The manufacturing process high-purity 99% phosphorous acid

The manufacturing process of electronic-grade, high-purity 99% phosphorous acid (CAS: 13598-36-2)

The production of electronic-grade, high-purity phosphorous acid,13598-36-2 is a sophisticated technological process that extends far beyond simple synthesis. The core challenge lies not in the initial reaction, but in a series of precise and stringent purification steps designed to achieve the extreme purity levels required by the semiconductor and pharmaceutical industries.

The typical industrial process can be broken down into two main stages: 1. Crude Synthesis and 2. High-Precision Purification.

Stage 1: Crude Synthesis

The objective of this stage is to efficiently produce industrial-grade phosphorous acid, which serves as the feed material for subsequent purification. The most common and industrialized method is the Hydrolysis of Phosphorus Trichloride (PCl₃).

Reaction Principle:

Phosphorus Trichloride undergoes a vigorous hydrolysis reaction with water to produce phosphorous acid and hydrogen chloride (HCl) gas.

Chemical Equation:

PCl₃+ 3H₂O → H₃PO + 3HCl↑

Process Details:

1. Raw Material Control: Even at this crude stage, high-purity industrial-grade PCl₃is selected to minimize the introduction of impurities from the source.

2. Reaction Control: This reaction is highly exothermic and produces large volumes of corrosive HCl gas. Therefore, it is typically carried out in a falling film absorber or a glass-lined reactor equipped with agitation and cooling systems. Precise control of the reaction temperature, PCl₃ feed rate, and water ratio is critical to ensure a safe and controlled reaction while maximizing yield.

3. By-Product Handling: The evolved HCl gas can be absorbed in water to produce industrial-grade hydrochloric acid, allowing for resource recovery.

The resulting crude phosphorous acid typically has a concentration above 95%, but it contains various impurities and is far from the electronic-grade standard.

Stage 2: High-Precision Purification (The Core Technology)

This is the most critical phase, transforming industrial-grade material into an electronic-grade product. It involves a combination of advanced physical and chemical purification techniques.

1. Crystallization & Re-crystallization

Principle: Separates phosphorous acid from impurities based on the difference in their solubility at various temperatures. By controlling the cooling rate, high-purity phosphorous acid crystals are formed and collected, while most soluble impurities remain in the mother liquor.

Operation: This process is often repeated multiple times (re-crystallization) to progressively enhance the product's purity. It is highly effective for removing inorganic salts and certain organic impurities.

Rectification (Fine Distillation)

Principle: Phosphorous acid can be distilled under specific conditions. Rectification exploits the differences in volatility between the components of the mixture, achieving highly efficient separation through multiple vapor-liquid equilibrium stages inside a fractionating column.

Role: This is a crucial step for removing both low-boiling-point and high-boiling-point impurities. For electronic-grade production, distillation must be performed under high vacuum to lower the boiling point and prevent thermal decomposition of the product.

3. Ion Exchange

Principle: This is the definitive step for removing metal ion impurities (e.g., Na⁺, K⁺, Fe²⁺/³⁺, Ca²⁺, Mg²⁺, Cu²⁺). An aqueous solution of the phosphorous acid is passed through columns filled with high-purity ion-exchange resins.

Role: Cation-exchange resins adsorb and remove metal cations, reducing their concentrations to parts-per-billion (ppb) or even parts-per-trillion (ppt) levels. This step is absolutely critical for meeting the requirements of semiconductor applications.

4. Precision Filtration

Principle: A cascade of filtration membranes with different pore sizes, typically involving microfiltration followed by ultrafiltration.

Role: This step removes suspended fine particles, colloids, and any sub-micron particles that may have been shed from equipment or resins. It ensures an extremely low particle count, meeting the cleanliness standards for electronic chemicals.

5. Final Processing and Packaging

The ultra-pure phosphorous acid solution may be concentrated to form high-purity crystals or directly packaged as a high-purity solution.

All final handling and packaging must be conducted in a cleanroom environment (e.g., Class 100 or better) using high-purity, inert materials for containers and piping (e.g., PFA, PTFE) to prevent any secondary contamination.

Summary Process Flow of 99% phosphorous Acid (CAS: 13598-36-2)

High-Purity PCl₃ + High-Purity Water → [Hydrolysis Reaction] → Crude Phosphorous Acid → [Crystallization/Re-crystallization] → [Rectification] → [Ion Exchange] → [Precision Filtration] → [Packaging in Cleanroom] → Electronic-Grade High-Purity Phosphorous Acid Final Product

Key Quality Control Points

Raw Material Purity: The purity of the starting PCl₃ and process water directly impacts the difficulty of purification and the final product quality.

Equipment Materials of Construction: The entire production system must use corrosion-resistant materials that do not leach metal ions, such as Hastelloy, glass-lining, PFA, or PTFE.

Product technical consultation: E-mail:Sales@hxochem.com Whatsapp: +8613330004268, WeChat: +8613285168509