The H permeation through a Pd membrane was measured in the presence of several gases, such as CO, N2, CO2, and Ar, both on the feed side and on the shell side of the (membrane) module. It was found that CO molecules markedly inhibited H permeation. In particular, in the presence of CO the permeation decreased with 2 different slopes. For low CO concentrations, the H permeation decreased quickly (surface effects). For higher ones it decreased smoothly (dilute effect). The permeation of H, in the presence of the other gases, i.e. N2, CO2 and Ar, always decreased with the same slope (dilute effect). In order to describe the CO inhibition, a theoretical investigation was proposed. In particular, the framework of density functional theory was used. The CO and N2 density functional full optimisations on Pd clusters showed that CO and N2 molecules exhibited 2 minima on the cluster surfaces, with bond lengths of 2.0 and 3.8Å, respectively. The CO minima were much more stable than N2 minima, resulting in a surface effect upon H permeation through the membrane.

The Effect of Mixture Gas on Hydrogen Permeation through a Palladium Membrane - Experimental Study and Theoretical Approach. F.Gallucci, F.Chiaravalloti, S.Tosti, E.Drioli, A.Basile: International Journal of Hydrogen Energy, 2007, 32[12], 1837-45