In Situ-Formed Tridentate Pd-SO_x Coordination for Sulfur-Tolerant CO Oxidation Catalysis

Area of Science:

• Catalysis
• Materials Science
• Environmental Science

Background:

• Sulfur dioxide (SO2) is a common industrial pollutant that poisons catalysts.
• The role of catalyst supports in sulfur tolerance is not fully understood.
• Developing sulfur-tolerant catalysts is crucial for environmental and economic reasons.

Purpose of the Study:

• To investigate the sulfur resistance mechanism of Pd-based catalysts with different supports (TiO2, Al2O3, CeO2) in CO oxidation.
• To elucidate the role of the support in mitigating SO2 poisoning.
• To provide strategies for designing robust catalysts.

Main Methods:

• Catalytic CO oxidation experiments under SO2 and H2O exposure.
• Characterization of catalyst structures and surface species.
• Density Functional Theory (DFT) calculations to analyze bonding and electronic effects.

Main Results:

• Pd/TiO2 demonstrated exceptional sulfur tolerance, maintaining 100% CO conversion for 200 hours at 175 °C.
• A unique tridentate sulfate structure formed on Pd/TiO2, preventing continuous sulfidation.
• Pd/Al2O3 and Pd/CeO2 showed significantly lower sulfur tolerance due to different sulfate formations.

Conclusions:

• The moderate reducibility and strong acidity of Pd/TiO2 facilitate the formation of a protective tridentate sulfate structure.
• This structure on Pd/TiO2 mitigates SO2 affinity while preserving catalytic activity.
• Findings offer insights into designing advanced sulfur-tolerant catalysts for industrial applications.