Variable‐Temperature Infrared Spectroscopy Studies on the Thermodynamics of CO Adsorption on the Zeolite Ca–Y (original) (raw)

Variable temperature FT–IR spectroscopy (in the range of 298–380 K) is used to study the thermodynamics of formation of Ca2+⋅⋅⋅CO carbonyl species upon CO adsorption on the faujasite‐type zeolite Ca–Y, and also the (temperature‐dependent) isomerization equilibrium between carbonyl and isocarbonyl (Ca2+⋅⋅⋅OC) species. The standard enthalpy and entropy changes involved in formation of the monocarbonyl species resulted to be ΔH0=−50.3 (±0.5) kJ mol−1 and ΔS0=−186 (±5) J mol−1 K−1, respectively. Isomerization of the (C‐bonded) Ca2+⋅⋅⋅CO carbonyl to yield the (O‐bonded) Ca2+⋅⋅⋅OC isocarbonyl involves an enthalpy change DeltaitHrmisorm0{\Delta {\it H}_{{\rm{iso}}}^{\rm{0}} }DeltaitHrmisorm0=+11.4 (±1.0) kJ mol−1. These results are compared with previously reported data for the CO/Sr–Y system; and also, a brief analysis of enthalpy–entropy correlation for CO adsorption on zeolites and metal oxides is given.