Production of Sodium Dihydrogen Phosphate Using Sodium Chloride and Orthophosphoric Acid

Abstract

Up-to-date, standard synthesis processes of sodium phosphates are based on the neutralization of orthophosphoric acid by sodium hydroxide or sodium carbonate. To the best of our knowledge, the reaction between sodium chloride and orthophosphoric acid has not yet been reported in the literature. This study demonstrated the feasibility of the synthesis of sodium dihydrogen phosphate by the reaction of sodium chloride with orthophosphoric acid. A detailed parametric study was done, wherein the influence of reaction temperature, air flow rate, water addition flow rate, and reaction time was investigated. As expected, the evacuation of hydrogen chloride (HCl) was crucial for getting high conversion of NaCl to HCl. The highest conversion of NaCl to HCl reached 91% after 24 h of synthesis reaction. Sodium dihydrogen phosphate (NaH 2 PO 4) was the main product. Pyrophosphate (P 2 O 7 4−) was only formed at trace amounts, and any trace of trimetaphosphate (P 3 O 9 3−) was observed.