Slow-release liquid fertilizer and preparation method thereof

Abstract

The invention discloses a slow-release liquid fertilizer and a preparation method thereof, and belongs to the technical field of fertilizers. The preparation method comprises the following steps: S1, mixing and stirring urea and a formaldehyde solution for reaction to prepare monomethylol urea and dimethylol urea; s2, pyrophosphoric acid is added into a reaction product in the S1, stirring reaction is continued, and a urea formaldehyde pyrophosphate monoester compound is prepared; and S3, firstly adding a potassium source into the reaction product in the S2 for reaction, and then adding a stabilizer for reaction again to obtain the product. The urea, the formaldehyde, the pyrophosphoric acid and the potassium source are used as preparation raw materials for preparing the slow-release liquid fertilizer, and the preparation method is simple, mild in condition, high in preparation efficiency and suitable for large-scale industrial production; the prepared slow-release liquid fertilizer has an excellent nitrogen fertilizer and phosphate fertilizer slow-release effect, has comprehensive and balanced nutritional value, can effectively promote the growth and yield increase of crops, has long-acting storage stability, and solves the problems that a traditional fertilizer is low in chemical fertilizer utilization rate and easily causes many environmental damages during use.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizers, and specifically relates to a slow-release liquid fertilizer and a preparation method thereof. Background Art

[0002] Chemical fertilizers are a kind of high-efficiency nutrients. Applying chemical fertilizers can not only directly increase the nutrient content in agricultural products, but also increase the content of organic matter and major elements such as nitrogen, phosphorus, and potassium in the soil, and are one of the material bases for agricultural production.

[0003] There are a series of prominent problems that need to be concerned in crop fertilization. In agricultural production practice, in most cases, a large amount of solid fertilizers are still relied on. This extensive fertilization method directly leads to soil nutrient imbalance, making it difficult for crops to efficiently absorb the nutrients required for growth, and the fertilizer utilization rate continues to decline. This not only causes a large amount of waste of fertilizer resources, but also leads to many serious environmental problems, such as soil compaction and hardening, resulting in the decline of soil fertility and water eutrophication, disturbing the ecological balance of water areas.

[0004] The use of slow-release fertilizers (SRF) is considered a promising strategy to improve the utilization rate of chemical fertilizers. Slow-release fertilizers are fertilizers that can slowly release nutrients, which can meet the nutrient requirements of crops by controlling the release rate of nutrients, while reducing nutrient loss and waste, and improving the utilization rate of nutrients. How to prepare a slow-release fertilizer with excellent slow-release effect, high utilization rate, and capable of effectively promoting crop growth and increasing production is one of the effective ways to solve the problems of low utilization rate of chemical fertilizers and easy occurrence of many serious environmental damages. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a slow-release liquid fertilizer and a preparation method thereof to solve the problems of low utilization rate and easy occurrence of many serious environmental damages when using existing traditional fertilizers.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: The first object of the present invention is to provide a preparation method of a slow-release liquid fertilizer, including the following steps: S1: Mix and stir urea and formaldehyde solution to react to prepare monohydroxymethylurea and dihydroxymethylurea; S2: Add pyrophosphoric acid to the reaction product of S1, and continue to stir and react to prepare a pyrophosphoric acid urea formaldehyde monoester compound; S3: First add a potassium source to the reaction product of S2 to react, and then add a stabilizer to react again to obtain it.

[0007] The beneficial effect of the present invention is that the present invention uses urea, formaldehyde, pyrophosphoric acid, and a potassium source as raw materials for preparing a slow-release liquid fertilizer. The preparation method is simple, the conditions are mild, the preparation efficiency is high, and it is suitable for large-scale industrial production.

[0008] Further, the mass concentration of the formaldehyde solution in S1 is 35 - 40%, and the mass ratio of urea to formaldehyde is 1:(0.8 - 1.5).

[0009] Further, the temperature of the stirring reaction in S1 is 60 - 90 °C, and the time is 10 - 30 min.

[0010] Further, the mass ratio of monohydroxymethylurea to dihydroxymethylurea is (2 - 4):1.

[0011] Further, the pyrophosphoric acid in S2 is a solid powder, and the mass ratio of urea to pyrophosphoric acid is 1:(0.3 - 0.7).

[0012] Further, the temperature of the stirring reaction in S2 is 0 - 10 °C, and the reaction time is 30 - 150 min.

[0013] Further, the urea pyrophosphate formaldehyde monoester compound in S2 includes: and ; They are respectively prepared by reacting monohydroxymethylurea and dihydroxymethylurea with pyrophosphoric acid.

[0014] Further, the potassium source in S3 is potassium hydroxide or potassium carbonate, and the mass ratio of urea to the potassium source is 1:(0.2 - 0.5).

[0015] Further, the temperature of the reaction in S3 is room temperature, and the time is 10 - 60 min.

[0016] Further, the stabilizer in S3 is a mixed stabilizer prepared by mixing tween and cocamidopropyl betaine in a mass ratio of (0.8 - 1.2):(0.8 - 1.2), and the addition amount is 0.2% - 1% of the mass of the slow-release liquid fertilizer.

[0017] Further, the temperature of the re-reaction is room temperature, and the time is 30 - 60 min.

[0018] The second object of the present invention is to provide a slow-release liquid fertilizer prepared by the above preparation method.

[0019] The beneficial effects of the present invention are as follows: The slow-release liquid fertilizer prepared by the present invention has excellent slow-release effects on nitrogen fertilizer and phosphate fertilizer, has comprehensive and balanced nutritional value, can effectively promote the growth and yield increase of crops, has long-term storage stability, and solves the problems of low utilization rate of chemical fertilizers and easy cause of many environmental damages during the use of traditional fertilizers.

[0020] The present invention has the following beneficial effects: By adding pyrophosphoric acid, the present invention reacts with monohydroxymethylurea and dihydroxymethylurea prepared from urea and formaldehyde as raw materials to generate pyrophosphoric acid urea formaldehyde monoester compounds, so that the prepared fertilizer has a large amount of slow-release nitrogen and slow-release phosphorus, and has excellent slow-release effects on nitrogen fertilizer and phosphorus fertilizer. By adding a potassium source, a slow-release liquid fertilizer with comprehensive and balanced nutrition is prepared. The fertilizer has a low crystallization temperature, remains a clear solution at ≤ -16 °C, and can be stored for more than 30 days. It has an excellent effect of promoting crop growth and increasing yield, and has broad application prospects and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the main reaction formula for the preparation of the fertilizer of the present invention. Among them, (a) is the formation of monohydroxymethylurea from urea and formaldehyde, (b) is the formation of dihydroxymethylurea from urea and formaldehyde, and (c) and (d) are the reactions of monohydroxymethylurea and dihydroxymethylurea with pyrophosphoric acid to form pyrophosphoric acid urea formaldehyde monoester compounds respectively. DETAILED DESCRIPTION OF THE INVENTION

[0022] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. Those not specified in the examples are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0023] Example 1: A slow-release liquid fertilizer, the preparation raw materials include the following components in parts by weight: 100 parts of urea, 100 parts of formaldehyde, 30 parts of pyrophosphoric acid, 20 parts of potassium hydroxide, and 1 part of compound stabilizer; The compound stabilizer is prepared by mixing tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0024] A preparation method of a slow-release liquid fertilizer, comprising the following steps: S1: Urea and formaldehyde solution (mass concentration 37%) are sequentially added into a stirring reactor at a temperature of 80 °C and reacted for 30 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1. The reaction formula is as Figure 1 shown in (a) and (b); S2: After the reaction in S1 is completed, the reaction temperature is lowered to 5 °C, and solid pyrophosphoric acid (purity > 98%) is slowly added and reacted for 120 min, and the temperature is maintained below 10 °C throughout the process to obtain pyrophosphoric acid urea formaldehyde monoester compounds. The reaction formula is as Figure 1 shown in (c) and (d); S3: After the reaction in S2 is completed, potassium hydroxide is added and the reaction continues at room temperature for 20 min, and then the compound stabilizer is added and the reaction continues for 30 min to obtain the slow-release liquid fertilizer.

[0025] Example 2: A slow-release liquid fertilizer, the preparation raw materials of which include the following components in parts by weight: 100 parts of urea, 80 parts of formaldehyde, 50 parts of pyrophosphoric acid, 30 parts of potassium hydroxide, 1 part of compound stabilizer and 40 parts of water; The compound stabilizer is prepared by mixing Tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0026] A preparation method of a slow-release liquid fertilizer, which includes the following steps: S1: Put urea and formaldehyde solution (mass concentration 37%) into a stirring reactor in sequence, at a temperature of 70 °C, react for 20 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1, and the reaction formula is as Figure 1 shown in (a) and (b) in; S2: When the reaction in S1 ends, lower the reaction temperature to 5 °C, slowly add solid pyrophosphoric acid (purity > 98%), react for 80 min, and keep the temperature below 10 °C throughout the process to obtain a pyrophosphate urea formaldehyde monoester compound, and the reaction formula is as Figure 1 shown in (c) and (d) in; S3: When the reaction in S2 ends, add water and then add potassium hydroxide and continue to react at room temperature for 30 min, and then add the compound stabilizer and continue to react for 30 min to obtain the slow-release liquid fertilizer.

[0027] Example 3: A slow-release liquid fertilizer, the preparation raw materials of which include the following components in parts by weight: 100 parts of urea, 120 parts of formaldehyde, 30 parts of pyrophosphoric acid, 40 parts of potassium hydroxide and 1 part of compound stabilizer; The compound stabilizer is prepared by mixing Tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0028] A preparation method of a slow-release liquid fertilizer, which includes the following steps: S1: Put urea and formaldehyde solution (mass concentration 37%) into a stirring reactor in sequence, at a temperature of 90 °C, react for 30 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1, and the reaction formula is as Figure 1 shown in (a) and (b) in; S2: When the reaction in S1 ends, lower the reaction temperature to 5 °C, slowly add solid pyrophosphoric acid (purity > 98%), react for 50 min, and keep the temperature below 10 °C throughout the process to obtain a pyrophosphate urea formaldehyde monoester compound, and the reaction formula is as Figure 1 shown in (c) and (d) in; S3: After the reaction in S2 is completed, add potassium hydroxide and continue the reaction at room temperature for 40 min, and then add the composite stabilizer and continue the reaction for 40 min to obtain the slow-release liquid fertilizer.

[0029] Example 4: A slow-release liquid fertilizer, the preparation raw materials of which include the following components in parts by weight: 100 parts of urea, 150 parts of formaldehyde, 50 parts of pyrophosphoric acid, 20 parts of potassium hydroxide, and 1 part of composite stabilizer; The composite stabilizer is prepared by mixing tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0030] A preparation method of a slow-release liquid fertilizer, comprising the following steps: S1: Put urea and formaldehyde solution (mass concentration 37%) into a stirring reactor in sequence, at a temperature of 90 °C, react for 20 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1, and the reaction formula is as Figure 1 shown in (a) and (b) in; S2: After the reaction in S1 is completed, lower the reaction temperature to 5 °C, slowly add solid pyrophosphoric acid (purity > 98%), react for 150 min, and maintain the temperature below 10 °C throughout the process to obtain a pyrophosphoric acid urea formaldehyde monoester compound, and the reaction formula is as Figure 1 shown in (c) and (d) in; S3: After the reaction in S2 is completed, add potassium hydroxide and continue the reaction at room temperature for 30 min, and then add the composite stabilizer and continue the reaction for 30 min to obtain the slow-release liquid fertilizer.

[0031] Example 5: A slow-release liquid fertilizer, the preparation raw materials of which include the following components in parts by weight: 100 parts of urea, 100 parts of formaldehyde, 70 parts of pyrophosphoric acid, 50 parts of potassium hydroxide, 2 parts of composite stabilizer, and 70 parts of water; The composite stabilizer is prepared by mixing tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0032] A preparation method of a slow-release liquid fertilizer, comprising the following steps: S1: Put urea and formaldehyde solution (mass concentration 37%) into a stirring reactor in sequence, at a temperature of 80 °C, react for 30 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1, and the reaction formula is as Figure 1 shown in (a) and (b) in; S2: After the reaction in S1 is completed, lower the reaction temperature to 5 °C, slowly add solid pyrophosphoric acid (purity > 98%), react for 90 min, and maintain the temperature below 10 °C throughout the process to obtain a pyrophosphoric acid urea formaldehyde monoester compound, and the reaction formula is as Figure 1 shown in (c) and (d) in; S3: After the reaction in S2 ends, add potassium hydroxide and continue the reaction at room temperature for 60 min, then add the composite stabilizer and continue the reaction for 60 min to obtain the slow-release liquid fertilizer.

[0033] Comparative Example 1: A slow-release liquid fertilizer, the preparation raw materials of which include the following components in parts by weight: 100 parts of urea, 120 parts of formaldehyde, 30 parts of phosphoric acid, 40 parts of potassium hydroxide, and 1 part of composite stabilizer; The composite stabilizer is prepared by mixing Tween and cocamidopropyl betaine in a mass ratio of 1:1.

[0034] A preparation method of a slow-release liquid fertilizer, comprising the following steps: S1: Sequentially put urea and formaldehyde solution (mass concentration 37%) into a stirring reactor, at a temperature of 80 °C, react for 30 min to obtain monohydroxymethylurea and dihydroxymethylurea with a mass ratio of about 3:1; S2: After the reaction in S1 ends, lower the reaction temperature to 5 °C, slowly add phosphoric acid, react for 90 min, and maintain the temperature below 10 °C throughout the process to obtain a transparent liquid; S3: After the reaction in S2 ends, add potassium hydroxide and continue the reaction at room temperature for 60 min. The reactant gradually becomes turbid from a clear liquid, and finally a large amount of precipitated crystals appear, and a clear liquid cannot be obtained.

[0035] Test Example 1: Nutrient Index and Stability Characterization Perform nutrient index and stability characterization on the slow-release liquid fertilizers prepared in Examples 1-5. The stability characterization is carried out by storing the slow-release liquid fertilizer at -16 °C for storage stability characterization.

[0036] The results of the nutrient index characterization of the slow-release liquid fertilizers prepared in Examples 1-5 are shown in Table 1, and the percentages in the table are all mass percentages. The results of the stability characterization are shown in Table 2: Table 1 Nutrient Indexes of the Slow-Release Liquid Fertilizers Prepared in Examples 1-5

[0037] Table 2 Stability of the Slow-Release Liquid Fertilizers Prepared in Examples 1-5

[0038] According to the data in Table 1 and Table 2, it can be seen that the slow-release liquid fertilizer prepared in the embodiments of the present invention has a high content of slow-release nitrogen and slow-release phosphorus and excellent storage stability. The proportion of slow-release nitrogen in the total nitrogen reaches more than 87%, and the slow-release liquid fertilizer prepared in Example 1 has the highest proportion of slow-release nitrogen, which is 90.56%; the proportion of slow-release phosphorus in the total phosphorus reaches more than 67%, and the slow-release liquid fertilizers prepared in Example 2 and Example 3 have the highest proportion of slow-release phosphorus, which is 75.41%; the slow-release liquid fertilizer prepared in the present invention has a low crystallization temperature and can be stored for a long time at -16°C and remain clear for more than 30 days. Among them, the slow-release liquid fertilizer prepared in Example 3 has the best storage stability.

[0039] Test Example 2: Fertilizer Efficiency Test The slow-release liquid fertilizer (T1) prepared in Example 3 and a commercially available non-slow-release liquid fertilizer with a similar nutrient content (T2) were selected for the test. The potting method was adopted, and the tomato seedlings at the seedling stage were selected for foliar spraying for the fertilizer efficiency test. The nutrient indexes of T1 and T2 are shown in Table 3.

[0040] Table 3 Nutrient Indexes of T1 and T2

[0041] A total of 3 treatments were set in the test, namely blank control (CK), T1 fertilization group, and T2 fertilization group.

[0042] Test method: 24 tomato seedlings with uniform growth were selected, 8 for each of the 3 treatments. CK was used as a blank control, and the same amount of clear water was sprayed on the leaves; T1 and T2 were diluted 500 times and then sprayed, 50 mL each time. Other test conditions were the same, and two conventional index detections were carried out after 1 week and 2 weeks. The results are shown in Table 4.

[0043] Table 4 Results of Fertilizer Efficiency Test

[0044] It can be seen from Table 4 that the growth conditions of the T1 and T2 experimental groups were basically the same in the first week, and the indexes of the T1 experimental group were slightly lower, indicating that the quick-acting nutrients of the present invention can basically meet the needs of crops; after the second week, the growth rate of each index of T1 was significantly greater than that of T2, indicating that the slow-release liquid fertilizer prepared in the present invention effectively improves the fertilizer utilization rate and plays a role in promoting crop growth and increasing production.

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a slow-release liquid fertilizer, characterized in that: The following steps are involved: S1: mixing urea and formaldehyde solution and stirring to react to prepare monomethylol urea and dimethylol urea; S2: adding pyrophosphoric acid to the reaction product of S1, and continuing to stir the reaction to prepare a pyrophosphate urea-formaldehyde monoester compound; S3: First, a potassium source is added to the reaction product of S2 to react, and then a stabilizer is added to react again to obtain S3.

2. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The mass concentration of the formaldehyde solution in S1 is 35-40%, and the mass ratio of urea to formaldehyde is 1:(0.8-1.5).

3. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The stirring reaction in S1 is performed at a temperature of 60-90° C. for 10-30 min.

4. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The pyrophosphoric acid in S2 is solid powder, and the mass ratio of urea to pyrophosphoric acid is 1:(0.3-0.7).

5. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The stirring reaction temperature in S2 is 0-10°C, and the reaction time is 30-150 min.

6. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The potassium source in S3 is potassium hydroxide or potassium carbonate, and the mass ratio of urea to the potassium source is 1:(0.2-0.5).

7. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The reaction temperature in S3 is room temperature and the reaction time is 10-60 min.

8. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The stabilizer in S3 is a mixed stabilizer prepared by mixing Tween and cocamidopropyl betaine in a mass ratio of (0.8-1.2): (0.8-1.2), and the added amount is 0.2%-1% of the mass of the slow-release liquid fertilizer.

9. The method for preparing a slow-release liquid fertilizer according to claim 1, characterized in that: The temperature of the second reaction is room temperature, and the time is 30-60 min.

10. A slow-release liquid fertilizer, characterized in that: The method is prepared by the method according to any one of claims 1 to 9.

Images