Synthesis method of saturated fatty amide and application of saturated fatty amide in chemical fertilizer anti-blocking agent

Abstract

The invention relates to a synthetic method of saturated fatty acid amide and application of the saturated fatty acid amide in a chemical fertilizer anti-blocking agent, and belongs to the technical field of chemical fertilizer auxiliaries. The method comprises the following steps that saturated fatty acid and ammonia gas serve as raw materials and react in an organic solvent under the action of a ferrite catalyst, a saturated fatty acid amide compound is obtained, and after the reaction is finished, reaction liquid can be directly used as the anti-blocking agent after being simply filtered. And the compound is friendly to plants, can be mixed with a moisture absorbent and a surfactant, and has better economical efficiency and application prospect.

Description

Technical Field

[0001] The invention relates to a synthesis method of saturated fatty amide and application of the saturated fatty amide in a fertilizer anti-caking agent, belonging to the technical field of fertilizer adjuvants. Background Art

[0002] Fertilizers play a vital role in modern agricultural production. As agriculture begins to transform towards large-scale and mechanized production, instant powdered phosphate fertilizers (such as potassium dihydrogen phosphate) can meet the requirements of modern irrigation technology (such as drip irrigation and sprinkler irrigation) and precision agriculture (such as drone spraying and intelligent fertilization systems) due to their unique physical and chemical properties, and their usage has increased year by year. Instant phosphate fertilizers are mostly in powder form, with fine particles and uneven distribution. They are prone to compaction during storage, affecting their use. Most of the existing anti-caking agents are designed for granular fertilizers, and have poor anti-caking effects on powdered phosphate fertilizers. It is particularly urgent to develop efficient anti-caking agents suitable for powdered phosphate fertilizers.

[0003] The Chinese invention patent CN101798248B formula uses bis(hexafluorononyl) succinate monoester amine salt, and adds a proper proportion of primary amine salt or secondary amine salt, industrial wax oil and the like. Although this method has an anti-caking effect, the mineral oil is difficult to degrade when it enters the soil with the fertilizer. The CN105294313B formula uses 90-97% inorganic powder and 3-10% surfactant, and uses inert powder to block the formation of crystal bridges between fertilizer particles to achieve an anti-caking effect. Although this method has an anti-caking effect, the process is complicated and the cost is high. The CN101654387B formula uses 1wt%-50wt% of water-based polymer, 1wt%-50wt% of surfactant and the rest of water. Although this method has an anti-caking effect, the water-based polymer and surfactant are not easily miscible, the amount used is large, and the cost is high. CN119100871A discloses an anti-caking agent and a preparation method thereof. The anti-caking agent comprises a surfactant capable of controlling the length of hydrophilic and hydrophobic chains, a macromolecular surfactant, and an inert powder, which are obtained by blending. The inert powder may clog the nozzle during sprinkler irrigation and aerial spraying, thus limiting the use scope of the fertilizer.

[0004] Chinese patent CN114560785B discloses a method for synthesizing primary amide compounds, using lipid compounds and ammonia borane as raw materials, and obtaining primary amide compounds under the action of sodium bis(trimethylsilyl)amide, but ammonia borane is toxic. In addition, the handling and storage of ammonia borane also require special conditions, which increases the complexity and cost of synthesis. Chinese patent CN101289413B discloses a method for preparing primary fatty amides by ammoniation, using ammonia and fatty acids, chromatography silica gel, activated carbon, trisodium phosphate (Na3PO4.12H2O), amidation catalyst (NC-301), activated aluminum oxide and zirconium dioxide as catalysts to synthesize primary fatty amides; however, this method has high requirements for ammonia recovery equipment, and there are problems such as harsh reaction conditions, strict dehydration of reactants, and difficulty in reusing catalysts.

[0005] In summary, the existing synthesis methods of primary fatty amides have problems such as harsh synthesis conditions, cumbersome product post-processing process, and high cost. Conventional anti-caking agents have limited effect on fine-grained powder phosphate fertilizers. In addition, anti-caking agents containing inert powders have limitations in the application of drip irrigation, sprinkler irrigation, and aerial spraying in modern agriculture. Summary of the invention

[0006] In order to overcome at least one of the many problems of the above-mentioned existing fatty amide preparation methods and / or anti-caking agents, the present invention proposes a new method for synthesizing saturated fatty amides, and a method for preparing a powdered phosphate fertilizer anti-caking agent using the saturated fatty amides obtained by the method.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for synthesizing saturated fatty acid amides, the method comprising the following steps: using saturated fatty acids and ammonia as raw materials, reacting in an organic solvent under the action of a catalyst to obtain saturated fatty acid amide compounds; the reaction equation is:

[0009]

[0010] Wherein, R is one or more of C5-C13 alkyl substituents; the saturated fatty acid is hexanoic acid (C6H 12 O2), heptanoic acid (C7H 14 O2), octanoic acid (C8H 16 O2), nonanoic acid (C9H 18 O2), decanoic acid (C 10 H 20 O2), undecanoic acid (C 11 H 22 O2), dodecanoic acid (C 12 H 24 O2), tridecanoic acid (C 13H 26 O2), tetradecanoic acid (C 14 H 28 The catalyst is a ferrite, preferably one or more of manganese ferrite (MnFe2O4), copper ferrite (CuFe2O4), and zinc ferrite (ZnFe2O4).

[0011] Preferably, the organic solvent is an alcohol solvent, preferably one or more of ethylene glycol, propylene glycol, glycerol, and oligoethylene glycol. The addition of an organic solvent will increase the frequency of collisions between molecules in the reaction system, promote the reaction, make the reaction environment relatively stable, and reduce the occurrence of side reactions.

[0012] The saturated fatty amide compound can be used directly as an anti-caking agent after simple filtration of the reaction liquid after the above reaction is completed. For example, most of the particles in the reaction liquid can be filtered out using conventional filter paper, filter screen or gauze; it can also be mixed with conventional soluble desiccant, emulsifier and / or surfactant and then used as an anti-caking agent.

[0013] Preferably, the surfactant is any one of fatty polyoxyethylene ethers or a mixture of two or more of them in any proportion.

[0014] Preferably, the method further comprises, after the reaction is completed, distilling under normal pressure with stirring to recover ammonia and water; and magnetically enriching the catalyst, which can be reused after cleaning and drying.

[0015] Preferably, the mass ratio of the catalyst to the saturated fatty acid is 1 to 5%, and the amount of the organic solvent is 0.4 to 4 times the mass of the saturated fatty acid.

[0016] Preferably, the reaction temperature is 120-180° C., the reaction is carried out under closed conditions, the pressure condition is 0.3-0.8 MPa, and the reaction time is 8-12 hours.

[0017] In the present invention, the amount of the anti-caking agent in the powdered phosphate fertilizer is 0.2-1.0%. The trace amount of free ammonia remaining in the anti-caking agent is a kind of fertilizer, and the trace amount of gold ions remaining are also elements beneficial to plants.

[0018] The present invention has the following beneficial effects:

[0019] 1. The catalyst in this synthesis method can be simply separated using magnetic force, without the need for traditional filtering, washing, evaporation and other processes. The trace metals remaining in the system belong to medium or trace element fertilizers.

[0020] 2. Due to its crystal structure characteristics, ferrite contains abundant Lewis acid sites and alkaline sites on its surface, which can effectively adsorb reactant molecules. The carboxyl group of fatty acids can interact with the Lewis acid sites on the catalyst surface through its oxygen atoms, resulting in changes in the electron density distribution of the C=O bond in the carboxyl group, thereby reducing the activation energy of the reaction between fatty acids and ammonia. This characteristic provides a more favorable path for the reaction between fatty acids and ammonia. At the same time, alcohol molecules have hydroxyl (-OH) functional groups, which can form intermolecular interactions with the carboxyl group of fatty acids through hydrogen bonds to stabilize the reaction intermediates; and the hydrogen bonds formed between the carboxyl group of fatty acids and the hydroxyl group of alcohol molecules can reduce the reaction energy barrier of the carboxyl group, thereby further improving the reaction activity; in addition, the high polarity of alcohol molecules helps to stabilize the active centers on the catalyst surface during the reaction and reduce the deactivation of active sites in the catalyst. Under appropriate reaction temperature and pressure conditions, alcohol molecules may undergo esterification reactions with fatty acids to generate ester intermediates, which further undergo aminolysis reactions with ammonia to generate the target product saturated fatty amide and release alcohol molecules, thereby realizing the recycling of alcohols. Therefore, in the present invention, the reaction can be carried out under closed conditions. This reaction pathway not only improves the efficiency of fatty acid conversion, but also reflects the auxiliary catalytic effect of alcohol in the reaction system. In addition, the alcohol reaction solvent in the synthesis method is an additive in fertilizers to increase crop resistance. It has a certain anti-caking effect and can be used directly, so the synthetic product does not need to be separated from the solvent.

[0021] 3. The main component of the anti-caking agent provided by the present invention, saturated fatty amide, adsorbs the surface of phosphate fertilizer to form a hydrophobic layer, reducing the moisture absorption of the fertilizer environment; relying on the hydrogen bonding of hydrophobic carbon chains and hydroxyl-containing solvents to increase the fluidity of fertilizer particles. There are two current methods for producing powdered phosphate fertilizers. One is that crystal fertilizers (or granular fertilizers) are used alone or mixed, and powdered fertilizers are obtained by crushing. The anti-caking agent of the present invention is a liquid, which can be directly added to the crystals (granules) for mixing. During the crushing process, the components of the anti-caking agent are firmly adsorbed on the surface of the powder; the second is that liquid potassium dihydrogen phosphate slurry is spray-dried to obtain fine-particle powder fertilizer, and the anti-caking agent of the present invention is directly put into the fertilizer liquid raw material for mixing, and the anti-caking agent is combined with fine fertilizer particles in the spray drying process. Therefore, the anti-caking agent provided by the present invention is directly added to the raw material when used, does not affect the normal production steps, and is very convenient to use; the fertilizer is directly bagged after the production is completed, which reduces the time that the fertilizer product is exposed to the environment and effectively reduces its environmental moisture absorption.

[0022] 4. The product of the traditional method needs to be purified, the steps are cumbersome, and the energy consumption is high. The product obtained by the synthesis method of the present invention does not need to be separated from the solvent and can be used directly, so it is time-saving, easy to operate, low in cost, and economical. The powdered phosphate fertilizer anti-caking agent prepared by the present invention has a simple synthesis method, is plant-friendly, can be mixed with a hygroscopic agent and a surfactant, and has good economy and application prospects. It is particularly suitable for current powdered phosphate and potassium fertilizers, and the anti-caking effect can be increased by 4 to 7 times compared with the anti-caking agent currently on the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the effect diagram of using anti-caking agent 1 in the present invention;

[0024] Figure 2 The NMR spectrum of anti-caking agent 1;

[0025] Figure 3 The effect diagram of using the anti-caking agent purchased on the market;

[0026] Figure 4 This is the effect picture without adding anti-caking agent. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0028] Method for testing the anti-caking agent obtained in the examples and comparative examples:

[0029] According to the operating method in 6.4.1 of HG / T5519~5520-2019, weigh a watch glass (m1), take 20g of the mixed sample of fertilizer and anti-caking agent respectively, and weigh the total mass of the watch glass and the mixed sample m2. Place a weight (100g) on ​​the surface of the mixed sample, place it in a constant temperature oven (40℃, 80%RH) for 4 hours, take it out, and then place it in a vacuum drying oven (35℃, vacuum degree 0.02Mpa) and dry it to constant weight. Take out the dried culture dish and invert it at a height of 6cm above the laboratory bench. The mixed sample falls naturally under the action of gravity. Take a clean weighing paper and place it on the laboratory bench to receive the fallen sample. Sieve it (4.75mm), and weigh the total mass of the sample remaining on the screen and the watch glass m3. Calculate the anti-caking rate w1 according to the following formula, and the value is calculated in %:

[0030] w1=((m2-m3) / (m2-m1))×100%.

[0031] Example 1

[0032] Add 700g of caproic acid, 7g of manganese ferrite, and 300g of propylene glycol to the reactor, and fill the sealed reactor with ammonia gas, the flow rate of ammonia gas in the pipeline is less than or equal to 50ml / s, the pressure in the reactor is maintained at 0.3MPa, and the reaction is stirred at 120℃ for 8h. After the reaction is completed, turn off the heating system, open the exhaust valve of the reactor, gradually restore the normal pressure, and continue stirring at normal pressure for 2 hours. The catalyst is enriched by magnetic force, washed and dried, and reused; the reaction liquid is transferred to a distillation device, and the residual water and unreacted ammonia gas are further recovered by reduced pressure distillation until no obvious water vapor is generated.

[0033] The reaction liquid is mechanically filtered through a filter cloth to obtain the anti-caking agent 1. The anti-caking agent is added dropwise to 200 kg of potassium pyrophosphate, and the amount of the anti-caking agent is 0.2%. The adding process is stirring while adding, and mixing for 5 minutes at 60 revolutions per minute. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are 150-200 meshes.

[0034] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 82.1%. Figure 1 shown.

[0035] Figure 2 The NMR spectrum shown is the NMR hydrogen spectrum of the anti-caking agent 1 in this embodiment ( 1 H-NMR), where the red peak is the peak position of hexanamide, δ=6.6-7.0 is the two hydrogens on the amide amine group, δ=0.8-2.2 is the hydrogen on the hexanamide fatty chain, and the remaining δ=3-4 is the hydrogen on the solvent.

[0036] Example 2

[0037] Add 600g of decanoic acid and copper ferrite (12g) dissolved in 400g of ethylene glycol to the reactor, slowly fill ammonia into the closed reactor, the ammonia flow rate is less than or equal to 50ml / s, the pressure in the reactor is maintained at 0.5MPa, the temperature in the reactor is gradually increased to 130℃, and the reaction is stirred for 12h. After the reaction is completed, turn off the heating system, open the exhaust valve of the reactor, gradually restore to normal pressure, stir at normal pressure for 2 hours, enrich the catalyst magnetically, wash and dry it for reuse; transfer the reaction liquid to a distillation device, and further recover the residual water and unreacted ammonia by reduced pressure distillation until no obvious water vapor is generated.

[0038] The reaction liquid is mechanically filtered through a filter cloth to obtain the anti-caking agent 2. The anti-caking agent and the surfactant are added dropwise to the raw materials in 200 kg of balanced fertilizer (19-19-19, urea, potassium dihydrogen phosphate, potassium nitrate), the amount of the anti-caking agent is 1.0%, and the amount of fatty alcohol polyoxyethylene ether is 0.2%. At the same time, 0.3% of anhydrous magnesium sulfate is added as a moisture absorbent, and the mixture is stirred while adding the materials, and mixed at 60 revolutions per minute for 5 minutes. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are about 40 meshes.

[0039] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 89.3%.

[0040] Example 3

[0041] Add 200g tetradecanoic acid, zinc ferrite (10g), 800g 1,2-propylene glycol to the reactor, slowly fill ammonia into the closed reactor, the ammonia flow rate is less than or equal to 50ml / s, the pressure in the reactor is maintained at 0.8MPa, the temperature in the reactor is gradually increased to 180℃, and the reaction is stirred for 10h. After the reaction is completed, turn off the heating system, open the exhaust valve of the reactor, gradually restore to normal pressure, stir at normal pressure for 2 hours, magnetically enrich the catalyst, wash and dry it, and reuse it; transfer the reaction solution to a distillation device, and further recover the residual water and unreacted ammonia by reduced pressure distillation until no obvious water vapor is generated.

[0042] The reaction liquid is simply filtered to obtain the anti-caking agent 3. The anti-caking agent is added dropwise to 200 kg of potassium phosphite, and the amount of the anti-caking agent is 0.5%. The adding process is stirring while adding the materials, and mixing for 5 minutes at 60 revolutions per minute. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are 300-400 meshes.

[0043] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 95.2%.

[0044] Example 4

[0045] Add 800g of dodecanoic acid, 12g of manganese ferrite and 12g of zinc ferrite to the reaction kettle and dissolve them in 1200g of triethylene glycol (C6H 14 O4, CAS number: 112-27-6), slowly fill ammonia into the closed reactor, the ammonia flow rate is less than or equal to 50ml / s, the pressure in the reactor is maintained at about 0.6MPa, the temperature in the reactor is gradually increased to 170℃, and the reaction is stirred for 10h. After the reaction is completed, turn off the heating system, open the exhaust valve of the reactor, gradually restore to normal pressure, stir at normal pressure for 2 hours, magnetically enrich the catalyst, wash and dry it for reuse; transfer the reaction liquid to a distillation device, and further recover the residual water and unreacted ammonia by reduced pressure distillation until no obvious water vapor is generated.

[0046] The reaction liquid is mechanically filtered through a filter cloth to obtain anti-caking agent 4. Anti-caking agent 1 and anti-caking agent 4 are added dropwise to 200 kg of crystalline potassium dihydrogen phosphate in a ratio of 1:1, and the amount of anti-caking agent is 0.3%. The adding process is stirring while adding, and mixing for 5 minutes at 60 revolutions per minute. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are 300-400 meshes.

[0047] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 96.5%.

[0048] Example 5

[0049] Set the spray dryer fan speed to 80%, the inlet air temperature to 160°C, the spray pressure to 1.0 MPa, adjust the peristaltic pump rate to 5.0 mL / min, weigh 0.5 kg of anti-caking agent 4 and put it into 100 kg of 50% fertilizer stock solution and stir for 0.5 h. After mixing, spray dry. The output particles are about 0.5 mm.

[0050] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 96.2%.

[0051] Comparative Example 1

[0052] Take a commercially available anti-caking agent and add it to 100 kg of crystalline potassium dihydrogen phosphate, the amount of anti-caking agent is 0.3%. The adding process is to add and stir at 60 revolutions per minute for 5 minutes. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are 300-400 mesh.

[0053] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 52.2%. Figure 3 shown.

[0054] Comparative Example 2

[0055] 100kg of crystalline potassium dihydrogen phosphate fertilizer raw material is crushed and discharged, and the discharged particles are 300-400 meshes.

[0056] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 23.9%. Figure 4 shown.

[0057] Comparative Example 3

[0058] Add 700g of caproic acid, manganese ferrite (7g), and 300g of methanol to the reactor, and fill the closed reactor with ammonia gas, with a flow rate of ammonia gas less than or equal to 50ml / s. Maintain the pressure in the reactor at 0.3MPa, and stir the reaction at 120℃ for 24h. After the reaction is completed, turn off the heating system, open the exhaust valve of the reactor, gradually restore the normal pressure, and continue stirring at normal pressure for 2 hours. The catalyst is enriched by magnetic force, washed and dried, and reused; the reaction liquid is transferred to a distillation device, and the residual water, methanol and unreacted ammonia gas are further recovered by vacuum distillation until no obvious water vapor is generated to obtain crude caproamide. The crude caproamide is transferred to a vacuum drying oven for vacuum drying, cooled to room temperature after drying, and crushed to obtain powdered caproamide.

[0059] Add powdered caproamide to 200kg potassium pyrophosphate, the amount of caproamide is 0.2%. The adding process is to stir while adding, and mix for 5 minutes at 60 revolutions per minute. The mixed fertilizer raw materials are crushed and discharged, and the discharged particles are 150-200 mesh.

[0060] According to the HG / T 5519~5520-2019 method, the anti-caking rate is 33.6%.

Claims

1. A method for synthesizing saturated fatty amides, characterized in that: The method comprises the following steps: using saturated fatty acid and ammonia as raw materials, reacting in an organic solvent under the action of a ferrite catalyst to obtain a saturated fatty amide compound; the reaction equation is: Wherein, R is one or more C5-C13 alkyl substituents.

2. The synthesis method according to claim 1, characterized in that The ferrite is one or more of manganese ferrite, copper ferrite and zinc ferrite; the saturated fatty acid is one or more of caproic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid and tetradecanoic acid.

3. The synthesis method according to claim 1, characterized in that The organic solvent is an alcohol solvent.

4. The synthesis method according to claim 3, characterized in that The alcohol solvent is one or more of ethylene glycol, propylene glycol, glycerol, and oligoethylene glycol.

5. The synthesis method according to claim 1, characterized in that The method also includes, after the reaction is completed, stirring and distilling at normal pressure to recover ammonia and water; and magnetically enriching the catalyst, washing it, drying it, and then reusing it.

6. The synthesis method according to claim 1, characterized in that The mass ratio of the catalyst to the saturated fatty acid is 1-5%; the amount of the organic solvent is 0.4-4 times the mass of the saturated fatty acid.

7. The synthesis method according to claim 1, characterized in that The reaction temperature is 120-180°C, the reaction is carried out under closed conditions, the pressure conditions are 0.3-0.8Mpa, and the reaction time is 8-12 hours.

8. A fertilizer anti-caking agent, characterized in that: The invention relates to a saturated fatty amide prepared by the synthesis method according to any one of claims 1 to 7.

9. The fertilizer anti-caking agent according to claim 8, characterized in that Surfactants are also included.

10. Use of the fertilizer anti-caking agent according to claim 8 or 9 in powdered phosphate fertilizer, characterized in that: The amount of the anti-caking agent used in the powdered phosphate fertilizer is 0.2-1.0%.

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