Vibrational and thermodynamic properties of Ar, N-2, O-2, H-2 and CO adsorbed and condensed into (H,Na)-Y zeolite cages as studied by variable temperature IR spectroscopy
| Autor: | Silvia Bordiga, Gabriele Ricchiardi, Adriano Zecchina, Giuseppe Spoto, Evgueni Gribov, Donato Cocina |
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| Jazyk: | angličtina |
| Rok vydání: | 2006 |
| Předmět: |
H-Y zeolite
simple molecular probes carbon-monoxide hydroxyl-groups NAA zeolite OH groups FT-IR adsorption-isotherms hydrogen complexes calorimetric heats Stereochemistry General Physics and Astronomy Infrared spectroscopy Molecular sieve Fourier transform spectroscopy chemistry.chemical_compound Adsorption chemistry Sodalite Physical chemistry Physical and Theoretical Chemistry Fourier transform infrared spectroscopy Brønsted–Lowry acid–base theory Zeolite |
| Popis: | The adsorption of Ar, H2, O2, N2 and CO on (H,Na)-Y zeolite (Si/Al = 2.9, H+/Na+ approximately 5) has been studied at variable-temperature (90-20 K) and sub-atmospheric pressure (0-40 mbar) by FTIR spectroscopy. Unprecedented filling conditions of the zeolite cavities were attained, which allowed the investigation of very weakly adsorbed species and of condensed, liquid-like or solid-like, phases. Two pressure regimes were singled out, characterized by: (i) specific interaction at low pressure of the probe molecules (P) with the internal Brønsted and Lewis sites, and (ii) multilayer adsorption at higher pressure. In the case of CO the perturbation of the protonic sites located inside the sodalite cages was also observed. As the molecule is too large to penetrate the sodalite cage, the perturbation is thought to involve a proton jump tunneling mechanism. The adsorption energy for the (HF)OH...P (P = Ar, H2, O2, N2 and CO) specific interaction involving the high frequency Brønsted acid sites exposed in the supercages was derived following the VTIR (variable temperature infrared spectroscopy) method described by E. Garrone and C. Otero Areán (Chem. Soc. Rev., 2005, 34, 846). |
| Databáze: | OpenAIRE |
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