High-Pressure Adsorption of Pure Gases on Coals and Activated Carbon: Measurements and Modeling

Abstract

High-pressure gas adsorption of pure methane, nitrogen, and CO2 were measured on five coals of varying rank and an activated carbon. All measurements were conducted at 328.2 K and pressures to 13.8 MPa using a volumetric method. The adsorption isotherm data are for dry Beulah Zap, Illinois no. 6, Pocahontas, Upper Freeport, and Wyodak coals and Filtrasorb (F-400) activated carbon. At about 7 MPa pressure, the ratio of excess adsorptions for N2/CH4/CO2 varied from about 1/1.9/2.8 for Pocahontas coal to 1/2.1/5.9 for Beulah Zap coal. A distinct maximum in excess adsorption was observed for CO2 on each coal between 6 and 8 MPa. For activated carbon at 7 MPa, the ratio of excess adsorptions for N2/CH4/CO2 was 1/1.5/2.3, which is consistent with our earlier data on this activated carbon at a different temperature (318.2 K). The isotherm measurements have expected experimental uncertainties that vary from 1 to 7% for the adsorption of the three gases. The simplified local-density (SLD) model was fit to describe...