IMPROVED METHOD TO MAKE CARBON MOLECULAR SIEVE HOLLOW FIBER MEMBRANES

• Main Authors: MARTINEZ, Marcos V, XU, Liren, SHARMA, Rahul, HARRIS, William J, BRAYDEN, Mark M
• Format: Patent
• Language: English; French; German
• Published: 02.10.2024
• Subjects: CHEMISTRY; COMPOSITIONS BASED THEREON; MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONSONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; THEIR PREPARATION OR CHEMICAL WORKING-UP; TRANSPORTING

An asymmetric hollow fiber (CMS) carbon molecular sieve is made by providing a dope solution comprised of a polyimide and a solvent, at a temperature greater than 250°C that is less than the storage modulus at a temperature of 250°C, but no more than ten times less as measured using dynamic mechanical thermal analysis from 250°C to a temperature where the polyimide carbonizes. The polyimide is shaped into a hollow polyimide fiber, the solvent removed and the polyimide hollow fiber is heated to pyrolyze the polyimide and form the asymmetric hollow carbon molecular sieve. The asymmetric hollow fiber carbon molecular sieve has a wall that is defined by an inner surface and outer surface of said fiber and the wall has an inner porous support region extending from the inner surface to an outer microporous separation region that extends from the inner porous support region to the outer surface. Surprisingly, when the polyimide has the particular storage modulus characteristics, the method allows for the hollow fiber CMS to be made without any pretreatments or additives to inhibit structural collapse of the inner microporous region.