Use of water in aiding olefin/paraffin (liquid + liquid) extraction via complexation with a silver bis(trifluoromethylsulfonyl)imide salt

• Silver-based ILs used as olefin extracting agents for olefin/paraffin mixtures.
• Each extraction process is based on the olefin complexation and solvation.
• The presence of water influences positively each extraction process.
• Each extraction process was evaluated by DFT calculations, NMR, IR and Raman.
• LLE data were then correlated by using the UNIQUAC model.

This paper describes the extraction of C5–C8 linear α-olefins from olefin/paraffin mixtures of the same carbon number via a reversible complexation with a silver salt (silver bis(trifluoromethylsulfonyl)imide, Ag[Tf2N]) to form room temperature ionic liquids [Ag(olefin)x][Tf2N]. From the experimental (liquid + liquid) equilibrium data for the olefin/paraffin mixtures and Ag[Tf2N], 1-pentene showed the best separation performance while C7 and C8 olefins could only be separated from the corresponding mixtures on addition of water which also improves the selectivity at lower carbon numbers like the C5 and C6, for example. Using infrared and Raman spectroscopy of the complex and Ag[Tf2N] saturated by olefin, the mechanism of the extraction was found to be based on both chemical complexation and the physical solubility of the olefin in the ionic liquid ([Ag(olefin)x][Tf2N]). These experiments further support the use of such extraction techniques for the separation of olefins from paraffins.

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