Copper surface-alloying of H-2-permeable Pd-based membrane for integration in Fischer-Tropsch synthesis reactors

Abstract

[EN] Self-supported palladium tubular membranes are surface-functionalized and tested for the selective and controlled addition of H-2 along a fixed-bed catalytic reactor for Fischer-Tropsch hydrocarbon synthesis (FTS). In order to avoid CO poisoning of the active sites of the metallic membrane at low working temperatures (similar to 250 degrees C), a Cu-based protective layer is deposited on the outer surface of a tubular membrane by RF sputtering at room temperature. Upon thermal treatment in H-2, the Cu layer alloys with Pd on the membrane surface, as confirmed by means of XRD, FESEM and TEM, while the membrane assembly is fully functional, i.e. the negative effect of CO surface adsorption is highly diminished and the membrane provides an appropriate H-2 flux (e.g. 12 ml/min.cm(2)) under the harsh operation conditions practiced in FT synthesis. When the Cu-functionalized membrane is fully integrated in the FTS reactor (250 degrees C, 20 bar, 30% CO in feed), the membrane delivers a stable H-2 permeation flux and enables to increase the yield of hydrocarbons in the range of gasoline (C-5-C-12) while reducing methane formation over a bifunctional CoRu/Al2O3-zeolite catalyst.