Аннотация:The removal of aromatic nitrogen- and sulfur-containing compounds has become an increasing technical challenge as oil refineries face growing environmental pressures and regulations. The use of novel catalytic and adsorption methods are among alternative technologies, but ionic liquids (ILs) as extraction agents are most promising for fine post-treatment of the hydroprocessed fuels as well as spent hydrocarbon products (oils, lubricants etc.). ILs provide a diversity of properties ranging from strongly hydrophilic to strongly hydrophobic liquids with different affinity to compounds containing heteroatoms like sulfur or nitrogen.
We have chosen 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl) imide as a moisture-stable IL causing no corrosion of the equipment, this IL can be recycled and used repeatedly in technological cycles. ILs are not miscible with gasoline or diesel oil. It is very important for preserving the optimal ratio of hydrocarbons in the fuel that harmful substances with some polarity, such as pyridines, carbazoles and thiophenes, are being extracted much better than non-polar aromatic compounds, for example, toluene.
The aim of the current research was to study the extraction of pyridine (Py), asphaltenes (APh), anthracene-9-carboxaldehyde, an organic dye С26Н27S2ON, and 4,6-dimethyldibenzothiophene (DMDBT) by 1-methyl-3-butylimidazolium bis(trifluoromethylsulfonyl) imide (BMImNTf2) from heptane using the transition metal ions as complexing centers. We studied the addition of different salts of d-elements, water and the illumination with UV-radiation on the extraction of Py, APh, DMDBT into BMImNTf2 from heptane.
The degree of the extraction (R, %) of aromatic nitrogen and sulfur-containing compounds are quite high. It follows from Table 1 that Py and anthracene-9-carboxaldehyde are extracted more efficiently in comparison with APh and DMDBT.
Table 1 demonstrated that the addition of water into the ionic liquid does not change the degree of extraction. On the contrary, the introduction of Ag+ moieties, results in a dramatic enhancement of the degree of extraction of Py and DMDBT as compared to the case of the pure ionic liquid. It is of practical interest that it is possible successfully to use the same IL in extraction at least 5-7 times.
The electrochemical approach enables one to purify the IL from Py and DMDBT by electrochemical oxidation or reduction, respectively.
