Ternary deep eutectic solvents for efficient denitrogenation of a model oil: thermodynamics, extraction efficiency, and recycling performance

Pyridine, which is nitrogen containing compounds is commonly found in crude oil and can lead to the production of NO_x upon combustion. Liquid–liquid extraction is employed for removing nitrogen containing compounds from oils. In the current study, ternary deep eutectic solvents (TDES) were synthesized and used for the extraction of pyridine from a model fuel. The effect of different experimental parameters such as temperature (20 to 60 °C), time (1 to 60 min), initial pyridine concentration (0.1 to 10wt%), and TDES-to-model fuel ratio (1:5 to 5:5) was studied on extraction performance of TDESs for pyridine. Extraction efficiencies greater than 95% were observed for all single batch liquid–liquid extraction experiments. The value of thermodynamic parameters such as ΔG (KJ/moL), ΔS (J/moL/K) and ΔH (KJ/moL) were determined from the data collected at different temperatures. The efficient removal of pyridine from model fuel was found to be due to protonation of the nitrogen. Furthermore, the removal efficiency of regenerated TDES after 5 cycles was approximately equal to first extraction cycle. Finally the synthesized TDES system was employed for removing pyridine from crude oil. By optimizing process parameters, TDES exhibited remarkable performance in removing these compounds from both model oil and crude oil. The results concluded that TDES can be an efficient, cost effective and environmentally benign solvent for the extractive pyridine and other nitrogen containing compounds from model fuel.