A study of Cu(I)-ethylene complexation for olefin–paraffin separation



The current cryogenic distillation technology used for olefin–paraffin separation incurs extensive capital and operating costs. An alternative olefin–paraffin separation process, based on reactive absorption, could yield significant cost reductions. The research efforts described herein explored the structural characteristics of an NMP-CuCl-aniline absorption solution with ethylene to aid future development of olefin–paraffin separation systems. Solution IR and 1H NMR spectroscopy suggested weak and labile Cu(I)-ethylene and Cu(I)-aniline coordination, which point to the coexistence of multiple structures in solution. Experiments also revealed solvent-dependent and temperature-dependent coordination. The agreement of the collected spectral data with literature implied single ethylene coordination, whereas the Cl ion likely remained coordinated with Cu(I). Solvent interference prohibited detailed investigation of IR spectra, but 1H NMR spectroscopy showed more promise as an analytical technique for the NMP-CuCl-aniline-ethylene system. Finally, a tradeoff appears to exist between ethylene capacity and complex stability, and thus, an optimal ligand must be found that balances these two competing needs. © 2010 American Institute of Chemical Engineers AIChE J, 2011