Propane selective carbon adsorbents from phenolic resin precursor

Novel carbon adsorbents for propane/propylene separation, with an unprecedented adsorption selectivity to propane – the minority component – were prepared from a phenolic resin precursor. The preparation conditions of the carbon molecular sieve adsorbents, such as pre-treatment with phosphoric acid; carbonization and post-treatment with propylene, were carefully investigated concerning their role on the separation performance. The best performing sample, MFF_8, was characterized by SEM, FTIR and small-angle X-ray scattering (SAXS). It was concluded that the pre-treatment with phosphoric acid was critical for obtaining the propane/propylene separation performance – adsorption ratio of ca. 2 at 1 bar and 25 °C; this sample was carbonized at 1100 °C and post-treated with propylene during 12 days. SAXS analysis indicates rod-shaped pores for the MFF_8 sample with a bimodal size distribution with averages of 0.4 nm and 3.7 nm, and HRTEM images show a network of earthworm micropores. The adsorption selectivity of this adsorbent to propane was assigned to the shape and size of the pores and the rigidity of propylene compared with propane for worming through the constriction of the ultra-micropores network. To the best knowledge of the authors, this is the first time a carbon molecular sieve (CMS) adsorbent with rod-shaped pores is reported. This new family of CMS adsorbents show great potential for equilibrium and kinetic based separations of adsorbates displaying different worming performances.