Adsorption of carbon dioxide in SAPO STA-7 and AlPO-18: Grand Canonical Monte Carlo simulations and microcalorimetry measurements

The adsorption properties of carbon dioxide in SAPO STA-7 has been investigated by combining Grand Canonical Monte Carlo simulation and microcalorimetry. The modeling approach, based on both newly derived interatomic potentials for describing the interaction between CO2 and the Bronsted acid sites, and a realistic description of the silicon distribution within the framework, provides isotherms and evolutions of the differential enthalpy of adsorption as a function of coverage for the STA-7 material characterised by a silicon fraction of 0.19. The simulated results are revealed to be in good agreement with the experimental data that allowed us to provide a possible microscopic mechanism of CO2 adsorption in this material. These whole results are thus compared to those obtained for the purely aluminophosphate form of the AlPO-18. It is clearly emphasized that distinct adsorption behaviours are observed in these two systems, depending on the energetic characteristics of their surfaces.