Composite mordenite/ZSM5/chabazite membranes were prepared on a alumina tubular supports by in situ liquid phase hydrothermal synthesis. The membranes obtained were approximately 10 mu m thick and were characterized by XRD, SEM and EPMA, as well as permeation of single gases (N-2 and it-butane). The membranes were then used to separate ternary mixtures, containing water, alcohol (methanol, ethanol or propanol), and a permanent gas (O-2) Wafer permeated faster because of the hydrophilic character of the composite membrane, with water/propanol selectivities as high as 149. The influence of operating conditions (temperature, pressure and feed composition) on the separation performance was analyzed. Also, the behavior of this composite zeolite membrane was compared with that of pure silicalite and ZSM5 membranes, and the differences observed are discussed in terms of relative organophilicity/hydrophilicity of the zeolites involved.