Synthesis and Characterization of Two Novel Fibrous Titanium Phosphates Ti₂O(PO₄)₂·2H₂O

Abstract

New crystalline phases of fibrous titanium(IV) oxophosphates were prepared hydrothermally from titanium(IV) chloride in phosphoric acid solutions. The influence of several factors (concentration of reagents, molar ratio P:Ti in the reaction mixture, and reaction times) was studied. A phase diagram of the system is given. On the basis of elemental and thermal analysis, X-ray powder diffraction, 31 P MAS NMR, and IR spectroscopy, the formula Ti 2 O(PO 4 ) 2 ·2H 2 O was assigned to the novel compounds. The new phases (π-TiP and ρ-TiP) have different structures. The crystal structure of ρ-TiP was solved from X-ray powder data and was shown to be of the framework type with tunnels parallel to the c -axis direction. The absence of n -alkylamine intercalation processes for both compounds and other physical and behavioral similarities suggests a framework type structure for π-TiP also. The ion-exchange behavior toward alkali and alkaline earth ions was studied.