Effects of sulfur on Mo_2C and Pt/Mo_2C catalysts: Water gas shift reaction

摘要

Molybdenum carbide (Mo_2C) and Pt/Mo_2C catalysts were evaluated for the water gas shift reaction without and with 5 ppm H _2S. The Mo_2C catalyst was quickly poisoned by sulfur, achieving a rate that was ～10% of that prior to sulfur exposure. The Pt/Mo_2C catalyst was initially more active than the Mo_2C catalyst and deactivated more gradually to a level similar to that for the Mo_2C catalyst. X-ray photoelectron spectroscopy revealed Mo _2C, MoS_2, and S-Mo on the spent catalysts; the Pt/Mo _2C catalyst also contained PtS. The results are consistent with Mo_2C sites on the Mo_2C and Pt/Mo_2C catalysts being partially sulfur tolerant, in that these sites could be reactivated on treatment in 15% CH_4/H_2 at 590 °C. High activity sites associated with Pt nanoparticles were irreversibly deactivated. Residual activities for the Mo_2C and Pt/Mo_2C catalysts in the presence of H_2S appeared to be associated primarily with the presence of MoS_2 domains.