Modification of activated carbon fiber pore structure by coke deposition

The pore structure of activated carbons can be tailored to produce carbon molecular sieves (CMS), by vapour phase thermal decomposition of hydrocarbons. Thermal cracking of propylene at 700 degreesC was used to deposit coke on activated carbon fibers. Pore structure development was studied by determining the adsorption isotherms of N-2 at 77 K and CO2 at 298 K, while the molecular sieving properties were investigated by the kinetic uptake curves of CO2 and CH4 at room temperature. Coke deposition resulted in the decrease of surface area and the enhancement of molecular sieving properties during the early stages of hydrocarbon decomposition.