Effects of sulfur on Mo2C and Pt/Mo2C catalysts: Water gas shift reaction

Molybdenum carbide (Mo2C) and Pt/Mo2C catalysts were evaluated for the water gas shift reaction without and with 5 ppm H2S. The Mo2C catalyst was quickly poisoned by sulfur, achieving a rate that was ∼10% of that prior to sulfur exposure. The Pt/Mo2C catalyst was initially more active than the Mo2C catalyst and deactivated more gradually to a level similar to that for the Mo2C catalyst. X-ray photoelectron spectroscopy revealed Mo2C, MoS2, and S–Mo on the spent catalysts; the Pt/Mo2C catalyst also contained PtS. The results are consistent with Mo2C sites on the Mo2C and Pt/Mo2C catalysts being partially sulfur tolerant, in that these sites could be reactivated on treatment in 15% CH4/H2 at 590 °C. High activity sites associated with Pt nanoparticles were irreversibly deactivated. Residual activities for the Mo2C and Pt/Mo2C catalysts in the presence of H2S appeared to be associated primarily with the presence of MoS2 domains.

Sulfur exposure caused the Mo2C surface to convert to MoS2, which is moderately active for the water gas shift reaction. After recarburization in 15% CH4/H2, the surface consisted of Mo2C and MoS2 domains.Figure optionsDownload high-quality image (104 K)Download as PowerPoint slide