Hydrogen is considered as a real alternative for improving the current energy scenario in\nthe near future and separation processes are a crucial step for the economy of the process in both\ncentralized and distributed production systems. In this context, Pd-based composite membranes\nappear as an attractive technology trying to reduce the Pd thickness by modifying the commercial\nsupports, mainly formed by metals to fit properly in conventional industrial devices. In most cases,\na final calcination step is required and hence, the metallic support can be oxidized. This work\nanalyzes in detail the properties of intermediate layers generated by in-situ oxidation of tubular PSS\nsupports as a crucial step for the preparation of Pd/PSS membranes. The oxidation temperature\ndetermines the modification of original morphology and permeability by increasing the presence\nof mixed iron-chromium oxides as temperature rises. A compromise solution need to be adopted\nin order to reduce the average pore mouth size and the external roughness, while maintaining\na high permeation capacity. Temperature of 600 ââ??¦C lets to reduce the average pore size from 3.5 to\n2.1 Ã?¼m or from 4.5 to 2.3 Ã?¼m in case of using PSS supports with 0.1 or 0.2 Ã?¼m porous media grades,\nrespectively but maintaining a hydrogen permeation beyond targets of United States of America\nDepartment of Energy (US DOE). Lower temperatures provoke an insufficient surface modification,\nwhile greater values derive in a drastic reduction of permeability. In these conditions, two composite\nmembranes were prepared by ELP-PP, obtaining 14.7 and 18.0 Ã?¼m thick palladium layers in case\nof modifying PSS tubes of 0.1 or 0.2 Ã?¼m media grades, respectively. In both cases, the composite\nPd membranes exhibited a hydrogen perm-selectivity greater than 2000 with permeances ranged\nfrom 2.83 to 5.84Ã?·10âË?â??4 mol mâË?â??2 sâË?â??1 PaâË?â??0.5 and activation energies of around 13ââ?¬â??14 kJ molâË?â??1.
Loading....