The effect of surface heterogeneity on the adsorption dynamics of ethane and propane in activated carbon is studied in this article. Assuming the micropore size distribution, from which the adsorption energy distribution can be derived, is the sole source for system heterogeneity and the local equilibrium isotherm is described by a Langmuir equation, we have developed a heterogeneous pore and surface diffusion model and tested its model capability with experimental data of hydrocarbons obtained over a range of conditions. A gamma distribution is used to describe the micropore size distribution. Results of this model are compared with those obtained from a previously proposed model based on a uniform energy distribution.