Olefin separation using silver impregnated ion-exchange membranes and silver salt/polymer blend membranes

Olefin separations through silver containing carrier membranes were investigated. A AgBF4/Nafion blend membrane and Nafion 117 membrane exchanged with Ag+ were used. A dry AgBF4/Nafion blend membrane showed butene selectivity over n-butane with dry feed butene pressures below the dissociation pressure. This result is evidence that there was some hydration of the Ag+ so the complexation was a gas-liquid type reaction. Moreover, the selectivity decreased with time, and after eight days of operation, the butene flux approached the n-butane flux even though the butene feed pressure was above the dissociation pressure. The AgBF4/Nafion blend membrane showed a high facilitation effect for C-4 separation with low humidity in comparison to Nafion ion-exchange membranes which require high humidity. A 1-butene flux of 8 X 10(-8) mol/cm(2) s and 1-butene selectivity of 50 over n-butane was measured with the AgBF4/Nafion blend membrane from a 1-butene/n-butane 80/20% feed mixture at 86 kPa total pressure with only 20% relative humidity at 50 degrees C. The membrane showed a 1,3-butadiene selectivity of 2 over 1-butene, and the total flux was greatly seduced by the presence of 1,3-butadiene. C-6 unsaturated hydrocarbon transport through these membranes was also investigated. Both AgBF4/Nafion blend membranes and Nafion ion-exchange membranes showed selectivity for 1,5-hexadiene over 1-hexene. The Nafion ion-exchange membrane showed better performance for the C-6 separation. Heat treated Nafion 117 containing silver ions produced a higher separation factor and flux than obtained with a normal silver form Nafion 117 membrane.