Resolving atomic SAPO-34/18 intergrowth architectures for methanol conversion by identifying light atoms and bonds

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Zeolite catalysts, particularly silicoaluminophosphates (SAPOs), are crucial for methanol conversion.
• Understanding the atomic-level microstructures of SAPO zeolites is key to optimizing their catalytic performance.
• Electron microscopy faces challenges in imaging beam-sensitive SAPO zeolites at atomic resolution.

Purpose of the Study:

• To achieve real-space atomic imaging of SAPO-34 and SAPO-18 zeolite lattices, including Al-O-P bonds.
• To resolve the spatial distribution of SAPO-34 and SAPO-18 domains in intergrowth structures.
• To correlate synthesis conditions with the resulting microstructures and catalytic performance of SAPO-34/18 intergrowth catalysts.

Main Methods:

• Utilized integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM) for atomic imaging.
• Synthesized hierarchical and sandwich SAPO-34/18 catalysts by varying Si content and templates.
• Analyzed the spatial distribution of SAPO-34 and SAPO-18 lattices and elemental composition.

Main Results:

• Successfully imaged atomic lattices of SAPO-34 and SAPO-18 zeolites, visualizing Al-O-P atoms and bonds.
• Clearly resolved the spatial distribution of SAPO-34 and SAPO-18 domains in SAPO-34/18 intergrowths.
• Demonstrated that hierarchical and sandwich catalysts exhibit distinct lattice mixing and improved methanol conversion due to reduced diffusion distances.

Conclusions:

• iDPC-STEM enables atomic resolution imaging of beam-sensitive SAPO zeolites.
• Catalyst architecture, specifically the mixing and separation of SAPO-34 and SAPO-18 lattices, significantly impacts methanol conversion efficiency.
• Understanding structure-property relationships allows for targeted modification of SAPO intergrowth catalysts for improved performance.