High-Performance Carbon Molecular Sieves for the Separation of Propylene and Propane.

High-performance carbon molecular sieves (CMSs) for the separation of propylene (C 3 H 6 ) and propane (C 3 H 8 ) were synthesized in this study by chemical vapor deposition (CVD) of benzene on the pore entrances of activated carbon. The C 3 H 6 and C 3 H 8 separation characteristics of the CMSs were controlled by altering the amount of carbon deposited during CVD, and the resulting characteristic curve featuring the kinetic selectivity of C 3 H 6 over C 3 H 8 as a function of the adsorption rate constant of C 3 H 6 is considered to be the upper bound of the C 3 H 6 -C 3 H 8 separation factor for current CMSs because of the presence of previously reported CMS data under this curve. Additionally, CMS models were constructed using grand canonical molecular dynamics (GCMD) simulations mimicking the process of CVD, which revealed that the kinetic selectivity of C 3 H 6 over C 3 H 8 strongly depended on the size of the pore entrances at the level of 0.01 nm, and that strict control of the pore-entrance size was crucial for obtaining high-performance CMSs for C 3 H 6 -C 3 H 8 separation. This was essentially achieved by controlling the duration of CVD, which led to the experimental realization of CMSs with a C 3 H 6 selectivity over C 3 H 8 of >2000 and a high uptake rate of C 3 H 6 . A design guideline for the development of high-performance CMSs for C 3 H 6 -C 3 H 8 separation was proposed based on theoretical calculations performed using idealized carbon structures, which extracted the characteristics of the CMS models obtained from the GCMD simulations.