NOVEL METHODS IN SEPARATION OF OLEFIN/PARAFFIN MIXTURES BY FUNCTIONAL POLYMERIC MEMBRANES

C-3 and C-4 olefin/paraffin mixtures were separated by means of a linear low density polyethylene (LLDPE) modified reversible complexing membrane, poly (ethylene-graft-acrylic acid) (PE-g-AA) incorporated with silver ions (PE-g-AA-Ag+). Owing to the formation of a (Ag-olefin)+ complex, olefin can be transported across the membrane by facilitated transport. The SEM-EDX spectrum of the complex membrane showed a homogeneous silver ion distribution across the cross-section of the dense membrane at a grafting higher than about 60%. The permeation properties of an olefin/paraffin gas mixture as measured by gas chromatography with a gas permeability analyzer implied a facilitating effect for olefin. The permeability coefficients, separation factors and permeation activation energies of C-3 and C-4 mixtures at various AA% grafts and temperatures were studied. The separation factor decreased upon exposure of the complex membrane to air, thereby showing decreased silver ion facilitated transport. A membrane regeneration method and the gas permeation properties of the regenerated complex membrane are also discussed.