Recovery of propylene from refinery off-gas using metal incorporated ethylcellulose membranes

Performance of certain modified ethylcellulose (EC) membranes was investiga ted for the recovery of propylene from a gas mixture, having the same compo sition as the absorber tail gas (ATC) of a fluid catalytic cracking unit of HPCL refinery, Vishakhapatnam. The mixture contains C-1-C-5 hydrocarbons a nd non-hydrocarbons such as CO, CO2, H-2 and N-2. Various metals such as si lver, ruthenium, palladium and iridium were incorporated into EC membranes to modify the membrane permeation properties for selectively increasing the propylene Aux by facilitating its transport. Ethylcellulose membranes appe ared to have good potential for the commercial recovery of propylene from a hydrocarbon rich off-gas mixture containing the olefin as a major constitu ent, A reasonably high selectivity of 5.1 accompanied by high transport rat es was obtained for propylene with respect to propane in the multicomponent mixture. Amongst the metal-incorporated membranes, the best results were o btained with a silver (5 wt.%)-EC membrane which yielded a permeate stream of around 65 mol% propylene. The permeation of the various other hydrocarbo n components present in the ATG mixture through the metal incorporated EC m embranes was also analyzed. Interaction of the metal ions with the membrane matrix has been explained by characterizing the films with the help of FTI R, WAXD and SEM-EDX techniques. (C) 2000 Elsevier Science B.V. All rights r eserved.