Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)In this work, liquid-liquid equilibrium data for 1-ethyl-3-methylimidazolium diethylphosphate ([emiml[DEtPO(4)]) or 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO(4)]) + 4-methyl-dibenzothiophene (4-MDBT) + n-dodecane systems at 25 and 40 degrees C and atmospheric pressure (approximate to 95 kPa) were determined by refractometry. 4-MDBT is a DBT derivative and it is one of the most difficult diesel sulfur pollutants to remove by the conventional process of hydrodesulfurization. The liquid-liquid equilibrium data were used to study the 4-MDBT extraction from n-dodecane as model diesel oil. 4-MDBT distribution coefficients, solvent selectivities, and extraction data also indicate that [emim][DEtPO(4)] is a better solvent for extractive desulfurization of n-dodecane than [emim][EtSO(4)]. For a solvent/n-dodecane mass ratio of 0.6, the sulfur content in n-dodecane decreases 17-24% and 5-15% for [emim][DEtPO(4)] and [emim][EtSO(4)]. respectively. The quality of the data was ascertained by the Hand and Othmer-Tobias correlations, which presented R(2) > 0.97 for all systems. The NRTL model was used to correlate the data and showed root-mean-square deviations of <0.15%.491994629468Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [07/53024-3, 07/52032-2]