Mayenite Synthesis from Hydroxide Precursors: Structure Formation and Active Sites on Its Surface

Area of Science:

• Materials Science
• Inorganic Chemistry
• Catalysis

Background:

• Mayenite (Ca12Al14O33 or C12A7) is a promising material with potential applications in catalysis.
• Understanding its formation process is crucial for optimizing its properties.

Purpose of the Study:

• To investigate the formation of mayenite from hydroxide precursors in different gas media.
• To characterize the resulting mayenite phase and its surface properties.

Main Methods:

• Synthesis of mayenite from hydroxide precursors at low temperatures (500-900 °C).
• X-ray diffraction (XRD) for phase identification and lattice parameter determination.
• Spin probe method for surface active site analysis.

Main Results:

• Well-crystallized mayenite (C12A7) was obtained at low temperatures with minimal CaO impurity.
• Mayenite synthesized in an argon atmosphere exhibited lower lattice parameters and oxygen nonstoichiometry compared to air-synthesized samples.
• Sintering and crystallization occurred at lower temperatures in argon.
• Donor and acceptor active sites were identified on the mayenite surface, with concentrations comparable to gamma-alumina.

Conclusions:

• Low-temperature synthesis of mayenite from hydroxide precursors is feasible and efficient, particularly in an inert argon atmosphere.
• The resulting mayenite possesses a high specific surface area and active sites, making it suitable for adsorption and catalytic applications.
• Control over synthesis atmosphere influences mayenite's structural and electronic properties.