Removal of nitrogen
and sulfur compounds from diesel fuel is essential
to comply with the increasing stringent regulations. The extraction
capability of two deep eutectic solvents, namely, tetrabutylphosphoniumbromide/ethylene
glycol, TBPBr/EG, with molar ratio 1:2, and tetrabutylammoniumbromide/ethylene
glycol, TBABr/EG, with molar ratio 1:2, in simultaneously extracting
basic nitrogen, nonbasic nitrogen, and sulfur compounds represented
by pyridine, indoline, and dibenzothiophene (DBT) from
n
-hexadecane, was investigated. Two pseudo-ternary phase diagrams
of (TBPBr/EG + (pyridine + indoline + DBT) +
n
-hexadecane)
and (TBABr/EG + (pyridine + indoline + DBT) +
n
-hexadecane)
were predicted via a conductor-like screening model for real solvents
(COSMO-RS) and experimentally validated at 298.15 K and 1 atm. Both
solvents showed zero cross-contamination, indicating the suitability
of all solvents as extraction solvents. The tie lines obtained for
both COSMO-RS and experiments were in agreement and had root-mean-square
deviation (RMSD) values of less than 5% for both systems. Selectivity
and distribution ratio calculated indicates the suitability of both
solvents in extracting sulfur and nitrogen compounds from hexadecane.
Two new parameters, namely, extraction efficiency, α, and extraction
affinity, β, were introduced to ease the performance comparison
of both solvents. TBPBr/EG shows a slightly better performance than
TBABr/EG. Other than that, the presence of multiple solutes shows
low effects on the performance of these solvents.