Highly active and stable MoWS2 catalysts in slurry phase hydrocracking of vacuum residue

Stability of MoS2 Nanocatalysts for the Slurry-Phase Catalytic Hydrogenation of Anthracene

The stability of both the structure and activity of MoS2 nanocatalysts is crucial for minimizing the catalyst cost of the slurry-phase (SP) catalytic hydrogenation. MoS2-GP and MoS2-SP catalysts were, respectively, obtained by gas-phase (denoted as GP) and SP aging of fresh MoS2 catalysts. The MoS2-SP catalyst demonstrated a comparable catalytic hydrogenation activity to that of the fresh MoS2 catalyst, which is about 1.7 times of that for the MoS2-GP catalyst. After 12 cycles of the MoS2-SP catalyst, the obtained Cy12 catalyst demonstrates a retention of 92.0% of its initial catalytic activity. The MoS2-SP catalyst exhibits an impressive stability of catalytic hydrogenation. The MoS2-SP catalyst exhibits average stacking layers of 3.3 and an average slab of 5.2 nm and exposes 14.0% of active sites. The MoS2-SP catalyst can serve as a highly active and stable catalyst for catalytic hydrogenation. This finding can offer valuable insights into the stability of the hydrogenation catalyst in SP hydrogenation technology.

Atomic coordination structural dynamic evolution of single-atom Mo catalyst for promoting H2 activation in slurry phase hydrocracking

Development of efficient catalysts with high atomic utilization and turnover frequency (TOF) for H₂ activation in slurry phase hydrocracking (SPHC) is crucial for the conversion of vacuum residue (VR). Herein, for the first time, we reported a robust and stable single atoms (SAs) Mo catalyst through a polymerization-pyrolysis-in situ sulfurization strategy for activating H₂ in SPHC of VR. An interesting atomic coordination structural dynamic evolution of Mo active sites was discovered. During hydrocracking of VR, the O atoms that coordinated with Mo were gradually replaced by S atoms, which led to the O/S exchange process. The coordination structure of the Mo SAs changed from pre-reaction Mo-O₃S₁ to post-reaction Mo-O₁S₃ coordination configurations, promoting the efficient homolytic cleavage activation of H₂ into H radical species effectively. The evolved Mo SAs catalyst exhibited robust catalytic hydrogenation activity with the per pass conversion of VR of 65 wt%, product yield of liquid oils of 93 wt%, coke content of only 0.63 wt%, TOF calculated for total metals up to 0.35 s^-1, and good cyclic stability. Theoretical calculation reveals that the significant variation of occupied Mo 4d states before and after H₂ interaction has a direct bearing on the dynamic evolution of Mo SAs catalyst structure. The lower d-band center of Mo-O₁S₃ site indicates that atomic H diffusion is easy, which is conducive to catalytic hydrogenation. The finding of this study is of great significance to the development of high atom economy catalysts for the industrial application of heavy oil upgrading technology.