The design of microporous graphitic adsorbents for selective separation of gases

We discuss the design of optimum graphitic microstructures for selective adsorption from gaseous mixtures. Binary mixtures of methane and nitrogen at 293.1 K and pressures up to 1 bar were chosen as model systems. Non-local density functional theory (DFT) was used to predict the adsorption of nitrogen and methane in slit-shaped pores for a pore size range of 0.5-5 nm. Predictions of gas mixture adsorption and selectivity factors were obtained from ideal adsorbed solution (IAS) theory. From the selectivity as a function of pore size and pressure it is possible to identify optimum structures for methane/nitrogen separations under a given set of conditions. Using our data we predict selectivities for the high surface area carbon AX21. (C) 2000 Elsevier Science B.V. All rights reserved.