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, 31P MAS NMR, and IR spectroscopy, the formula Ti2O(PO4)2·2H2O 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.