Concurrent Desulfurization and Denitrogenation of Fuels Using Deep Eutectic Solvents

Abstract

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.

A simple model for precisely describing liquid–liquid equilibrium and better understanding extraction mechanism

“…Liquid–liquid extraction is a widely used separation technology in many fields of chemical industry, for example, removal of aromatic sulfurs and nitrogens from fuel oil, 1‐9 separation of phenols or cresols from coal tar oil or water, 10‐15 recovery of organic acids and metal ions from aqueous solution, 16‐20 and so forth. Between two solvent phases (α and β), the distribution of solute (A) equilibrium concentrations ( C A ) is crucial for liquid–liquid equilibrium (LLE) systems 21,22 .…”

Deep Eutectic Solvents and Multicomponent Reactions: Two Convergent Items to Green Chemistry Strategies

“… [77] In this field, preliminary investigations have been carried out with DESs to remove sulfur compounds from fuels. [78] …”

Novel phenolic deep eutectic solvents for desulfurisation of petrodiesel

“…Recently, DESs have been successfully utilized to extract sulfur and nitrogen compounds from petroleum derivatives [23]. It is well-known that the constituents of DESs are biodegradable, cheap and environmentally friendly.…”