Views: 587 Author: Site Editor Publish Time: 2017-06-07 Origin: Site
Etidronic Acid, referred to as HEDP, structural formula: (H2PO3) 2C (OH) CH3. Pure white crystal, soluble in water and methanol, its melting point is 198-199 ℃. HEDP is usually used as complexing agent, water stabilizer, masking agent, extractant, etc., widely used in circulating cooling water, boiler water, oil field water injection, oil pipeline corrosion and other aspects.
HEDP is a cathodic corrosion inhibitor, which is about 4 times more than the inorganic polymerized phosphate. HEDP is used in combination with other corrosion inhibitors, scale inhibitors such as chromates, polymeric phosphates, molybdates, silicates, zinc salts, polycarboxylates and derivatives thereof, which has synergistic effect, can improve efficacy. As the environmental protection departments strictly controlled emission standards of chromium and phosphate, low phosphorus or phosphorus-free drugs are often used in the circulating cooling water system and boiler system. In several kinds of low phosphorus preparations, HEDP is most commonly used. The dosage is generally less than 1-3PPm. In recent years, the recipe of low phosphorus pharmacy formulations are as follows:
1.Glycolic acid, HEDP, polyacrylic acid, BTA
2. NaMcO4, HEDP,BTA
4. HEDP, Zn++
It has been reported that the synthesis of hydroxyethylidene diphosphonic acid is roughly the following:
1. Phosphorus trichloride and glacial acetic acid as raw materials
Phosphorus trichloride, acetic acid hydrolysis, obtained hydroxy ethylidene diphosphonic acid.
2PC13+CH3COOH+5H2O →HEDP+6HCl
2. Phosphorous acid and acetic anhydride as raw materials
With nitrous acid, acetic anhydride as raw material reaction, hydrolysis obtained HEDP.
3. Phosphorous acid and acetyl chloride as raw materials
Use phosphoric acid and acetyl chloride as raw materials to produce HEDP.
Synthesis of HEDP by reaction of phosphorus trichloride and glacial acetic acid, has the following advantages:
1.Easy to get raw materials, and the price is cheap
2. Reaction conditions are mild, atmospheric pressure, temperature 25 - l20 ℃
3. Simple process, easy operation, production safety
4. Product purity of up to 97%, the yield of 95% or more
Thus, using this method to produce HEDP is more economical and practical.
