Synthesis of saturated fatty amides and their use as anti-caking agents in fertilizers

Abstract

The application relates to a synthesis method of saturated fatty amides and application of the saturated fatty amides in chemical fertilizer anti-caking agents, and belongs to the technical field of chemical fertilizer auxiliaries. The method comprises the following steps: taking saturated fatty acids and ammonia gas as raw materials, reacting in an organic solvent under the action of a ferrite catalyst to obtain a saturated fatty amide compound, and the reaction liquid after the reaction is finished can be directly used as an anti-caking agent after simple filtration. The prepared powder phosphorus fertilizer anti-caking agent has the advantages of simple synthesis method, friendliness to plants, mixability with hygroscopic agents and surfactants, good economy and application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a synthesis method of saturated fatty amides and application of the saturated fatty amides in chemical fertilizer anti-caking agents, and belongs to the technical field of chemical fertilizer auxiliaries. BACKGROUND

[0002] Chemical fertilizers play a vital role in modern agricultural production. With the transformation of agriculture towards scale and mechanization, fast-dissolving powder phosphorus 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 unmanned aerial spraying and intelligent fertilization systems) due to their unique physical and chemical properties, and their use is increasing year by year. Fast-dissolving phosphorus fertilizers are mostly in the form of powder, with small and unevenly distributed particles, which are prone to caking during storage and affect use. Existing anti-caking agents are mostly designed for granular fertilizers, and have poor anti-caking effect on powder phosphorus fertilizers. It is particularly urgent to develop high-efficiency anti-caking agents suitable for powder phosphorus fertilizers.

[0003] Chinese patent CN101798248B uses double-hexadecafluorononanol succinic acid monoester amine salt, and adds a proper proportion of primary amine salt or secondary amine salt, industrial wax oil, etc. for compounding. Although this method has anti-caking effect, mineral oil is difficult to degrade when it enters the soil with the fertilizer. CN105294313B uses inorganic powder 90-97% and surfactant 3-10% to achieve anti-caking effect by blocking the formation of crystal bridges between fertilizer particles. Although this method has anti-caking effect, the process is complex and the cost is high. CN101654387B uses 1wt%-50wt% of water-based polymer, 1wt%-50wt% of surfactant, and the rest of water. Although this method has anti-caking effect, water-based polymer and surfactant are not easily miscible, and the use amount is large, so the cost is high. CN119100871A discloses an anti-caking agent and a preparation method thereof. The anti-caking agent includes a surfactant with controllable hydrophilic and hydrophobic chain length, a macromolecular surfactant, and an inert powder. The anti-caking agent is obtained by blending. The inert powder may block the spray head during sprinkling and aerial spraying, which limits the use range of the fertilizer.

[0004] Chinese patent CN114560785B discloses a synthesis method of primary amide compounds, which takes lipid compounds and ammonia borane as raw materials, and obtains primary amide compounds under the action of sodium bis(trimethylsilyl) amine, but ammonia borane is toxic, in addition, the treatment 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 amide by ammonia method, which synthesizes primary fatty amide by taking ammonia gas and fatty acid as raw materials, taking chromatographic silica gel, activated carbon, trisodium phosphate (Na3PO4.12H2O), amidation catalyst (NC-301), active aluminum oxide and zirconium dioxide as catalysts; but this method has high requirements for ammonia gas recovery equipment, and has problems such as strict water removal of reactants, difficult reuse of catalysts and harsh reaction conditions.

[0005] As can be seen from the above, the existing synthesis method of primary fatty amide has problems such as harsh synthesis conditions, complicated product post-treatment process and high cost. Conventional anti-caking agents have limited effect on fine particle powder phosphorus fertilizer, in addition, anti-caking agents containing inert powder have limitations in the application of drip irrigation, sprinkler irrigation and aerial spraying in modern agriculture. SUMMARY

[0006] In order to overcome at least one of the above problems of the existing fatty amide preparation method and / or anti-caking agent, the present application proposes a new synthesis method of saturated fatty amide, and a powder phosphorus fertilizer anti-caking agent prepared by using the saturated fatty amide obtained by the method.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] In a first aspect of the present application, a synthesis method of saturated fatty amide is provided, which comprises the following steps: taking saturated fatty acid and ammonia gas as raw materials, reacting in an organic solvent under the action of a catalyst to obtain a saturated fatty amide compound; the reaction equation is as follows:

[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 O2). The catalyst is ferrite, preferably one or more of manganese ferrite (MnFe2O4), copper ferrite (CuFe2O4), zinc ferrite (ZnFe2O4).

[0011] Preferably, the organic solvent is an alcohol, preferably one or more of ethylene glycol, propylene glycol, glycerol, oligoethylene glycol. The addition of the organic solvent increases the collision frequency between molecules in the reaction system, promotes the reaction, and the reaction environment is relatively stable, reducing the occurrence of side reactions.

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

[0013] Preferably, the surfactant is any one of fatty polyoxyethylene ether or a mixture of two or more thereof in any ratio.

[0014] Preferably, the method further comprises, after the reaction is completed, normal pressure stirring distillation to recover ammonia and water; and magnetic enrichment of the catalyst, which can be reused after cleaning and drying.

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

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

[0017] In the present application, the amount of the anti-caking agent in the powder phosphorus fertilizer is 0.2-1.0%. The trace amount of free ammonia remaining in the anti-caking agent is itself a fertilizer, and the trace amount of gold ions remaining is also an element beneficial to plants.

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

[0019] 1. The catalyst in the present synthesis method can be simply separated by magnetic force, without the traditional processes of filtration, washing and evaporation, and the trace amount of metal remaining in the system is a medium or microelement fertilizer.

[0020] 2.Fe2O3 has rich Lewis acid sites and basic sites on its surface due to its crystal structure characteristics, which can effectively adsorb reactant molecules, the carboxyl group of fatty acid can interact with the Lewis acid sites on the surface of the catalyst through its oxygen atom, causing the electron density distribution of the C=O bond in the carboxyl group to change, thereby reducing the activation energy of the reaction of fatty acid and ammonia, which provides a more favorable path for the reaction of fatty acid and ammonia. At the same time, alcohol molecules have hydroxyl (-OH) functional groups, which can form intermolecular interactions with the carboxyl group of fatty acid through hydrogen bonds to stabilize the reaction intermediates; and the hydrogen bonds formed between the carboxyl group of fatty acid 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 surface of the catalyst during the reaction, reducing the deactivation of the active sites in the catalyst. Under appropriate reaction temperature and pressure conditions, alcohol molecules may undergo esterification reaction with fatty acid to generate ester intermediates, which further undergo ammonolysis reaction with ammonia to generate the target product saturated fatty amide and release alcohol molecules, thereby realizing the recycling of alcohol, therefore, in the present application, the reaction can be carried out under closed conditions. This reaction path not only improves the conversion efficiency of fatty acid, but also reflects the auxiliary catalytic effect of alcohol in the reaction system, and the alcohol reaction solvent in the present synthesis method is an additive for increasing the resistance of crops in chemical fertilizers, which itself has certain anti-caking effect and can be directly used, so the synthesis product does not need to be separated from the solvent.

[0021] 3.The main component of the anti-caking agent provided by the present application is saturated fatty amide, which can adsorb phosphate fertilizer surface to form a hydrophobic layer and reduce the moisture absorption amount of the fertilizer in the environment; and the hydrophobic carbon chain and the hydrogen bond effect of the hydroxyl-containing solvent can increase the flowability of the fertilizer particles. There are two current powder phosphate fertilizer production methods, one is to use crystal fertilizer (or granular fertilizer) alone or in mixture, and then to obtain powder fertilizer by crushing, the anti-caking agent of the present application is a liquid, which can be directly added to the crystal (granule) and mixed evenly, and the components of the anti-caking agent are firmly adsorbed on the surface of the powder during the crushing process; the other is to obtain fine particle powder fertilizer by spray drying of liquid monopotassium phosphate slurry, and the anti-caking agent of the present application is directly added to the fertilizer liquid raw material for mixing, and the anti-caking agent is combined with the fine particles of chemical fertilizer in the spray drying process. Therefore, the anti-caking agent provided by the present application is directly added to the raw material for use, which does not affect the normal production steps and is very convenient to use; after the production of the fertilizer is completed, the fertilizer product is directly packed, which reduces the time of the fertilizer product exposed to the environment and effectively reduces the environmental moisture absorption amount.

[0022] 4. The product of the traditional method needs to be purified, the steps are complicated, the energy consumption is high, the product obtained by the synthesis method of the present application does not need to be separated from the solvent and can be directly used, so time is saved, the operation is simple, the cost is low, and the economy is good; the powder phosphorus fertilizer anti-caking agent prepared by the present application has a simple synthesis method, is friendly to plants, can be mixed with hygroscopic agents and surfactants, has good economic efficiency and application prospect. Especially suitable for the current powder phosphorus potassium fertilizer, compared with the anti-caking agent on the market, the anti-caking effect can be increased by 4-7 times. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Effect diagram of using anti-caking agent 1 of the present application;

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

[0025] Figure 3 Effect diagram of using market-purchased anti-caking agent;

[0026] Figure 4 Effect diagram of no addition of anti-caking agent. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0028] The method for testing the anti-caking agent obtained from the examples and comparative examples is as follows:

[0029] According to the operation method in 6.4.1 of HG / T5519-5520-2019, a watch glass (m1) is weighed, 20 g of the fertilizer mixed with the anti-caking agent is taken, and the total mass m2 of the watch glass and the mixed sample is weighed. A weight (100 g) is placed on the surface of the mixed sample, and then placed in a constant temperature box (40℃, 80% RH) for 4 h and taken out, and then placed in a vacuum drying box (35℃, vacuum degree 0.02 Mpa) for drying to constant weight. After drying, the watch glass is taken out and inverted at a height of 6 cm above the experimental table, and the mixed sample falls naturally under the action of gravity. Clean weighing paper is placed on the experimental table to receive the falling sample, and sieved (4.75 mm), and the total mass m3 of the sample left on the screen and the watch glass is weighed. The anti-caking rate w1 is calculated according to the following formula, and the value is calculated in %:

[0030] w1=((m2-m3) / (m2-m1))×100%.

[0031] Example 1

[0032] Add 700g hexanoic acid, 7g manganese ferrite, and 300g glycerol to the reactor. Introduce ammonia gas into the sealed reactor, maintaining a flow rate of at least 50ml / s. Keep the pressure inside the reactor at 0.3MPa and stir at 120℃ for 8 hours. After the reaction is complete, turn off the heating system, open the vent valve of the reactor, and gradually restore the pressure to atmospheric level. Continue stirring at atmospheric pressure for 2 hours. The catalyst is magnetically enriched, cleaned, dried, and reused. Transfer the reaction solution to a distillation apparatus and further recover residual water and unreacted ammonia through vacuum distillation until no significant water vapor is produced.

[0033] The reaction solution is mechanically filtered through a filter cloth to obtain anti-caking agent 1. The anti-caking agent is added dropwise to 200 kg of potassium pyrophosphate at a dosage of 0.2%. The addition process involves simultaneous addition and stirring at 60 rpm for 5 minutes. The mixed fertilizer raw material is then pulverized and discharged, producing particles of 150-200 mesh.

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

[0035] Figure 2 The NMR spectrum shown is the 1H NMR spectrum of the anti-caking agent 1 in this embodiment. 1 (H-NMR), where the red peaks represent the elution positions of hexamethylenetetramine, the two hydrogens at δ = 6.6-7.0 represent the two hydrogens on the amide amino group, the hydrogens at δ = 0.8-2.2 represent the hydrogens on the hexamethylenetetramine aliphatic chain, and the remaining hydrogens at δ = 3-4 represent the hydrogens on the solvent.

[0036] Example 2

[0037] Add 600g of decanoic acid and 12g of copper ferrite dissolved in 400g of ethylene glycol to the reactor. Slowly introduce ammonia gas into the sealed reactor at a flow rate of ≤50ml / s, maintaining the pressure inside the reactor at 0.5MPa. Gradually increase the temperature inside the reactor to 130℃ and stir the reaction for 12 hours. After the reaction is complete, turn off the heating system, open the vent valve of the reactor, and gradually restore the pressure to atmospheric pressure. Stir at atmospheric pressure for 2 hours to magnetically enrich the catalyst. After cleaning and drying, the catalyst can be reused. Transfer the reaction solution to a distillation apparatus and further recover residual water and unreacted ammonia gas through vacuum distillation until no obvious water vapor is produced.

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

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

[0040] Example 3

[0041] Into the reaction kettle, 200 g of myristic acid, zinc ferrite (10 g), and 800 g of 1,2-propanediol are added. Ammonia gas is slowly charged into the closed reaction kettle at a flow rate of less than or equal to 50 ml / s. The pressure in the reaction kettle is maintained at 0.8 MPa, and the temperature in the reaction kettle is gradually increased to 180°C. The reaction is stirred for 10 h. After the reaction is completed, the heating system is turned off, the exhaust valve of the reaction kettle is opened, and the normal pressure is gradually restored. The mixture is stirred at normal pressure for 2 h. The catalyst is magnetically enriched, washed and dried, and then reused. The reaction solution is transferred to a distillation device, and residual water and unreacted ammonia gas are further recovered by vacuum distillation until no obvious water vapor is generated.

[0042] The reaction solution is simply filtered to obtain the anti-caking agent 3. The anti-caking agent is added dropwise into 200 kg of potassium phosphite, and the anti-caking agent is used in an amount of 0.5%. The feeding process is stirring at 60 revolutions per minute for 5 minutes. After mixing, the fertilizer raw material is crushed and discharged, and the discharged particles are 300-400 mesh.

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

[0044] Example 4

[0045] Into the reaction kettle, 800 g of lauric acid, manganese ferrite (12 g), and zinc ferrite (12 g) are dissolved in 1200 g of triethylene glycol (C6H 14 O4, CAS number: 112-27-6). Ammonia gas is slowly charged into the closed reaction kettle at a flow rate of less than or equal to 50 ml / s. The pressure in the reaction kettle is maintained at about 0.6 MPa, and the temperature in the reaction kettle is gradually increased to 170°C. The reaction is stirred for 10 h. After the reaction is completed, the heating system is turned off, the exhaust valve of the reaction kettle is opened, and the normal pressure is gradually restored. The mixture is stirred at normal pressure for 2 h. The catalyst is magnetically enriched, washed and dried, and then reused. The reaction solution is transferred to a distillation device, and residual water and unreacted ammonia gas are further recovered by vacuum distillation until no obvious water vapor is generated.

[0046] The reaction solution was mechanically filtered through filter cloth to obtain anti-caking agent 4. Anti-caking agent 1 and anti-caking agent 4 were added dropwise into 200 kg of crystalline potassium dihydrogen phosphate at a ratio of 1:1, and the amount of anti-caking agent was 0.3%. The feeding process was stirring at 60 revolutions per minute for 5 minutes. After mixing, the fertilizer raw material was crushed and discharged, and the discharge particle size was 300-400 mesh.

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

[0048] Example 5

[0049] The spray dryer fan speed was set to 80%, the inlet air temperature was 160°C, the spray pressure was 1.0 MPa, the peristaltic pump rate was adjusted to 5.0 mL / min, 0.5 kg of anti-caking agent 4 was weighed and added into 100 kg of fertilizer raw solution with a concentration of 50%, stirred for 0.5 h, and then spray dried after mixing. The discharge particle size was about 0.5 mm.

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

[0051] Comparative Example 1

[0052] A commercially available anti-caking agent was added to 100 kg of crystalline potassium dihydrogen phosphate, and the amount of anti-caking agent was 0.3%. The feeding process was stirring at 60 revolutions per minute for 5 minutes. After mixing, the fertilizer raw material was crushed and discharged, and the discharge particle size was 300-400 mesh.

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

[0054] Comparative Example 2

[0055] The 100 kg of crystalline potassium dihydrogen phosphate fertilizer raw material was crushed and discharged, and the discharge particle size was 300-400 mesh.

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

[0057] Comparative Example 3

[0058] A reaction kettle is charged with 700 g of hexanoic acid, manganese ferrite (7 g), and 300 g of methanol. Ammonia gas is charged into the closed reaction kettle at a flow rate of 50 ml / s or less, and the pressure in the reaction kettle is maintained at 0.3 MPa. The reaction is stirred at 120°C for 24 h. After the reaction is completed, the heating system is turned off, the exhaust valve of the reaction kettle is opened, and the normal pressure is gradually restored. The stirring is continued for 2 h under normal pressure. The catalyst is enriched by magnetic force, washed and dried, and then reused. The reaction liquid is transferred to a distillation device, and residual water, methanol and unreacted ammonia gas are further recovered by vacuum distillation until no obvious water vapor is generated. A crude hexanamide is obtained. The crude hexanamide is transferred to a vacuum drying box for vacuum drying. After drying is completed, the product is cooled to room temperature, and then crushed to obtain a powder of hexanamide.

[0059] The powder of hexanamide is added to 200 kg of potassium pyrophosphate, and the amount of hexanamide is 0.2%. The feeding process is stirring at 60 rpm for 5 min while feeding. The mixed fertilizer raw material is crushed and discharged. The discharge particles are 150-200 mesh.

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

Claims

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

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

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

4. The synthesis method as described in claim 3, characterized in that, The alcohol solvent is one or more of ethylene glycol, propylene glycol, glycerol, and oligomeric polyethylene glycol.

5. The synthesis method as described in claim 1, characterized in that, The method also includes atmospheric pressure stirring distillation after the reaction is complete to recover ammonia and water; the catalyst is magnetically enriched, cleaned, dried and reused.

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

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

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