Permeation Rate of Hydrogen through Palladium Membrane and Hydrogenation Rate of Ethylene by Permeated Hydrogen

Abstract

The permeation rate of hydrogen through a palladium membrane was measured at upstream hydrogen pressures ranging from 0.01 to 1 atm and at temperatures from 27 to 100° C. For a uniphase palladium membrane, either ce- or 8-phase, the permeation rate was expressed as a function of the upstream hydrogen pressure, the downstream hydrogen pressure, the membrane thickness, and the Fick diffusion coefficient (Figs.2, 3, 4). The permeation force was explained to be drived by the difference in concentration of dissolved hydrogen between both surfaces of the membrane in equilibrium with the hydrogen pressure in the gas phase. For a palladium membrane consisting of both a- and R-phase, a hysteresis was observed on the permeation rate vs. hydrogen pressure curve (Fig.9), indicating that the hydrogen pressure at a 8 phase transition differs from that at a phase transition.
The hydrogenation rate of ethylene by permeated hydrogen through the palladium membrane was measured at 100° C over the hydrogen pressure ranging from 0.01 to 1 atm and over the ethylene pressure ranging from 0.01 to 0.8 atm. It was analyzed that, at low pressures of ethylene, the overall rate of reaction controlled by the reaction on the palladium surface is proportional to the ethylene pressure and that, at higher pressue of ethylene, the overall rate is controlled by the diffusion of hydrogen through the palladium membrane, which is expressed as a function of the upstream hydrogen pressure (Fig.11).