A detailed survey of the effect of moisture on the CO2/N2 permeation and separation performance of Mobile Five (MFI) zeolite membranes in view of downstream postcombustion CO2 capture applications in power plants and incinerators is presented. The membranes, displaying a nanocomposite architecture, have been prepared on a-alumina tubes by pore-plugging hydrothermal synthesis at 443 K for 89 h using a precursor clear solution with molar composition 1 SiO2:0.45 tetrapropylammonium hydroxide:27.8 H2O. The synthesized membranes present reasonable permeation and CO2/N2 separation properties even in the presence of high water concentrations in the gas stream. A critical discussion is also provided on the technico-economical feasibility (i.e., CO2 recovery, CO2 purity in the permeate, module volume, and energy consumption) of a membrane cascade unit for CO2 capture and liquefaction/supercritical storage from standard flue gases emitted from an incinerator. Our results suggest that the permeate pressure should be kept under primary vacuum to promote the CO2 driving force within the membrane. (c) 2011 American Institute of Chemical Engineers AIChE J, 58: 31833194, 2012