Nanocomposite MFI-alumina hollow fiber membranes: influence of NOx and propane on CO2/N2 separation properties

This study provides a detailed survey of the effect of moisture, NOx and light hydrocarbons (i.e., propane) on the CO2/N2 permeation and separation properties of MFI-type hollow-fiber membranes in view of on board CO2 capture applications in Diesel vehicles. Five different MFI-alumina samples have been prepared including different degrees of isomorphous boron and germanium substitution, as well as ex framework proton exchange by copper. The quality of the synthesized hollow fibers has been primarily assessed by pure N2 permeation and n-butane/H2 and SF6/N2 separation at room temperature. The different materials show preferential CO2/N2 and CO2/NO selectivity at low CO2 feed concentrations (∼10%) in the temperature range 298–373 K, which can be appreciably promoted under the presence of propane (1 v/v %). The materials show stable and high CO2 permeances even in the presence of large amounts of water in the feed stream. On the basis of the permeation and separation data measured in this study, we present a refined simulation study of a membrane cascade system constituted of two hollow-fiber membrane modules coupled to a DeNox unit for on board CO2 capture and liquefaction/supercritical storage in heavy vehicles (>40 tn)