Improved method of making carbon molecular sieve membranes

A process for separating a gas molecule from a feed gas comprised of the gas molecule and at least one other gas molecule comprising

• (i) providing the carbon molecular sieve membrane of any one of the preceding claims;
• and
• (ii) flowing the gas feed through said carbon molecular sieve membrane to produce a first stream having an increased concentration of the gas molecule and a second stream having an increased concentration of the other gas molecule.

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A method of making a carbon molecular sieve membrane comprising,

• (i) providing a polyimide precursor polymer;
• (ii) heating, in a furnace, said polyimide precursor polymer to a final pyrolysis temperature of 500° C. to 1500° C. at a pyrolysis heating rate of 0.01 to 200° C./minute to the final pyrolysis temperature, the final pyrolysis temperature being held for a pyrolysis time of several seconds to several days in a non-oxidizing atmosphere;
• (iii) cooling the carbon molecular sieve membrane to room temperature at an accelerated cooling rate of at least 23° C./min from the final pyrolysis temperature to 400° C.