A process for preparing value-added urea and its application

Abstract

The invention discloses a preparation process and application of value-added urea, belonging to the technical field of fertilizers. A bio-based alcohol solution, diphenylmethane diisocyanate and a thermosensitive macromolecular monomer are prepared into a coating liquid, and then the coating liquid is sprayed onto the surface of a fertilizer core material for coating, and dried to complete the preparation process of the value-added urea. The phase transition temperature of the thermosensitive macromolecular monomer corresponds to the environmental temperature of slow plant growth, and the thermosensitive macromolecular monomer is applied to the coating liquid. By regulating the hydrophilic groups, the coating exhibits hydrophilicity at an environmental temperature below 38°C, and the value-added urea can release nitrogen slowly and long-term to meet the growth requirements of plants. When the environmental temperature reaches 38°C, the thermosensitive groups on the surface of the coating curl up to close the gaps on the coating, so that the coating polymer exhibits hydrophobicity, which helps to reduce the loss of nitrogen.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizers, and in particular relates to a preparation process of value-added urea and application thereof. Background Art

[0002] Value-added fertilizer refers to a fertilizer value-added product produced by scientifically combining biologically active synergistic carriers such as humic acid, alginate, and amino acids with bulk fertilizers such as urea, ammonium phosphate, and compound fertilizers. Compared with conventional fertilizers, value-added fertilizers have the potential to increase yield and reduce fat for grain crops.

[0003] Value-added urea is a type of value-added fertilizer, an upgraded product of urea, and a long-term nitrogen fertilizer product. Urea is the main type of chemical nitrogen fertilizer in my country, accounting for about 65% of nitrogen fertilizer consumption. In addition to being absorbed by crops and retained in the soil, most nitrogen is lost through ammonia volatilization, runoff and leaching, so it is necessary to upgrade conventional urea to value-added urea with higher effective nutrients.

[0004] The Chinese patent with announcement number CN103694038B discloses a value-added humic acid type urea and its preparation method, which slows down the decomposition and volatilization of urea by humic acid. The existing method of coating fertilizer particles with resin can also play a slow release role of urea, but the release process of urea is still uncontrollable. In a high temperature environment, the transpiration of plants will increase, and the high temperature and water loss will affect the photosynthesis of plants, slowing down the growth of plants. The utilization ability of plant roots for nutrients such as nitrogen, phosphorus, and potassium will also decrease. The nitrogen accumulated in the soil will further affect the normal growth and metabolism of plants, and will also cause the loss of nitrogen through ammonia volatilization and other methods. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation process of value-added urea, by coating a fertilizer core material containing urea with a coating liquid, thereby reducing the nitrogen release rate in a high temperature environment, and solving the problem that plants cannot utilize nitrogen in a high temperature environment, resulting in low nitrogen utilization rate; the second purpose is to provide an application of value-added urea to reduce the nitrogen release rate in a high temperature environment.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A process for preparing value-added urea comprises the following steps:

[0008] Step 1: Evenly mix urea powder, biochar, humic acid, hydroxyapatite powder and diatomaceous earth in a mass ratio of 16-20:3-4:3-4:2-4:3-6, and prepare a granular fertilizer core material by a granulator;

[0009] Step 2: adding the bio-based alcohol solution, diphenylmethane diisocyanate and the temperature-sensitive macromonomer into the reaction kettle in a mass ratio of 12:13-15:3.5-4, stirring at 60-65° C. for 80-100 minutes to obtain a coating solution;

[0010] Step 3: Transfer the fertilizer core material to the coating machine, spray the coating liquid onto the surface of the fertilizer core material at 40-60r / min and 60-80°C. After the coating liquid is sprayed, the coating machine continues to work for 8-12 minutes. Take out the particles and dry them at 60-80°C for 8-12 hours to obtain the value-added urea with coating, thus completing the preparation process of value-added urea.

[0011] The value-added urea prepared by the above preparation process reduces the nitrogen release rate at an ambient temperature of ≥38°C and can be applied to crop planting in high temperature environments.

[0012] Furthermore, the mass ratio of the fertilizer core material to the coating liquid is 80-100:1.

[0013] Further, the bio-based alcohol solution is prepared by the following steps:

[0014] The straw is dried at 60-80°C for 2-3 days, then crushed and ground through a 40-60 mesh sieve to obtain straw powder; glycerol and the straw powder are added into a stirring kettle, stirred at 400-600r / min and 60-90°C for 10-20min, then concentrated sulfuric acid is added into the stirring kettle, stirred at 150-160°C for 50-60min, and cooled naturally to obtain a bio-based alcohol solution.

[0015] Furthermore, the mass ratio of the straw powder, glycerol and concentrated sulfuric acid is 10:100:1.5-2.

[0016] Furthermore, the temperature-sensitive macromonomer is prepared by the following steps:

[0017] Step 1: Add glycidyl ether, tetrahydrofuran and 25% ammonia water into a hydrothermal reactor, keep the temperature at 95-100° C. for 60-80 minutes, and remove tetrahydrofuran as a solvent by rotary evaporation to obtain an alcoholamine monomer; the reaction process is as follows:

[0018]

[0019] Step 2: Add anhydrous methanol and alcohol amine monomer to the reactor at 0°C, stir and mix, add methyl acrylate under nitrogen protection, heat to 25-30°C and stir to react for 18-24h, the double bonds on methyl acrylate and the amino groups on the alcohol amine monomer undergo polymerization, rotary evaporate, and then extract the remaining liquid with anhydrous ether for 2-3 times to obtain a dendrimer liquid; the reaction process is as follows:

[0020]

[0021] Step 3: Add the dendrimer liquid and a 4% sodium hydroxide aqueous solution into a reactor, stir and react for 20-24 hours under nitrogen protection and 30-35° C., hydrolyze the ester group at the end of the dendrimer liquid molecule into -COONa under alkaline conditions, add 36% hydrochloric acid into the reactor after the reaction, stir for 6-8 hours at 20-25° C. and 200-300 r / min, -COONa is converted into -COOH, then dialyze with deionized water for desalination, and freeze-dry the product to obtain a macromonomer powder;

[0022] Step 4: Add deionized water, N-isopropylacrylamide and macromolecular monomer powder into a reactor, stir at 15-25° C. for 10-30 minutes, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent into the reactor, continue stirring for 20-24 hours, and the carboxyl group at the end of the macromolecular monomer powder condenses with the amino group on N-isopropylacrylamide to form an amide group. Deionized water is used for dialyzing and desalting, and the product is freeze-dried to obtain a thermosensitive macromolecular monomer.

[0023] Furthermore, in step 1, the usage ratio of glycidyl ether, tetrahydrofuran and aqueous ammonia is 7-8 g: 20-25 mL: 20-25 mL.

[0024] Furthermore, in step 2, the usage ratio of anhydrous methanol, amine monomer and methyl acrylate is 25-30 mL: 14-15 g: 110-120 g.

[0025] Furthermore, in step 3, the usage ratio of the dendrimer liquid, the sodium hydroxide aqueous solution and the hydrochloric acid is 10 g: 40-50 mL: 80-100 mL.

[0026] Furthermore, in step 4, the usage ratio of deionized water, N-isopropylacrylamide, macromonomer powder and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 10 mL: 1.5 g: 1-1.2 g: 1.5-2 mg.

[0027] Beneficial effects of the present invention:

[0028] The preparation process of the value-added urea of ​​the present invention first prepares a fertilizer core material through urea powder, and then coats it with a coating liquid to further improve the slow-release effect of nitrogen in the value-added urea. The coating can reduce the nitrogen release rate at 38° C., and reduce the release of nitrogen under the condition that the ambient temperature is too high and not suitable for plant growth, which helps to reduce nitrogen loss and avoid damage to plants.

[0029] Urea powder in the fertilizer core material serves as a nitrogen source to provide nitrogen for plant growth; biochar, humic acid, hydroxyapatite powder and diatomaceous earth serve as carriers and fillers, which help to reduce production costs and reduce the volatilization and leaching of urea. Humic acid can serve as a urease inhibitor to reduce the decomposition of urea by urease in the soil.

[0030] The coating liquid of the present invention is a polyurethane type polymer, and the use of a bio-based alcohol solution is conducive to the resource utilization of straw; the hydroxyl group in the bio-based alcohol solution and the hydroxyl group on the temperature-sensitive macromolecular monomer react with the isocyanate group in diphenylmethane diisocyanate, and the coating has good wear resistance and barrier properties after curing; glycidyl ether reacts with ammonia water to prepare an alcohol amine monomer containing amino groups and hydroxyl groups, and then a highly branched dendritic polymer liquid is prepared through a polymerization reaction of methyl acrylate and amino groups, and then hydrolyzed and converted into carboxyl groups, and a temperature-sensitive group N-isopropyl acrylamide is grafted to prepare a temperature-sensitive macromolecular monomer with a phase transition temperature of 38°C, which helps to increase the cross-linking degree of subsequent coating and increase the barrier effect of the coating material.

[0031] The phase transition temperature of the thermosensitive macromolecular monomer corresponds to the ambient temperature where plants grow slowly. It is applied to the coating liquid. By regulating the hydrophilic groups, at an ambient temperature below 38°C, the coating exhibits hydrophilicity, and the value-added urea can release nitrogen slowly and for a long time to meet the growth needs of plants. When the ambient temperature reaches 38°C, the thermosensitive groups on the surface of the coating curl up and close the gaps on the coating, making the coating polymer hydrophobic, which helps to reduce the loss of nitrogen. DETAILED DESCRIPTION

[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Example 1

[0034] A process for preparing value-added urea comprises the following steps:

[0035] Step 1: Evenly mix urea powder, biochar, humic acid, hydroxyapatite powder and diatomaceous earth in a mass ratio of 16:3:3:2:3, and prepare a granular fertilizer core material using a granulator.

[0036] Step 2: 1: Dry the straw at 6°C for 2 days, then crush and grind it through a 40-mesh sieve to obtain straw powder; add 100 kg of glycerol and 10 kg of straw powder into a stirring tank, stir at 400 r / min and 60°C for 10 minutes, then add concentrated sulfuric acid into the stirring tank, stir at 150°C for 50 minutes, and cool naturally to obtain a bio-based alcohol solution.

[0037] 2: Add 70 kg of glycidyl ether, 200 L of tetrahydrofuran and 200 L of 25% ammonia water into a hydrothermal reactor, keep the reaction at 95° C. for 60 min, and remove the tetrahydrofuran as a solvent by rotary evaporation to obtain an alcoholamine monomer.

[0038] 3: Add 25L of anhydrous methanol and 14kg of olamine monomer to the reactor at 0°C, stir and mix, then add 110kg of methyl acrylate under nitrogen protection, heat to 25°C and stir to react for 18h, the double bonds on the methyl acrylate and the amino groups on the olamine monomer undergo polymerization, rotary evaporate, and then extract the remaining liquid twice with anhydrous ether to obtain a dendrimer liquid.

[0039] 4: Add 10 kg of dendrimer liquid and 40 L of 4% sodium hydroxide aqueous solution into a reactor, stir and react for 20 hours under nitrogen protection and 30°C. Under alkaline conditions, the ester group at the end of the dendrimer liquid molecule is hydrolyzed into -COONa. After the reaction, add 80 L of 36% hydrochloric acid into the reactor, stir at 20°C and 200 r / min for 6 hours, -COONa is converted into -COOH, and then dialyze with deionized water to remove salt. The product is freeze-dried to obtain a macromolecular monomer powder.

[0040] 5: Add 50L of deionized water, 7.5kg of N-isopropylacrylamide and 5kg of macromonomer powder into the reactor, stir at 15°C for 10min, then add 7.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent into the reactor, continue stirring for 20h, the carboxyl group at the end of the macromonomer powder molecule condenses with the amino group on N-isopropylacrylamide to form an amide group, dialyze with deionized water to desalt, and freeze-dry the product to obtain a temperature-sensitive macromonomer.

[0041] 6: Add 12 kg of bio-based alcohol solution, 13 kg of diphenylmethane diisocyanate and 3.5 kg of temperature-sensitive macromolecular monomer into the reactor, stir at 60° C. for 80 min to obtain the coating solution.

[0042] Step 3: Transfer 80 kg of fertilizer core material to the coating machine, spray 1 kg of coating liquid onto the surface of the fertilizer core material at 40 r / min and 60°C. After the coating liquid is sprayed, the coating machine continues to work for 8 minutes. Take out the particles and dry them at 60°C for 8 hours to obtain value-added urea, thereby completing the preparation process of value-added urea.

[0043] Example 2

[0044] A process for preparing value-added urea comprises the following steps:

[0045] Step 1: Evenly mix urea powder, biochar, humic acid, hydroxyapatite powder and diatomaceous earth in a mass ratio of 18:3.5:3.5:3:4.5, and prepare a granular fertilizer core material using a granulator.

[0046] Step 2: 1: Dry the straw at 70°C for 2.5 days, then crush and grind it through a 50-mesh sieve to obtain straw powder; add 100kg of glycerol and 10kg of straw powder into a stirring tank, stir at 500r / min and 75°C for 15min, then add concentrated sulfuric acid into the stirring tank, stir at 155°C for 55min, and cool naturally to obtain a bio-based alcohol solution.

[0047] 2: Add 75 kg of glycidyl ether, 225 L of tetrahydrofuran and 225 L of 25% ammonia water into a hydrothermal reactor, keep the reaction at 98° C. for 70 min, and remove the tetrahydrofuran as a solvent by rotary evaporation to obtain an alcoholamine monomer.

[0048] 3: Add 28L of anhydrous methanol and 14.5kg of olamine monomer to the reactor at 0°C, stir and mix, then add 115kg of methyl acrylate under nitrogen protection, heat to 28°C and stir to react for 21h, the double bonds on the methyl acrylate and the amino groups on the olamine monomer undergo polymerization, rotary evaporate, and then extract the remaining liquid twice with anhydrous ether to obtain a dendrimer liquid.

[0049] 4: Add 10kg of dendrimer liquid and 45L of 4% sodium hydroxide aqueous solution into a reactor, stir and react for 22h under nitrogen protection and 30-35°C. Under alkaline conditions, the ester group at the end of the dendrimer liquid molecule is hydrolyzed into -COONa. After the reaction, add 90L of 36% hydrochloric acid into the reactor, stir for 7h at 22°C and 250r / min, -COONa is converted into -COOH, then dialyze with deionized water for desalination, and freeze-dry the product to obtain a macromolecular monomer powder.

[0050] 5: Add 50L of deionized water, 7.5kg of N-isopropylacrylamide and 5.5kg of macromonomer powder into the reactor, stir at 20°C for 20min, then add 8.5g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent into the reactor, continue stirring for 22h, the carboxyl group at the end of the macromonomer powder molecule condenses with the amino group on N-isopropylacrylamide to form an amide group, dialyze with deionized water to desalt, and freeze-dry the product to obtain a temperature-sensitive macromonomer.

[0051] 6: Add 12 kg of bio-based alcohol solution, 14 kg of diphenylmethane diisocyanate and 3.8 kg of temperature-sensitive macromolecular monomer into the reactor, stir at 62° C. for 90 minutes to obtain a coating solution.

[0052] Step 3: Transfer 90 kg of fertilizer core material to the coating machine, spray 1 kg of coating liquid onto the surface of the fertilizer core material at 50 r / min and 70°C. After the coating liquid is sprayed, the coating machine continues to work for 10 minutes. Take out the particles and dry them at 70°C for 10 hours to obtain value-added urea, thereby completing the preparation process of value-added urea.

[0053] Example 3

[0054] A process for preparing value-added urea comprises the following steps:

[0055] Step 1: Evenly mix urea powder, biochar, humic acid, hydroxyapatite powder and diatomaceous earth in a mass ratio of 10:2:2:2:3, and prepare a granular fertilizer core material using a granulator.

[0056] Step 2: 1: Dry the straw at 80°C for 3 days, then crush and grind it through a 60-mesh sieve to obtain straw powder; add 100 kg of glycerol and 10 kg of straw powder into a stirring tank, stir at 600 r / min and 90°C for 20 minutes, then add concentrated sulfuric acid into the stirring tank, stir at 160°C for 60 minutes, and cool naturally to obtain a bio-based alcohol solution.

[0057] 2: 80 kg of glycidyl ether, 250 L of tetrahydrofuran and 250 L of 25% ammonia water were added into a hydrothermal reactor, and the reaction was carried out at 100° C. for 80 min. The tetrahydrofuran as a solvent was removed by rotary evaporation to obtain an alcoholamine monomer.

[0058] 3: Add 30L of anhydrous methanol and 15kg of olamine monomer into the reactor at 0°C, stir and mix, then add 120kg of methyl acrylate under nitrogen protection, heat to 30°C and stir to react for 24h, the double bonds on the methyl acrylate and the amino groups on the olamine monomer undergo polymerization, rotary evaporate, and then extract the remaining liquid with anhydrous ether 3 times to obtain a dendrimer liquid.

[0059] 4: Add 10kg of dendrimer liquid and 50L of 4% sodium hydroxide aqueous solution into a reactor, stir and react for 24h under nitrogen protection and 35°C. Under alkaline conditions, the ester group at the end of the dendrimer liquid molecule is hydrolyzed into -COONa. After the reaction, add 100L of 36% hydrochloric acid into the reactor, stir at 25°C and 300r / min for 6-8h, -COONa is converted into -COOH, then dialyze with deionized water for desalination, and freeze-dry the product to obtain a macromolecular monomer powder.

[0060] 5: Add 50L of deionized water, 7.5kg of N-isopropylacrylamide and 6kg of macromonomer powder into the reactor, stir at 25°C for 30min, then add 10g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride as a coupling agent into the reactor, continue stirring for 24h, the carboxyl group at the end of the macromonomer powder molecule condenses with the amino group on N-isopropylacrylamide to form an amide group, dialyze with deionized water to desalt, and freeze-dry the product to obtain a temperature-sensitive macromonomer.

[0061] 6: Add 12 kg of bio-based alcohol solution, 15 kg of diphenylmethane diisocyanate and 4 kg of temperature-sensitive macromolecular monomer into the reactor, stir at 65° C. for 100 min to obtain the coating solution.

[0062] Step 3: Transfer 100 kg of fertilizer core material to the coating machine, spray 1 kg of coating liquid onto the surface of the fertilizer core material at 60 r / min and 80°C. After the coating liquid is sprayed, the coating machine continues to work for 12 minutes. Take out the particles and dry them at 80°C for 12 hours to obtain value-added urea, thereby completing the preparation process of value-added urea.

[0063] Comparative Example 1: Based on Example 3, the macromolecular monomer powder is directly used to replace the temperature-sensitive macromolecular monomer, and the other steps remain unchanged to complete the preparation process of value-added urea.

[0064] Comparative Example 2: Based on Example 3, polymaleic anhydride was used instead of the macromonomer powder to prepare a temperature-sensitive macromonomer, and the other steps remained unchanged to complete the preparation process of value-added urea.

[0065] Comparative Example 3: Based on Example 3, the temperature-sensitive macromolecular monomer is not added, and the other steps remain unchanged to complete the preparation process of value-added urea.

[0066] In the embodiments and comparative examples, urea powder was purchased from Shandong Guangxun Chemical Co., Ltd., with an effective content of 99%; the straw used was corn straw; the biochar was straw biochar purchased from Henan Xingnuo Environmental Protection Materials Co., Ltd.; the humic acid was sodium humate purchased from Jinan Huayi Chemical Technology Co., Ltd.; and the diatomaceous earth was purchased from Jinan Huayi Chemical Technology Co., Ltd.; the particle diameter of the fertilizer core material was 2.5±0.3 mm.

[0067] Performance tests were performed on Examples 1 to 3 and Comparative Examples 1 to 3. The value-added urea in the Examples and Comparative Examples were divided into 4 groups, each group of 5 g, and placed in corresponding 100-mesh mesh bags. The mesh bags were then transferred to closed containers, 100 mL of deionized water was added to submerge the mesh bags, and the containers were allowed to stand at 25° C. for 10 days. After the mesh bags were taken out, the remaining liquid was collected in a centrifuge tube, and the nitrogen release rates of different value-added ureas were measured and recorded (nitrogen release rate = total cumulative nitrogen release in the remaining liquid / total nitrogen in the value-added urea for testing × 100). The results are shown in Table 1:

[0068] Table 1

[0069]

[0070] It can be seen from Table 1 that the value-added urea in Examples 1 to 3 will reduce the release rate of nitrogen when the ambient temperature reaches 38°C. Comparative Examples 1 and 3 show that the temperature-sensitive macromonomer coupled with N-isopropylacrylamide can increase the temperature-sensitive effect of the value-added urea coating. Comparative Example 2 shows that the tree-like structure of the macromonomer powder molecule helps to improve the basic sustained-release effect of the value-added urea and the sustained-release effect of urea under the temperature-sensitive state.

[0071] It should be noted that, in this article, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0072] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for preparing value-added urea, characterized in that: The steps include: Step 1: Evenly mix urea powder, biochar, humic acid, hydroxyapatite powder and diatomaceous earth in a mass ratio of 16-20:3-4:3-4:2-4:3-6, and prepare a granular fertilizer core material by a granulator; Step 2: adding the bio-based alcohol solution, diphenylmethane diisocyanate and the temperature-sensitive macromonomer into the reaction kettle in a mass ratio of 12:13-15:3.5-4, stirring at 60-65° C. for 80-100 minutes, and obtaining a coating solution; Step 3: Transfer the fertilizer core material to the coating machine, spray the coating liquid onto the surface of the fertilizer core material at 40-60r / min and 60-80°C, and then continue to work for 8-12 minutes. Take out the particles and dry them at 60-80°C for 8-12 hours to complete the preparation process of value-added urea. The temperature-sensitive macromonomer is prepared by the following steps: Deionized water, N-isopropylacrylamide and macromonomer powder are added to a reaction kettle, stirred at 15-25°C for 10-30 minutes, then 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is added and stirred for 20-24 hours, dialyzed with deionized water for desalination, and the product is freeze-dried to obtain a thermosensitive macromonomer; The macromonomer powder is prepared by the following steps: Add the dendrimer liquid and 4 wt% sodium hydroxide aqueous solution into a reactor, and react for 20-24 h at 30-35° C. under nitrogen protection, then add 36 wt% hydrochloric acid into the reactor, and stir at 20-25° C. and 200-300 r / min for 6-8 h, dialyze with deionized water for desalination, and freeze-dry the product to obtain a macromolecular monomer powder; The dendrimer liquid is prepared by the following steps: Add anhydrous methanol and alcohol amine monomer to the reaction kettle at 0°C, stir and mix, add methyl acrylate under nitrogen protection, stir and react at 25-30°C for 18-24h, rotary evaporate, extract the remaining liquid with anhydrous ether 2-3 times to obtain a dendrimer liquid; The alcoholamine monomer is prepared by the following steps: Glycidyl ether, tetrahydrofuran and 25 wt % ammonia water are added into a hydrothermal reactor, and the mixture is kept at 95-100° C. for 60-80 min. The tetrahydrofuran is removed by rotary evaporation to obtain an alcoholamine monomer.

2. The process for preparing value-added urea according to claim 1, characterized in that: The mass ratio of the fertilizer core material to the coating liquid is 80-100:

1.

3. The process for preparing value-added urea according to claim 1, characterized in that: The usage ratio of the deionized water, N-isopropylacrylamide, macromolecular monomer powder and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 10 mL: 1.5 g: 1-1.2 g: 1.5-2 mg.

4. The process for preparing value-added urea according to claim 1, characterized in that: The bio-based alcohol solution is prepared by the following steps: The straw is dried at 60-80° C. for 2-3 days, crushed and ground through a 40-60 mesh sieve to obtain straw powder; glycerol and straw powder are added into a stirring kettle, stirred at 400-600 r / min and 60-90° C. for 10-20 min, concentrated sulfuric acid is added and stirred at 150-160° C. for 50-60 min, and naturally cooled to obtain a bio-based alcohol solution; the mass ratio of the straw powder, glycerol and concentrated sulfuric acid is 10:100:1.5-2.

5. The process for preparing value-added urea according to claim 1, characterized in that: The usage ratio of the dendrimer liquid, the sodium hydroxide aqueous solution and the hydrochloric acid is 10g:40-50mL:80-100mL.

6. The process for preparing value-added urea according to claim 1, characterized in that: The usage ratio of anhydrous methanol, alcohol amine monomer and methyl acrylate is 25-30 mL: 14-15 g: 110-120 g.

7. The process for preparing value-added urea according to claim 1, characterized in that: The usage ratio of the glycidyl ether, tetrahydrofuran and ammonia water is 7-8 g: 20-25 mL: 20-25 mL.

8. Use of the value-added urea prepared by the preparation process according to any one of claims 1 to 7 to reduce the nitrogen release rate at an ambient temperature of ≥38°C.

Images