Thermodynamics of hydrogen adsorption on the zeolite Ca-Y

Variable-temperature infrared spectroscopy was used for a thermodynamic study on hydrogen adsorption on the zeolite Ca-Y. Adsorption renders the H–H stretching mode infrared active, at 4078 cm−1; and simultaneous measurement of IR absorbance and hydrogen equilibrium pressure, over a range of temperature, allowed standard adsorption enthalpy and entropy to be determined. They resulted to be ΔH°= −15.0(±1.0) kJ mol−1 and ΔS° = −127(±10) J mol−1 K−1, respectively. These relatively high values of adsorption enthalpy and entropy are discussed in the broader context of corresponding data for other hydrogen adsorbents.