Hydrogen purification of synthetic water gas shift gases using microstructured palladium membranes

Novel microstructured palladium composite membranes are fabricated using microfabrication technologies. The membranes have a thickness of 1 micron, and are supported by a microstructured nickel lattice 10 micron in thickness. The membranes' flux versus hydrogen partial pressure are evaluated, and a linear correlation found, indicating a deviation from Sieverts Law due to their relative thinness. The permeance of the membrane are found to be approximately 3 × 10−6 mol*m−2*s−1*Pa−1. The membranes are tested under Department of Energy specified synthetic water gas shift mixtures at temperatures of 320 °C and 380 °C and exhibited fluxes between 0.2 and 0.4 mol*m−2*s at 275 kPag (40 psig). The membranes have stable performance at 320 °C, while alloying of the palladium and nickel support slowly occurs at 380 °C, causing a decline in flux. A permeance selectivity of 458:1 H2:He is observed at a pressure gradient of 1.37 MPag (205 psig) and 380 °C, however a true 'burst pressure' is unable to be determined due to the maximum output limitations of the pressure regulator. Hydrogen sulfide reduces membrane performance, as expected of a pure palladium membrane.