Method of making composite porous carbonaceous membranes
Reference Number: N 04-02
Inventors: Rao, Madhukar B.; Sircar, Shivaji; Golden, Timothy C.
Owner: NISTAC
USPTO Link:5431864
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.