Preparation method of 1-hydroxyethane-1,1-diphosphonic acid (HEDP)

1-hydroxyethane-1,1-diphosphonic acid (HEDP)

[Structural formula]

1-Hydroxyethane 1,1-diphosphonic acid is abbreviated as HEDP, which is a polyacid, easily soluble in water, and can dissociate 4 hydrogen ions in water
.

[Physical and chemical properties] The pure product of HEDP is white crystalline powder, and its industrial product is generally 50% to 60% colorless or light yellow viscous transparent aqueous solution
.

When the purity is 97%～98%, the melting point is 196～198℃

[Preparation method] The preparation methods of HEDP mainly include phosphorus trichloride glacial acetic acid-water method, phosphorous acid-acetic anhydride method, orthophosphoric acid -acetic anhydride method, orthophosphoric acid-acetic anhydride-acetyl chloride method
.

Among them, the phosphorus trichloride - glacial acetic acid -water method has a short process route, less equipment investment and easier operation, and is widely used by domestic and foreign manufacturers

Add acetic acid and water into the reaction kettle, and then add phosphorus trichloride dropwise to control the temperature in the kettle not to be higher than 40°C
.

After the addition is completed, the temperature is slowly raised

When the material in the kettle is below 40°C, the product can be obtained when the material is discharged
.

The main reaction equation for synthesizing HEDP with phosphorous acid, acetyl chloride and water as raw materials is as follows:

The synthesis steps are as follows:

(1) Add 20.

5g of phosphorous acid and 29.
5g of acetyl chloride to the three-necked flask, and fix the three-necked flask in the oil bath with an iron stand.
The rotation speed of the electromagnetic stirrer is 200r/min and the temperature of the oil bath is 40℃.

(2) Add 25 g of n-butanol to a three-necked flask, and distill out the n-butanol by heating at 115° C.
to take away hydrochloric acid and excess acetyl chloride
.

After 0.

In this way, the HEDP synthesized by the "two-step method" is a pale yellow viscous liquid, which is easily soluble in water
.

Except for the formation of CH ₃ COOH and HCI during the reaction process , no other by-products are formed

The dosage of HEDP synthesized in this study is 70mg/L, when the water temperature is 45～50℃, and pH=7, the corrosion inhibition rate is close to 90%, and when the dosage is 5mg/L, the scale inhibition rate reaches more than 90%
.

It simplifies the process route of the traditional synthesis method, avoids the occurrence of a large number of side reactions, and has high technical practicability and market development value

[Technical index]HG/T3537-1999

Related Links: Application of Amino Trimethylene Phosphonic Acid (ATMP)