Active site tuning based on pseudo-binary alloys for low-temperature acetylene semihydrogenation

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Low-temperature acetylene semihydrogenation is crucial for producing pure ethylene, a key monomer for polymers.
• Existing non-noble metal catalysts often suffer from low activity and selectivity, hindering cost-effective production.
• Developing efficient and stable catalytic systems remains a significant challenge in the field.

Purpose of the Study:

• To design and synthesize a highly active, selective, and durable non-noble metal catalyst for low-temperature acetylene semihydrogenation.
• To investigate the effect of tunable pseudo-binary alloy structures on catalytic performance.
• To understand the mechanism behind the enhanced catalytic activity and selectivity.

Main Methods:

• Preparation of a series of (Ni_1-xCu_x)₃Ga/TiO₂ catalysts with varying copper content (x = 0.2–0.75).
• Characterization of the catalysts' pseudo-binary alloy structures (L1₂-type).
• Evaluation of catalytic performance in acetylene semihydrogenation at low temperatures, including activity, selectivity, and stability tests.
• Mechanistic studies to elucidate the role of active sites (Ni₂Cu hollow sites) in the hydrogenation process.

Main Results:

• The optimal catalyst, (Ni_0.8Cu_0.2)₃Ga/TiO₂, demonstrated exceptionally high catalytic activity compared to other 3d transition metal-based systems.
• Achieved excellent ethylene selectivity (96%) and long-term stability (100 hours) with near-complete conversion at 150 °C.
• Mechanistic studies revealed that Ni₂Cu hollow sites on the (111) surface effectively weakened acetylene adsorption and accelerated hydrogenation, suppressing ethane formation.

Conclusions:

• A flexibly tunable pseudo-binary alloy catalyst design concept significantly enhances catalytic performance for acetylene semihydrogenation.
• The developed Ni-based catalyst offers a promising, cost-effective alternative for producing polymer-grade ethylene.
• Understanding the active site structure-performance relationship provides insights for designing future advanced catalysts.