Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous composite

Adsorption of pure CO2 and N2 and separation of CO2/N2 mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations. Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized. A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small- and broad-angle X-ray diffraction patterns. The density of MFI/MCM-41 is lower than MFI, while its free volume and specific surface area are greater than MFI due to the presence of mesopores. CO2 is preferentially adsorbed than N2, and thus, the loading and isosteric heat of CO2 are greater than N2 in both MFI and MFI/MCM-41. CO2 isotherm in MFI/MCM-41 is similar to that in MFI at low pressures, but resembles that in MCM-41 at high pressures. N2 shows similar amount of loading in MFI, MCM-41 and MFI/MCM-41. The selectivity of CO2 over N2 in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41. With increasing pressure, the selectivity increases in MFI and MFI/MCM-41, but decreases in MCM-41. The self-diffusivity of CO2 and N2 in MFI decreases as loading increases, while in MFI/MCM-41, it first increases and then drops. © Higher Education Press and Springer-Verlag Berlin Heidelberg 2010.