A new method for the preparation of peroxymonophosphoric acid

Abstract

A new method for the preparation of peroxymonophosphoric acid (H3PO5) has been developed. It utilizes a biphasic solution to moderate the vigorous reaction between phosphorous pentoxide (P2O5) and hydrogen peroxide (H2O2). P2O5 is suspended in carbon tetrachloride (CCl4), and concentrated H2O2 is slowly added while being vigorously stirred at low temperature. Careful control of the reaction temperature through the slow addition of H2O2 is critical. Using typical preparation conditions (P2O5:H2O2 = 0.5:1, H2O2 70 wt %, 2°C, 120–180 min), ~70% of the H2O2 is effectively converted to H3PO5. Increasing the concentration of H2O2, as well as the mole ratio of P2O5:H2O2, leads to an even higher % conversion of H2O2 to H3PO5. The addition of glacial acetic acid to the P2O5:H2O2 suspension at the end of the 120–180 min reaction (P2O5:H2O2:CH3COOH = 0.5:1:0.3) leads to the formation of peracetic acid in addition to H3PO5, and to an overall increase in the conversion ratio of total peroxy acids based on H2O2 (>95%).Key words: peroxymonophosphoric acid, synthesis, stability, conversion ratio.