Abstract
Composite asymmetric Pd-Au membranes were prepared on porous Inconel and Hastelloy tubular supports by electroless deposition and galvanic displacement techniques and tested both before and after Au deposition in pure H2 atmosphere. The final membranes with average Au bulk content up to 16.7 wt % were 9-15 μm thick and showed H2/He ideal selectivities in excess of 900 for the entire period of their characterization. The annealing of the as-prepared membranes was conducted through the coating and diffusion mechanism in He and H2 atmospheres at 500 C. The annealing conditions were chosen after nonisothermal and isothermal HT-XRD studies were carried out on Pd-Au coupons prepared with the same techniques used for the membranes fabrication. After the formation of the Pd-Au layer, the membranes showed steady H2 flux and stable Au gradient on the membrane top layer. Comparisons between permeance for Pd-Au and pure Pd membranes indicated that the membranes with an average Au bulk content of 4.5 and 5.4 wt % had an enhancement up to 20% of the H2 permeability with respect to pure Pd membranes in the temperature range 250-450 C. On the other hand, the membrane having the highest Au concentration, even though characterized by a lower H 2 permeability (77% of pure Pd), had a rather high surface Au content (approximately 46 wt %), which might improve the tolerance against H 2S poisoning.
Original language | English |
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Pages (from-to) | 8732-8744 |
Number of pages | 13 |
Journal | Industrial and Engineering Chemistry Research |
Volume | 52 |
Issue number | 26 |
DOIs | |
State | Published - Jul 3 2013 |