Synthesis and Evaluation of Metal−Ligand Complexes for Selective Olefin Solubilization in Reactive Solvents

Abstract

The separation of 1-hexene from Fischer−Tropsch streams is an expensive and difficult separation because of the low relative volatilities encountered. Applying metal−ligand complexes, which π-complex olefins, can increase the selectivity and capacity of these separations. In this paper, potential metal−ligand combinations are screened for this purpose using ethylene as the olefin. Ethylene solubility measurements with the metal−ligand complexes show a qualitative relationship between the stability and ability of the metal−ligand complex. The ligands LIX 26 (a hydroxyquinoline) and LIX 54 (a diketone) do not easily extract silver, and the resulting metal−ligand complex is unstable as silver precipitates. In contrast, Cyanex 301 and 302, thiophosphoric acids, easily extract silver and are very stable, but here the silver ion no longer forms π complexes. The ligands, bis(2-ethylhexyl)phosphoric acid and dinonylnaphthalenesulfonic acid, result in a stable metal−ligand complex that can also selectively complex...