Composite porous carbonaceous membranes

Reference Number: N 04-02

Inventors: Rao, Madhukar B.; Sircar, Shivaji; Golden, Timothy C.

Owner: NISTAC

USPTO Link: 5507860

Invention Summary

The invention is a composite semipermeable membrane for the separation of a multicomponent fluid mixture containing one or more primary components and one or more secondary components and a method for making the membrane which comprises coating a surface of an inert porous substrate with a layer of an organic precursor material, heating the resulting coated porous substrate in an inert atmosphere to a first temperature, maintaining this temperature for a time sufficient to convert the precursor material into a layer of microporous carbonaceous adsorptive material, and cooling the resulting composite membrane to a temperature below the first temperature. The permeability and selectivity of the membrane are improved by heating the cooled membrane to a second temperature, oxidizing the heated membrane at this temperature in an oxidizing atmosphere selected from the group consisting of air, oxygen, carbon oxides, nitrogen oxides, steam, and mixtures thereof, and cooling the resulting oxidized membrane to ambient temperature. The microporous carbonaceous adsorptive material so produced can selectively adsorb portions of the primary components which diffuse through the membrane by selective surface flow.

In an alternate embodiment, the invention is a densified composite semipermeable membrane for the separation of a multicomponent fluid mixture containing one or more primary components and one or more secondary components and a method for making the membrane which comprises introducing an organic precursor into the pores of an inert porous substrate, heating the porous substrate containing the organic precursor to a first temperature, maintaining the membrane at this temperature under conditions sufficient to convert the precursor to microporous carbonaceous adsorptive material within the pores, and cooling the resulting densified membrane to a temperature below the first temperature. The permeability and selectivity of the membrane are improved by heating the cooled membrane to a second temperature in an oxidizing atmosphere selected from the group consisting of air, oxygen, carbon oxides, nitrogen oxides, steam, and mixtures thereof, and cooling the resulting oxidized membrane to ambient temperature. The microporous carbonaceous adsorptive material so produced can selectively adsorb portions of the primary components which diffuse through the membrane by selective surface flow.