A density functional theory study on how γ-Al₂O₃ - Boehmite transformation affects carbon evolution during...

Area of Science:

• Materials Science
• Surface Chemistry
• Catalysis

Background:

• Gamma-alumina (γ-Al2O3) is widely used in catalysis but suffers from rapid deactivation.
• Coke formation is a primary cause of deactivation in γ-Al2O3 catalysts.
• Understanding coke formation mechanisms is crucial for improving catalyst longevity.

Purpose of the Study:

• To elucidate the mechanism of coke formation and evolution on γ-Al2O3(110) surfaces.
• To investigate the role of surface hydroxylation in coke deposition and growth.
• To determine the preferred structure of higher coke species.

Main Methods:

• Computational surface science approach.
• Simulations of coke deposition and evolution under varying surface conditions (clean, partially hydroxylated, fully hydroxylated).
• Analysis of thermodynamic preferences for coke structures.

Main Results:

• The γ-Al2O3(110) surface facilitates initial atomic coke deposition and dimerization.
• Hydroxyl (OH) species on the surface promote the evolution of coke to higher oligomers (Cₙ, n ≥ 3).
• Cyclic coke structures are thermodynamically favored over aliphatic structures for higher coke formation.

Conclusions:

• Surface hydroxylation plays a critical role in the progression of coke formation on γ-Al2O3.
• The electron-donating nature of the γ-Al2O3 surface influences coke deposition.
• Insights into coke formation mechanisms can guide the development of more stable γ-Al2O3 catalysts.