Formation of Aluminum Phosphates by the Reaction of Diphosphorus Pentaoxide (H-, 0- and O′-form) with Aluminum Hydroxide

Abstract

The reaction of aluminum hydroxide [Al(OH)3] with diphosphorus pentaoxide [P2O5(H-, O- and O′-form)] has been studied to clarify the conditions of formation of various aluminum phosphates and the role of hydroxyl group contained in Al(OH)3. (1) The species of aluminum phosphate and their amounts largely depended on the heating temperature, heating time and the molar ratio (R) of P2O5 to Al(OH)3. Aluminum ortho-phosphate [A1PO4 (berlinite and cristobalite form)] and metaphosphate [A1(PO3)3 (A-form)] were formed at R = 1/2. Triphosphate [AlH2P3O10 (Worm)] and A1(PO3)3 (A- and B-form) were mainly produced at R=3/2. The predominant formation of A1(PO3)3 (A-, B- and E-form) was found in the reaction of R=3. (2) Of three kinds of P2O5, H-form P2O5 had the highest reactivity with Al(OH)3 and the reactivity of O′-form P2O5 was higher than that of O-form P2O3. These results were in good agreement with the tendency of hydrolysis of these three forms of P2O3. (3) The hydroxide ions in Al(OH)3 are very important to form aluminum phosphate by the reaction of aluminum hydroxide with diphosphorus pentaoxide. © 1990, The Chemical Society of Japan. All rights reserved.