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

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Efficient conversion of heavy oils like vacuum residue (VR) is critical for energy production.
• Slurry phase hydrocracking (SPHC) requires catalysts with high atomic utilization and turnover frequency (TOF) for hydrogen (H₂) activation.
• Developing stable and active catalysts for VR upgrading remains a significant challenge.

Purpose of the Study:

• To develop a robust and stable single-atom (SA) molybdenum (Mo) catalyst for H₂ activation in SPHC of VR.
• To investigate the dynamic structural evolution of Mo active sites during the hydrocracking process.
• To understand the relationship between catalyst structure, H₂ activation, and catalytic performance.

Main Methods:

• A polymerization-pyrolysis-in situ sulfurization strategy was employed to synthesize the SA Mo catalyst.
• The catalyst's performance was evaluated in SPHC of VR, measuring conversion, product yield, and coke content.
• Atomic coordination structures and electronic properties were analyzed using advanced characterization techniques and theoretical calculations.

Main Results:

• The SA Mo catalyst demonstrated an O/S exchange process, evolving from Mo-O₃S₁ to Mo-O₁S₃ coordination configurations.
• This structural evolution promoted efficient homolytic cleavage of H₂ into H radicals.
• The catalyst achieved 65 wt% VR conversion, 93 wt% liquid oil yield, low coke content (0.63 wt%), and a high TOF of 0.35 s^-1, with good cyclic stability.

Conclusions:

• The dynamic structural evolution of Mo SAs is key to enhanced H₂ activation and catalytic hydrogenation in SPHC.
• The Mo-O₁S₃ active site facilitates atomic H diffusion, improving catalytic efficiency.
• This study offers significant insights for developing high atom economy catalysts for industrial heavy oil upgrading.