Concurrent Desulfurization and Denitrogenation of Fuels Using Deep Eutectic Solvents

The concurrent removal of both nitrogen- and sulfur-containing compounds, from simulated fossil fuels, was studied in this work. Four different deep eutectic solvents (DES) were prepared and ranked according their performance to remove thiophene (Th), dibenzothiophene (DBT), pyridine (Py), and carbazole (Carb), from n-heptane in binary mixtures. The simultaneous extractive desulfurization (EDS) and extractive denitrogenation (EDN) was then performed with the TBPB:Sulf (1:4) DES, through the removal of a mixture of model compounds from n-heptane and also from a simulated gasoline and a simulated diesel. In the case of concurrent EDS and EDN from n-heptane, the capacity to extract the sulfur compounds only decreases slightly, but in the case of the nitrogen compounds, their removal is favored by the presence of the other compounds in the model mixture. Regarding the studied complex matrices, simulated gasoline and simulated diesel, the presence of diverse and more complex hydrocarbons has no practical effect on the extraction efficiencies of the nitrogen compounds, while a negative effect was registered for sulfur compounds in diesel. In addition, the reusability of the DES was carried over 5 cycles, where it lost 78% and 44% of its capacity to extract Th and DBT, respectively, but only 4% and 2% for Py and Carb, respectively. Moreover, after a regeneration step, the performance of the DES was fully recovered.