The denitrogenation behavior of several model nitrogen compounds has been investigated during a novel desulfurization and simultaneous denitrogenation process based on alkylation using CH3I and AgBF4 (alkylating agents) and subsequent precipitation of the resulting materials. The denitrogenation reactivities obtained for basic nitrogen compounds (aniline, pyridine, quinoline, and acridine) dissolved in xylene solution were compared to those for neutral compounds (pyrrole, indole, and carbazole). The basic compounds and carbazole were removed from xylene by reaction with the alkylating agents as precipitates of the corresponding N-methylated tetrafluoroborates, whereas pyrrole and indole produced insoluble polymerized materials on their unsaturated bonds. It was found that the denitrogenation reactivities lie in the order pyridine > aniline > acridine > quinoline for basic compounds and pyrrole > indole > carbazole for neutral compounds. Semiempirical MO calculations show that the reactivities of the basic compounds depend on the electron density on the pi orbital for the nitrogen atom lying perpendicular to the plane of the molecules.