Catalysis-spillover-membrane. III: The effect of hydrogen spillover on the palladium membrane reactor in the steam reforming reactions

In this paper, the effect of varying the distance between a palladium membrane and the steam reforming catalyst in a packed bed catalytic membrane reactor is studied. A set of the specially structured palladium membrane tube is prepared and used for the steam reforming reaction of n-hexane and of methanol. This specially designed palladium membrane structure has a long tube at the upstream-end of membrane tube, and it is electroplated with thin nickel or palladium film. This nickel or palladium plated metal surface serves as a bridge for the surface diffusion of the nascent hydrogen atoms over a 10 cm distance to the membrane surface for permeation out of the system after they are formed on the catalyst site and spillover from the catalyst surface to the diffusion bridge. As a result, the conversion level of steam reforming reaction is increased while byproduct formation of methane is suppressed. Furthermore, it is believed that the direct migration of the nascent hydrogen atom from the catalyst site to the membrane surface via direct spillover or via surface diffusion brings about a stronger positive contribution to the steam reforming reaction than does the vapor phase diffusion of the molecular hydrogen on the reaction.