A water-soluble calcium-magnesium aspartate chelate fertilizer compatible with phosphate fertilizer and a preparation method thereof

Abstract

The application discloses a kind of ascorbic acid chelated calcium magnesium water-soluble fertilizer compatible with phosphate fertilizer and a preparation method thereof.The method comprises adding EDTA accelerator to ascorbic acid calcium magnesium solution to promote reaction until the reaction solution is clear, drying the reaction solution to obtain ascorbic acid chelated calcium magnesium water-soluble fertilizer compatible with phosphate fertilizer.The chelated calcium magnesium prepared by the method has a solubility of greater than or equal to 60 g, and a total calcium magnesium content of greater than or equal to 10%, which meets the technical index requirements of the industry standard NY2266-2012 for water-soluble fertilizer solid products.Meanwhile, due to the synergistic chelation of ascorbic acid and EDTA, a mixed solution obtained by dissolving 1 g of the ascorbic acid chelated calcium magnesium water-soluble fertilizer compatible with phosphate fertilizer, 5 g of potassium dihydrogen phosphate and 100 ml of water can remain clear for more than 8 hours, greatly improving the compatibility with phosphate fertilizer.

Description

Technical Field

[0001] This invention relates to the field of chemical industry, and more specifically, to an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer and its preparation method. Background Technology

[0002] L-Aspartic acid is used in plant nutrition for two reasons. First, as the smallest molecule that makes up proteins, it is easily absorbed and utilized by crops, making it green and environmentally friendly. Second, aspartic acid is a natural chelating agent. Compared with inorganic fertilizers, amino acid chelates of minor elements are not easily fixed in the soil and do not reduce fertilizer efficiency.

[0003] However, L-aspartic acid has a weak chelating ability, and calcium and magnesium aspartate have relatively poor solubility with phosphorus. Even trace amounts of calcium or magnesium in calcium or magnesium aspartate in the system cannot be miscibly soluble with potassium dihydrogen phosphate, and will quickly precipitate after dissolving in water. Furthermore, according to the industry standard NY2266-2012, the technical specifications for water-soluble fertilizer solid products containing medium-quantity elements require a content of ≥10% (referring to calcium content, magnesium content, or the sum of calcium and magnesium content; sulfur is not included in the medium-quantity element content). However, due to the presence of phosphate in water-soluble fertilizer compounding and application, simply mixing calcium aspartate with other chelated magnesium cannot meet the requirement of a total calcium and magnesium content ≥10% while ensuring miscibility.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer and its preparation method, thereby improving the compatibility of the medium-quantity elements calcium and magnesium with phosphate.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer, comprising adding EDTA to a solution containing L-aspartic acid calcium magnesium and reacting until the reaction solution is clear, drying the reaction solution, and obtaining an aspartic acid calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0008] In an optional embodiment, the reaction temperature is 40-60°C.

[0009] In an optional embodiment, the drying is carried out by spray drying, with the spray inlet temperature being 185-195°C and the outlet temperature being 90-100°C.

[0010] In an optional embodiment, the solution containing L-aspartic acid calcium magnesium is obtained by adding a calcium source to an aqueous solution of L-aspartic acid and reacting it initially until it becomes clear, and then adding a magnesium source and reacting it again until it becomes clear.

[0011] In an optional embodiment, the calcium source is at least one of calcium carbonate and calcium oxide.

[0012] In an optional embodiment, the intermediate reaction temperature is 50-70°C.

[0013] In an optional embodiment, the initial reaction temperature is 85-95°C.

[0014] In an optional embodiment, the magnesium source is at least one of magnesium oxide and magnesium carbonate.

[0015] In an optional embodiment, the mass ratio of L-aspartic acid, calcium source, magnesium source and EDTA is 50:9-11:7-9:16-18, and the mass ratio of L-aspartic acid to water in the L-aspartic acid aqueous solution is 50:200-300.

[0016] Secondly, the present invention provides an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer, prepared by any of the aforementioned embodiments, with a total calcium and magnesium content of 10wt%-15wt%, and the mixed solution obtained by dissolving 1g of the aspartic acid chelated calcium-magnesium water-soluble fertilizer and 5g of potassium dihydrogen phosphate in 100ml of water can remain clear for more than 8 hours.

[0017] The present invention has the following beneficial effects:

[0018] The chelated calcium and magnesium prepared by this method has a total calcium and magnesium content of ≥10%, which meets the technical requirements for water-soluble solid products of macronutrient fertilizers in the industry standard NY2266-2012. At the same time, due to the synergistic chelation effect with EDTA, the mixed solution obtained by dissolving 1g of the aspartic acid chelated calcium and magnesium water-soluble fertilizer and 5g of potassium dihydrogen phosphate in 100ml of water can remain clear for more than 8 hours, which greatly improves the compatibility of chelated calcium and magnesium with phosphate fertilizer. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] In a first aspect, the present invention provides a method for preparing an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer, comprising adding EDTA to a calcium magnesium solution containing L-aspartic acid and reacting until the reaction solution is clear, drying the reaction solution, and obtaining an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0021] In this embodiment, the elements calcium and magnesium have a synergistic effect on aspartic acid. The molar ratio of calcium and magnesium to aspartic acid far exceeds the theoretical 1:2 molar ratio, resulting in a calcium and magnesium content of ≥15% in aspartic acid calcium magnesium, which has a weak chelating strength with aspartic acid. However, due to its weak chelating strength, even a trace amount mixed with phosphate will cause turbidity. The calcium content in EDTA calcium sodium can reach up to 9.5 wt%, and the magnesium content in EDTA magnesium sodium can reach up to 5.8 wt%. Theoretically, a large amount of EDTA needs to be added to the L-aspartic acid calcium magnesium solution to achieve a calcium and magnesium content ≥10% while being miscible with phosphate.

[0022] However, experiments have shown that using aspartic acid and EDTA to synergistically chelate calcium and magnesium ions significantly enhances the chelating ability for magnesium and calcium. When the two carboxyl groups of aspartic acid react completely with the calcium salt to near neutrality, further addition of magnesium salt can lead to a significantly alkaline reaction. At this point, adding an appropriate amount of EDTA allows the nitrogen and oxygen atoms of both chelating agents to form covalent and coordinate bonds with the calcium and magnesium ions, resulting in a multi-coordinate chelate of calcium and magnesium ions with aspartic acid as the main component and EDTA as the auxiliary component. Therefore, with a calcium and magnesium content ≥10%, adding only a small amount of EDTA is sufficient to keep the sample and phosphate aqueous solution stable (i.e., the solution remains clear and transparent, without precipitation, turbidity, or crystallization) for more than 8 hours, and only a small amount of crystals are formed thereafter.

[0023] In an optional embodiment, the reaction temperature is 40-60°C.

[0024] In an optional embodiment, the drying is carried out by spray drying, with the spray inlet temperature being 185-195°C and the outlet temperature being 90-100°C.

[0025] The temperature during spray drying affects the water content of the product, which in turn affects the calcium and magnesium content. Generally, the higher the temperature, the more thoroughly the product is dried.

[0026] In an optional embodiment, the solution containing L-aspartic acid calcium magnesium is obtained by adding a calcium source to an aqueous solution of L-aspartic acid and reacting it initially until it becomes clear, and then adding a magnesium source and reacting it again until it becomes clear.

[0027] In order to ensure that the calcium and magnesium sources are evenly dispersed in the solution and to improve the reaction rate, the calcium and magnesium sources can be added to the solution in batches while stirring.

[0028] In an optional embodiment, the calcium source is at least one of calcium carbonate and calcium oxide.

[0029] In an optional embodiment, the intermediate reaction temperature is 50-70°C.

[0030] In an optional embodiment, the initial reaction temperature is 85-95°C.

[0031] In an optional embodiment, the magnesium source is at least one of magnesium oxide and magnesium carbonate.

[0032] In an optional embodiment, the mass ratio of L-aspartic acid, calcium source, magnesium source and EDTA is 50:9-11:7-9:16-18, and the mass ratio of L-aspartic acid to water in the L-aspartic acid aqueous solution is 50:200-300.

[0033] In this application, the temperature of the reaction is gradually reduced by adding calcium source, magnesium source and EDTA to the aqueous solution of L-aspartic acid, which can achieve uninterrupted reaction during the cooling process of the reaction solution and is beneficial to improving the reaction efficiency.

[0034] Secondly, the present invention provides an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer, prepared by any of the aforementioned embodiments, with a total calcium and magnesium content of 10wt%-15wt%, and the mixed solution obtained by dissolving 1g of the aspartic acid chelated calcium-magnesium water-soluble fertilizer and 5g of potassium dihydrogen phosphate in 100ml of water can remain stable for more than 8 hours.

[0035] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0036] Example 1

[0037] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0038] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0039] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0040] (3) Lower the temperature to 45℃, add 17 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190℃ and the outlet temperature is 95℃, to obtain an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0041] The calcium and magnesium content of the aspartic acid chelated calcium and magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0042]

[0043] Example 2

[0044] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0045] (1) Add 50 parts of L-aspartic acid to 250 parts of water and stir until homogeneous. Heat to 95°C and slowly add 12 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0046] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 7.2 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0047] (3) Lower the temperature to 45°C, add 18 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190°C and the outlet temperature is 95°C to obtain aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with a phosphate fertilizer.

[0048] The calcium and magnesium content of the aspartic acid chelated water-soluble fertilizer that is compatible with phosphate fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0049]

[0050] Example 3

[0051] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0052] (1) Add 50 parts of L-aspartic acid to 300 parts of water and stir until homogeneous. Heat to 90°C and slowly add 5.6 parts of calcium oxide in batches. Stir for 30 minutes and react until clear.

[0053] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 16.8 parts of magnesium carbonate in batches, stirring for 30 minutes until the reaction is clear.

[0054] (3) Lower the temperature to 45℃, add 17 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190℃ and the outlet temperature is 95℃, to obtain an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0055] The calcium and magnesium content of the aspartic acid chelated calcium and magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0056]

[0057]

[0058] Example 4

[0059] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0060] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 9.5 parts of calcium carbonate in batches. Stir for 30 minutes and react until clear.

[0061] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 17.2 parts of magnesium carbonate in batches, stirring for 30 minutes until the reaction is clear.

[0062] (3) Lower the temperature to 45℃, add 17 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190℃ and the outlet temperature is 95℃, to obtain an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0063] The calcium and magnesium content of the aspartic acid chelated calcium and magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0064]

[0065] Example 5

[0066] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0067] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 85°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0068] (2) Lower the temperature to 50°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0069] (3) Lower the temperature to 40℃, add 16.5 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 195℃ and the outlet temperature is 90℃, to obtain an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0070] The calcium and magnesium content of the aspartic acid chelated calcium and magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0071]

[0072] Example 6

[0073] This embodiment provides a method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizers. The specific steps are as follows:

[0074] (1) Add 50 parts of L-aspartic acid to 300 parts of water and stir until homogeneous. Heat to 95°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0075] (2) Lower the temperature to 60°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0076] (3) Lower the temperature to 50℃, add 16.0 parts of EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190℃ and the outlet temperature is 95℃, to obtain an aspartic acid chelated calcium magnesium water-soluble fertilizer that is compatible with phosphate fertilizer.

[0077] The calcium and magnesium content of the aspartic acid chelated calcium and magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0078]

[0079]

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a water-soluble fertilizer containing medium-quantity elements. The specific steps are as follows:

[0082] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 1.0 part of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0083] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 1.0 part of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0084] (3) Lower the temperature to 45℃, stir for 30 minutes until clear, cool down and spray, spray inlet temperature is 190℃, outlet temperature is 95℃, calcium magnesium water-soluble fertilizer.

[0085] The calcium and magnesium content in the calcium-magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0086]

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a water-soluble fertilizer containing medium-quantity elements. The specific steps are as follows:

[0089] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0090] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0091] (3) Lower the temperature to 45℃, add 17 parts of disodium EDTA, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190℃ and the outlet temperature is 95℃ to obtain calcium magnesium water-soluble fertilizer.

[0092] The calcium and magnesium content in the calcium-magnesium water-soluble fertilizer obtained in this embodiment, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0093]

[0094] Comparative Example 3

[0095] This comparative example provides a method for preparing a water-soluble fertilizer containing medium-quantity elements. The specific steps are as follows:

[0096] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0097] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0098] (3) Lower the temperature to 45°C and add 17 parts of ammonium citrate. The system is unstable and gradually becomes turbid as the stirring time increases.

[0099] Comparative Example 4

[0100] This comparative example provides a method for preparing a water-soluble fertilizer containing medium-quantity elements. The specific steps are as follows:

[0101] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0102] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0103] (3) Lower the temperature to 45°C, add 17 parts of mixed sugar alcohol, stir for 30 minutes until clear, cool down and spray, the spray inlet temperature is 190°C and the outlet temperature is 95°C to obtain calcium magnesium water-soluble fertilizer.

[0104] The calcium and magnesium content in the calcium-magnesium water-soluble fertilizer obtained in this comparative example, as well as the test results of its compatibility with potassium dihydrogen phosphate, are shown in the table below.

[0105]

[0106] Comparative Example 5

[0107] This comparative example provides a method for preparing a water-soluble fertilizer containing medium-quantity elements. The specific steps are as follows:

[0108] (1) Add 50 parts of L-aspartic acid to 200 parts of water and stir until homogeneous. Heat to 90°C and slowly add 10 parts of calcium carbonate in batches. Stir for about 30 minutes until the reaction is clear.

[0109] (2) Lower the temperature to 70°C, keep stirring, and continue to slowly add 8 parts of magnesium oxide in batches, stirring for 30 minutes until the reaction is clear.

[0110] (3) Cool down and spray, with the spray inlet temperature at 190℃ and the outlet temperature at 95℃.

[0111] (4) Mix 17 parts of EDTA evenly into the calcium magnesium water-soluble fertilizer solid after spraying to obtain calcium magnesium water-soluble fertilizer.

[0112] The calcium and magnesium water-soluble fertilizer obtained in this comparative example had EDTA-assisted chelating agent added in the later stage through solid blending. The calcium and magnesium content and the results of the compatibility test with potassium dihydrogen phosphate are shown in the table below.

[0113]

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer, characterized in that, The process involves adding EDTA to a solution containing L-aspartic acid calcium magnesium and reacting until the reaction solution becomes clear. The reaction temperature is 40-60℃. The reaction solution is then dried to obtain a water-soluble aspartic acid chelated calcium magnesium fertilizer that is compatible with phosphate fertilizer. The total calcium and magnesium content of the water-soluble aspartic acid chelated calcium magnesium fertilizer is 10wt%-15wt%. The solution containing L-aspartic acid calcium magnesium is obtained by adding a calcium source to an aqueous solution of L-aspartic acid and reacting it initially until it becomes clear, with the initial reaction temperature being 85-95℃, and then adding a magnesium source and reacting it again until it becomes clear, with the secondary reaction temperature being 50-70℃. The mass ratio of L-aspartic acid, calcium source, magnesium source and EDTA is 50:5.5-12:7-17.2:16-18, and the mass ratio of L-aspartic acid to water in the L-aspartic acid aqueous solution is 50:200-300.

2. The method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer according to claim 1, characterized in that, The drying process employs spray drying, with an inlet temperature of 185-195℃ and an outlet temperature of 90-105℃.

3. The method for preparing an aspartic acid chelated calcium-magnesium water-soluble fertilizer that is compatible with phosphate fertilizer according to claim 1, characterized in that, The calcium source is at least one of calcium carbonate and calcium oxide.

4. The method for preparing a water-soluble fertilizer of calcium magnesium aspartate that is compatible with phosphate fertilizer according to claim 1, characterized in that, The magnesium source is at least one of magnesium oxide and magnesium carbonate.

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