(401g) Development of a Porous Stainless Steel Supported Pd Membrane for High Performance Hydrogen Production

Hydrogen production and purification are critical operations in the production of commodity chemicals. One purification option, membrane purification, offers a cost-effective alternative to pressure swing adsorption. Specifically, palladium-based membranes offer high flux and selectivity for high temperature separations, but as metal foils they are prohibitively expensive for many processes. To deal with this cost limitation, composite membranes, based on the deposition of a thin Pd layer on porous supports, offers a route to both minimize the Pd inventory and enhance performance. Porous ceramic supports are typically employed for this purpose because they are receptive to electroless deposition of Pd. However, they can add significant flow resistance that limits overall performance. Moreover, ceramics are difficult to seal and are prone to fracture. Porous metal supports have high promise for this application due to their low flow resistance, mechanical strength, and high thermal conductivity. However, they are difficult to plate directly due to their poor surface morphology and intermetallic diffusion barriers are required to prevent poisoning of the Pd membrane. In this work a multistage modification process was developed to make as-received porous stainless steel, of various media grades, suitable for thin palladium membrane deposition. Vibratory tumbling and sanding were compared as techniques to minimize surface roughness. Vacuum infiltration and atomic layer deposition (ALD) were used for large and small pore size reduction, respectively. Lastly, oxidation and ALD were used to create intermetallic diffusion barriers. The impact of various parameters involved in each process step were characterized and refined using an array of techniques. These include porometry, optical and electron microscopy, permeance and profilometry measurements. In this talk we will describe the details of the various modification steps and compare the performance of SS composite membranes to our baseline ceramic supports.