A study of ETS-4 molecular sieves and of their adsorption of water and ammonia

T. Armaroli; G. Busca; F. Milella; F. Bregani; G. P. Toledo; A. Nastro; P. De Luca; G. Bagnasco; M. Turco

doi:10.1039/A909761I

T. Armaroli,^a G. Busca,^a F. Milella,^a F. Bregani,^b G. P. Toledo,^b A. Nastro,^c P. De Luca,^c G. Bagnasco^d and M. Turco*^d

Author affiliations

* Corresponding authors

^a Dipartimento di Ingegneria Chimica e di Processo "G.B. Bonino", Università, Genova, Italy

^b ENEL Ricerca, Area Generazione, Segrate (Mi), Italy

^c Dipartimento di Pianificazione Trasporti ed Ambiente, Università della Calabria, Arcavacata di Rende, Cosenza, Italy

^d Dipartimento di Ingegneria Chimica, Università "Federico II", Napoli, Italy
E-mail: turco@irc.na.cnr.it
Fax: 39-081-5936936
Tel: 39-081-7682259

Abstract

Structural and water and ammonia adsorption properties of ETS-4 were studied by means of XRD, FT-IR, Raman, UV-vis and temperature programmed desorption (TPD) techniques. XRD analysis showed that the sample was pure and highly crystalline. Skeletal IR and Raman vibrational spectra are interpreted in agreement with the structure containing chains of corner sharing TiO₆ octahedral zig-zag chains, tetrahedral silicate units bridging two TiO₆ octahedra (so giving rise to Ti–O–Si–O–Ti structures) and "isolated" Ti ions with an octahedral coordination involving two short bonds with oxide ions also bonded to extraframework Na⁺ cations. Electronic spectra agree with the predominance of condensed TiO₆ octahedra and the absence of TiO₂ impurities. Two forms of molecular adsorbed water were observed from FT-IR and TPD measurements. ETS-4 adsorbed about 2 mole of water per mole of material by coordination to Na⁺ ions. Ammonia was adsorbed in molecular form both by hydrated and anhydrous ETS-4 through hydrogen bonding with H₂O molecules or coordination to Na⁺ ions, respectively. 0.24 mole of NH₃ per mole ETS-4 was adsorbed in both cases.

Article information

https://doi.org/10.1039/A909761I

Article type

Paper

Submitted

13 Dec 1999

Accepted

07 Apr 2000

First published

21 Jun 2000

Download Citation

J. Mater. Chem., 2000,10, 1699-1705

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