Performance analysis and thermal stability of Pd–Ag/ <scp>2B</scp> ‐graphite/ <scp> <i>α</i> </scp> ‐ <scp> Al ₂ O ₃ </scp> membrane for hydrogen separation and purification from various mixture gases

Abstract Three composite Pd–Ag/2B‐graphite/ α ‐Al 2 O 3 membranes (M1, M2, and M3) were prepared following the ELP technique whose pore mouth was modified using a 2B‐graphite lead owing to its enhanced ductility, higher thermo‐electrical conductivity, and resistance to thermal shocks. The present study provides critical insight into membrane permeation and optimizing operational parameters. This systematic study is quite useful for the modelling and commercialization of such membranes. A maximum of 0.26 mol m −2 s −1 of permeate H 2 was achieved at 773 K and 300 kPa(g). The investigation also encompasses the effect of mixture gases H 2 /N 2 , H 2 /CO 2 , H 2 /CO, and H 2 /CH 4 on membrane (M1) performance. Increasing the feed load increased the permeate H 2 flux and finally reached a stationary value. The permeate H 2 flux achieved saturation at approximately 258, 645, and 1130 L min −1 of feed load for 100, 200, and 300 kPa(g), respectively. Once the permeate H 2 flux reaches saturation, there was a considerable drop in H 2 recovery. The effect of the H 2 /CO mixture gas was determined over M3 membrane. The relative H 2 flux was reduced to 0.53 at 573 K when the CO content was maintained at 20%. Lastly, the long‐term thermal heat cycle stability of the membrane (M2) was performed. The H 2 /N 2 selectivity of the membrane was found to be above 5000 after 10 thermal cycles and 60 h of continuous operation. The microstructure revealed dislocations in the grain boundaries and evidence of migration of Ag to the membrane surface due to recrystallization and grain development during long‐term operation.