Synthesis and characterization of a novel layered titanium phosphate
- PDF / 239,748 Bytes
- 9 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 236 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Synthesis and characterization of a novel layered titanium phosphate Anatoly I. Bortun, Lyudmila Bortun, and Abraham Clearfield Department of Chemistry, Texas A&M University, College Station, Texas 77843
Mar´ıa A. Villa-Garc´ıa, Jos´e R. Garc´ıa, and Julio Rodr´ıguez Departamento de Qu´ımica Org´anica e Inorg´anica, Universidad de Oviedo, 33071 Oviedo, Spain (Received 2 January 1996; accepted 4 June 1996)
A novel metastable layered titanium phosphate has been synthesized by the treatment of layered titanates (Na2 Ti3 O7 and Na4 Ti9 O20 ) with 1–2 M phosphoric acid solution at 120–150 ±C. Based on the data of 31 P MAS NMR and IR spectroscopy, x-ray powder diffraction, and thermal and elemental analysis, the formula Ti2 O3 (H2 PO4 )2 ? 2H2 O was assigned to the novel compound. The layered nature of the compound was confirmed from n-alkylamine intercalation and the ion exchange behavior toward alkali, alkaline earth, and some transition metal ions.
I. INTRODUCTION
Layered titanium and zirconium phosphates have received considerable attention in the last decades.1–6 This is connected with their unique properties: high thermal and chemical stability, resistance to oxidation, selectivity to certain ions and molecules, etc., which allow the use of such materials as ion exchangers and adsorbents, molecular sieves, catalysts, ion and proton conductors, and also as convenient matrices for chemical modification. At the present time, two main types (a- and gphases) of layered titanium and zirconium phosphates are known, both containing two phosphorus atoms per one atom of group IV element. The difference between them is that a –TiP and a –ZrP have only one type of functional group °°HPO4 , and their formula can be represented as M(HPO4 )2 ? H2 O,7–10 whereas in the corresponding g-phases half of the phosphorus atoms exist in the form of 2H2 PO4 and the rest in the form of PO4 groups; hence, the formula is M(H2 PO4 )(PO4 ) ? 2H2 O.10–12 By ion exchange substitution of the hydrogen ions in the functional groups by cations, as well as by reactions of a- and g-phosphates with different organic reagents, a great variety of derivatives and novel compounds possessing valuable properties have been prepared.13–22 Closer investigation of the peculiarities of the reaction between titanium- and phosphorus-containing reagents at the elevated temperatures usually used for the preparation of crystalline layered titanium phosphates has shown that this is a complex multistep process.23 The typical scheme of such a process is the formation in the first stage of an amorphous material where the P : Ti molar ratio is close to 1 : 1.24 This amorphous titanium phosphate gradually transforms into a semicrys2490
http://journals.cambridge.org
J. Mater. Res., Vol. 11, No. 10, Oct 1996
Downloaded: 17 Jul 2014
˚ (the talline phase with an interlayer distance of 10.1 A P : Ti molar ratio is 1 : 1 again) or, depending on the reagent concentrations and temperature, into g-titanium phosphate. Finally, the r
Data Loading...
