In this paper we present a theoretical analysis of multicomponent adsorption dynamics of hydrocarbons into a medium-sized activated carbon. The mathematical model allows for the diffusions of the free and adsorbed species into the particle, with the driving force for the adsorbed species being the chemical potential gradient rather than the concentration gradient. The adsorbed species diffuse in two directions inside the particle. One direction is the direction along the particle coordinate while the other is the direction along the grain coordinate. The multicomponent adsorption equilibrium is calculated using the ideal adsorbed solution theory, with the single-component isotherm described by Langmuir equation.