Abstract
Fully dehydrated and partially sodium-cesium containing RHO zeolite (Na,Cs-RHO) shows a genuine inflection in the CO2 isotherms in the temperature range 293333 K that can be attributed to a sorbate-induced framework deformation from an acentric (A) to a centric (C) phase due to a partial cation rearrangement. This peculiar sorption pattern can be captured by the formulation of thermodynamic isotherms, providing a direct enthalpic and entropic signature of the CO2 adsorptiondesorption process during deformation. Using this formulation, the energy barrier between the acentric and centric phases for CO2 adsorptiondesorption was estimated in the range 4.79.6 J g−1 of solid (1532 kJ mol−1), reflecting a higher CO2 affinity for the acentric phase, whereas the elastic energy involved during framework distortion was estimated in the range 612 J g−1 of solid (1939 kJ mol−1) with a relative maximum at 303 K and showing a dominant entropic contribution.
