Carbon nanotubes can be doped with alkali metals as a way to change the adsorption potential for other molecules on the inside and outside of the nanotubes. We present results from ab initio density functional theory calculations and temperature programmed desorption experiments that characterize the interaction of alkali metals with carbon nanotubes and the interaction of alkanes on alkali metal doped nanotubes. We investigate the interaction of Li atoms with carbon nanotubes (CNTs), both with and without defects. We find that Li atoms are highly mobile on defect free CNTs but are bound strongly to oxygen containing defect sites. Experiments show that the desorption of heptane is significantly altered by the presence of Li. We present calculations to probe the nature of the interaction between Li and alkanes within CNTs.