Water-soluble fertilizer and preparation method thereof

Abstract

The present application relates to a kind of water-soluble fertilizer and its preparation method, the water-soluble fertilizer is urea ammonium nitrate solution, including nitramine, urea, water, it is characterized in that, it further includes formaldehyde and buffer solution;The buffer solution pH is 6.0~7.5;The total nitrogen content in the urea ammonium nitrate solution is ≥28.0%, wherein, amide nitrogen is ≥14.0%, nitrate nitrogen is ≥7.0%.The present application can effectively solve the problem of urea nitramine solution storage process and reduce nutrient loss.

Description

Technical Field

[0001] This invention relates to a water-soluble fertilizer and its preparation method. Background Technology

[0002] Ammonium nitrate urea solution, or UAN solution for short, is made from urea, ammonium nitrate, and water. It combines three nitrogen sources into one, giving full play to the advantages of each type of nitrogen. Nitrate nitrogen is a fast-acting nitrogen that can be directly absorbed by plants; ammonium nitrogen is a medium-acting nitrogen, a small portion of which can be absorbed by plants, while the rest is adsorbed by soil colloids, thus prolonging the fertilizer effect; amide nitrogen needs to be hydrolyzed into ammonium nitrogen and nitrate nitrogen before it can be absorbed by plants, so it is a slow-acting nitrogen. Therefore, ammonium nitrate urea solution can both quickly replenish nitrogen and achieve a long-lasting nitrogen replenishment effect.

[0003] The production of ammonium nitrate urea solution began in the United States in the 1970s and is now widely used. In 2012, global production of ammonium nitrate urea solution exceeded 20 million tons. In my country, a chemical industry standard was established in 2016 (standard number HG / T 4848-2016), and an agricultural industry standard was officially adopted in 2015 (standard number NY / T 2670-2015). The latest standard is NY / T2670-2020, which clearly defines the total nitrogen content, amide nitrogen content, nitrate nitrogen content, and ammonium nitrogen content, indicating a relatively high overall nitrogen content. The production process is not complex, as it can be done in a stirred tank. However, the product suffers from packaging gas expansion with prolonged storage, especially severe in summer. Currently, the gas expansion problem of ammonium nitrate urea solution is solved by using a breathable but waterproof bottle cap, allowing the generated gas to enter the air through the cap. However, this method suffers from a decrease in nutrient content with prolonged storage.

[0004] The patent name is urea-ammonium nitrate water-soluble fertilizer and its preparation method. The patent number is CN 105565909A. Its product characteristics are: (1) stable, extremely low corrosiveness, non-flammable, colorless, liquid under normal pressure, good safety performance, easy to transport and store; (2) universally accepted standards, consistent quality, and the nitrate content of plants after application is far lower than the national safety standards; (3) compound fertilizer in nitrogen fertilizer, with three forms of nitrogen element, with both fast-acting and long-acting effects, greatly expanding the absorption and utilization rate of nitrogen element by plants and improving crop quality; (4) contains plant growth factors that promote rapid growth, and nutrients can quickly reach the root, stem and leaf cell tissues of plants, providing plants with rapid and long-lasting nutritional supplementation; (5) 100% water-soluble, without any impurities, with a utilization rate of over 90%, especially suitable for sprinkler irrigation, drip irrigation and foliar fertilization, saving water, saving time, environmental protection and high efficiency. (6) Extremely high stability; can be mixed with other chemical pesticides and fertilizers; highly compatible with other fertilizers and chemicals; can be used with mixable plant chemical protection adjuvants; one application, multiple uses; saves time, effort, and money. It is evident that it does not solve the problems of gas expansion during storage of ammonium nitrate urea solution and nutrient reduction during storage.

[0005] There are currently no reports on how to solve the problems of gas expansion and nutrient loss during storage of ammonium nitrate urea solution. Summary of the Invention

[0006] This invention provides a water-soluble fertilizer and its preparation method, which solves the technical problems of 1) gas expansion during storage of ammonium nitrate urea solution; and 2) nutrient reduction during storage of ammonium nitrate urea solution.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A water-soluble fertilizer is an ammonium nitrate urea solution, comprising ammonium nitrate, urea, and water, and further comprising formaldehyde and a pH buffer; the pH buffer has a pH of 6.0 to 7.5 and is capable of buffering the pH of the ammonium nitrate urea solution; the total nitrogen content in the urea ammonium nitrate solution is ≥28.0%, of which amide nitrogen is ≥14.0% and nitrate nitrogen is ≥7.0%, and the molar ratio of ammonium nitrate to formaldehyde is 5 to 7:1.

[0009] The pH buffer is one or both of a pH buffer solution and the raw materials for preparing the pH buffer solution.

[0010] The buffer solutions are: a barbiturate buffer solution with pH 7.4, whose corresponding raw materials are sodium barbiturate and 2 mol / L hydrochloric acid; a citrate buffer solution with pH 6.2, whose corresponding raw materials are citric acid and 50% sodium hydroxide; an acetate-sodium acetate buffer solution with pH 6.0, whose corresponding raw materials are acetic acid and sodium acetate; and a phosphate buffer solution with pH 6.5–7.0, whose corresponding raw materials are potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, and sodium chloride.

[0011] The preparation method of water-soluble fertilizer involves dissolving ammonium nitrate, urea, and a pH buffer in water to form a solution with a buffered pH, then introducing formaldehyde to obtain an ammonium nitrate urea solution water-soluble fertilizer.

[0012] The pH buffer is one or both of pH buffer solution and raw materials for preparing pH buffer solution, and the dissolution temperature is 20-50°C.

[0013] The method for preparing water-soluble fertilizer involves dissolving ammonium nitrate and urea in a pH buffer to form a solution with a buffered pH, then introducing formaldehyde to obtain an ammonium nitrate urea solution water-soluble fertilizer.

[0014] The pH buffer is a pH buffer solution, and the dissolution temperature is 20–50°C.

[0015] The solution formed has a buffered pH range of 6.0 to 7.5.

[0016] The preparation methods and raw materials for each buffer solution are as follows:

[0017] The pH 7.4 barbital buffer solution is prepared by dissolving 4.42 g of sodium barbital in water and diluting it to 400 ml. The pH is then adjusted to 7.4 with 2 mol / L hydrochloric acid solution and filtered.

[0018] Citrate buffer solution with pH 6.2: Take a 2.1% citric acid aqueous solution and adjust the pH to 6.2 with 50% sodium hydroxide solution.

[0019] Acetic acid-sodium acetate buffer solution with pH 6.0: Dissolve 54.6g of sodium acetate in 20ml of 1mol / L acetic acid solution, then dilute with water to 500ml.

[0020] Acetic acid-ammonium acetate buffer solution with pH 6.0: Dissolve 100g of ammonium acetate in 300ml of water, add 7ml of glacial acetic acid, and shake well.

[0021] Phosphate buffer solution 6.5: Take 0.68g of potassium dihydrogen phosphate, add 15.2ml of 0.1mol / L sodium hydroxide solution, and dilute with water to 100ml.

[0022] Phosphate buffer 6.6: Dissolve 1.74g of sodium dihydrogen phosphate, 2.7g of disodium hydrogen phosphate and 1.7g of sodium chloride in water to make 400ml.

[0023] Phosphate buffer 6.8: Take 250 ml of 0.2 mol / L potassium dihydrogen phosphate solution, add 118 ml of 0.2 mol / L sodium hydroxide solution, dilute with water to 1000 ml, and shake well.

[0024] Phosphate buffer (pH 7.0): Take 0.68 g of potassium dihydrogen phosphate, add 29.1 ml of 0.1 mol / L sodium hydroxide solution, and dilute with water to 100 ml.

[0025] Phosphate buffer (pH 7.2): Take 50 ml of 0.2 mol / L potassium dihydrogen phosphate solution and 35 ml of 0.2 mol / L sodium hydroxide solution, add freshly boiled and cooled water to dilute to 200 ml, shake well, and the solution is ready.

[0026] Phosphate buffer (pH 7.3): Dissolve 1.9734 g of disodium hydrogen phosphate and 0.2245 g of potassium dihydrogen phosphate in water to make 1000 ml, and adjust the pH to 7.3.

[0027] Phosphate buffer (pH 7.4): Take 1.36 g of potassium dihydrogen phosphate, add 79 ml of 0.1 mol / L sodium hydroxide solution, and dilute with water to 200 ml.

[0028] In this application, the raw materials corresponding to the preparation of the buffer solution can be weighed and added to the ammonium nitrate urea solution according to the addition ratio of each substance in the buffer solution and the water content in the ammonium nitrate urea solution.

[0029] The present invention has the following beneficial technical effects:

[0030] 1. This application can effectively solve the problems of gas expansion and nutrient reduction during the storage of ammonium nitrate urea water-soluble fertilizer.

[0031] 2. The chemical equation present in this application is:

[0032] 1) 4NH4 + +6HCHO=[(CH2)6N4]H + +3H + +6H2O,

[0033] 2) NH4 + +OH - --H2O+NH3,

[0034] 3)CO(NH2)2+H2O=CO2↑+2NH3↑

[0035] This method uses the addition of formaldehyde to remove some of the free NH4+. + Fix and maintain the acidity of the system to prevent NH4 + +OH - --H2O+NH3, This application prevents 4NH4+ by adding a pH buffer. + +6HCHO=[(CH2)6N4]H + +3H + The pH level caused by adding 6H2O is too low because the hydrolysis of urea is affected by pH. The lower the pH in an acidic environment or the higher the pH in an alkaline environment, the faster the reaction of CO(NH2)2 + H2O = CO2↑ + 2NH3↑ will occur, resulting in bloating and loss of nutrients.

[0036] 3. This application limits the amount of formaldehyde added. If the amount of formaldehyde added is too small, fewer ammonium ions will be fixed, which will not prevent the problems of gas expansion and nutrient loss. If too much formaldehyde is added, too many ammonium ions will be fixed, resulting in too many hydrogen ions, which may exceed the buffer range of the buffer solution and cause the pH to be too low, thereby accelerating the hydrolysis of urea. Similarly, this will not solve the problems of gas expansion and nutrient loss during storage.

[0037] 4. This application selects to form a solution with a buffered pH range of 6.0 to 7.5 because urea will react with formaldehyde under alkaline (pH above 8) and acidic (pH below 3.0) conditions. Detailed Implementation

[0038] The invention will be further illustrated below with specific examples.

[0039] Example 1

[0040] A water-soluble fertilizer is an ammonium nitrate urea solution, which is prepared by stirring and mixing ammonium nitrate, urea, formaldehyde, and a pH buffer. The pH buffer is a citrate buffer solution with a pH of 6.2. The total nitrogen content of the urea ammonium nitrate solution is ≥28.0%, of which amide nitrogen is ≥14.0% and nitrate nitrogen is ≥7.0%. The specific ratio is 42 parts ammonium nitrate, 31 parts urea, and 27 parts citrate buffer solution with a pH of 6.2. The molar ratio of ammonium nitrate to formaldehyde is 5:1. The theoretical values ​​are: amide nitrogen 14.3%, nitrate nitrogen 7.1%, ammonium nitrogen 7.1%, and total nitrogen 28.5%.

[0041] Ammonium nitrate and urea are dissolved in a pH buffer, and formaldehyde is then introduced to obtain a water-soluble fertilizer solution of ammonium nitrate and urea.

[0042] The melting temperature is 30°C.

[0043] Example 2

[0044] A water-soluble fertilizer is an ammonium nitrate urea solution, which is prepared by stirring and dissolving ammonium nitrate, urea, water, formaldehyde and pH buffer, wherein the pH buffer is a barbital buffer solution with pH 7.4;

[0045] The specific ratio is 42 parts ammonium nitrate, 31 parts urea, and 27 parts barbital buffer solution at pH 7.4; the molar ratio of ammonium nitrate to formaldehyde is 6:1; the theoretical values ​​are: 14.3% amide nitrogen, 7.1% nitrate nitrogen, 7.1% ammonium nitrogen, and 28.9% total nitrogen, of which the added barbital buffer solution at pH 7.4 contains 0.4% organic nitrogen.

[0046] The method for preparing water-soluble fertilizer involves dissolving ammonium nitrate and urea in a pH buffer, then introducing formaldehyde to obtain an ammonium nitrate urea solution water-soluble fertilizer.

[0047] The melting temperature is 30°C.

[0048] Example 3

[0049] A water-soluble fertilizer is an ammonium nitrate urea solution, which is prepared by stirring and dissolving ammonium nitrate, urea, formaldehyde and a pH buffer; the pH buffer is a phosphate buffer solution with a pH of 6.8.

[0050] The specific ratio is 42 parts ammonium nitrate, 31 parts urea, and 27 parts phosphate buffer solution with pH 6.8. The molar ratio of ammonium nitrate to formaldehyde is 7:1. The theoretical values ​​are: amide nitrogen 14.3%, nitrate nitrogen 7.1%, ammonium nitrogen 7.1%, and total nitrogen 28.5%.

[0051] The preparation method of water-soluble fertilizer involves dissolving ammonium nitrate, urea, and a pH buffer in water to form a solution with a buffered pH, then introducing formaldehyde to obtain an ammonium nitrate urea solution water-soluble fertilizer.

[0052] The melting temperature is 40°C.

[0053] Example 4

[0054] A water-soluble fertilizer is an ammonium nitrate urea solution, comprising ammonium nitrate, urea, water, formaldehyde, and a pH buffer; wherein the molar ratio of ammonium nitrate to formaldehyde is 6:1.

[0055] The pH buffer is a raw material for preparing phosphate buffer 6.6, specifically sodium dihydrogen phosphate, disodium hydrogen phosphate, and sodium chloride.

[0056] The specific ratio is 42 parts ammonium nitrate, 31 parts urea, 0.12 parts sodium dihydrogen phosphate, 0.18 parts disodium hydrogen phosphate, 0.11 parts sodium chloride, and 26.59 parts water. The molar ratio of ammonium nitrate to formaldehyde is 7:1. The theoretical values ​​are: 14.3% amide nitrogen, 7.1% nitrate nitrogen, 7.1% ammonium nitrogen, and 28.5% total nitrogen.

[0057] The preparation method of water-soluble fertilizer involves dissolving ammonium nitrate, urea, and a pH buffer in water to form a solution with a buffered pH, then introducing formaldehyde to obtain an ammonium nitrate urea solution water-soluble fertilizer.

[0058] The melting temperature is 30°C.

[0059] The following experimental data further illustrates the beneficial effects of the present invention:

[0060] Experiment 1

[0061] 1.1 Test site: Gansu Provincial Engineering Technology Research Center for Smart Agriculture.

[0062] 1.2 Experimental testing: Check whether the polyethylene bottle is swollen, measure the circumference (mm) of the polyethylene bottle used in the experiment; test the total nitrogen (%) and nitrate nitrogen (%) (including initial and final values).

[0063] 1.3 Test materials: Ammonium nitrate urea solution prepared by CK (except that formaldehyde and pH buffer were not added, the preparation method was the same as in Example 1), ammonium nitrate urea solution prepared by Comparative 1 (except that formaldehyde was added but pH buffer was not added, the preparation method was the same as in Example 1), ammonium nitrate urea solution prepared by Comparative 2 (except that pH buffer was added but formaldehyde was not added, the preparation method was the same as in Example 1), ammonium nitrate urea solution prepared by Comparative 3 (except that the molar ratio of ammonium nitrate to formaldehyde was 10:1, the preparation method was the same as in Example 1), ammonium nitrate urea solution prepared by Comparative 4 (except that the molar ratio of ammonium nitrate to formaldehyde was 2:3, the preparation method was the same as in Example 1), and ammonium nitrate urea solutions prepared by Examples 1 to 4.

[0064] 1.4 Experimental Implementation: Ammonium nitrate urea solution was prepared from freshly produced CK (except for the absence of formaldehyde and pH buffer, all other preparation methods were the same as in Example 1); ammonium nitrate urea solution was prepared from Control 1 (except for the addition of formaldehyde but no pH buffer, all other preparation methods were the same as in Example 1); ammonium nitrate urea solution was prepared from Control 2 (except for the addition of pH buffer but no formaldehyde, all other preparation methods were the same as in Example 1); and ammonium nitrate urea solution was prepared from Control 3 (except that the molar ratio of ammonium nitrate to formaldehyde was 1:1). The total nitrogen and nitrate nitrogen of the ammonium nitrate urea solution prepared in Examples 1 to 4 were measured. The solutions were prepared in Example 1 (except that the molar ratio of ammonium nitrate to formaldehyde was 2:3, otherwise the total nitrogen and nitrate nitrogen were measured). The solutions were placed in 1L polyethylene bottles, capped, placed in parallel, and placed in an oven at 35°C for 14 days. The diameter of the polyethylene bottles was measured with a tape measure, and the total nitrogen and nitrate nitrogen were measured.

[0065] 1.5 Test methods: Nitrogen content was tested according to GB / T 8572-2010, with total nitrogen tested according to 6.2.5 and the result obtained as N1. Amide nitrogen and ammonium nitrogen were tested according to 6.2.3 and the result obtained as N2. Nitrate nitrogen content was equal to N1-N2.

[0066] Use a measuring tape to measure the circumference of a polyethylene bottle, and measure at the middle of the bottle.

[0067] 1L of polyethylene has a diameter of 81mm and a circumference of 254.3mm.

[0068] Except for the different treatments, the procedures were the same in this experiment.

[0069] 2 Results and Analysis

[0070] Total nitrogen content (initial and final values), nitrate nitrogen content (initial and final values), and polyethylene bottle circumference are shown in Table 1.

[0071] Table 1

[0072]

[0073] Note: The absolute value of the test error in the same laboratory shall not exceed 0.3%.

[0074] As can be seen from Table 1, CK and Comparisons 1 to 4 all showed a decrease in total nitrogen content and bloating, while Examples 1 to 4 of this application were able to maintain nutrients well and slow down or avoid bloating.

[0075] The data comparison between Comparison 1, Comparison 2 and Example 1 shows that the combination of formaldehyde and pH buffer can better solve the problems of nutrient loss and gas expansion during the storage of ammonium nitrate urea solution.

[0076] Compared to sample 3, which contains less formaldehyde and relatively fewer fixed ammonium ions, some nutrients are lost and bloating occurs.

[0077] In contrast, the formaldehyde added in Example 4 reacts with ammonium ions, producing a large number of hydrogen ions. However, the buffer solution in Example 1, formed by a weak acid and a strong base, has a relatively small buffering capacity and cannot buffer the hydrogen ions produced. This leads to a decrease in the pH of the ammonium nitrate urea solution, which promotes the hydrolysis of urea, resulting in an increase in ammonia and carbon dioxide. Consequently, some nutrients are lost, and gas is produced.

Claims

1. An aqueous fertilizer, which is a solution of nitroammonium urea, comprising nitroammonium, urea and water, characterized in that, The formaldehyde and the pH buffer agent; the pH buffer agent has a pH of 6.2-7.4, and the pH buffer agent can buffer the pH of the ammonium nitrate urea solution; the total nitrogen content in the ammonium nitrate urea solution is ≥28.0%, wherein the amide nitrogen is ≥14.0%, and the nitrate nitrogen is ≥7.0%, and the molar ratio of the ammonium nitrate and the formaldehyde is 5-7:

1.

2. The water-soluble fertilizer of claim 1, wherein the water-soluble fertilizer is a granular water-soluble fertilizer. The pH buffer agent is one or both of a pH buffer solution and raw materials for preparing the pH buffer solution.

3. The water-soluble fertilizer according to claim 1 or 2, wherein The buffer solution is a barbital buffer solution with a pH of 7.4, and the corresponding raw materials are sodium barbital and 2 mol / L hydrochloric acid, a citric acid buffer solution with a pH of 6.2, and the corresponding raw materials are citric acid and 50% sodium hydroxide, an acetic acid-sodium acetate buffer solution with a pH of 6.0, and the corresponding raw materials are acetic acid and sodium acetate, and a phosphate buffer solution with a pH of 6.5-7.0, and the corresponding raw materials are potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide and sodium chloride.

4. The method for producing a water-soluble fertilizer according to any one of claims 1 to 3, characterized by, The ammonium nitrate, the urea and the pH buffer agent are dissolved in water to form a solution with a buffered pH, and formaldehyde is introduced to obtain the ammonium nitrate urea solution water-soluble fertilizer. The pH buffer agent is one or both of a pH buffer solution and raw materials for preparing the pH buffer solution; and the dissolving temperature is 20-50°C.

5. The method of producing the water-soluble fertilizer according to any one of claims 1 to 3, characterized by, The ammonium nitrate and the urea are dissolved in the pH buffer agent to form a solution with a buffered pH, and formaldehyde is introduced to obtain the ammonium nitrate urea solution water-soluble fertilizer. The pH buffer agent is a pH buffer solution; and the dissolving temperature is 20-50°C.

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