Selective continuous flow extractive denitrogenation of oil containing S- and N-heteroaromatics using metal-containing ionic liquids supported on monolithic silica with hierarchical porosity

Abstract

The removal of heteroaromatic nitrogen and sulfur impurities from a model oil through extraction with ionic liquids (ILs) containing metal salts was performed in view of the purification of fuel feeds. Chloride and bis(trifluoromethanesulfonyl)imide salts of Cu⁺, Cu²⁺ and Fe³⁺ were used. The systems based on ILs and metal compounds were applied both in batch-like liquid–liquid and continuous flow liquid–solid conditions. In a first phase, liquid–liquid biphasic extraction was used to choose the most adequate IL classes; the suitable systems were immobilized on a solid support to form metal-containing supported ionic liquid phases (SILPs). In a next phase, these SILPs were applied in breakthrough experiments. A selective extraction of N-compounds was achieved with metal-containing ionic liquids, in both liquid–liquid and liquid–solid conditions. The breakthrough experiments using Cu(NTf₂)₂⁻ and FeCl₄⁻-containing [BMIM][NTf₂] SILPs immobilized on hierarchically structured silica monoliths resulted in an efficient separation of all the nitrogen compounds from the other impurities in the model oil.