Abstract: Effect ion-exchange of an alpha-alumina supported zeolite (e.g. a MFI zeolite, an LTA zeolite or a FAU zeolite) membrane, which process comprises: a) placing the membrane, which has a first surface and a spaced apart second surface, the first and second surfaces defining therebetween the membrane, in an ion exchange apparatus such that the first surface is in contact with an ion exchange solution and the second surface is in contact with a vapor space that is connected to a source of reduced pressure; b) actuating the source of reduced pressure to create a pressure differential between the first and second membrane surfaces of at least 0.4 atmosphere (0.