A theoretical model is proposed to describe hydrogen permeation in palladium and silver-palladium membranes in presence of a non-inert gas as CO; it is known indeed that hydrogen flux through palladium-based membranes drastically decreases when H2 is fed in mixtures containing carbon monoxide due to the interaction of the latter gas with the membrane surface. To model this process, the adsorption step of the well known approach suggested by Ward and Dao has been modified by considering the competitive adsorption of the different non-inert molecules on the metal interface. In particular, the competitive adsorption of CO and H2 has been examined accounting for the spectrum of information available for CO adsorption on palladium, as well as for hydrogen in palladium and palladium-silver alloys. A validation of the model proposed has been performed through a comparison between several literature data and model calculations, over a rather broad range of operative conditions, obtaining a quite good agreement with the use of a limited number of adjustable parameters. The data available in the open literature indeed allow an estimation of the parameters involved in the model so that only one quantity, namely the change of CO heat of adsorption with carbon monoxide surface coverage, needed to be adjusted to obtain a satisfactory representation of the system behaviour. The model, is able to describe quantitatively the hydrogen permeation in Pd and Pd/Ag membranes in the presence of carbon monoxide and can be profitably used for predictive purposes and as a tool for membrane modules design; furthermore it represents a solid base to describe adequately the effects of other non-inert molecules on hydrogen permeation in Pd based membranes.
Hydrogen permeation in palladium-based membranes in the presence of CO
GIACINTI BASCHETTI, MARCO;SARTI, GIULIO CESARE
2010
Abstract
A theoretical model is proposed to describe hydrogen permeation in palladium and silver-palladium membranes in presence of a non-inert gas as CO; it is known indeed that hydrogen flux through palladium-based membranes drastically decreases when H2 is fed in mixtures containing carbon monoxide due to the interaction of the latter gas with the membrane surface. To model this process, the adsorption step of the well known approach suggested by Ward and Dao has been modified by considering the competitive adsorption of the different non-inert molecules on the metal interface. In particular, the competitive adsorption of CO and H2 has been examined accounting for the spectrum of information available for CO adsorption on palladium, as well as for hydrogen in palladium and palladium-silver alloys. A validation of the model proposed has been performed through a comparison between several literature data and model calculations, over a rather broad range of operative conditions, obtaining a quite good agreement with the use of a limited number of adjustable parameters. The data available in the open literature indeed allow an estimation of the parameters involved in the model so that only one quantity, namely the change of CO heat of adsorption with carbon monoxide surface coverage, needed to be adjusted to obtain a satisfactory representation of the system behaviour. The model, is able to describe quantitatively the hydrogen permeation in Pd and Pd/Ag membranes in the presence of carbon monoxide and can be profitably used for predictive purposes and as a tool for membrane modules design; furthermore it represents a solid base to describe adequately the effects of other non-inert molecules on hydrogen permeation in Pd based membranes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
