High flux and selectivity SAPO-34 membranes for CO2/CH4separations
AssigneeThe Regents of the University of Colorado
InventorsShiguang Li, John L. Falconer, Richard D. Noble
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Abstract
SAPO-34 membranes and methods for their preparation and use are described. The SAPO-34 membranes are prepared by contacting at least one surface of a porous membrane support with a synthesis gel. The Si/Al ratio of the synthesis gel can be from 0.3 to 0.15. SAPO-34 crystals are optionally applied to the surface of the support prior to synthesis. A layer of SAPO-34 crystals is formed on at least one surface of the support. SAPO-34 crystals may also form in the pores of the support. SAPO-34 membranes of the invention can have improved selectivity for certain gas mixtures, including mixtures of carbon dioxide and methane.
Claims19
A method for making a crystalline silicoaluminophosphate-34 (SAPO-34) membrane, the method comprising the steps of:
- a) providing a porous support having a pore size between 0.1 microns and 6 microns, the surface of the support having non-porous and porous portions;
- b) applying a first quantity of SAPO-34 crystalline material to at least part of the surface of the porous support prior to step e) by contacting SAPO-34 crystals with the surface, wherein the first quantity of crystalline material is in the form of SAPO-34 crystals, the average size of the SAPO-34 crystals applied to the surface of the support is between 100 nm and 1000 nm and the size of the crystals is small enough so that some of the crystals lodge within the pores of the support and the SAPO-34 crystals on the nonporous portions of the surface do not form a continuous layer;
- c) preparing an aqueous SAPO-34 forming gel comprising an organic templating agent;
- d) aging the gel;
- e) contacting the porous support with the gel;
- f) following step e), heating the porous support and the aged gel to form a second quantity of SAPO-34 crystalline material on the support, thereby forming a cumulative layer of SAPO-34 crystals on the surface of the support, wherein said support and said gel are heated to a temperature between 470 and 515 K;
- g) repeating steps e) and f) at least once to form a cumulative layer of SAPO-34 crystals on the surface of the porous support having a thickness less than 5 microns ;
- and
- h) calcining the SAPO-34 layer to remove the templating agent, wherein the gel comprises aluminum, phosphorus, silicon, oxygen, a templating agent and water, with the ratio of silicon to aluminum being greater than 0.1 and less than or equal to 0.6 and following step h) the permeance of CO2 through the membrane is greater than 3.0×10−7 mol/(m2 s Pa) and the CO2/CH4 separation selectivity is greater than 90 for a 50/50 CO2/CH4 mixture at 295 K with a feed pressure of 222 kPa and a pressure differential across the membrane of 138 kPa.
A supported membrane comprising a layer of SAPO-34 crystals on the surface of a porous support, the layer having a thickness less than 5 microns and the support having a pore size between 0.1 microns and 6 microns wherein the permeance of CO2 through the membrane is greater than 3.0×10−7 mol/ m2 s Pa and the CO2/CH4 separation selectivity is greater than 90 for a 50/50 CO2/CH4 mixture at 295 K with a feed pressure of 222 kPa and a pressure differential across the membrane of 138 kPa.
Dependencies are inferred from the claim text.