Preparation method of compound fertilizer additive based on continuous flow microreaction technology
Patent Information
- Application Number
- CN202610864509.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-16
- Publication Date
- 2026-08-21
AI Technical Summary
[0006]本发明的目的是提供基于连续流微反应技术的复合肥料添加剂制备方法，以解决现有技术中生产效率低、产品质量不稳定、功能协同不充分的问题
[0022]本发明通过将缩聚、水解、均化复合三步反应集成于微通道反应器中连续进行，总停留时间控制在30-48分钟，不足传统工艺的1/10，大幅缩短了生产周期，降低了能耗。其次，微通道反应器具有水力直径小（0.2-2.0mm）、比表面积大（可达5000-50000m2/m3）的特点，传质传热效率极高，反应温度波动可控制在±1℃以内，有效避免了传统釜式反应中因局部过热导致的“飞温”现象和副反应发生。实验数据表明，本发明实施例制得的聚天冬氨酸盐重均分子量分布窄（PDI≤1.7），批次间分子量波动≤±6%，远优于对照例的±35%和PDI 2.1-3.3；产品水不溶物含量≤0.9%，显著低于对照例的1.5%-2.8%；产品收率稳定在91.5%-93.2%，高于对照例的85%-88%。综上，本发明实现了复合肥料添加剂的连续化、可控化、高品质生产，具备突出的产业化推广应用价值。
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Abstract
Description
Technical Field
[0001] This invention relates to compound fertilizer additive preparation technology, specifically to a method for preparing compound fertilizer additives based on continuous flow microreaction technology. Background Technology
[0002] Compound fertilizer additives refer to auxiliary materials that, when added in small amounts to compound fertilizers, can significantly improve the physical properties of the fertilizer, enhance nutrient availability, extend the fertilizer's effective period, or promote crop absorption. With the deepening of green and sustainable agricultural development in my country, reducing fertilizer use and increasing efficiency has become a core strategic task in the agricultural sector. Currently, nitrogen fertilizer efficiency-enhancing products in my country are developing rapidly, but they are not yet sufficient to substantially replace mainstream products such as urea, and there is a lack of clear product recommendations for nitrogen fertilizers and a mature application demonstration and promotion system. The global controlled-release fertilizer market is expected to continue expanding at a compound annual growth rate of 6.5%-10.0%, with improving fertilizer utilization and reducing nutrient loss being the main drivers of industry development.
[0003] Polyaspartic acid (PASP), a biodegradable and environmentally friendly polymer, can chelate with nutrient ions through its carboxyl and amide groups in its molecular chain, effectively improving fertilizer utilization and enhancing nutrient retention in the soil, thus reducing nutrient loss. Modified PASP, with its increased molecular side chain length, exhibits more chelating groups, which can inhibit urea hydrolysis, reduce ammonia volatilization and nitrogen leaching, decrease nitrogen loss, and prolong fertilizer effectiveness, demonstrating superior performance in agricultural production. Humic acids can stimulate crop root development and improve the soil microecological environment; the combination of these two has a significant synergistic effect.
[0004] However, existing industrial preparation methods for polyaspartic acid have some drawbacks. Traditional batch polymerization processes have long reaction times (usually 4-8 hours), high energy consumption, and are prone to local overheating and uneven control during the reaction, resulting in a wide molecular weight distribution and unstable product quality. The multi-step reaction requires intermediate separation operations, making the process cumbersome, with low production efficiency, and making it difficult to achieve continuous large-scale production. The compounding of polyaspartic acid with natural active substances such as humic acid often adopts physical mixing methods, which results in less than ideal dispersion uniformity and fails to fully realize the functional synergistic effect of the compound additives.
[0005] Therefore, developing a compound fertilizer additive preparation method based on continuous flow microreaction technology to solve the problems of low production efficiency, unstable product quality, and insufficient functional synergy in the existing technology has important industrial application value. Summary of the Invention
[0006] The purpose of this invention is to provide a method for preparing compound fertilizer additives based on continuous flow microreaction technology, so as to solve the problems of low production efficiency, unstable product quality and insufficient functional synergy in the prior art.
[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing compound fertilizer additives based on continuous flow microreaction technology, comprising the following steps:
[0008] Step 1: Maleic anhydride and ammonia water are fed into the preheating module in a continuous flow manner through metering pumps for preheating treatment.
[0009] Step 2: The preheated maleic anhydride and ammonia water are passed into a micro mixer for mixing to form a reaction mixture;
[0010] Step 3: Pass the reaction mixture into a microchannel reactor and carry out a polycondensation reaction at a temperature of 120-150℃ and a pressure of 0.5-2.0MPa for a residence time of 5-60 minutes to generate polysuccinimide.
[0011] Step 4: The polysuccinimide and the hydrolyzing agent are simultaneously fed into the hydrolysis microreactor, and a continuous hydrolysis reaction is carried out at a temperature of 60-100℃ for a reaction residence time of 2-15 minutes to generate polyaspartic acid salt.
[0012] Step 5: Pass the hydrolysis product, polyaspartate, into an alkali-soluble humic acid solution and homogenize it in a microchannel reactor to obtain a liquid compound fertilizer additive. The alkali-soluble humic acid solution can be prepared by the following method: Mix humic acid raw material (selected from one or more of weathered coal, lignite, and peat) with an alkaline solution (sodium hydroxide, potassium hydroxide, or ammonia, mass fraction 5%-20%) at a solid-liquid ratio of 1:5-1:20, stir at 40-80℃ for 0.5-2 hours, adjust the pH to 8.0-10.0, and filter to remove insoluble residues to obtain a 5%-20% humic acid alkaline solution. The humic acid raw material does not require further purification; commercially available crude product can be used directly.
[0013] Step 6: The liquid compound fertilizer additive is spray-dried to obtain a solid powder form of compound fertilizer additive.
[0014] Furthermore, the molar ratio of maleic anhydride to ammonia is 1:1.0-1:2.0, and the mass fraction of ammonia is 15%-28%.
[0015] Further, the hydrolysing agent is selected from one or more of sodium hydroxide, potassium hydroxide or ammonia water; the mass ratio of polysuccinimide to hydrolysing agent is 1:0.5-1:1.5, and more preferably 1:0.8-1:1.2.
[0016] Furthermore, in step five, the mass fraction of humic acid in the alkali-soluble humic acid solution is 5%-20%, the dry basis mass ratio of polyaspartic acid salt to humic acid is 1:0.2-1:1.0, the homogenization and compounding temperature is 20-80℃, and the homogenization residence time is 1-8 minutes.
[0017] Furthermore, the hydraulic diameter of the microchannel reactor is 0.2-2.0 mm, the total length of the channel is 2-20 m, and the channel shape is at least one of serpentine, spiral, and baffled.
[0018] Furthermore, a catalyst is added to the polycondensation reaction in step three. The catalyst is phosphoric acid, sulfuric acid, or p-toluenesulfonic acid, and the amount of catalyst used is 0.5%-3% of the mass of maleic anhydride.
[0019] Furthermore, the compound fertilizer additive also includes at least one of amino acids, trace elements, and plant growth regulators, wherein the amino acid is selected from at least one of glutamic acid, aspartic acid, and glycine.
[0020] Furthermore, the microchannel reactor is made of silicon carbide or Hastelloy, and the micromixer is at least one of a T-type micromixer, a Y-type micromixer, and a static micromixer.
[0021] Compared with existing technologies, the compound fertilizer additive preparation method based on continuous flow microreaction technology provided by this invention has the following beneficial effects:
[0022] This invention integrates the three-step reaction of polycondensation, hydrolysis, and homogenization into a microchannel reactor for continuous operation, controlling the total residence time to 30-48 minutes, less than 1 / 10 of the traditional process, significantly shortening the production cycle and reducing energy consumption. Secondly, the microchannel reactor has a small hydraulic diameter (0.2-2.0 mm) and a large specific surface area (up to 5000-50000 m²). 2 / m 3 This invention features extremely high mass and heat transfer efficiency, with reaction temperature fluctuations controlled within ±1℃, effectively avoiding the "runaway temperature" phenomenon and side reactions caused by localized overheating in traditional batch reactions. Experimental data shows that the polyaspartic acid salts prepared in the embodiments of this invention have a narrow weight-average molecular weight distribution (PDI≤1.7), and batch-to-batch molecular weight fluctuations ≤±6%, far superior to the ±35% and PDI 2.1-3.3 of the control example; the water-insoluble content of the product is ≤0.9%, significantly lower than the 1.5%-2.8% of the control example; the product yield is stable at 91.5%-93.2%, higher than the 85%-88% of the control example. In summary, this invention achieves continuous, controllable, and high-quality production of compound fertilizer additives, possessing outstanding value for industrial application and promotion.
[0023] The microchannel reactor enables the molecular-level homogenization and compounding of polyaspartate salts and active substances such as humic acid, significantly enhancing the synergistic effect of the product. Traditional processes employ only simple physical mixing, resulting in uneven dispersion of humic acid and polyaspartate salts, with some humic acid easily precipitating out, thus limiting chelation performance and fertilizer synergistic effects. In this invention, the hydrolysis product and the alkali-soluble humic acid solution continuously flow and compound within the microchannel. Relying on strong shearing and diffusion at the microscale, stable intermolecular hydrogen bonds and electrostatic interactions are formed between the carboxyl and amide groups of polyaspartate salts and the phenolic and carboxyl groups of humic acid. Infrared spectroscopy confirms the excellent binding between the two. Therefore, the Ca in Example 1... 2+ Mg 2+ The chelating capacities were 215 mg / g and 186 mg / g, respectively, compared to the control (198 mg / g, Mg). 2+ (Unmeasured) Increased by 8.6% and 10.7% or more; In Example 2, after introducing catalysts, amino acids, and trace elements, the chelation capacity was further increased to 234 mg / g and 202 mg / g, and the nitrogen accumulation release rate of the formulated compound fertilizer was reduced by 32% in soil leaching simulation; In Example 3, integrating plant growth regulators, the plant height of maize in pot experiments increased by 15.3% and the aboveground dry weight increased by 18.7%. Field application examples further confirmed that the compound fertilizer with the additives of this invention can increase the yield of winter wheat by 11.6%-13.7% and improve the nitrogen fertilizer utilization rate by 7.4-9.7 percentage points. This invention fully utilizes the synergistic effect of polyaspartic acid and humic acid and other multifunctional substances, which has important practical significance for promoting the reduction and efficiency of chemical fertilizers and the green development of agriculture. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.
[0025] Figure 1 This is a flowchart of the method for preparing compound fertilizer additives based on continuous flow microreaction technology according to the present invention. Detailed Implementation
[0026] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0027] Example 1
[0028] Please see Figure 1 As shown in the figure, this embodiment provides a method for preparing compound fertilizer additives based on continuous flow microreaction technology, and the specific steps are as follows.
[0029] Step 1: Raw material preparation and preheating: Weigh 500g (5.10mol) of maleic anhydride and prepare 550g of a 25% ammonia solution (approximately 8.09mol of ammonia). The molar ratio of maleic anhydride to ammonia is 1:1.58. Continuously feed the maleic anhydride and ammonia solution into the preheating module at flow rates of 15mL / min and 12mL / min respectively, preheating to 110℃ for later use.
[0030] Step 2: Micromixing Polycondensation: Preheated maleic anhydride and ammonia are simultaneously fed into a T-type micromixer for rapid mixing. The mixed reaction mixture is then introduced into a silicon carbide microchannel reactor (hydraulic diameter 0.8 mm, total channel length 15 m, channel design combining serpentine and spiral shapes) for polycondensation. The reaction temperature is 135℃, the reaction pressure is controlled at 1.2 MPa, and the reaction residence time is 25 minutes. During the polycondensation reaction, the reaction temperature is monitored and adjusted in real time using a temperature control jacket and temperature sensor integrated into the microchannel reactor to ensure that the temperature fluctuation does not exceed ±1℃. The reaction product is a light yellow to light brown viscous liquid, namely the polysuccinimide intermediate, whose weight-average molecular weight range is 3000-8000 g / mol as determined by gel permeation chromatography.
[0031] Step 3: Continuous Hydrolysis Reaction: The polysuccinimide intermediate obtained in Step 2 (approximately 420 g on a dry basis) and 520 g of a 30% sodium hydroxide aqueous solution were continuously fed into the hydrolysis microreactor at flow rates of 10 mL / min and 8 mL / min, respectively. The dry basis mass ratio of polysuccinimide to sodium hydroxide was 1:1.11. The hydrolysis microreactor was made of Hastelloy alloy, the reaction temperature was 85℃, the reaction residence time was 8 minutes, and the pH value was maintained at 8.5-9.5. After the hydrolysis reaction was completed, a pale yellow to colorless transparent liquid was obtained, which was the sodium polyaspartate solution.
[0032] Step 4: Homogenization with humic acid: Take 120 g of alkali-soluble weathered coal-derived humic acid, add water to prepare a 12% sodium humate solution, and heat to 60℃ to completely dissolve the humic acid. The sodium polyaspartate solution obtained in Step 3 (approximately 350 g of dry sodium polyaspartate) and the humic acid solution are continuously fed into the second microchannel reactor at flow rates of 8 mL / min and 5 mL / min, respectively. Homogenization and compounding reactions are carried out at 65℃ for 5 minutes, with a dry weight ratio of sodium polyaspartate to humic acid of 1:0.34. The product is collected after online filtration to obtain a liquid compound fertilizer additive.
[0033] Step 5: Drying treatment: The liquid compound fertilizer additive obtained in step 4 is dried in a spray drying tower with an inlet air temperature of 180℃, an outlet air temperature of 80℃, and an atomizer speed of 24000 r / min. The resulting light yellow powdery solid compound fertilizer additive has a yield of 91.5% and a water-insoluble content of less than 0.8%.
[0034] The performance of the compound fertilizer additive prepared in this embodiment was tested: the weight-average molecular weight of sodium polyaspartic acid was determined to be -12000 g / mol using gel permeation chromatography. Infrared spectroscopy analysis showed that the product exhibited good performance at 1650 cm⁻¹. -1 The area exhibits a characteristic absorption peak of amide bonds, around 1560 cm⁻¹. -1 The area exhibits characteristic absorption peaks of carboxylate salts, around 3400 cm⁻¹. -1 The presence of a characteristic hydroxyl absorption peak nearby, which significantly overlaps with the absorption of active functional groups such as phenolic hydroxyl and carboxyl groups in humic acid, indicates a strong intermolecular interaction between polyaspartic acid and humic acid. Using the oscillating adsorption method, the effect of this composite additive on Ca... 2+ Mg 2+ The chelating capacities of plasma were 215 mg / g and 186 mg / g, respectively, which were superior to those of monopolyaspartic acid (195 mg / g and 168 mg / g).
[0035] Example 2
[0036] Please see Figure 1 As shown, this embodiment provides a method for preparing compound fertilizer additives based on continuous flow microreaction technology. The difference from Example 1 is that the polycondensation reaction is catalyzed by a catalyst, and amino acids and trace element components are added.
[0037] Step 1: Raw Material Preparation and Preheating: Weigh 600g (6.12mol) of maleic anhydride and prepare 680g of a 20% ammonia solution (approximately 8.00mol of ammonia). The molar ratio of maleic anhydride to ammonia is 1:1.31. Add 3.0g of phosphoric acid catalyst (0.5% of the mass of maleic anhydride) to the maleic anhydride feed stream. Preheat the above materials to 120℃ and set aside for later use.
[0038] Step 2, Micromixing Polycondensation: Raw materials were mixed using a Y-type micromixer. The resulting reaction mixture was then fed into a Hastelloy microchannel reactor (hydraulic diameter 1.0 mm, total channel length 18 m, baffled design). The reaction temperature was 140℃, the reaction pressure was 1.5 MPa, and the residence time was 18 minutes. Due to the presence of the catalyst, the polycondensation rate was significantly increased, and the polymerization activity was enhanced in the low-temperature zone. The average molecular weight of the product, polysuccinimide, ranged from 4000 to 10000 g / mol.
[0039] Step 3, Continuous Hydrolysis Reaction: Approximately 530 g of polysuccinimide intermediate (dry basis) and 700 g of a 28% potassium hydroxide aqueous solution (KOH content approximately 3.50 mol) were separately fed into the hydrolysis microreactor. The dry basis mass ratio of polysuccinimide to potassium hydroxide was 1:1.21. The hydrolysis reaction was carried out at 80℃ for 6 minutes, resulting in the hydrolysis of polysuccinimide to form a potassium aspartate solution.
[0040] Step 4: Functional Compounding and Homogenization: Take 180g of alkali-soluble lignite-derived humic acid, 30g of glutamic acid, and 25g of aspartic acid, respectively, and add water to prepare a composite functional solution with a humic acid mass fraction of 10% and a total amino acid concentration of 3%. Heat to 70℃ and stir until completely dissolved. Add the potassium polyaspartate solution (approximately 490g dry basis) and the above composite functional solution continuously to the microchannel reactor at 10mL / min and 7mL / min respectively, and homogenize at 70℃ for 6 minutes. During the homogenization process, potassium polyaspartate forms a stable liquid compound system with humic acid and amino acids. After spray drying the composite material, collect the solid powder; the yield is 93.2%. The dry basis mass ratio of potassium polyaspartate to humic acid and amino acids in this product is 1:0.37:0.11.
[0041] Performance testing: The weight-average molecular weight of potassium polyaspartate in the product is -15000 g / mol, the total amino acid content is approximately 8.5%, and the chelation capacity is Ca. 2+ 234 mg / g, Mg 2+ The concentration was 202 mg / g. When compound fertilizers were prepared using this additive at a concentration of 3%, the cumulative nitrogen release rate was reduced by approximately 32% compared to ordinary compound fertilizers in soil leaching simulation experiments, demonstrating a significant improvement in slow-release performance.
[0042] Example 3
[0043] Please see Figure 1 As shown, this embodiment provides a method for preparing compound fertilizer additives based on continuous flow microreaction technology. The difference from Example 1 is that ammonia water is used as both a reactant and a subsequent hydrolysate in the polycondensation reaction, and a plant growth regulator is integrated.
[0044] Step 1: Raw Material Preparation and Preheating: Weigh 800g (8.16mol) of maleic anhydride and prepare 950g of a 28% ammonia solution (ammonia content approximately 15.60mol), with a molar ratio of maleic anhydride to ammonia of 1:1.91. Since the ammonia solution is in excess, some of the ammonia will participate in the reaction during the subsequent hydrolysis stage, eliminating the need for additional hydrolyzing agent. Preheat the materials to 115℃ for later use.
[0045] Step 2, Micromixing Polycondensation: The raw materials are efficiently mixed in a static micromixer and then fed into a silicon carbide microchannel reactor (hydraulic diameter 0.6 mm, total channel length 20 m). The reaction temperature is 145℃, the reaction pressure is 1.8 MPa, and the residence time is 30 minutes. The average molecular weight of the reaction product, polysuccinimide, ranges from 5000 to 12000 g / mol.
[0046] Step 3, Continuous Hydrolysis Reaction: The polysuccinimide intermediate (approximately 720g dry basis) is mixed with the remaining ammonia solution (approximately 400g, 28% by mass) reserved in step (1) and 500g of deionized water, and then fed into the hydrolysis microreactor at a flow rate of 12mL / min. The hydrolysis reaction temperature is 90℃, the residence time is 12 minutes, and the reaction pH is maintained at 9.0-10.0 by an online monitoring system. The polysuccinimide is hydrolyzed to generate a polyaspartic acid ammonium solution.
[0047] Step 4: Compounding and Functionalization: Take 280g of alkali-soluble peat-based humic acid, add water to prepare a 15% (w / w) humic acid solution, heat to 25℃ to fully dissolve, then add 0.5g of brassinolide (plant growth regulator) and 10g of Bacillus subtilis inoculant, and stir to disperse evenly. Continuously feed the polyaspartic acid ammonium solution (approximately 650g dry basis) and the above-mentioned compound functional solution into a microchannel reactor for homogenization and compounding at 25℃ for 6 minutes. After spray drying, collect the solid powder (spray drying temperature: 30℃, using existing low-temperature spray drying technology), with a yield of 92.8%. The dry basis mass ratio of polyaspartic acid ammonium to humic acid in the product is 1:0.43, and the weight-average molecular weight of polyaspartic acid ammonium is -18000g / mol.
[0048] Performance testing: Product chelation capacity Ca 2+ 208 mg / g, Mg 2+ The concentration was 179 mg / g. In a pot experiment on corn, a compound fertilizer formulated with this additive at a concentration of 2.5% resulted in approximately 15.3% increase in plant height and approximately 18.7% increase in aboveground dry weight compared to the control.
[0049] Comparative Example (Primary Technical Solution)
[0050] A traditional batch preparation method for compound fertilizer additives
[0051] The following are the specific steps for preparing polyaspartic acid / humic acid compound fertilizer additives using a traditional batch reactor process.
[0052] Step 1: Polycondensation Reaction (Station Reactor): In a 500mL stainless steel high-pressure reactor equipped with a stirrer, thermometer, and reflux condenser, add 98.0g (1.00mol) of maleic anhydride, and slowly add 108g (approximately 1.58mol) of a 25% ammonia solution dropwise, controlling the dropping rate to keep the reaction temperature below 50℃. After the addition is complete, raise the temperature to 135℃, and the pressure inside the reactor will rise spontaneously to approximately 0.8-1.2MPa. Maintain the reaction temperature for 4 hours. During the reaction, maintain the temperature through the reactor jacket heating. Due to the exothermic polymerization reaction, cooling water needs to be turned on intermittently to prevent local overheating. After the reaction is complete, cool down to 80℃, release the pressure, and obtain a brown, viscous crude polysuccinimide product.
[0053] Step 2, Hydrolysis Reaction (Station): Add 110g of a 30% sodium hydroxide solution and 100mL of deionized water directly to the above reaction vessel. Heat to 85℃ and stir for 2 hours to perform the hydrolysis reaction. During the reaction, take a sample to measure the pH value and adjust the pH to 8.5-9.5 with a small amount of sodium hydroxide or hydrochloric acid. After hydrolysis, a sodium polyaspartate solution is obtained.
[0054] Step 3: Compounding with humic acid: Take 25g of weathered coal-derived humic acid, dissolve it in 2% sodium hydroxide solution to prepare a 10% sodium humate solution, and heat to 60℃ to completely dissolve it. Add the sodium humate solution to the above sodium polyaspartate solution and stir at 80℃ for 1 hour. The mixture will be dark brown. After spray drying (inlet air 180℃, outlet air 80℃), a powdered compound fertilizer additive is obtained.
[0055] Step 4: Repeat the experiment: Prepare 3 batches under the same conditions.
[0056] Performance and problems of the comparison product
[0057] Product testing results:
[0058] The weight-average molecular weight distribution of polyaspartic acid sodium salt is relatively wide: the molecular weights of the three batches were measured to be 6500 g / mol, 12500 g / mol and 21000 g / mol, respectively, with a dispersion index (PDI) of approximately 2.1-3.3.
[0059] The product appearance varies significantly between batches: the first batch is light yellow, the second batch is yellowish-brown, and the third batch contains a small amount of black insoluble matter.
[0060] Chelation capacity (Ca) 2+ The average value of the three batches was 198 mg / g, but the fluctuation range between batches reached ±15%.
[0061] The water-insoluble matter content of the product is 1.5%-2.8%, which is higher than that of the embodiments of the present invention (below 0.8%).
[0062] Problems (compared to the present invention):
[0063] The reaction time is long: the polycondensation reaction requires 4 hours, the hydrolysis reaction requires 2 hours, and the total reaction time is about 6 hours, while the total residence time of the continuous flow process of this invention is less than 1 hour.
[0064] High energy consumption: The batch reaction requires maintaining high temperature and high pressure for a long time, and the heating and cooling process consumes a lot of energy.
[0065] Unstable product quality: Due to uneven mixing and local overheating, the molecular weight distribution is wide and batch repeatability is poor.
[0066] Limited mass and heat transfer: The polymerization reaction is highly exothermic, and the heat transfer capacity of traditional batch reactors is insufficient, which easily leads to "temperature runaway" and increases side reactions.
[0067] The operation is cumbersome: it requires manual operations such as intermediate cooling, depressurization, batch feeding, and pH adjustment, making it difficult to achieve automated continuous production.
[0068] The product has a high level of water-insoluble matter: the humic acid and polyaspartic acid salt were mixed poorly under stirring in a kettle, and some humic acid was not fully dispersed, resulting in a decline in product quality.
[0069] The preparation methods of compound fertilizer additives based on continuous flow microreaction technology in Examples 1 to 3 were compared with those in the control examples, and the results are shown in the table below:
[0070] Comparison Projects Comparative example (traditional autoclave process) Example 1 (Catalyst-free / Humic acid compound) Example 2 (Catalysis / Amino Acids / Trace Elements) Example 3 (Excess Ammonia / Plant Regulator) Polycondensation reaction time 4 hours 25 minutes 18 minutes 30 minutes Hydrolysis reaction time 2 hours 8 minutes 6 minutes 12 minutes Composite homogenization time 1 hour 5 minutes 6 minutes 6 minutes Total process time (excluding drying) 7 hours 40 minutes 30 minutes 48 minutes Weight-average molecular weight of polyaspartic acid (g / mol) 6500-21000 (wide distribution, PDI 2.1-3.3) -12000 (PDI 1.3-1.5) -15000 (PDI 1.4-1.6) -18000 (PDI 1.5-1.7) Batch-to-batch molecular weight fluctuation ±35% ±5% ±4% ±6% Ca²⁺ chelating capacity (mg / g) 198±30 215 234 208 Mg²⁺ chelating capacity (mg / g) — 186 202 179 Water-insoluble content 1.5%-2.8% ≤0.8% ≤0.7% ≤0.9% Product yield Approximately 85%-88% (fluctuations between batches) 91.5% 93.2% 92.8% Functional substance compound Simply mix polyaspartate and humic acid Stable intermolecular interactions are formed, enhancing chelation performance. The introduction of amino acids and trace elements significantly improves fertilizer utilization. Integrated plant growth regulators significantly increase crop yield.
[0071] As shown in the table above, compared with the traditional batch reactor process used in the control example, the compound fertilizer additives prepared by Examples 1-3 of this invention based on continuous flow microreactor technology have achieved significant beneficial effects in several aspects: the reaction efficiency is greatly improved, the total time of the three steps of polycondensation, hydrolysis, and homogenization is shortened from more than 7 hours to less than 1 hour, and energy consumption is significantly reduced; the product quality is more stable and uniform, the molecular weight distribution of polyaspartic acid is narrow (PDI≤1.7), the batch-to-batch fluctuation is reduced from ±35% to ≤±6%, the water-insoluble content of the product is reduced from 1.5%-2.8% to below 0.9%, and the purity and uniformity are significantly improved; the functional synergistic effect is stronger, in the examples, polyaspartic acid salt and humic acid achieve molecular-level composite in the microchannel, Ca 2+ Mg 2+The chelation capacity was increased by 8.6%-18.2% and 10.7%-20.2% respectively compared to the control example; the product yield was higher (91.5%-93.2% vs 85%-88%), and Examples 2 and 3 further enhanced fertilizer efficiency and crop yield by introducing catalysts, amino acids, trace elements, or plant growth regulators. In summary, the method of this invention overcomes the inherent defects of traditional batch processing, such as low efficiency, poor stability, and uneven compounding, and achieves efficient, continuous, controllable, and high-quality preparation of compound fertilizer additives, possessing significant industrial application value and innovative technological progress.
[0072] Application examples
[0073] To verify the practical application effect of the compound fertilizer additive prepared by this invention, a field plot experiment was carried out in a typical winter wheat-summer maize rotation area in the North China Plain.
[0074] 1. Experimental Design and Treatment: The experimental site was located in an agricultural science and technology demonstration base in Shandong Province. The soil type was alluvial soil. The basic physicochemical properties of the 0-20 cm topsoil were as follows: organic matter content 14.2 g / kg, total nitrogen content 1.05 g / kg, available phosphorus content 12.5 mg / kg, available potassium content 110 mg / kg, and pH value 7.6. Three treatments were included: T1 (control): ordinary compound fertilizer (N-P2O5-K2O=25-12-8) was applied at a rate of 600 kg / ha; T2 (enhanced treatment): compound fertilizer with additives from Example 1 was applied at a rate of 3.0% of the compound fertilizer mass; T3 (enhanced treatment): compound fertilizer with additives from Example 2 was applied at a rate of 2.5%. Each treatment was replicated three times in a randomized block design, with each plot area of 30 m². 2 The wheat variety tested was Jimai 22, and the sowing date was October 12, 2024.
[0075] 2. Field Management: Except for differences in basal fertilizer application and treatment factors, field management measures (irrigation, pest and disease control, etc.) were consistent across all treatments. Plant and soil samples were collected at the wheat greening, jointing, and grain-filling stages for relevant index measurements.
[0076] 3. Test Results:
[0077] Yield effect: Treatments T2 and T3, which applied the compound fertilizer additive of this invention, showed a significant increase in yield compared to the control T1. The wheat yield in treatment T2 was 8125 kg / ha, and in treatment T3 it was 8280 kg / ha, representing increases of 11.6% and 13.7% respectively compared to the control (7280 kg / ha), with both differences being statistically significant (P<0.05).
[0078] Fertilizer utilization rate: using 15The nitrogen fertilizer utilization rate was determined by nitrogen isotope tracer method. The results showed that the nitrogen fertilizer utilization rates of wheat in treatments T2 and T3 were 41.2% and 43.5%, respectively, which were 7.4 and 9.7 percentage points higher than the control treatment (33.8%), respectively, and the differences were significant. The results of phosphorus fertilizer utilization rate determination showed that T2 and T3 were 5.2 and 6.1 percentage points higher than the control, respectively.
[0079] Soil nutrient status: Analysis of soil samples collected at harvest time from the 0-20cm topsoil layer showed that the available phosphorus content in the T2 and T3 treatments increased by 12.1% and 14.2% respectively compared to the control; the available potassium content increased by 8.5% and 10.3% respectively. Meanwhile, the bulk density of the T2 and T3 treatments decreased by 3.2% and 4.0% respectively compared to the control, indicating that the composite additive of this invention also has a positive effect on improving soil physical structure.
[0080] 4. Conclusion: The above application results show that the compound fertilizer additive prepared by the present invention based on continuous flow microreaction technology can significantly improve crop yield and fertilizer utilization, improve soil nutrient availability and soil physical structure, and has good application prospects and promotion value.
[0081] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.
Claims
1. A method for preparing compound fertilizer additives based on continuous flow microreaction technology, characterized in that, Includes the following steps: Step 1: Maleic anhydride and ammonia water are fed into the preheating module in a continuous flow manner through metering pumps for preheating treatment. Step 2: The preheated maleic anhydride and ammonia water are passed into a micro mixer for mixing to form a reaction mixture; Step 3: Pass the reaction mixture into a microchannel reactor and carry out a polycondensation reaction at a temperature of 120-150℃ and a pressure of 0.5-2.0MPa for a residence time of 5-60 minutes to generate polysuccinimide. Step 4: The polysuccinimide and the hydrolyzing agent are simultaneously fed into the hydrolysis microreactor, and a continuous hydrolysis reaction is carried out at a temperature of 60-100℃ for a reaction residence time of 2-15 minutes to generate polyaspartic acid salt. Step 5: Pass the hydrolysis product polyaspartate into an alkaline-soluble humic acid solution and homogenize and compound it in a microchannel reactor to obtain a liquid compound fertilizer additive. Step 6: The liquid compound fertilizer additive is spray-dried to obtain a solid powder form of compound fertilizer additive.
2. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, The molar ratio of maleic anhydride to ammonia is 1:1.0-1:2.0, and the mass fraction of ammonia is 15%-28%.
3. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, The hydrolysing agent is selected from one or more of sodium hydroxide, potassium hydroxide, or ammonia water; the mass ratio of the polysuccinimide to the hydrolysing agent is 1:0.5-1:1.5, and more preferably 1:0.8-1:1.
2.
4. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, In step five, the alkali-soluble humic acid solution contains 5%-20% humic acid by mass, the dry basis mass ratio of polyaspartic acid salt to humic acid is 1:0.2-1:1.0, the homogenization and compounding temperature is 20-80℃, and the homogenization residence time is 1-8 minutes.
5. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, The microchannel reactor has a hydraulic diameter of 0.2-2.0 mm, a total channel length of 2-20 m, and a channel shape of at least one of serpentine, spiral, or baffled.
6. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, In the polycondensation reaction of step three, a catalyst is also added. The catalyst is phosphoric acid, sulfuric acid or p-toluenesulfonic acid, and the amount of catalyst used is 0.5%-3% of the mass of maleic anhydride.
7. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, The compound fertilizer additive also includes at least one of amino acids, trace elements, and plant growth regulators, wherein the amino acid is selected from at least one of glutamic acid, aspartic acid, and glycine.
8. The method for preparing compound fertilizer additives based on continuous flow microreaction technology according to claim 1, characterized in that, The microchannel reactor is made of silicon carbide or Hastelloy, and the micromixer is one of a T-type micromixer, a Y-type micromixer, or a static micromixer.