Effect of CO and CO2 on H2 permeation through finger-like Pd–Ag membranes

The permeance of a 50 μm thick PdAg (25 wt.% of silver) tubular membrane towards hydrogen was evaluated for hydrogen feed streams or binary mixtures of industrial relevance, namely of H2/CO or H2/CO2.It was proposed a rearrangement of the Sieverts–Langmuir (SL) equation to account for the inhibition effect on the membrane permeance towards H2 due to the presence of CO or CO2. Such modification is based on the average partial pressure of CO or CO2 and the logarithm-mean driving-force to account for concentration gradients along the axial length of the tubular membrane. Comparison with the original SL equation evidenced relative deviations < 10.7%. The experimental data showed good agreement with the SL model.It was found that carbon monoxide has a much stronger inhibition effect on hydrogen permeation than carbon dioxide. Considering the values obtained for the adsorption enthalpy of each gas, it was concluded that both CO and CO2 adsorb physically on the membrane surface.

► Permeance of a PdAg membrane towards H2 was evaluated in presence of CO or CO2.
► A modified Sieverts–Langmuir equation was proposed to describe H2 permeation flux.
► Comparison between the original SL equation and the proposed one is made.
►  Experimental data showed good agreement with the model.
► It was possible to completely restore H2 permeance after exposition to CO/CO2.