Evaluation of Conventional Polar Solvents for Extractive Desulfurization of Model Diesel Fuels

Extractive desulfurization (EDS) of model diesel fuels was examined using several polar solvents such as nitriles, esters, sulfoxides, amides, and ureas. EDS of 49-86 % of dibenzothiophene in model diesel fuels (10 g) was performed using these solvents (5 g). Among the solvents, amide solvents such as 1-methylpyrrolidin-2-one (NMP) achieved the best EDS. Relationships between the extractability and the characteristics of solvents were evaluated. The results indicated that polarity of the solvents, i.e., dipole moments, strongly affects extraction yield. Relationships between the structures of the sulfur compounds and extraction efficiency were also investigated. The results suggested that highly condensed aromatic compounds have high extraction yields, whereas methyl group substitution caused significant decreases. Finally, the partition equilibria were investigated. Amide solvents showed behavior that deviated from the normal partition equilibria.