Cuprous-chloride-modified nanoporous alumina membranes for ethylene- ethane separation

This paper reports an attempt to synthesize a CuCl-modified γ-alumina membrane for separation of ethylene from ethane. CuCl was effectively coated in the 4 nm pore γ-alumina top layers of disk-shaped and tubular alumina membranes by the reservoir method. Permeation of a single gas and binary mixture of ethylene and ethane was measured to characterize separation properties of the modified membranes. Pure ethylene permeance of the CuCl- modified membrane is 10-40% lower than that predicted from the pure ethane permeance by the Knudsen theory. This result is explained by a model based on the adsorbed layer of ethylene via π-complexation. Such an adsorbed layer hinders the diffusion of ethylene in the nanopores of CuCl-modified γ- alumina. Multiple gas permeation measurements on the CuCl-modified membranes show a separation factor for ethylene over ethane larger than the Knudsen value. This confirms a positive contribution of the surface flow of ethylene to the permeance of ethylene in the multiple gas permeation system. A maximum separation factor for ethylene over ethane of 1.4 is obtained for the CuCl- modified membrane at 60 °C.