ABSTRACT
High-performance carbon molecular sieves (CMSs) for the separation of propylene (C3H6) and propane (C3H8) were synthesized in this study by chemical vapor deposition (CVD) of benzene on the pore entrances of activated carbon. The C3H6 and C3H8 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 C3H6 over C3H8 as a function of the adsorption rate constant of C3H6 is considered to be the upper bound of the C3H6-C3H8 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 C3H6 over C3H8 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 C3H6-C3H8 separation. This was essentially achieved by controlling the duration of CVD, which led to the experimental realization of CMSs with a C3H6 selectivity over C3H8 of >2000 and a high uptake rate of C3H6. A design guideline for the development of high-performance CMSs for C3H6-C3H8 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.
