The water-gas shift reaction: from conventional catalytic systems to Pd-based membrane reactors - a review

The water-gas shift (WGS) reaction is a well-known step for upgrading carbon monoxide to hydrogen in the production of synthesis gas. For more than 90 years after its first industrial application, many issues in respect of the catalyst, process configuration, reactor design, reaction mechanisms and kinetics have been investigated. More recently, a renewed interest in the WGS reaction carried out in hydrogen perm-selective membrane reactors (MRs) has been observed because of the growing use of polymeric electrolyte membrane (PEM) fuel cells that operate using high-purity hydrogen. Moreover, MRs are viewed as an interesting technology in order to overcome the equilibrium conversion limitations in traditional reactors. This article reviews the most relevant topics of WGS MR technology - catalysis and membrane science. The most used catalysts and relevant progress achieved so far are described and critically reviewed. The effects of the most important parameters affecting the WGS in MRs are detailed. In addition, an overview on the most used membranes in MRs is also presented and discussed. (C) 2009 Curtin University of Technology and John Wiley & Sons, Ltd.