To ensure the technical use of natural gas it is necessary to remove heavy (cyclic) hydrocarbons from the crude gas. In this article the adsorption of two cyclic hydrocarbons in a N-2-carrier gas is investigated on two commercial silica alumina gels. Adsorption isotherms are determined from cumulative breakthrough experiments in a fixed-bed adsorber. The isosteric heat of adsorption is calculated from the temperature-dependent isotherms. The experimental data is discussed regarding the molecular structure of the adsorptive agents as well as surface chemistry and pore structure of the adsorbents.