Thin palladium layer deposited on ceramic materials: application in hydrogen transport and catalytic membrane process

The objective of this work was to develop a thin, highly permeable, composite inorganic membrane based on palladium supported on a porous ceramic for high temperature hydrogen separation. The palladium layer (1-2 µm thick) was deposited by electroless plating on an asymmetric tubular alumina support. High temperature hydrogen permeation tests were done showing interesting hydrogen permselectivity properties with a H2/N2 separation factor at 60 (400°C) with a trans-membrane pressure difference of 1 bar. The transport of the hydrogen through the Pd membrane is mixed, solution-diffusion through the metal bulk and surface diffusion/Knudsen diffusion through the pores/defects of the film. As predicted, the membrane reactor for the dry reforming of methane shifts the equilibrium of the reaction in the direction of a higher hydrogen production. An enhancement of the methane conversion of 18% was observed in the membrane reactor configuration due to the selective removal of the hydrogen during the reaction as well as a limitation of side reactions.