3. Results and discussion 3.1. Exploratory experiments with MM1. In the present work, 17 ILs with different cations and anions were synthesized to evaluate the effect of different molecular structures on the extraction of N-compounds. To our knowledge, the synthesis of some ILs from Table 4, for example, tetra alkyl ammonium with different carboxylic anions has not been published yet. As it was stated in the objectives, the selection of the Feed/IL ratio aimed at the least amount of IL required for reducing the N-content just enough to facilitate the HDS process. In this case, by using IL 1 and the MM1, MM2 and MM3 mixtures (Figure 2), it could be seen that a ratio of 20/1 was sufficient for attaining a good extraction level. It seems that the …show more content…
It was difficult to find an IL that worked well extracting all the N-compounds. In general, it was observed that the nitrogen removal of the synthesized ILs was higher for indole and carbazole than for quinoline (Figure 3). The reason behind this behavior is that quinoline is a Lewis acid, while indole and carbazole are Brӧnsted acids. The imidazolium ILs containing halogen anions showed a good removal efficacy, while the change of anion from chloride IL 1 to dicyanamide IL 2 decreased the extraction efficiency of N-compounds. The presence of double imidazolium rings in the structure of the ILs (ILs 4-5) or aromatic derivatives (IL 7) led to the reduction of the removal properties. Butyrate, hexanoate and octanoate of triethylmethylammonium showed excellent indole extraction capabilities , while the change of the triethylmethylammonium cation (ILs 9-12) for the choline cation (ILs 15-17) resulted in the decrease of the extraction efficiency. It is also noteworthy that the increase in the carbon number of the carboxylic chain in ILs from 9 to 12 and from 15to 17 increased the carbazole removal capabilities of the