Durability of PSS-supported Pd-membranes under mixed gas and water–gas shift conditions

The palladium-based catalytic membrane reactor (Pd-CMR) as well as the palladium-based membrane separator have demonstrated a wide ranging applicability to the fields of H2 production and clean power generation. One of the key requirements in these two application fields remains the synthesis of robust, composite, dense metal membranes which exhibit high H2 permeance as well as long-term selectivity stability. Within such a context, a porous stainless steel supported thin Pd-membrane with an H2 permeance of 34 m3/m2-h-bar0.5 (400 °C) has been prepared and tested under H2/H2O(10−37%) mixed gas conditions, 2.6−6.1 bar and 400−450 °C for up to 190 h. Two similar membranes with H2 permeance of 23 and 28 m3/m2-h-bar0.5, were also tested under water–gas-shift (WGS) reaction conditions (42% CO, 40% H2, 18% CO2), H2O/CO ratio of 2–3, 7.9–14.7 bar, 400 °C and 2700 h−1 for up to 1000 h. At the highest pressure level a stable CO conversion and H2 recovery of 97 and 88% respectively were achieved for 900 h which is indicative of the overall system stability. All the membranes exhibited leak growth under mixed and WGS conditions at similar rates (3.1×10−7–2.2×10−5 m3/m2-h-bar) as those measured during pure H2 testing, suggesting that the reactive atmosphere did not permanently harm the dense Pd-layer. Additionally, a significant part of the leak growth that was experimentally observed during the 1000 hour WGS test can be reasonably attributed to defects inherent to the welded regions of the PSS316L supports utilized in the present research study.