A new carbon molecular sieve for propylene/propane separations

Abstract

A new carbon molecular sieve (CMS) with a propylene/propane separation factor of approximately 27 was synthesized by a facile pyrolysis process from a gel-type strong acid cation exchange resin. The micropore shrinkage process during pyrolysis was investigated using a new high throughput adsorption technique with 48 parallel cells. This significantly reduced the characterization time. The ratio of propylene/propane adsorption rate in the CMS adsorbent changes from 1 to more than 150 when the final pyrolysis temperature changes from 550 to 1000°C. The best performing CMS pyrolyzed at 850°C was further characterized using a gravimetric adsorption method. The propylene and propane diffusivities are 1.0×10−9 and 1.1×10−11cm2s−1 at 100kPa and 90°C. The high propylene/propane diffusivity ratio of 90 is similar to that in zeolite 4A, while the propylene diffusivity was more than 30 times higher than that in zeolite 4A. An effluent of 90mol% propylene was obtained from a feed of 25mol% propylene during adsorption/desorption tests using the CMS adsorbent pyrolyzed at 850°C in a fixed-bed configuration. The new CMS adsorbent is a promising candidate for industrial scale propylene/propane separations.