Carbon molecular sieves and methods for making the same
First Claim
1. A carbon molecular sieve particle comprising a pyrolyzed carbon-based polymer body having numerous ultramicropores therethrough which may act as sieves to substantially inhibit the passage of gas molecules larger than 10 Angstroms in size and wherein the pyrolyzed body is less than 2 microns in size.
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Abstract
Mixed matrix membranes capable of separating carbon dioxide from mixtures including carbon dioxide and methane, and processes for purifying methane using the membranes, are disclosed. The membranes are preferably polymer membranes, that include discrete carbon-based molecular sieve particles with sizes of between about 0.5 microns to about 5.0 microns. The particles are formed by pyrolyzing a precursor polymer in the form of a powder or film. The pyrolyzed polymer is then ideally milled to desired small size particles. The preferred ratio of particles to polymer is about 0.25 to about 1.0 by volume. A preferred method for preparing the mixed matrix membrane is by dispersing the particles in a solvent, adding a small quantity of the desired polymer or “sizing agent” to “size” or “prime” the particles, adding a polymer, casting a film of the polymer solution, and evaporating the solvent to form a mixed matrix membrane film. The mixed matrix membrane film permits passage of carbon dioxide and methane, but at different permeation rates, such that the ratio of the relative permeation rates of carbon dioxide to methane is larger through the mixed matrix membrane film than through the original polymer. The mixed matrix membrane is preferably in the form of a dense film or a hollow fiber. A mixture containing carbon dioxide and methane can be enriched in methane by selective passage of carbon dioxide over methane in a gas-phase process through the membrane.
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Citations
19 Claims
- 1. A carbon molecular sieve particle comprising a pyrolyzed carbon-based polymer body having numerous ultramicropores therethrough which may act as sieves to substantially inhibit the passage of gas molecules larger than 10 Angstroms in size and wherein the pyrolyzed body is less than 2 microns in size.
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14. A method for preparing carbon molecular sieves comprising subjecting a polymer powder to pyrolysis conditions to form a carbon molecular sieve, wherein the polymer powder results in an amorphous carbonized structure when pyrolyzed;
- and when dispersed in a polymer and used to prepare a mixed matrix membrane film at about 20 wt. % loading, the membrane shows a pure gas selectivity enhancement of 10% or more in the permeability of CO2 versus CH4, compared to a membrane of the same polymer without sieve added.
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15. A method of preparing carbon molecular sieve particles comprising pyrolyzing a carbon based polymer to create ultramicropores within the pyrolyzed polymer;
- and fracturing the pyrolyzed powder until the size of the particles is less than 2 microns in diameter thereby opening up close ended pores formed in the pyrolyzed polymer.
- View Dependent Claims (16, 17, 18, 19)
Specification