Effect of ceria particle size as intermediate layer for preparation of composite Pd-membranes by electroless pore-plating onto porous stainless-steel supports
The use of H2-selective membranes for ultra-pure H2 production has been assigned as an attractive technology, particularly those based on Pd-films deposited onto porous stainless-steel (PSS) supports. The ability to incorporate thin Pd-films with enough adherence on any internal or external surfaces becomes essential to minimize their complexity and cost while improving their performance. The modification of original PSS substrates with diverse intermediate layers, especially those made of ceria, is presented as a promising alternative. In this context, the current study addresses for the first time the use of different CeO2 particle sizes to generate an intermediate layer and facilitate the subsequent generation of a thin Pd-film by electroless pore-plating (ELP-PP). The membrane containing the smallest CeO2 particle size (membrane S) demonstrated the lowest performance, which was assigned to the high compaction of the material and generation of cracks on its surface during calcination that consequently led to the deposition of a greater amount of Pd. On the other hand, the morphology of membranes M (medium CeO2 particle size) and L (large CeO2 particle size) were very similar, although the first one demonstrated a slightly smaller interparticle porosity, which led to the deposition of a more homogeneous and thinner Pd-film. Therefore, an outstanding performance in terms of H2 permeance (5.98 × 10− 4 mol⋅m− 2 ⋅s − 1 ⋅Pa− 0.5 at 400 ◦C) was obtained for this membrane. Permeation tests with binary mixtures (H2-N2, H2-CO2, or H2-CO) revealed a concentration-polarization effect in all cases, as well as a certain inhibition effect in the presence of CO. Finally, it should be highlighted the high stability of the membranes during the entire set of experiments, independently of the considered particle size. Thus, enough mechanical and thermal resistances can be assured for future applications.
This work was financially supported by i) Spanish Research Estate Agency through the project of reference PID2020-117273RB-I00, and ii) Base Funding – LA/P/0045/2020 of the Associate Laboratory in Chemical Engineering (ALiCE) and UIDB/00511/2020 – UIDP/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE) – through the national funds provided by FCT/MCTES (PIDDAC). Moreover, M. Salomé Macedo is especially grateful to the Portuguese Foundation for Science and Technology (FCT) for her Ph.D. grant (SFRH/BD/137106/2018) with national funds of the Ministry of Science, Technology and Higher Education and the European Social Fund (ESF) through the Human Capital Operational Programme (POCH). Finally, M. A. Soria also thanks the FCT for the financial support of his work contract through the Scientific Employment Support Program (Norma Transitória DL 57/2017).
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