Selective adsorption of hydrocarbon gases on clays and organic matter

The adsorption selectivity for C-1-C-6, hydrocarbons in a gas mixture on a variety of adsorbents was measured at 26 and 80 degreesC at total pressures of' 1, 2 and 3 atm. The adsorption isotherm reveals that the adsorption levels are higher for organic matter than for clays, although the selectivity is similar. Coal adsorbs gases more than oil shale, kaolinite adsorbs less total gases but more methane than montmorillonite whereas activated carbon shows much stronger adsorption capacity than the other studied samples. The proportion of the adsorptive amount relative to the initial amount for each gas component at steady state condition increases with decreasing their vapor pressures (p(o)) (from C-1 to C-6). The normalized adsorptive amount for each adsorbed gas increases with increasing partial pressures (p) of the gas in the system. The trends, in the case of oil shale, follow nearly a single trend curve as the adsorption level was plotted against relative pressure (p(i)/p(o)). This confirms that the adsorption selectivity is mainly caused by variations in the vapor pressure of the gases. In addition, the measured adsorption rates of gases on the studied adsorbents can be reasonably described using the Elovich kinetic model. (C) 2004 Elsevier Ltd. All rights reserved.