Hydrogen recovery from ethylene mixture with PD-AU composite membrane

Hydrogen separation from the refinery off-gas of the ethylene decomposition was carried out with Pd-1wt.%Au alloy membranes deposited on a porous nickel support using the sputtering and polishing method. In order to verify the effect of ethylene on the membrane, hydrogen permeation tests were carried out with 5% ethylene mixtures at temperatures ranging from 573 to 673 K and pressure differences ranging from 500 to 1500 kPa. Hydrogen permeation tests, which were carried out with the membranes that had an effective area of 16.6 cm2, revealed that the ethylene mixture did not affect hydrogen permeation behavior when the feed streams were 3000 ml min−1 and the pressure difference was 500 kPa at 673 K. As the pressure difference and temperature increased and the feed flow rate decreased, hydrogen permeation flux became less than ideal, indicating that depletion was a major factor in the hydrogen permeation behavior. From the aspect of process design, the membrane with an effective area of 16.6 cm2 could enrich 5% ethylene of 2000 ml min−1 up to 76, 80, and 82% at 573 K, 623 K, and 673 K, respectively with a hydrogen recovery ratio of >96% at a pressure difference of 1500 kPa.