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• #Molar entropy series#

If adsorption follows the Langmuir model, the characteristic C−O stretching frequency of adsorbed CO will remain constant along the series of measurements.

Such an assumption would be erroneous for Li‐containing systems, being the corresponding cation mass comparable to that of the atoms constituting the CO molecule hence Li‐containing systems are not considered herein. Throughout the text, the zeolite adsorption site will be considered to remain fixed, and all changes will be attributed to the adsorbed molecule alone. From here onwards, the Z representing the zeolite framework will be dropped for simplicity. Where Z−M + stands for the adsorption site and Z−M +⋅⋅⋅CO is the adsorption complex. Referring to CO adsorption on single‐cation adsorption sites of alkaline zeolites, let Eq. (1) below represent the adsorption equilibrium: Herein, an extension of those studies to include determination of the molar enthalpy and entropy of the adsorbed gas is proposed and discussed.Īn outline of the VTIR spectroscopic method is reported below. Over the years, several cases have been studied, so that some more general considerations are now possible. 16, 17 As briefly reported below, application of basic thermodynamics to a set of VTIR data gives access to the fundamental quantities for the (Langmuirian) adsorption process, i. e. This procedure has been termed VTIR (Variable‐Temperature IR) spectroscopy. 14, 15 However, for Langmuir type adsorption, a method has been designed in the recent past, envisaging the recording of IR spectra of an adsorbed species at different temperatures, while simultaneously measuring the temperature and equilibrium pressure. 13 For such a purpose, classical infrared spectroscopy (IR) can give valuable structural information, derived from analysis of the wavenumber shifts undergone by vibrational modes of the adsorbed molecule but determination of the gas‐solid interaction energy is out of reach, unless some other complementary technique is also used. 12Ĭrystallinity of their aluminosilicate framework and regular layout of their internal channels (and cages) endow zeolites with a regular distribution of charge balancing cations, which can form arrays of all equal and non‐mutually‐interacting adsorption sites, thus facilitating the use of the Langmuir model for studying gas adsorption thermodynamics. Possible redox processes that can take place when the adsorbents show exposed transition metal ions ( e. g., supported NiO).