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13530-50-2
futurechem
13530-50-2
Aluminum dihydrogen phosphate (also known as aluminum acid phosphate, aluminum dihydrogen phosphate, or aluminum monophosphate) is an acid phosphate produced by the reaction of phosphoric acid and aluminum hydroxide. It is the most widely used inorganic chemical binder in the refractory materials industry. Its chemical formula is usually written as:
Al(H2PO4)3 (CAS No.: 13530-50-2, EINECS No.: 236-875-9, molecular weight approximately 317.94)
It is a white crystalline powder at room temperature, and commercially available products are often supplied as a colorless, transparent, viscous aqueous solution (commonly with a solid content of 30-50%). It is easily soluble in water, and the aqueous solution is weakly acidic and does not contain sodium ions. Aluminum dihydrogen phosphate is produced by reacting phosphoric acid with aluminum hydroxide (or aluminum salts). Upon heating, a condensation reaction occurs, and aluminum metaphosphate is formed above 900°C.
From a molecular structure perspective, aluminum dihydrogen phosphate molecules contain three dihydrogen phosphate ions (H₂PO₄⁻) coordinated to one aluminum ion (Al³⁺), and retain a large number of acidic hydroxyl groups (-OH) and PO bonds. At high temperatures, these acidic groups react with the basic oxides on the surface of refractory aggregates to form an aluminum phosphate (AlPO₄) composite phase. In scientific research, this process of "acidic phosphate condensation-phase formation" is a classic model system for studying phosphate chemistry, sol-gel transformation, and phase transitions in inorganic materials.
Chemically, aluminum dihydrogen phosphate undergoes sequential dehydration and condensation upon heating, ultimately forming a high-temperature-resistant aluminum metaphosphate phase. It is acidic, corrosive to metals, and reacts with alkaline materials. While non-flammable and non-toxic, its dust and acidic solutions are irritating to skin and eyes. It should be stored in a sealed, moisture-proof container and should not be stored with alkaline substances.
Non-industrial grade aluminum dihydrogen phosphate refers to products intended for testing, scientific research, and R&D applications. These mainly include reagent-grade and research-grade specifications, with a solid purity generally above 98%. Compared to industrial grade, non-industrial grade products place greater emphasis on the following indicators:
Content (purity)
Reagent-grade reagents require high purity (generally above 98%), as purity directly determines the accuracy of analytical results and experiments.
Free phosphoric acid
The content of free phosphoric acid affects the acidity of the solution and the reaction behavior, and must be strictly controlled to ensure the stability of the reagent properties.
Heavy metal limits
Reagent-grade reagents have strict limits on heavy metal content to ensure experimental safety and analytical reliability.
Water-insoluble matter
The solution must be extremely low in water-insoluble matter to ensure clarity and transparency, and to avoid impurities interfering with analysis and reaction.
Iron impurity content
Iron impurities affect the purity and color of reagents, and when used in materials research, they affect the performance of products, making them an important quality indicator.
1. Refractory material binder (core application)
Aluminum dihydrogen phosphate is the core chemical binder of unshaped refractories (refractory castables, ramming mixes, sprayed mixes, and plastics). It reacts with refractory aggregates at high temperatures to form an aluminum phosphate binder phase, giving the material excellent high-temperature resistance, vibration resistance, and spalling resistance. It is widely used in high-temperature kilns in steel, cement, glass, and non-ferrous metallurgy.
2. Silicon steel sheet insulating coating (electrical steel coating)
Aluminum dihydrogen phosphate is the main component of the phosphate-based chromium-free insulating and environmentally friendly coating for silicon steel sheets (electrical steel). After coating, it forms an insulating layer, reducing eddy current losses and energy losses in the magnetic core. It is used for silicon steel sheet insulation in transformers, motors, and generators.
3. High-temperature adhesives and sealants
Aluminum dihydrogen phosphate is used as a core raw material for high-temperature adhesives, high-temperature resistant mortar materials and sealants. It is formulated with refractory aggregates to form high-temperature resistant cementitious materials for bonding and sealing in high-temperature kilns, heat treatment furnaces and flue gas ducts.
4. Ceramic-kiln furniture binder
Aluminum dihydrogen phosphate is used as a binder for ceramic bodies, honeycomb ceramics, and kiln furniture, helping to improve the strength, thermal shock stability, and service temperature of ceramic products. It is an important inorganic binder in the ceramic industry.
5. Flame-retardant coatings
Aluminum dihydrogen phosphate is used in intumescent flame-retardant coatings for fibers, wood, and building materials. At high temperatures, it forms a heat-insulating and flame-retardant carbon layer and a phosphate layer, which helps improve the flame-retardant properties of the materials and is an important component of environmentally friendly flame-retardant systems.
6. Casting binders and mold materials
Aluminum dihydrogen phosphate is used as a binder for casting sand molds and a bonding agent for mold materials, helping to improve the strength and heat resistance of sand molds and molds, serving the casting and precision forming industries.
7. Laboratory and New Material Research and Application
( 1 ) Aluminum dihydrogen phosphate can be used as a standard reagent for the detection and analysis of refractory materials, phosphates, coating materials, and for the determination and calibration of phosphorus pentoxide content analysis methods;
(1) Research-grade products are mostly used for basic research in areas such as phosphate polycondensation, sol-gel conversion, and inorganic material phase transition.
(3) High-purity aluminum dihydrogen phosphate can be used for the formulation development and high-temperature performance evaluation of refractory castables, high-temperature adhesives and ceramic binders. It can also be used as a precursor raw material to customize the synthesis of aluminum phosphate crystals, porous materials and catalyst carriers, supporting the research and development of new materials in the fields of nanotechnology and catalysis.
8. Other Applications
With the development of high-temperature industry and green environmental protection technologies, the application scope of aluminum dihydrogen phosphate continues to expand, including standard reagents for refractory and phosphate analysis, aluminum phosphate catalyst supports, glass fiber treatment, and sol-gel material research.
Aluminum dihydrogen phosphate (Al(H2PO4)3, CAS No. 13530-50-2) is an acidic phosphate obtained by reacting phosphoric acid with aluminum hydroxide. It is a white crystalline powder or supplied as a 30-50% aqueous solution. It is readily soluble in water, weakly acidic, and reacts in situ at high temperatures to form an aluminum phosphate-bound phase. In daily life, we indirectly encounter it through testing and analysis services, scientific research and university laboratories, refractory material and coating development, teaching experiments, flame retardant and functional material research, and industrial supply chains. In non-industrial applications, reagent-grade and research-grade aluminum dihydrogen phosphate with a purity of over 98% is widely used in refractory material and phosphate analysis, phosphate chemistry and sol-gel research, high-temperature material development, coating and functional material development, teaching experiments, and custom synthesis. It is an important reagent for studying "inorganic bonding and material phase formation."
