Development of Pd-based double-skinned membranes for hydrogen production in fluidized bed membrane reactors

This paper reports the preparation and performance characterization of new PdAg supported membranes with a porous protecting layer to protect the membrane surface from particles in a fluidized bed membrane reactor. Supported membranes with a selective layer of 1 mu m and a protective layer have been prepared. Outstanding H-2 permeance (5.10(-6) mol m(-2) s(-1) Pa-1) and H-2/N-2 perm-selectivity (over 25,000) were measured at 400 degrees C and 1 bar of pressure difference. One membrane has been tested for more than 750 h in the presence of fluidized glass beads showing a decay in the perm-selectivity to approximately 5000, mainly due to sealing leakage. However, the protective layer was removed during this long-term test. Another membrane has been tested for more than 2000 h in a fluidized bed membrane reactor with a Rh reforming catalyst supported on promoted alumina in the bubbling fluidization regime. During tests with binary mixtures mass transfer limitations toward the membrane were observed due to large H-2 permeance of the membranes.