Performance controlled via surface oxygen-vacancy in Ti-based oxide catalyst during methyl oleate epoxidation

Area of Science:

• Catalysis
• Materials Science
• Surface Chemistry

Background:

• Titanium-based oxide catalysts exhibit high conversion and selectivity in methyl oleate (MO) epoxidation.
• Catalyst stability is crucial for industrial applications but remains poorly understood.
• Deactivation mechanisms, including fouling and oxygen vacancies (O_V), limit catalyst longevity.

Purpose of the Study:

• To investigate the deactivation mechanisms of P25 and TS-1 Ti-based oxide catalysts during MO epoxidation.
• To differentiate the roles of fouling and O_V formation in catalyst deactivation.
• To elucidate the fundamental reasons behind irreversible catalyst deactivation.

Main Methods:

• Combined computational modeling and experimental techniques.
• Analysis of catalyst deactivation through fouling and O_V formation.
• Characterization using X-ray Photoelectron Spectroscopy (XPS) and Bader charge analysis.
• Density of States (DOS) profiling to study electronic structure changes.

Main Results:

• Fouling causes temporary deactivation by blocking active sites, reversible by calcination.
• Oxygen vacancy (O_V) formation leads to permanent deactivation, unrecoverable by regeneration.
• O_V formation increases Ti³⁺ species, reduces the energy gap (E_g), and modifies active site binding energies.
• Reduced E_g impacts Ti-OOH active site and MO bonding strength, lowering conversion.

Conclusions:

• Catalyst deactivation is primarily driven by O_V formation, not just fouling.
• O_V formation permanently alters catalyst surface chemistry and electronic properties.
• Strategies to prevent O_V formation are essential for designing stable Ti-based catalysts for MO epoxidation.