A pure-component equilibrium adsorption isotherm of methane, ethane, propane, and CO2 at different temperatures and the binary adsorption data of methane with the other three species measured at 500 torr (66.7 kPa) and temperatures of 273 K and 303 K are presented and discussed. These measurements were carried out on three nutshell-derived KOH chemically activated carbon (AC) samples and one commercial activated carbon. The binary adsorption data of another commercial AC (Nuxit-al) from the literature are also used for comparison purposes. The single and binary experimental data were applied to six models: IAST, loading-dependent isosteric heat, micropore-size distribution (MPSD), energy distribution (ED), extended Langmuir, and extended Sips models. The models were found to describe the experimental data of the commercial ACs with a reasonably good accuracy, but only the model assuming isosteric heat as a function of loading could reasonably predict the data of KOH chemically activated carbons.