METHOD OF PRODUCING SODIUM TRIPOLYPHOSPHATE Russian patent published in 2009 - IPC C01B25/41 

FIELD: chemistry.

SUBSTANCE: method of producing sodium tripolyphosphate from wet-process phosphoric acid involves its pre-neutralisation to pH=0.7 using calcium carbonate and subsequent neutralisation of the obtained reaction mass with soda in two stages until molar ratio Na₂O/P₂O₅ in liquid phase after the second stage equals 1.63-1.67, separation of the liquid phase from precipitate, washing, drying the liquid phase and calcination of the dried product. The wet-process phosphoric acid used is evaporated phosphoric acid, diluted to 18-22% P₂O₅. At the first stage of neutralising the reaction mass, soda is added until ratio Na₂O/P₂O₅=0.24-0.26. Temperature is kept at 35-40°C at all stages of the process.

EFFECT: reduced content of fluorine in the end product, simplification of the process and cutting its duration, increased extraction of P₂O₅ from wet-process phosphoric acid.

2 cl, 3 ex