PREPARATION OF CARBON MOLECULAR-SIEVES .1. 2-STEP HYDROCARBON DEPOSITION WITH A SINGLE HYDROCARBON

A process is described for preparing a carbon molecular sieve that is suitable for the kinetic separation of gases, such as oxygen from nitr ogen. The process involves modifying a carbon support, having a majori ty of micropores with an effective pore size of about 4.5 to 20 angstr om, using a two-step process in which the sieve is contacted with two different concentrations of a volatile carbon-containing organic compo und. The concentration of the carbon-containing compound used in the f irst step is larger than that in the second step, so that the pore ope nings of the micropores of the support are narrowed successively in tw o distinct steps without excessively filling the micropores themselves .