Recent Advances in Pd-Based Membranes for Membrane Reactors

Abstract

Palladium-based membranes for hydrogen separation have been studied by several research groups during the last 40 years. Much effort has been dedicated to improving the hydrogen flux of these membranes employing different alloys, supports, deposition/production techniques, etc. High flux and cheap membranes, yet stable at different operating conditions are required for their exploitation at industrial scale. The integration of membranes in multifunctional reactors (membrane reactors) poses additional demands on the membranes as interactions at different levels between the catalyst and the membrane surface can occur. Particularly, when employing the membranes in fluidized bed reactors, the selective layer should be resistant to or protected against erosion. In this review we will also describe a novel kind of membranes, the pore-filled type membranes prepared by Pacheco Tanaka and coworkers that represent a possible solution to integrate thin selective membranes into membrane reactors while protecting the selective layer. This work is focused on recent advances on metallic supports, materials used as an intermetallic diffusion layer when metallic supports are used and the most recent advances on Pd-based composite membranes. Particular attention is paid to improvements on sulfur resistance of Pd based membranes, resistance to hydrogen embrittlement and stability at high temperature.

Long-Term Stability of Thin-Film Pd-Based Supported Membranes

“…The performance of different membranes and membrane reactor configurations has been reported in the literature. Full conversions of the feedstock, as well as a high hydrogen recovery through the membranes with the production of pure hydrogen, have been reported [3]. Unfortunately, very few works have focused on the long-term stability of the system and durability of the membranes, which is an important aspect for the Pd-based membrane reactors to become a viable technology.…”

“…Supported membranes have the advantage of maintaining high mechanical stability for a very thin membrane layer. Metallic and ceramic supported Pd-based membranes have been prepared by various methods yielding a wide range of permeances and perm-selectivities [3].…”

Interlayer Properties of In-Situ Oxidized Porous Stainless Steel for Preparation of Composite Pd Membranes

“…In this context, new routes from waste materials are being widely studied in the last years, considering both solid matter such as biomass [11], plastics [11], tea [12] or industrial municipal wastes [13] and liquids, in example olive mill wastewater [14]. In most of these cases, hydrogen purification is required for particular applications, i.e., combustion engines, turbines or fuel cell systems and Pd-based membranes are suggested as an attractive technology [15][16][17] to be used as independent separator [18,19] or in a membrane reactor configuration [17,20]. These membranes are usually incorporated onto a substrate to reduce the film thickness and simultaneously maintain a suitable mechanical stability [21][22][23].…”

Progress in Methanol Steam Reforming Modelling via Membrane Reactors Technology

“…Many publications were addressed at the subject of hydrogen perm-selective membranes and much attention was received by metallic materials, such as Pd, Pd-alloy, Ti, Va, Mb, etc. [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. Among them, palladium played a relevant role in this field and most of the literature is focused on this metal as a membrane material.…”