Optimal Faujasite structures for post combustion CO₂ capture and separation in different swing adsorption processes

Grand Canonical Monte-Carlo (GCMC) simulations are used in this work, to assess optimum faujasite structures, the well-known family of zeolites, in CO₂ capture processes. Pressure Swing Adsorption (PSA) and Vacuum Swing Adsorption (VSA) procedures have been considered to evaluate purity, working capacity and breakthrough time. To this purpose, ten faujasite structures with different Al content were selected, and the best conditions for CO₂ capture maximization have been calculated for each structure. Further results show that zeolites having intermediate Al content are the most effective for VSA processes, whereas low Al content faujasites perform better at PSA conditions. Remarkably, present work best results clearly improve Faujasite 13X VSA-PSA performances, so far considered the industrial reference in absence of water. Moreover, combined VPSA processes, in terms of working capacity and adiabatic work required for compression/expansion, have also been studied, showing that VPSA systems are more efficient than pure PSA/VSA, for structures with intermediate Al content. Finally, an improved methodology has been derived, where GCMC mixture isotherms and energetic cost calculations are combined, and a more accurate way of estimating working capacities and breakthrough times is proposed. This new approach allows more realistic evaluations of adsorbents' performances, than those found in the literature based on pure adsorption data.