TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The inorganic porous support is in the form of a honeycomb monolith. The inorganic porous support comprises alumina, cordierite, alpha-alumina, mullite, aluminum titanate, titania, zirconia, zeolite, metal, stainless steel, silica carbide and/or ceria. The inner channels of the inorganic porous support have a median inside diameter of 0.5-3 millimeters. The porous walls of the inorganic porous support comprise a median pore size of 1-25 microns, preferably 5-15 microns. The inorganic porous support has a porosity of 20-80%, preferably 40-50%. The porous intermediate layers comprise alpha -alumina, cordierite, alumina, mullite, aluminum titanate, titania, zirconia and/or ceria particles. The porous intermediate layers comprise a median pore size of 1-10 microns, preferably 50 nanometer to 1 micron. The porous intermediate layers have a combined thickness of 1-100 microns. The median pore size of the porous walls of the inorganic porous support is larger than the median pore size of each of the porous intermediate layers, and the median pore size of each of the porous intermediate layers is larger than the crystal channel size of the zeolite membrane. The inorganic membrane structure comprises two or more porous intermediate layers, where the median pore size of the intermediate layer which contacts the inorganic porous support is greater than the median pore size of the intermediate layer which contacts the zeolite seed layer. The zeolite seed layer comprises seed particles having a median particle size of 50-500 nanometers, preferably 50-150 nanometers. The barrier layer comprises a material comprising a metal, a polymer coating, a polymer wrap, Teflon (RTM:Polytetrafluoroethylene), a plastic wrap, syran wrap, aluminum foil, a shrink wrap tubing, an epoxy, a glass, a ceramic, a glass/ceramic, a rubber and/or a latex. Preferred Method: The preparation of the inorganic membrane structure further comprises: applying a barrier layer to the outer surface of the inorganic porous support prior to hydrothermally growing the zeolite intergrown layer from the zeolite seed layer; heating the inorganic porous support and the one or more porous intermediate layers prior to applying the zeolite seed layer to the one or more porous intermediate layers; heating the inorganic porous support, the one or more porous intermediate layers and the zeolite seed layer prior to hydrothermally growing the zeolite intergrown layer from the zeolite seed layer; and heating the inorganic porous support and the applied intermediate and zeolite seed and intergrown layers. The applying the porous intermediate layers comprise dip coating, flow coating, slip casting and/or immersion. The applying the zeolite seed layer comprises dip coating, flow coating, slip casting and/or immersion. The zeolite seed layer is applied from a coating composition, which further comprises a dispersant, a binder, an anti-cracking agent and/or an anti-foam agent. The heating the inorganic porous support and the one or more porous intermediate layers comprise sintering the inorganic particles in the one or more intermediate layers. The hydrothermally growing a zeolite intergrown layer from the zeolite seed layer step is assisted by microwave energy.