Process for sodium hypophosphite
AssigneeFMC Corporation
InventorsDennis C. Annarelli, Richard E. Hall
Life of this patent
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Abstract
Either commercial yellow phosphorus or a phosphorus sludge is reacted with a slurry of calcium hydroxide in aqueous sodium hydroxide to form a sodium hypophosphite solution containing calcium and hydroxide ions. The solution is neutralized with phosphoric acid or an acid phosphate salt with the co-production of an insoluble calcium phosphate. The neutral solution is contacted with an ion exchange resin charged with sodium ions to remove any remaining calcium ions.
Claims14
A method for producing sodium hypophosphite by reacting elemental phosphorus with aqueous sodium hydroxide in the presence of a sufficient excess of solid calcium hydroxide to convert substantially all of the phosphite ions formed in the reaction to insoluble calcium phosphite whereby a solution of sodium hypophosphite is formed in which excess calcium ions remain in solution as calcium hydroxide and calcium hypophosphite, wherein the improvement comprises:
- (a) adding sufficient phosphoric acid or an acid phosphate salt to the solution of sodium hypophosphite to adjust the pH of the solution to be between 6.5 and 7.0, thereby neutralizing any hydroxide ions in the solution and precipitating the equivalent calcium ions as insoluble calcium phosphate,
- (b) separating the insoluble calcium phosphate from the neutralized solution, and
- (c) contacting the neutralized solution from step (b) with a cation ion exchange resin bearing sodium ions thereby exchanging calcium ions with sodium ions.
A process of purifying a solution containing sodium, hypophosphite, calcium, and hydroxide ions comprising:
- (a) adding sufficient phosphoric acid or an acid phosphate salt to adjust the pH of the solution to between 6.5 and 7.0 thereby neutralizing the hydroxide ions in solution and precipitating the equivalent calcium ions as an insoluble calcium phosphate,
- (b) separating the insoluble calcium phosphate from the neutralized solution, and
- (c) contacting the neutralized solution with a cation ion exchange resin bearing sodium ions thereby exchanging the calcium ions with sodium ions.
Dependencies are inferred from the claim text.