Chitosan membranes chelated with silver or cuprous material may be used to separate olefins from a mixture of olefins and paraffins. The feed stream is humidified, demisted, treated to remove sulfur compounds and passed to a cell having a chitosan membrane containing chelated silver or cuprous compounds. The process has a reasonable flux rate and is operable at reasonable temperatures and pressures. The process could be used in an olefin separation train.