Method for regulating and controlling polymerization distribution of oligomeric APP and ammonium oligomeric phosphate fertilizer

Abstract

The invention relates to the technical field of ammonium oligomeric phosphate fertilizers, and discloses a method for regulating and controlling polymerization distribution of oligomeric APP and an ammonium oligomeric phosphate fertilizer, the method is characterized in that a blocking agent is added in the process of preparing the oligomeric APP through a urea condensation method, the blocking agent is a dilute solution of alkali metal hydroxide, and the addition amount of the blocking agent is 6-20% of the use amount of a condensing agent. In the process of preparing ammonium polyphosphate through urea condensation, the blocking agent is added to terminate the polymerization reaction, so that the polymerization distribution of the product can be controlled. The blocking agent is added in the reaction process, so that the reaction temperature can be increased, the dosage of the condensing agent can be increased, target polymerization distribution can be quickly achieved, the reaction time is greatly shortened, and the efficiency is improved. On the basis of the regulation and control method provided by the invention, the ammonium oligomeric phosphate fertilizer prepared by the urea condensation method is distributed towards oligomers (n is equal to 2-3 and the content is high), the highest polymerization degree is not higher than 9, and the ammonium oligomeric phosphate fertilizer is high in water solubility, fast in hydrolysis and high in chelating capacity.

Description

Technical Field

[0001] This invention relates to the field of ammonium oligophosphate fertilizer technology, specifically to a method for regulating the polymerization distribution of oligomeric APP and an ammonium oligophosphate fertilizer. Background Technology

[0002] Ammonium polyphosphate (APP) is a nitrogen- and phosphorus-containing polyphosphate with the general molecular formula (NH4). n+2 P n O 3n+1 Based on their degree of polymerization (n), polymers can be classified into three types: oligomers, mesomers, and polymers. The higher the degree of polymerization, the lower the water solubility, and vice versa. When the degree of polymerization (n) ≤ 20, the water solubility is good, and it is usually called oligomerized APP, which is an important raw material for liquid fertilizers.

[0003] In ammonium polyphosphate (APP) fertilizers, the chain length of the phosphate (i.e., the degree of polymerization, n value) is the core factor determining its physicochemical properties and agronomic effects. Oligopolyphosphate fertilizers are fertilizers that mix ammonium phosphate, dipolyphosphate, tripolyphosphate, and other polyphosphates with varying chain lengths. By controlling the distribution (polymerization distribution) of polyphosphates with different chain lengths in the fertilizer, oligomeric APP fertilizer products tailored to different needs can be formulated.

[0004] The urea condensation method is a common method used by small and medium-sized enterprises to produce water-soluble oligomeric ammonium polyphosphate. It involves using urea as one of the main raw materials and as a condensing agent in the production of ammonium polyphosphate. By controlling reaction conditions (temperature, time, material ratio, and partial pressure, etc.), urea and a phosphorus source undergo a condensation reaction to form ammonium polyphosphate. The essence of this condensation reaction is the formation of polyphosphate chains (POP chains). Since the degree of polymerization of ammonium polyphosphate is related to factors such as reaction temperature, reaction time, and the amount of condensing agent, theoretically, by controlling production conditions (reaction temperature, reaction time, amount of condensing agent, etc.), the relative proportion of polyphosphate with different chain lengths in the product (i.e., polymerization distribution) can be adjusted. However, in actual production, due to the mutual interference of factors affecting the degree of polymerization, it is difficult to accurately control the polymerization distribution of the product to obtain the desired target product. Currently, there is no effective means to control the polymerization distribution. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a method for regulating the polymerization distribution of oligomeric APP and an ammonium oligophosphate fertilizer prepared based on the aforementioned regulation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution.

[0007] First, the present invention provides a method for controlling the polymerization distribution of oligomeric APP. The method involves adding an inhibitor during the preparation of oligomeric APP by urea condensation. The inhibitor is a dilute solution of an alkali metal hydroxide, and the amount of the inhibitor added is 6 to 20% of the amount of urea used as the condensing agent.

[0008] Furthermore, the dilute solution of the alkali metal hydroxide includes a 0.1 wt% NaOH solution and a 0.1 wt% KOH solution.

[0009] The essence of preparing oligomeric ammonium phosphate (APP) via urea condensation is the condensation reaction between urea and a phosphorus source to form ammonium polyphosphate with different chain lengths. During this process, by adding an inhibitor (a dilute solution of alkali metal hydroxide), the alkali preferentially reacts with the more acidic -P-OH groups at the ends of the polyphosphate chains, converting them into -P-ONa or -P-OK. The condensation activity of the ends capped by alkali metal ions decreases sharply, essentially pressing the "pause button" on the chain growth. The addition of alkali shifts the average degree of polymerization towards lower chain lengths. By controlling the amount of inhibitor added, a portion of molecules with specific chain lengths can be selectively "frozen," thereby regulating the polymerization distribution of oligomeric APP.

[0010] The control method provided by this invention can precisely adjust the proportion of each chain length component in oligomeric APP products, thereby obtaining oligomeric APP products for the target purpose.

[0011] Secondly, this invention provides an ammonium oligophosphate fertilizer, which is prepared by urea condensation, and the preparation method includes the following steps: Step 1: Mix urea and phosphorus source evenly at an N / P molar ratio of 1.1 to 3.5, and place the mixture into the reactor; Step 2: Heating maintains the temperature inside the reactor between 120 and 300°C for the reaction. During the reaction, a neutralizing agent is introduced to maintain the ammonia partial pressure between 0.01 and 0.02 MPa. Step 3: After reacting in the reactor for 0.5–3 hours, stop heating and the introduction of neutralizing agent, and add an inhibitor to the reactor. The inhibitor is a dilute solution of an alkali metal hydroxide, and the amount of inhibitor added is 6–20% of the amount of urea used. Step 4: Cool, solidify, crush, and sieve to obtain ammonium oligophosphate fertilizer.

[0012] Furthermore, the dilute solution of the alkali metal hydroxide includes a 0.1 wt% NaOH solution and a 0.1 wt% KOH solution.

[0013] Furthermore, the phosphorus source includes phosphoric acid, monoammonium phosphate, diammonium phosphate, and urea phosphate.

[0014] Furthermore, the neutralizing agent includes ammonia and melamine.

[0015] The ammonium oligophosphate fertilizer provided by this invention is predominantly composed of oligomers (high content of n=2-3) with a maximum degree of polymerization not exceeding 9. The product contains more pyrophosphate (n=2) and tripolyphosphate (n=3), has strong water solubility, and hydrolyzes rapidly, providing very rapid phosphorus supply in the initial stage. It is suitable for crops with short critical periods for phosphorus demand and requiring rapid response. Furthermore, tripolyphosphate is considered to be the strongest component for chelating divalent ions such as calcium and magnesium. The ammonium oligophosphate fertilizer provided by this invention has strong chelating ability, which can improve the availability of trace elements and the long-term stability of the solution.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention innovatively proposes a method to control the polymerization distribution of ammonium polyphosphate during the urea condensation process by adding an inhibitor. When the target polymerization distribution appears during the ammonium polyphosphate preparation process, the inhibitor is added to terminate the polymerization reaction, thus controlling the product's polymerization distribution. Adding an inhibitor during the reaction process can also increase the reaction temperature and the amount of condensing agent, rapidly achieving the target polymerization distribution, significantly shortening the reaction time and improving efficiency. Based on the control method provided by this invention, the oligomeric ammonium polyphosphate fertilizer prepared by the urea condensation method exhibits a predominantly oligomer distribution (high content of n=2-3), with a maximum degree of polymerization not exceeding 9, strong water solubility, rapid hydrolysis, and strong chelating ability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0018] Figure 1 This is a process flow diagram for preparing ammonium oligophosphate fertilizer according to the present invention. Specific implementation methods

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the raw materials and reagents used in the following embodiments and comparative examples can be obtained through commercial channels.

[0020] See Figure 1The process flow for preparing ammonium oligophosphate fertilizer shown in this invention provides a method for controlling the polymerization distribution of oligomeric APP. This method involves reacting a phosphorus source with an excess of condensing agent and applying high temperature. After reaching the target polymerization distribution, an inhibitor is added to consume the excess condensing agent, thereby terminating the polymerization reaction and achieving controllable polymerization distribution.

[0021] Example 1:

[0022] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0023] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 2.2 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 180°C to carry out the polymerization reaction. S3. The reaction time is controlled at 150 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction. S4. Terminate the reaction by adding 0.1% NaOH solution as the blocking agent, based on 11.59% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0024] Example 2:

[0025] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0026] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 2.2 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 180°C to carry out the polymerization reaction. S3. The reaction time is controlled at 150 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction. S4. Terminate the reaction by adding 0.1% KOH solution as the blocking agent, based on 11.59% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0027] Example 3:

[0028] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0029] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 3.5 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 180°C to carry out the polymerization reaction. S3. The reaction time is controlled at 90 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction.

[0030] S4. Terminate the reaction by adding 0.1% NaOH solution as the blocking agent, based on 18.43% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0031] Example 4:

[0032] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0033] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 3.5 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 180°C to carry out the polymerization reaction. S3. The reaction time is controlled at 30 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction.

[0034] S4. Terminate the reaction by adding 0.1% NaOH solution as the blocking agent, based on 18.43% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0035] Example 5:

[0036] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0037] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 1.2 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 180°C to carry out the polymerization reaction. S3. The reaction time is controlled at 180 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction.

[0038] S4. To terminate the reaction, add 0.1% NaOH solution as the blocking agent, according to 6% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0039] Example 6:

[0040] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0041] S1. Mix urea and phosphoric acid evenly at an N / P molar ratio of 1.8 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 120°C to carry out the polymerization reaction. S3. The reaction time is controlled at 150 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction.

[0042] S4. To terminate the reaction, add 0.1% NaOH solution as the blocking agent, according to 7.5% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0043] Example 7:

[0044] An ammonium oligophosphate fertilizer, as described above Figure 1 The process shown is achieved through the following steps.

[0045] S1. Mix urea and monoammonium phosphate evenly at an N / P molar ratio of 2.8 and place them in the reactor; S2. Heating: The temperature of the material in the reactor is raised to 240°C to carry out the polymerization reaction; S3. The reaction time is controlled at 60 min, and the ammonia partial pressure is maintained at 0.01-0.02 MPa during the reaction.

[0046] S4. To terminate the reaction, add 0.1% NaOH solution as the blocking agent, based on 15.5% of the urea dosage. S5. Crushing and screening to obtain ammonium oligophosphate.

[0047] Comparative Example 1: An ammonium oligophosphate fertilizer is prepared using the same process and parameters as in Examples 1 and 2, except that no blocking agent, 0.1% NaOH solution or 0.1% KOH solution, is added during the reaction.

[0048] Comparative Example 2: An ammonium oligophosphate fertilizer is prepared using the same process and parameters as in Example 4, except that no 0.1% NaOH solution, an inhibitor, is added during the reaction.

[0049] Comparative Example 3: An ammonium oligophosphate fertilizer is prepared using the same process and parameters as in Example 5, except that no 0.1% NaOH solution, an inhibitor, is added during the reaction.

[0050] The components of the ammonium oligophosphate fertilizers prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were analyzed (total P2O5 was determined by the quinoline phosphomolybdate volumetric method, orthophosphate was determined by the phosphomolybdic blue spectrophotometric method, and total N was determined by the Kjeldahl method). The polymerization rate was calculated according to the formula "polymerization rate = (total P2O5 - orthophosphate) / total P2O5". The results are shown in Table 1 below. The polymerization distribution was obtained by ion chromatography (IC) analysis.

[0051] Table 1. Component analysis results

[0052] As can be seen from Table 1, the addition of the blocking agent did not affect the composition and polymerization rate of ammonium oligophosphate.

[0053] Table 2. Aggregate Distribution Results

[0054] Note: In Table 2, P1 to P14 represent the spectral peaks of orthophosphate to tetradecyl polyphosphate.

[0055] As can be seen from Table 2, in the examples, by adding an inhibitor, the polymerization distribution of ammonium polyphosphate was controlled below P9, and the high-content polymerization was distributed in P2 and P3; while in the comparative example, without the addition of an inhibitor, the distribution of ammonium polyphosphate reached P14, with a significant increase in the contents of P5, P6, and P7.

[0056] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be considered as limitations on the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating the aggregation distribution of oligomeric APP, characterized in that: In the process of preparing oligomeric APP by urea condensation, an inhibitor is added. The inhibitor is a dilute solution of an alkali metal hydroxide, and the amount of the inhibitor added is 6-20% of the amount of urea used as the condensing agent.

2. The method according to claim 1, characterized in that: The dilute solution of the alkali metal hydroxide includes a 0.1 wt% NaOH solution and a 0.1 wt% KOH solution.

3. An ammonium oligophosphate fertilizer, characterized in that: It is prepared by urea condensation, and the preparation method includes the following steps: Step 1: Mix urea and phosphorus source evenly at an N / P molar ratio of 1.1 to 3.5, and place the mixture into the reactor; Step 2: Heating maintains the temperature inside the reactor between 120 and 300°C for the reaction. During the reaction, a neutralizing agent is introduced to maintain the ammonia partial pressure between 0.01 and 0.02 MPa. Step 3: After reacting in the reactor for 0.5–3 hours, stop heating and the introduction of neutralizing agent, and add an inhibitor to the reactor. The inhibitor is a dilute solution of an alkali metal hydroxide, and the amount of inhibitor added is 6–20% of the amount of urea used. Step 4: Cool, solidify, crush, and sieve to obtain ammonium oligophosphate fertilizer.

4. The ammonium oligophosphate fertilizer according to claim 3, characterized in that: The dilute solution of the alkali metal hydroxide includes a 0.1 wt% NaOH solution and a 0.1 wt% KOH solution.

5. The ammonium oligophosphate fertilizer according to claim 3, characterized in that: The phosphorus source includes phosphoric acid, monoammonium phosphate, diammonium phosphate, and urea phosphate.

6. The ammonium oligophosphate fertilizer according to claim 3, characterized in that: The neutralizing agent includes ammonia and melamine.

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