Sulfur-Resistant Lanthanide Oxysulfide Catalysts for the High-Temperature Water-Gas Shift Reaction

We report here on the suitability of the oxysulfides of La and Pr as active and stable catalysts for the high temperature water–gas shift reaction (WGS). The oxygen shuttling mechanism between the oxysulfide and the correspondent oxysulfate occurs at temperatures higher than 600^oC, thus making these materials perfect candidates for the high temperature water gas shift reaction. The reaction lights off at around 400^oC and at high temperatures CO conversions close to equilibrium are achieved. The redox mechanism is shown to operate under these conditions. The most important feature of these materials is their tolerance to sulfur compounds as confirmed by spiking the feed gas with different amounts of H₂S. Extension of these catalysts into the low-temperature region can be achieved by addition of a precious metal, such as gold. Structural characterization and kinetic analysis will be presented.