Abstract
Titanium phosphates were prepared by the reaction of titanium dioxide (anatase, rutile), titanyl hydroxide, or titanium metal with phosphoric acid, and their formation conditions and acidic properties were examined. Titanium (IV) pyrophosphate, TiP2O7, was the main product in the reaction of titanium dioxide or titanyl hydroxide with phosphoric acid. TiP2O7 was formed in the system of Ti-H3PO4, but titanium (III) tetra-metaphosphate, Ti4(P4O12)3, was additionally formed. This tetrametaphosphate was easily obtained by heating the primary product of Ti/P (R)=1/6-1/10 in a nitrogen stream (50 ml/min) or vacuum (0.01 mmHg) at 500-700°. Titanium phosphate produced in this study was a solid acid, its acidity being mainly concentrated at acid strength of H0=+1.5. Titanium phosphate made from anatase had the largest amount qf acid (4.3 mmol/g) at the reactant ratio of R=1, while that prepared from rutile or titanyl hydroxide had a large acidity (0.6 mmol/g) at R=1/2. It was clear that the amount of acid in titanium phosphate was closely related to its water content.
