The selective influence of sulfur on the performance of novel cobalt-based water-gas shift catalysts Original Research Article

Novel Cosingle bondMnO and CoCr2O4 catalysts were found to be tolerant to sulfur up to levels of 220 ppm under WGS reaction conditions. However in coal-derived process gas containing between 0.25 and 0.3 mol% sulfur, and at a reaction temperature of 400°C the Cosingle bondMnO catalyst deactivated rapidly and irreversibly with formation of bulk Co9S8 and a surface manganese sulfide species. The CoCr2O4 catalyst partially deactivated under similar conditions, a phenomenon related to the formation of a surface sulfate species. Bulk sulfiding of the CoCr2O4 catalyst to CoCr2S4 occurred at 550°C and this catalyst gave near-equilibrium CO conversions in the WGS reaction. A pre-sulfided cobalt chromium catalyst demonstrated typical sulfur dependent mechanistic characteristics, with a maximum activity above 400°C.