[Background and Overview][1][2]
Monoammonium phosphate Also known as ammonium dihydrogen phosphate. Colorless and transparent tetragonal crystal or white crystalline powder. Relative molecular mass 115.03. Relative density 1.803 (19℃). Melting point 180℃. It decomposes at 190.5℃, losing ammonia and water, and generating a mixture of ammonium metaphosphate (NH4PO3) and phosphoric acid. Refractive index 1.479 and 1.525. Insoluble in acetone and acetic acid, slightly soluble in ethanol, soluble in water, solubility in water: 22.6 at 0℃, 28.20 at 10℃, 35.5 at 20℃, 39.5 at 25℃, 43.9 at 30℃, 57.0 at 40℃, 82.5 at 60℃, 118.3 at 80℃, 173.2 at 100℃. The pH of an aqueous solution with a concentration of 3% is 3.8~4.4. Stable in air. At 100℃, there is partial decomposition. It has piezoelectric properties and no strong dielectric properties. It transforms into the orthorhombic crystal system at low temperature (-125°C). This property is similar to potassium dihydrogen phosphate.
In food, it is used as buffering agent, dough conditioner, leavening agent, yeast nutrient, fermentation aid; fertilizer; sugar industry processing aid; fire retardant for wood, paper and fabric; pharmaceutical raw material. Ammonium dihydrogen phosphate has high nitrogen and phosphorus content and is often used as a basic compound fertilizer in agricultural production. However, the low utilization rate of conventional chemical fertilizers is a common problem in agricultural production. The low utilization rate of fertilizers not only causes a waste of resources, but also nitrogen fertilizers. The large-scale use of phosphate fertilizers brings harm to the environment and human health. At the same time, the phosphate fertilizer market situation is severe, and the world’s phosphate fertilizer supply exceeds demand. The survival and development of the phosphate fertilizer industry faces serious challenges. As an important chemical raw material, ammonium dihydrogen phosphate is looking for new application prospects and broadening the application fields of phosphorus resources, which will bring unprecedented new opportunities to the development of phosphorus chemical companies.
At present, there are many studies on ammonium dihydrogen phosphate at home and abroad, but most of them are aimed at the production and development of basic phosphate fertilizers. As the competition in the world’s conventional phosphate fertilizer market becomes more and more fierce, the development of ammonium dihydrogen phosphate slow-release/controlled-release fertilizers Research will be a hot topic in the future. By studying the slow-release/controlled-release mechanism, preparing new slow-release/controlled-release coating materials and improving the performance of slow-release/controlled-release fertilizers will be the focus of the next step. At the same time, the preparation of high-purity ammonium dihydrogen phosphate such as food grade and battery grade, and expanding the application of ammonium dihydrogen phosphate in food additives, battery materials, etc. are also important research directions in the future. In addition, phosphate rare earth metal-doped glass has good optical properties, and the development of phosphate optical glass and special glass materials will also have broad prospects.
[Application][2]
1. Fire protection field
1) Fire extinguishing agent
Ammonium dihydrogen phosphate dry powder fire extinguishing agent is highly efficient, safe and clean, has strong universal applicability, and is environmentally friendly. It has been widely welcomed by the domestic and foreign fire protection circles. In recent years, scientific researchers have done a lot of research on the preparation and modification of ultrafine ammonium dihydrogen phosphate dry powder fire extinguishing agent. Using the vibration ball milling method, by adding an appropriate amount of CA-type grinding aid and dispersant, an ultrafine ammonium dihydrogen phosphate dry powder fire extinguishing agent with a particle size of about 10 μm was produced, and then the siliconization process was used, using methyl hydrogenated silicone oil as the Surface modifier is used to modify the surface. The final product has good hydrophobicity and strong caking resistance. The fire extinguishing agent injection rate is 98.7%, the fire extinguishing time is 3 s, and the average fire extinguishing dosage is 60 g/m3. Spherical hollow ultrafine ammonium dihydrogen phosphate fire extinguishing agent was prepared by centrifugation and air spray drying methods respectively. The products prepared by the air flow spray method have small particles but poor uniformity, while the products prepared by the centrifugal spray method have uniform particle sizes but coarse particles. The product prepared by spray drying method has short fire extinguishing time, less critical fire extinguishing dosage, and its fire extinguishing performance is much better than commercially available fire extinguishing powder.
2) Flame retardant
Ammonium dihydrogen phosphate is a basic raw material for preparing new excellent inorganic flame retardants, ammonium polyphosphate or composite flame retardants, and has good applications in the field of flame retardants. Ammonium dihydrogen phosphate and urea are used as raw materials. After foaming, polymerization and solidification, I-type ammonium polyphosphate products are obtained. The degree of polymerization of the product is 52.08. The mass fractions of ammonia nitrogen and available phosphorus reach the national standard, which are 14.32% and 69.53% respectively. The flame retardant rate is 49.94%.
2. Material field
1) Glass material
Phosphate glass has the advantages of low glass transition temperature, moderate phonon energy, high thermal expansion coefficient, high solubility to rare earth ions, good spectral performance of rare earth ions in it, low nonlinear refractive index, ultraviolet transmission, and low dispersion. , has become a widely used optical glass medium and is widely used in the fields of colored filters, optical fibers and laser materials; however, when phosphate glass is melted, it has greater corrosion on the refractory crucible and has poor stability. hinder their application. Experimental studies have shown that changing the glass composition and introducing aluminum, boron and rare earth elements can effectively improve the chemical stability of phosphate glass. Fe2O3+NH4H2PO4 and Fe respectively 2O3 +NH4H2PO4 +Ce 2CO3 was used as raw material, n(Fe)/n(P) was 0.67, iron phosphate glass and cesium-doped iron phosphate glass were prepared, and the temperature was 26.85～426.85 ℃. Under the conditions, the thermal expansion and specific heat of the glass-like rubber additives were measured using a push rod dilatometer in an air atmosphere and a differential scanning calorimetry method under a flowing argon atmosphere. The thermal expansion of iron phosphate glass increases with the increase of cesium content.�� decreases with increasing cesium content, indicating that cesium doping reduces the stability of iron phosphate glass.
2) Lithium battery
Lithium iron phosphate material has become the preferred cathode material for lithium-ion power batteries due to its simple preparation process, long product cycle life, high temperature stability, low cost, and high safety performance, and has also become a hot spot in new energy research in various countries. At present, lithium iron phosphate manufacturing companies that are technically at the forefront of the world include companies such as A123, Valence and Photech. The main companies in China that promote lithium iron phosphate batteries are led by BYD. One or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium dihydrogen phosphate, etc. are used as the phosphorus source, and the carbon source is used as the additive. The material ratio of the phosphorus source, iron source, and lithium source is 1:1. ∶ (1~1.05) are mixed and sintered twice under a protective atmosphere to obtain lithium iron phosphate. The products prepared by this method can achieve a good balance between high volume specific capacity and excellent high current discharge performance. Lithium-iron-phosphate is synthesized under hydrothermal conditions. This method combines at least one lithium-containing compound, at least one iron-containing compound with an oxidation state of iron of 0, and at least one phosphorus-containing compound with an oxidation state of +5. Materials (such as NH4H2PO4) are heated at 100 ~ 500 ℃ and autogenous pressure, and the general formula is: Lia- Particles or agglomerates of bM1bFe1-cM2cPd-eM3eOx. This method has a simple process, does not have any interfering by-products, and does not require calcination and purification steps.
3. Matrix improver field
When measuring metals using atomic absorption spectrometry, transition metals or transition metal salts such as palladium and palladium chloride are often used as matrix modifiers. However, heavy metal ions can easily cause harm to the environment and are expensive. As a matrix modifier, ammonium dihydrogen phosphate can effectively eliminate matrix interference, increase the ashing temperature of the measured elements, reduce the ashing loss of the analyzed elements, and significantly improve the measurement accuracy when measuring elements such as lead and cadmium by atomic absorption spectrometry. and anti-interference ability, while being environmentally friendly and low cost. Graphite furnace atomic absorption method (GFAAS method) was used to study NH4H2PO4, (NH4)3PO4, NH4H2PO4+Mg ( NO3)2+NH4NO3, NH4Cl and other matrix The improvement effect of modifiers on the determination of lead in primary treated sewage irrigated soil, and 40 g/L NH4H2PO4 was determined to be the best modifier. The ashing and atomization temperatures were 850 ℃ and 1600 ℃ respectively. The deuterium lamp background correction GF-AAS method was used for measurement. The RSD was 2.6% and the recovery rate was above 92.4%.
The GF-AAS method was used to determine cadmium in fly ash, soil, and sediment, and the effects of different matrix modifiers were evaluated. The cadmium recovery rate is higher when matrix modifier is added than when not added. By comparing several matrix modifiers, 2% (mass fraction) NH4H2PO4 +0.4% (mass fraction) Mg (NO3)2 is used as the modifier to have the highest recovery rate of cadmium. When using the Zeeman effect background correction, NH4H2PO4 and NH4H 2PO4+Mg (NO3)2 are all good matrix modifiers. The recovery rates of the three samples Both reach more than 98%, and the optimal ashing temperature is also 300 ~ ℃ higher than other matrix modifiers, but NH4H2PO4 +Mg(NO3)2 produces a stronger background absorption than transition metals.
【Preparation】[1] [3]
Method 1: Slowly add 28% ammonia water to dilute phosphoric acid. This reaction is an exothermic reaction. After the reaction is completed and cooled, when the pH value of the solution is measured to be in the range of 3.8 to 4.5, cool, crystallize and filter. Wash with cold water and recrystallize in hot water to obtain monoammonium phosphate. In the reaction between phosphoric acid and ammonia, when the reaction temperature is in the range of 0 to 75°C, NH4H5(PO4)2·H2O, NH4H5(PO4)2, NH4H2PO4, (NH4)2 HPO4· 2(NH4)2HPO4, (NH4 )3PO4, (NH4)3PO4 >·3H2O and other phosphates, so it is very important to control the pH value of the solution.
Method 2: A method for producing monoammonium phosphate, which uses high-purity urea phosphate and ammonia to directly undergo a metathesis reaction to prepare monoammonium phosphate. The reaction equation is:
Control the reaction temperature to 40-80°C, stir the reaction for 20-60 minutes, and the pH value of the reaction end point is 4.2-4.6. Through cooling crystallization, centrifugal separation and drying steps, the monoammonium phosphate product is obtained. Specifically, it includes the following steps:
1) Preparation of urea phosphate solution: Add water to the urea phosphate solid with a purity of 98% in the dissolution tank and measure it. After raising the temperature to 40-80°C, stir, dissolve and mix evenly, and control the stirring speed to 30 -50r/min, obtain urea phosphate solution;
2) Synthesis of monoammonium phosphate: Use a transfer pump to input the urea phosphate solution into the synthesis tank, control the temperature to 40-80°C, and follow the molar ratio of urea phosphate to ammonia: (0.99-1.05): 1 Add ammonia in proportion to react; add solvent ammonia while stirring, the stirring speed is 60-70r/min, when the stirring reaction is 20-60 minutes, when the pH value is detected to be 4.2-4.6, the reaction is terminated, and monoammonium phosphate slurry is obtained;
3) Crystallization centrifugal separation: Transfer the monoammonium phosphate slurry into the crystallizer and cool it to ≤40°C to precipitate the crystals, and transfer the crystals into a centrifuge for centrifugal separation to obtain the filtrate and filter cake. The filtrate The urea slurry is transferred to the urea phosphate production process to produce urea phosphate raw materials; the filter cake is monoammonium phosphate, which is placed in a dryer at a drying temperature of 80°C and dried for 3-5 minutes to obtain a monoammonium phosphate product.
The process flow is as follows:
[Main reference materials]
[1] Practical Fine Chemical Dictionary
[2] Zheng Run, Xie Tian, Liu Fei, Li Tianxiang, Zhu Jing. Research progress on the application of ammonium dihydrogen phosphate. Inorganic Salt Industry, 2014, 46(4). Volume 46, Issue 4
[3] Liao Jixing; Peng Baolin; Zhu Feiwu; Shi Xiuming; Han Chaoying; Zhou Yong. A production method of monoammonium phosphate CN201410213411.9, application date 2014-05-20
At 40-80℃, add ammonia for reaction according to the molar ratio of urea phosphate to ammonia: (0.99-1.05): 1; add solvent ammonia while stirring, the stirring speed is 60-70r/min, and the stirring reaction is 20 -60min, when the pH value is detected to be 4.2-4.6, the reaction is terminated and monoammonium phosphate slurry is obtained;
3) Crystallization centrifugal separation: Transfer the monoammonium phosphate slurry into the crystallizer and cool it to ≤40°C to precipitate the crystals, and transfer the crystals into a centrifuge for centrifugal separation to obtain the filtrate and filter cake. The filtrate The urea slurry is transferred to the urea phosphate production process to produce urea phosphate raw materials; the filter cake is monoammonium phosphate, which is placed in a dryer at a drying temperature of 80°C and dried for 3-5 minutes to obtain a monoammonium phosphate product.
The process flow is as follows:
[Main reference materials]
[1] Practical Fine Chemical Dictionary
[2] Zheng Run, Xie Tian, Liu Fei, Li Tianxiang, Zhu Jing. Research progress on the application of ammonium dihydrogen phosphate. Inorganic Salt Industry, 2014, 46(4). Volume 46, Issue 4
[3] Liao Jixing; Peng Baolin; Zhu Feiwu; Shi Xiuming; Han Chaoying; Zhou Yong. A production method of monoammonium phosphate CN201410213411.9, application date 2014-05-20
