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.
Highlights
When compared with pressure swing adsorption (PSA) and cryogenic distillation, hydrogen permeable Pd-based membranes are a very promising alternative for the separation of pure hydrogen at small- and medium-scales, while concerns about the Pd availability could hamper the exploitation of this kind of membranes at very large industrial scales, such as pre-combustion capture [1,2,3,4,5]
In this review we will 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
Many more theoretical works were reported to confirm the superior performance of membrane reactors compared with conventional systems [22,23,24,25,26,27,28,29,30,31]. The summary of these results show that packed bed membrane reactors (PBMR) are affected by severe mass and heat transfer limitations that result in reduced membrane fluxes and difficulties in maintaining a uniform temperature close to the membranes that could eventually damage the membranes
Summary
When compared with pressure swing adsorption (PSA) and cryogenic distillation, hydrogen permeable Pd-based membranes are a very promising alternative for the separation of pure hydrogen at small- and medium-scales, while concerns about the Pd availability could hamper the exploitation of this kind of membranes at very large industrial scales, such as pre-combustion capture [1,2,3,4,5]. Membrane materials and alloys have been investigated with the aim of developing high-flux membranes showing long-term stability at industrially relevant conditions. The early investigations were based on self-supported thick membranes which presented a very high selectivity (required for niche applications such as nuclear), but low permeation rates and extremely high costs. A recent paper by Fernandez et al shows that the integration of membranes in membrane reactors can be hampered by chemical interaction between the membrane itself and (some component of) the catalyst used in the reactor [17] For instance they showed that by using a catalyst bed containing TiO2 a strong interaction between this component and the membrane surface made the permeation flux decrease by a factor of 14 within a few h of experiments under fluidized conditions. The characteristics and properties of the membranes are reviewed, focussing on: (a) effect of the support; (b) resistance of the membrane to embrittlement and poisoning with sulfur (by using palladium alloys); (c) resistance to damage caused by interactions with the catalyst by using cermet or “pore filled” membranes
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
