Epitaxial Bilayer MWW Zeolite with Enriched Surface Al Sites

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Zeolites are crystalline microporous materials crucial for catalysis, with performance dependent on acid site characteristics.
• Achieving optimal acid strength, abundance, accessibility, and endurance in a single zeolite structure remains a challenge.
• Bilayer zeolites offer short diffusion paths and accessible surface sites, beneficial for bulky molecule catalysis.

Purpose of the Study:

• To demonstrate the direct synthesis of bilayer Molybdenum Tungsten Vanadium (MWW) zeolite.
• To investigate the structural and catalytic properties of the synthesized bilayer MWW (BL-MWW) zeolite.
• To evaluate the performance of BL-MWW in challenging catalytic reactions.

Main Methods:

• Direct synthesis of BL-MWW using hexagonal boron nitride (h-BN) as a template seed.
• Utilizing hexamethylenimine (HMI) and cyclohexanone (CYCL) as dual organic structure-directing agents.
• Characterization of BL-MWW structure, thickness, and acid site distribution.

Main Results:

• Successfully synthesized bilayer MWW (BL-MWW) zeolite with an average thickness of 5 nm and a covalent interlayer structure.
• BL-MWW exhibits enhanced accessibility of stronger acid sites (T2 aluminum) on its external surface (11.1%) compared to internal sites (6.3%).
• The BL-MWW structure demonstrated excellent hydrothermal stability up to 800 °C.

Conclusions:

• The synthesized BL-MWW zeolite offers superior catalytic performance in terms of conversion and endurance for alkylation and cracking reactions.
• The unique bilayer structure and enriched external acid sites of BL-MWW make it highly effective for bulky molecular catalysis.
• BL-MWW represents a promising advancement in zeolite design for demanding catalytic applications.