Zeolite Membranes for Separation of Mixtures Containing Water, Alcohols, or Organics
Zeolite membrane sheets for separation of mixtures containing water, alcohols, or organics are provided, as well as methods for making the same. Thin, but robust, zeolite membrane sheets having a zeolite membrane layer formed directly on a thin porous metal support sheet provide improved separations performance. The zeolite membrane layers have a thickness less than 3 μm and are formed on a thin porous metal support sheet having a thickness less than or equal to approximately 200 μm. The porous metal support sheet comprises an average pore size of less than 3 μm, a porosity between 25% and 75%, and a thickness of less than or equal to 200 μm.
1 . A method for making a zeolite membrane sheet, the method characterized by the steps of:
Applying a uniform seeding layer having a thickness less than 3 μm and comprising zeolite crystals having an average diameter less than or equal to 1 μm to a bare metal surface of a front side of a porous metal support sheet, the support sheet comprising an average pore size of less than 3 μm, a porosity between 25% and 75%, and a thickness of less than or equal to 200 μm; and
Hydrothermally forming an inter-crystal growth layer by immersion of the support sheet with the seeding layer in a zeolite growth solution, the inter-crystal growth layer incorporating the seeding layer, comprising the same zeolite as the zeolite crystals, and having a thickness less than or equal to 3 μm.
2 . The method of claim 1 , wherein the zeolite comprises a water-selective zeolite selected from the group consisting of 3A, 4A, and 5A-type zeolite framework.
3 . The method of claim 1 , wherein the zeolite comprises a hydrocarbon-selective or alcohol-selective zeolite selected from the group consisting of silicalite, titanium silicate, MFI-type, and Y-type zeolite frameworks.
4 . The method of claim 1 , wherein said applying a uniform seeding layer further comprises performing multiple applications of the zeolite crystals in a graded pore-size structure, initially using larger zeolite crystals having average diameters between 0.5 and 3 μm and subsequently using smaller zeolite crystals having average diameters between 50 and 500 nm.
5 . The method of claim 1 , further comprising assembling a plurality of the zeolite membrane sheets into a mini-channel module comprising one or more permeate flow channels and one or more membrane channels, the permeate flow channel formed by stacking two membrane sheets back side to back side, and the membrane channel formed by stacking two membrane sheets with the front sides facing one another separated by spacers.
6 . The method of claim 5 , further comprising orienting the permeate flow channels and the membrane channels in a cross-flow configuration.
7 . The method of claim 1 , further comprising assembling two zeolite membrane sheets into a membrane plate module comprising a permeate flow channel, the permeate flow channel formed by stacking the zeolite membranes sheets back side to back side with the front sides exposed to feed mixtures on the exterior of the membrane plate module.
8 . The method of claim 1 , wherein the metallic support sheet comprises porous Ni or a porous Ni alloy.
9 . The method of claim 1 , wherein the metallic support sheet comprises porous Ti.
10 . The method of claim 1 , wherein the zeolite growth solution is a template-free solution.
11 . A zeolite membrane sheet characterized by:
a seeding layer having a thickness less than 3 μm and comprising zeolite crystals having an average diameter less than or equal to 1 μm to a bare metal surface of a front side of a porous metal support sheet, the support sheet comprising an average pore size of less than 3 μm, a porosity between 25% and 75%, and a thickness of less than or equal to 200 μm; and
An inter-crystal growth layer incorporating the seeding layer, comprising the same zeolite as the zeolite crystals, and having a thickness less than or equal to 3 μm.
12 . The membrane of claim 11 , wherein the zeolite comprises a water-selective zeolite selected from the group consisting of 3A, 4A, 5A-type zeolite framework.
13 . The membrane of claim 11 , wherein the zeolite comprises a hydrocarbon-selective or alcohol-selective zeolite selected from the group consisting of silicalite, titanium silicate, MFI-type, and Y-type zeolite frameworks . . . .
14 . The membrane of claim 11 , wherein the seeding layer comprises zeolite crystals in a graded pore-size structure with larger zeolite crystals having average diameters between 0.5 and 5 μm near the bare metal surface and smaller zeolite crystals having average diameters between 50 and 500 nm formed on the larger zeolite crystals.
15 . The membrane of claim 11 , further comprising an assembly of a plurality of the membranes into a mini-channel module comprising one or more permeate flow channels and one or more membrane channels, the permeate flow channel formed by two membrane sheets stacked back side to back side, and the membrane channel formed by two membrane sheets stacked with the front sides facing one another separated by spacers.
16 . The membrane of claim 15 , wherein the permeate flow channels and the membrane channels are oriented in a cross-flow configuration.
17 . The membrane of claim 11 , further comprising an assembly of two zeolite membrane sheets into a membrane plate module comprising a permeate flow channel, the permeate flow channel formed by the zeolite membranes sheets stacked back side to back side with the front sides exposed to feed mixtures on the exterior of the membrane plate module.
18 . The membrane of claim 11 , wherein the metallic support sheet comprises porous Ni or a porous Ni alloy.
19 . The membrane of claim 11 , wherein the metallic support sheet comprises porous Ti.