Ultrathin ethylcellulose/poly(4-methylpentene-1) permselective membranes
AssigneeMembrane Technology and Research, Inc.
InventorIngo Pinnau
Life of this patent
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Abstract
An ultrathin, permselective membrane for use in gas or vapor separations. The membrane comprises a permselective layer of ethylcellulose in combination with one or more permselective layers of poly(4-methylpentene-1). The permselective membrane is preferably coated onto a microporous substrate, such as an asymmetric Loeb-Sourirajan type membrane. The resulting membrane has high gas fluxes and selectivities, and can be used, for example, to separate oxygen and nitrogen; hydrogen sulfide from nitrogen, methane or carbon dioxide; hydrogen from nitrogen; sulfur dioxide or ammonia from nitrogen; or water vapor from air. A method of preparing such a membrane is also provided, as is a gas separation process using the membrane.
Claims13
A membrane useful for gas separation, comprising:
- an ultrathin, permselective ethylcellulose layer having the general formula ##STR5## wherein the ethoxyl content is in the range 35% to 50%;
- and an ultrathin, permselective poly(4-methylpentene-1) layer having the formula ##STR6## said poly(4-methylpentene-1) layer forming a coating on one surface of said ethylcellulose layer, said membrane having an O.sub.2 /N.sub.2 selectivity which is greater than the intrinsic O.sub.2 /N.sub.2 selectivity of said ethylcellulose and which is greater than 90% of the intrinsic O.sub.2 /N.sub.2 selectivity of said poly(4-methylpentene-1).
A process for producing a membrane useful for gas separation comprising the steps of:
- preparing an ethylcellulose solution from ethylcellulose having the general formula ##STR7## wherein the ethoxyl content is in the range 35% to 50%;
- coating said ethylcellulose solution onto a support;
- drying said coated support, to produce a first ultrathin, permselective layer of ethylcellulose;
- preparing a poly(4-methylpentene-1) solution from poly(4methylpentene-1) having the formula ##STR8## coating said poly(4-methylpentene-1) solution onto said coated support;
- and drying said coated support, to produce a second ultrathin, permselective layer of poly(4-methylpentene-1, whereby a composite membrane, having an O.sub.2 /N.sub.2 selectivity which is greater than the intrinsic O.sub.2 /N.sub.2 selectivity of said ethylcellulose and which is greater than 90% of the intrinsic O.sub.2 /N.sub.2 selectivity of said poly(4-methylpentene-1), is formed.
Dependencies are inferred from the claim text.