that is, after maintaining the temperature at 60 °C for 1 h, it was quickly transferred to an environment at 40 °C for crystallization for 15 h.

[0087] The recovered liquid obtained was 426.77, and the crystals were 79.63 g; during the concentration process of the recovered liquid, a large amount of crystals appeared, and a stable and uniform solution could not be formed, which did not meet the requirements of liquid fertilizer products; in addition, the recovered liquid became turbid after being stored for 3 days and was not resistant to storage.

[0088] Comparative Example 4

[0089] Using the temperature difference phase separation method, liquid zinc iminodisuccinate chelate fertilizer was prepared under different material pH conditions. The materials used, their dosages, the chelation process, the crystallization process, and the separation operation were the same as those in Example 1. The only difference was that a step of adjusting the pH of the liquid potassium iminodisuccinate product to 4.0 with sulfuric acid was added before chelation.

[0090] The recovered liquid obtained was 482.86 g, and the crystals were 28.64 g; during the concentration process of the recovered liquid, turbidity appeared, indicating a high impurity content in the recovered liquid and it could not be made into a product meeting the standard requirements.

[0091] Performance Test 1: Concentration Stability and Storage Stability (at room temperature)

[0092] After concentrating the recovered liquids of the above Examples 1 and 3 and Comparative Examples 1 to 4, their concentration stability and appearance stability were observed to determine whether they could be formulated into a stable liquid chelate fertilizer; the specific results are shown in Table 1 below. The states of the samples of Examples 1 and 3 and Comparative Examples 1, 2, 3-1, and 4 after being stored for 3 days are as shown in the appendix Figure 2 as follows.

[0093] Table 1 Observation of Appearance Stability of Different Treatments

[0094]

[0095] As can be seen from the concentration stability in the above table, no crystallization occurred in the samples of Example 1 and Example 3 during the concentration process, which proves that under the crystallization conditions of the present invention, the impurities therein are basically completely crystallized and there is not too much residue; while crystallization occurred in the comparative examples during the concentration process, which proves that the impurity removal is incomplete and quality problems will still occur during subsequent storage.

[0096] The storage stability (room temperature) phenomenon also proves the above conclusion; on the 3rd day of room temperature storage, turbidity occurred in the comparative examples. In particular, in Comparative Example 4, due to the decrease in acidity, the solubility of impurities increased, and stability problems occurred soon after crystal separation (within 2 hours after crystal separation).

[0097] Performance test 2: Stability of 28-day rapid storage (54 °C)

[0098] Seal 100 mL of each of the samples of Example 1 and Example 3 in ampoules and store them at 54 °C for 28 days. Regularly observe their appearance stability, and measure the free zinc content and chelated zinc content at the 0th day, 7th day, 14th day, 21st day, and 28th day to determine their chelation stability performance; the specific data are shown in Table 2 below. The states of Example 1 and Example 3 at the 0th day and after 28 days of storage are as attached Figure 3 as shown.

[0099] Table 2 Observation of thermal storage stability of different treatments

[0100]

[0101] As can be seen from the data in the above table, after 28 days of thermal storage at 54 °C, the appearance stability of the samples of Example 1 and Example 3 did not show any abnormalities; at the same time, through the determination of the zinc chelation rate, it was found that during the storage period, the zinc chelation rate did not show obvious fluctuations, but only showed a small decrease with the extension of time, which also conforms to the well-known fact that chelates will slowly hydrolyze. According to the well-known fact that if there is no obvious quality change during the storage of an aqueous solution system at 54 °C for 28 days, it can be considered that the quality will not change significantly during 2 years of room temperature storage, it can be obtained that the storage period of the liquid chelated zinc fertilizer obtained by the present invention is more than 2 years.

[0102] Performance test 3: Stability of low-temperature storage (-5 °C)

[0103] Seal 100 mL of each of the samples of Example 1 and Example 3 in ampoules and store them at -5 °C for 28 days. Regularly observe their appearance stability, and measure the free zinc content and chelated zinc content at the 0th day and 28th day to determine their chelation stability performance; the specific data are shown in Table 3 below. The states of Example 1 and Example 3 at the 0th day and after 28 days of storage are as attachedFigure 4 as shown

[0104] Table 3 Observation on the low-temperature storage stability of different treatments

[0105]

[0106] From the data in the above table, it can be seen that after 28 days of low-temperature storage at -5°C, there was no abnormality in the appearance stability of the samples of Example 1 and Example 3; at the same time, through the determination of the zinc chelation rate, it was found that during the storage period, the zinc chelation rate did not show obvious fluctuations, but only showed a small amount of decrease with the extension of time; this also conforms to the well-known fact that chelates will slowly hydrolyze.

[0107] In summary, the present invention uses the temperature difference phase separation method to chelate the nitrates / sulfates of divalent metals corresponding to medium and trace elements with iminodisuccinate and then controls the crystallization conditions to effectively separate salts, impurities, etc. by precipitating them as crystals, thereby obtaining a liquid IDS chelate fertilizer for medium and trace elements, which has been significantly improved in terms of product quality, stability and applicability.

Claims

1. A medium and trace element liquid iminodisuccinic acid chelated fertilizer, characterized in that: The liquid obtained by chelating iminodisuccinate with divalent metal salts corresponding to medium and trace elements, crystallizing and separating through pH temperature difference method is prepared by regulating nutrient element indicators; the divalent metal salt is at least one of a nitrate containing a divalent metal and a sulfate containing a divalent metal.

2. According to claim 1, the liquid iminodisuccinic acid chelated fertilizer containing trace elements is characterized in that: The iminodisuccinate is selected from at least one of tetrasodium iminodisuccinate and tetrapotassium iminodisuccinate.

3. According to claim 1, the liquid iminodisuccinic acid chelated fertilizer containing trace elements is characterized in that: The nitrate containing divalent metals is selected from nitrate compounds containing at least one divalent metal of calcium, magnesium, copper, iron, zinc, and manganese; the sulfate containing divalent metals is selected from sulfate compounds containing at least one divalent metal of magnesium, copper, iron, zinc, and manganese.

4. According to claim 1, the liquid iminodisuccinic acid chelated fertilizer containing trace elements is characterized in that: The molar ratio of the iminodisuccinate to the divalent metal salt is 1:1 or 1:

2.

5. According to claim 1, the liquid iminodisuccinic acid chelated fertilizer containing trace elements is characterized in that: The operating conditions of pH temperature difference crystallization are: Crystallize nitrate, maintain pH at 6.0-10.0, and control the crystallization temperature difference at 39-51°C; Crystallize sulfate, maintain pH at 5.0-7.5, and control the crystallization temperature difference at 44-66°C; Preferably, the crystallization temperature is lowered to below 15°C.

6. According to claim 5, the liquid iminodisuccinic acid chelated fertilizer containing trace elements is characterized in that: For crystallizing nitrate, the crystallization temperature is controlled from 45-55℃ to 5±1℃; for crystallizing sulfate, the crystallization temperature is controlled from 50-70℃ to 5±1℃; the crystallization time is more than 12h.

7. The liquid iminodisuccinic acid chelated fertilizer containing trace elements according to claim 1, characterized in that: Protective agents and stabilizers are added during the nutrient element index regulation process to achieve the standard requirements of liquid fertilizers with medium and trace elements through concentration; Preferably, the protective agent is a substance with antioxidant function, and vitamin C and sodium dehydroacetate are more preferably selected; Preferably, the stabilizer includes at least one of a solubilizer and a precipitant, more preferably the solubilizer is an amino acid, and more preferably the precipitant is an organic acid.

8. A method for preparing the liquid iminodisuccinic acid chelated fertilizer containing trace elements as claimed in any one of claims 1 to 7 by using a temperature difference phase separation method, characterized in that: The method comprises the following preparation steps: a. Prepare a chelating solution: add water, iminodisuccinate, and divalent metal salt under stirring, mix evenly until the solid is completely dissolved, and adjust the pH of the solution by adjusting the amount of iminodisuccinate and divalent metal salt to obtain an iminodisuccinic acid chelated metal salt solution; b. Crystallization by pH temperature difference method: Heat the iminodisuccinic acid chelate metal salt solution to the crystallization high temperature, keep it warm for 1 hour, and then quickly transfer it to the crystallization low temperature environment. Control the crystallization time to be no less than 12 hours, separate the crystals, and collect the liquid; c. Preparation of chelated fertilizer: quantitatively weigh the liquid after the crystallization, add protective agent and stabilizer, stir to dissolve and then concentrate to obtain liquid iminodisuccinic acid chelated fertilizer containing medium and trace elements.

9. The method for preparing liquid iminodisuccinic acid chelated fertilizer containing trace elements by temperature difference phase separation method according to claim 8, characterized in that: The solid content of the iminodisuccinic acid chelated metal salt solution prepared in step a is 40-45%.

10. The method for preparing liquid iminodisuccinic acid chelated fertilizer containing trace elements by temperature difference phase separation method according to claim 8, characterized in that: In the crystal separation process of step b, the separation temperature is maintained at no more than 10°C above the crystallization low temperature; or / and; in step c, the amount of the protective agent added is 0.1 to 0.15‰ of the mass of the liquid material, the amount of the solubilizer added is 25 to 30% of the mass of the protective agent, and the amount of the precipitant added is 15 to 20% of the mass of the protective agent.

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