Uses and preparation methods of hypophosphorous acid_Industrial additives

Background and overview^[1]

Hypophosphorous acid is also called “lpvc resin dquo; hypophosphorous acid”, chemical formula H (H₂PO₂), molecular weight 66.00, colorless oil or deliquescent crystal, melting point 26.5℃, relative density 1.49319. Hypophosphorous acid is easily soluble in water, ethanol and ether. It decomposes into phosphine and phosphorous acid at 130℃, and reacts with the generated hydrogen to form phosphine. Hypophosphorous acid has strong reducing properties and can make heavy metal salt solutions. Reduced to metal. In previous production, hypophosphorous acid can generally be produced by reacting yellow phosphorus and barium hydroxide and adding sulfuric acid to remove barium. However, due to the low solubility of barium salt, the concentration of hypophosphorous acid produced is not high and it takes many times. There is another method for recrystallization and purification.

Purpose^[2-3]

Hypophosphorous acid is a very useful product in the fine phosphorus chemical industry. It can be used as a reducing agent for electroless plating. It can be used to prevent the discoloration of phosphoric acid resin. It can also be used as a catalyst refrigerant for esterification and for the production of sodium hypophosphite. .

CN200310107264.9 discloses a method for preparing nickel hypophosphite by electrolysis. It uses alkali metal hypophosphite as the raw material, the nickel plate as the anode, and stainless steel as the cathode. It uses the method of electrodialysis cell electrolysis for electrolysis; among them, the raw material chamber has a sodium hypophosphite aqueous solution with a concentration of 300~500g/L, and the anode chamber The initial solution in the cathode chamber and its adjacent buffer chamber is a sulfuric acid solution with a concentration of 5~15g/L. The initial solution in the cathode chamber and its adjacent buffer chamber is an alkali solution with a concentration of 5~15g/L. The product chamber and its adjacent buffer chamber are The initial solution is a hypophosphorous acid solution with a concentration of 5~15g/L. The present invention can prepare a mixed solution of nickel hypophosphite and hypophosphorous acid that can be directly used for electroless nickel plating, enrich it under reduced pressure, and also obtain a concentrated solution that can be used as a supplementary liquid in the electroless nickel plating matting process. Use nickel hydroxide to adjust the pH value of the nickel hypophosphite solution to 3, and then enrich it under reduced pressure to obtain Ni(H2PO2)2·6H2O crystals with a purity of 99%. The invention produces no waste residue or waste liquid and belongs to clean production.

Preparation^[4]

1) Reaction of yellow phosphorus and barium hydroxide

Hypophosphorous acid is generally produced by reacting yellow phosphorus with barium hydroxide, and adding sulfuric acid to remove the barium. However, the solubility of barium salt is small, and the concentration of hypophosphorous acid produced is not high, and it needs to be concentrated and recrystallized for purification.

2) Ion exchange method

The production of hypophosphorous acid using ion exchange resin is a much-researched method, that is, sodium hypophosphite is used as raw material, and a strong acid cation exchange resin is used to remove sodium to obtain a dilute hypophosphorous acid solution. This method requires a large amount of resin. , and the resin regeneration and cleaning steps are cumbersome. This method is suitable for small batch production. The concentration of the obtained dilute hypophosphorous acid solution is not much different from that of the barium salt method, but the product purity is higher.

3) Electrodialysis

The principle of electrodialysis is: after the electrodialysis tank is supplied with direct current, the positive electrode chamber and the negative electrode chamber produce the following reaction:

The positive electrode chamber and the negative electrode chamber are separated by an anion membrane and a cation membrane. After direct current is passed, the positive and negative ions move to the negative electrode and the positive electrode respectively. The anion membrane only allows negative ions to pass, and the cation membrane only allows positive ions to pass. At the same time, The positive electrode electrolyzes water to release oxygen and hydrogen ions, which combine with the dialyzed hypophosphite to form hypophosphorous acid. The negative electrode releases hydrogen and releases hydroxide, which combines with the dialyzed sodium ions to form sodium hydroxide. The electrodialysis method is simple. , suitable for large-scale production, no waste water and residue are generated, but the purity of the product must be further improved.

4) High temperature reaction of phosphorus

Phosphorus directly reacts with oxygen at high temperature to form phosphorous anhydride or hypophosphorous anhydride, which is hydrolyzed to obtain the corresponding acid. After separation, hypophosphorous acid and phosphorous acid are obtained. This method has high production efficiency and high total phosphorus yield, but it needs to be relatively Complex separation processes are rarely used.