CN1418883A - Method for producing 1-hydroxy ethylene-1,1-diphosphonic acid - Google Patents

Abstract

The invention is a production method of hydroxyethylidene diphosphonic acid. At a temperature of 100°C to 120°C, drop phosphorus trichloride directly into acetic acid to rapidly obtain acetylated hydroxyethylidene diphosphonic acid, and simultaneously separate and recover acetyl chloride and hydrogen chloride. Then steam hydrolysis, recovery of acetic acid, to obtain hydroxy ethylidene diphosphonic acid solution. The invention can accelerate the reaction speed, shorten the reaction time, reduce the energy consumption, save the cost and improve the reaction safety.

Description

A kind of production method of hydroxyethylidene diphosphonic acid

technical field

The invention belongs to the technical field of chemical industry, and in particular relates to a production method of hydroxyethylidene diphosphonic acid.

Background technique

Hydroxyethylidene diphosphonic acid has good complexing and buffering effects, and is widely used in industries, such as scale inhibitors for circulating water treatment, metal corrosion inhibitors and detergents. There are many production methods of hydroxyethylidene diphosphonic acid. The synthesis method using phosphorus trichloride and acetic acid as raw materials has low raw material price and relatively simple operation, and has become the main method for industrially producing hydroxyethylidene diphosphonic acid at present. French patent Fr1521963, under the condition of 35°C, after adding phosphorus trichloride to acetic acid and aqueous solution, gradually raise the temperature, collect the by-product acetyl chloride, and drop the collected acetyl chloride back into the reaction system. In this method, the dropwise addition of phosphorus trichloride must be controlled at a lower temperature, the reaction time is long, and the energy consumption is large. Chinese patent CN1091137 improves the cooling system in the method of Fr1521963, and adds the collected by-product acetyl chloride to the acetic acid solution, reducing the consumption of raw material acetic acid. However, the reaction time is long and the energy consumption is large. U.S. Patent No. 3,366,676 proposes adding phosphorus trichloride to acetic acid and tributylamine, and the reaction mixture is heated to 136° C. in a closed container. Although the reaction is complete in a short time, the presence of amine affects the purity of the product. Belgian patent Belg.672168 adds phosphorus trichloride to acetic acid at room temperature, then slowly raises the temperature to 60°C, then rises to 110°C, separates the acetylated intermediate product, and hydrolyzes to obtain the product. This method needs to separate the acetylated product, which complicates the operation process.

Contents of the invention

The purpose of the present invention is to propose an improved production method of hydroxyethylidene diphosphonic acid, to shorten the reaction time, reduce energy consumption and improve the safety of the reaction.

The improved production method of hydroxyethylidene diphosphonic acid proposed by the present invention is to directly react acetic acid with phosphorus trichloride to obtain acetylated hydroxyethylidene diphosphonic acid, and then hydrolyze to generate hydroxyethylidene diphosphonic acid solution. The specific steps are to place the acetic acid at the bottom of the reaction kettle and raise the temperature to 100°C-120°C. Stirring is started, phosphorus trichloride is added dropwise, and the condenser is opened at the same time to separate and recover acetyl chloride and hydrogen chloride, and acetylated hydroxyethylidene diphosphonic acid is produced rapidly. With the generation of acetylated hydroxyethylidene diphosphonic acid, the reaction solution gradually becomes viscous. After the phosphorus trichloride is added, keep it warm for 1-3 hours, and then pass steam for hydrolysis to obtain the hydroxyethylidene diphosphonic acid solution, and recover the acetic acid solution at the same time.

The route of the present invention is to directly react the raw material acetic acid and phosphorus trichloride, and the reaction temperature should be above 100°C, preferably above 110°C. At this temperature, phosphorus trichloride and acetic acid rapidly generate acetylated hydroxyethylidene diphosphonic acid, and release acetyl chloride and hydrochloric acid. The reaction formula is as follows:

In the present invention, the molar ratio of acetic acid to phosphorus trichloride is 3.5:1-8:1. When the molar ratio of acetic acid to phosphorus trichloride is large, the resulting acetylated hydroxyethylidene diphosphonic acid and acetic acid are obviously layered and can be separated, and the acetylated hydroxyethylidene diphosphonic acid is separated and hydrolyzed to obtain hydroxyethylidene diphosphonic acid. bisphosphonic acid. The separated acetic acid is merged into the reaction raw materials and continues to be recycled. This process can also be without separation, that is to say, the separation process is not necessary.

The selected raw material acetic acid has a concentration greater than 98%, preferably more than 99%. The recovered acetic acid solution can also be recycled after absorbing the recovered acetyl chloride in the reaction process. Through this step, raw material consumption can be reduced.

By implementing the present invention, the reaction can be carried out quickly, greatly shortening the reaction time, reducing energy consumption, and saving costs; because the content of water in the reactor is very little or almost anhydrous, the safety of the phosphorus trichloride dropping process is increased; the reaction process The collected acetyl chloride does not need to be dripped back into the reactor, and all of it can be used as the raw material of the present invention.

Detailed ways

The present invention is further described below by way of example.

Example 1 Add 90 grams of acetic acid to the bottom of the reaction kettle, start the agitator, heat up to 100°C, add 68 grams of phosphorus trichloride dropwise, and simultaneously open the condenser to collect acetyl chloride and hydrochloric acid. Half an hour later, after adding phosphorus trichloride, continue to heat up to 115° C., keep warm for 1 hour, pass steam for hydrolysis, and obtain 90 grams of hydroxyethylidene diphosphonic acid solution with a content of 47%. Wherein the content of phosphorous acid is 0.5%.

Example 2 Add 120 grams of acetic acid to the bottom of the reaction kettle, start the agitator, heat up to 110°C, add 68 grams of phosphorus trichloride dropwise, and simultaneously open the condenser to collect acetyl chloride and hydrochloric acid. After 25 minutes, after adding phosphorus trichloride, continue to heat up to 115° C., keep warm for 1.5 hours, and conduct steam hydrolysis to obtain 102 grams of 46% hydroxyethylidene diphosphonic acid solution. Wherein the content of phosphorous acid is 0.3%.

Example 3 Add 180 grams of acetic acid to the bottom of the reaction kettle, start the agitator, heat up to 105°C, add 68 grams of phosphorus trichloride dropwise, and simultaneously open the condenser to collect acetyl chloride and hydrochloric acid. After 30 minutes, after adding phosphorus trichloride, continue to heat up to 115° C., keep warm for 2 hours, pass steam for hydrolysis, and obtain 90 grams of hydroxyethylidene diphosphonic acid solution with a content of 48%. Wherein the content of phosphorous acid is 0.2%.

Example 4 150 grams of 98% acetic acid was added to the bottom of the reaction kettle, the stirrer was started, the temperature was raised to 100°C, 68 grams of phosphorus trichloride was added dropwise, and the condenser was opened simultaneously to collect acetyl chloride and hydrochloric acid. After 25 minutes, after adding phosphorus trichloride, continue to heat up to 115° C., keep warm for 1 hour, pass steam for hydrolysis, and obtain 86 grams of 50% hydroxyethylidene diphosphonic acid solution. Wherein the content of phosphorous acid is 0.2%.

Example 5 120 grams of 99% acetic acid was added to the bottom of the reaction kettle, the stirrer was started, the temperature was raised to 105°C, 68 grams of phosphorus trichloride was added dropwise, and the condenser was opened simultaneously to collect acetyl chloride and hydrochloric acid. After 20 minutes, after adding phosphorus trichloride, continue to heat up to 115° C., keep warm for 2 hours, pass steam for hydrolysis, and obtain 88 grams of hydroxyethylidene diphosphonic acid solution with a content of 49%. Wherein the content of phosphorous acid is 0.3%.

Claims (4)

1. An improved production method of hydroxyethylidene diphosphonic acid is characterized in that acetic acid is placed at the bottom of a reaction kettle, the temperature is raised to 100-120 ℃, phosphorus trichloride is dripped under stirring, a condenser isopened simultaneously, acetyl chloride and hydrogen chloride are separated and recovered, and acetylated hydroxyethylidene diphosphonic acid is rapidly generated; then steam is introduced for hydrolysis to obtain hydroxyethylidene diphosphonic acid solution, and simultaneously, the acetic acid solution is recovered.

2. The production process as set forth in claim 1, wherein the molar ratio of acetic acid to phosphorus trichloride is 3.5: 1 to 8: 1.

3. The process according to claim 1, wherein the concentration of acetic acid is greater than 98%.

4. The process according to claim 1, wherein the acetyl chloride recovered in the reaction is absorbed in the recovered acetic acid solution and recycled.