Modelling and simulation of permeation behaviour on Pd/PSS composite membranes prepared by “pore-plating” method R. Sanz a , J.A. Calles a , S. Ordóñez b,n , P. Marín b , D. Alique a , L. Furones a a Department of Chemical and Energy Technology, Rey Juan Carlos University, C/Tulipán s/n, 28933 Móstoles, Madrid, Spain b Department of Chemical Engineering and Environmental Technology, University of Oviedo, Facultad de Química, Julián Clavería 8, 33006 Oviedo, Spain article info Article history: Received 24 April 2013 Received in revised form 19 June 2013 Accepted 29 June 2013 Available online 10 July 2013 Keywords: Hydrogen separation Palladium Electroless plating Pore-plating Modelling abstract The performance of selective hydrogen permeation of different Pd-containing (Pd thickness in the range 11–30 μm) structured membranes has been studied in this work. Pd was deposited over tubular porous stainless steel supports by the novel electroless pore-plating method. The permeation properties of the membranes have been tested at different operating conditions: retentate pressure (1–4 bar), temperature (623–723k) and hydrogen molar fraction of feed gas (0.7–1). A complete selectivity to hydrogen was observed for all tested conditions, ensuring 100% purity in the hydrogen permeate flux. Permeances in the range of 2.3–6.4 Â 10 À4 mol/m 2 s Pa 0.5 were obtained, maintaining a good mechanical stability of the composite system. A mathematical model considering the different mass transfer resistances in series of the composite membrane, e.g. Pd active layer, porous support and gas phase film layer, has been proposed to describe the permeation of hydrogen. The model also considers the axial variations of hydrogen concentration that takes place in tubular membranes. A set of experimental data has been used to fit the empirical parameters of the model, using another set of experiments for validating the proposed model. & 2013 Elsevier B.V. All rights reserved. 1. Introduction In the last few years, the use of hydrogen as an energetic vector has been proposed as a good alternative to solve most important drawbacks of the current oil-based energy system, such as the limited reservoirs, the dependence of unstable political regions and generation of air pollutants [1]. However, purification processes and storage alternatives are still representing challenging issues hinder- ing the development of a sustainable hydrogen economy [2]. In this context, palladium or palladium alloy membranes are an interesting alternative for hydrogen separation and membrane reactor applica- tions. The good mechanical and thermal stability as well as the potential to reach a complete permselectivity for hydrogen are the major goals of this kind of membranes [3]. Nevertheless, they may suffer some important operation drawbacks such as hydrogen embrittlement [4], relatively low fluxes [5] or limited mechanical stability when ultra-thin Pd layers are used [6]. The use of a composite system based on the deposition of a selective palladium layer onto a porous support reduces the minimum thickness of the palladium layer necessary to obtain a free-defect membrane and consequently increases the hydrogen permeate flux and decreases the overall cost of the membrane manufacturing. Moreover, the support increases both the thermal and the mechanical stability of the Pd layer [7, 8]. Membranes have been successfully prepared using a wide variety of supports, such as Vycor glass [9], ceramic [10] or metallic [11] supports. The use of porous stainless steel supports (PSS) represents an attractive alternative due to their mechanical resistance, simplicity of manufacture, high thermal resis- tance, and thermal expansion coefficient similar to palladium [12–14]. However, the presence of large pores creating a high roughness of the PSS surface and the possible atomic inter-diffusion phenomena of some metals from the stainless steel support to the palladium layer are the main drawbacks for obtaining an ultrathin and totally dense palladium layer [15]. The incorporation of different inorganic inter- mediate layers between the PSS and the Pd layer has been proposed by several authors as a good alternative to overcome these problems. Among them, silica [16], alumina [17], aluminium hydroxide [18], cerium hydroxide [19] or zirconium oxide [20] can be mentioned as an example. The intermediate layer has a smoother surface with smaller pore mouths than the PSS, and due to the completely different chemical nature prevents the intermetallic diffusion of the Pd. However, the use of these interlayers can increase significantly the manufacturing cost of the membrane module [21]. In the last few years, a large number of methods for palladium deposition have been developed, Electroless Plating being one of the most popular ones [22–26]. This method is based on the deposition of Pd from aqueous solutions over a porous support and it can be used on both conducting and non-conducting Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/memsci Journal of Membrane Science 0376-7388/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.memsci.2013.06.060 n Corresponding author. Tel.: +34 98 510 34 37; fax: +34 98 510 34 34. E-mail address: sordonez@uniovi.es (S. Ordóñez). Journal of Membrane Science 446 (2013) 410–421