Hydrogen adsorption on the faujasite-type zeolite Mg-X: An IR spectroscopic and thermodynamic study |
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Authors: | G Turnes Palomino C Otero Areán MR Llop Carayol |
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Institution: | Departamento de Química, Universidad de las Islas Baleares, Palma de Mallorca, Spain |
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Abstract: | Hydrogen adsorption (physisorption) on the faujasite-type zeolite Mg-X was studied by means of variable-temperature (80-140 K) FT-IR spectroscopy. Perturbation of the adsorbed H2 molecules by the cationic adsorbing centres of the zeolite renders the H-H stretching mode IR active, at 4065 cm−1. Simultaneous measurement of IR absorbance and hydrogen equilibrium pressure, for a series of spectra recorded at the increasing temperature, allowed standard adsorption enthalpy and entropy to be determined. They resulted to be ΔH0 = −13 kJ mol−1 and ΔS0 = −114 J mol−1 K−1, respectively. Both, spectroscopic and thermodynamic results are discussed in the broader context of corresponding data for hydrogen adsorption on other alkali and alkaline-earth cation exchanged zeolites, showing that, while an approximate correlation exists between ΔH0 and H-H stretching frequency, deviations can be expected for the case of zeolites containing small metal cations. |
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Keywords: | Adsorption enthalpy Adsorption entropy Hydrogen Infrared spectroscopy Zeolites |
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