Extractive Catalytic Oxidative Denitrogenation of Fuels and Their Promoting Effect for Desulfurization Catalyzed by Vanadium Substituted Heteropolyacids and Molecular Oxygen

In this contribution, we successfully apply our recently developed extractive catalytic oxidative desulfurization technology (ECODS) for the removal of different nitrogen-containing compounds (ECODN) from both gasoline and diesel fuels. Hereby, indole, 1-methylindole, 2-methylindole, 3-methylindole, quinoline, and quinaldine are completely removed from different model fuels under oxidative conditions, i.e., 120 degrees C and 20 bar oxygen, with the use of an aqueous HPA-5 catalyst solution within minutes. Indole and quinoline species are oxidized selectively to water-soluble compounds such as acetic acid (6-16%), formic acid (4-13%), and oxalic acid (0-4%), which are extracted in situ into the aqueous catalyst solution. Moreover, mainly carbon dioxide (71-86%) is formed in the gas phase. Our catalyst system is also very effective for denitrogenation at ambient conditions. In contrast to the removal of N-compounds at 120 degrees C and 20 bar oxygen, the reaction at 25 degrees C and atmospheric pressure produces solid N-containing compounds. By combining ECODS and ECODN in one vessel, desulfurization and denitrogenation of different model oils is possible in parallel. Interestingly, N-compounds present in the fuel are found to significantly promote the desulfurization reaction.