Inhibition by Carbon Monoxide in Palladium-based Membranes

Inhibition by Carbon Monoxide in Palladium-based Membranes 

It is well known that CO inhibits the ability of hydrogen to permeate through Pd membranes. The CO-Pd bond involves a physical adsorption phenomenon that is favored at low temperatures. Several studies on the performance decrease of Pd-based membranes and Pd-based membrane reactors due to inhibition have been carried out/ highlighting the under-estimation of the membrane area caused by the non-consideration of the inhibition by CO in the design of a reactor and/or a separation equipment. In fact, the membrane inhibition phenomenon can be relevant not only in gas separation, but also in reactive processes like the water gas shift carried out in Pd-based membrane reactors, where CO is involved as a principal reactant at a relatively low temperature (280-350 °C). 

Some authors observed the effects on superficial modifications induced on Pd-based surfaces by interfacial reactions, which also modify the intrinsic membrane performances by causing a change in the number of superficial active sites. 

The importance of understanding CO adsorption on Pd surfaces and its alloys is shown by the number of theoretical and experimental works performed and published in the last four decades. Basically, the main aim of these papers is an investigation of the mutual interaction of CO with several Pd and Pd-based surfaces - Pd(l 11), Pd(lOO), etc. - characterizing the adsorption kinetics in terms of activation energy and pre-exponential factor of the kinetic constant as functions of surface coverage and temperature by means of several different techniques. If correctly used, this information can be very useful to describe 

6 Coupled Effect of Concentration Polarization and Inhibition by Carbon Monoxide 

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