Structure and properties of BETA zeolite for catalytic applications
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BETA zeolite is a versatile and widely studied crystalline microporous material that has found extensive applications in catalysis due to its unique structure and properties. Below are some key aspects of BETA zeolite:
Structure
Framework Type: The framework of BETA zeolite belongs to the BEA family, with a three-dimensional pore system characterized by intersecting 12-ring channels. These channels run parallel to the [010] direction and have dimensions of approximately 7.6 x 7.6 Å, which allows for the diffusion of larger molecules compared to many other zeolites.
Silicon-to-Aluminum Ratio (Si/Al): This ratio influences the acidity and hydrophobicity/hydrophilicity of the zeolite. A higher Si/Al ratio typically results in stronger hydrophobicity and less acid site density but can improve thermal and hydrothermal stability.
Isomorphous Substitution: Besides silicon and aluminum, other elements like boron, iron, or titanium can be incorporated into the framework through isomorphous substitution, modifying the chemical properties and activity of the catalyst.
Properties
High Surface Area and Porosity: BETA zeolite exhibits high specific surface areas, often exceeding 500 m²/g, and well-defined porosity, which is crucial for catalytic reactions involving bulky molecules.
Acidic Sites: It contains both Brønsted and Lewis acid sites, providing it with excellent catalytic activity in acid-catalyzed reactions such as cracking, alkylation, and isomerization.
Thermal and Hydrothermal Stability: Due to its robust framework, BETA zeolite maintains good structural integrity even under harsh conditions, making it suitable for industrial processes where temperature and steam exposure are concerns.
