The membrane surface/module volume ratio is one of the main criteria in designing separation units. This parameter can be increased by one order of magnitude when dropping the membrane tube diameter from the cm to the mm scale. Alumina hollow fibres have been used as supports and submitted to pore-plugging MFI zeolite synthesis. Ail alumina-MFI nanocomposite structure, showing no surface film. has been obtained, as observed by SEM and EDX analysis and confirmed by high temperature variation of H-2 and N-2 permeances. Maxwell-Stefan modeling provides ail equivalent thickness lower than 1 mu m. The membrane quality has been assessed by gas separation of n-butane/H-2. A first application to CO2/H-2 separation has been achieved, reaching separation factors close to 10. Such a system. based oil cheap symmetric supports, could lead to an important decrease in module costs for gas separation applications.