Perfluorosulfonic acid-functionalized carbon nanotubes were prepared by liquid deposition of the perfluorosulfonic acid-polytetrafluoroethylene copolymer and characterized by N2 adsorption, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and acid-base titration. The effects of reaction temperature and the type of solvent were investigated. The results showed that these solid acids are very stable in both polar and non-polar solvents and can maintain their acidity up to 300 °C. Higher activity and better stability were observed over these materials in the alkylation of hydroquinone compared with poly(styrene sulfonic acid)-grafted carbon nanotubes.