Identification and estimation of extra-framework aluminium in acidic mazzite by diffuse reflectance spectroscopy

Area of Science:

• Materials Science
• Spectroscopy
• Zeolite Chemistry

Background:

• Mazzite zeolite is susceptible to structural modifications under various chemical treatments.
• Extra-framework aluminum species are key indicators of these structural changes.
• Diffuse reflectance spectroscopy (DRS) is a valuable tool for probing these modifications.

Purpose of the Study:

• To investigate structural modifications in mazzite zeolite using DRS.
• To identify and characterize extra-framework aluminum species formed during treatments.
• To evaluate the efficacy of acetylacetone treatment in altering aluminum coordination.

Main Methods:

• Diffuse reflectance spectroscopy (DRS) was employed to analyze mazzite zeolite.
• Samples were subjected to calcination, acid leaching, and acetylacetone treatments.
• UV-Visible spectrophotometry was used in conjunction with DRS.

Main Results:

• DRS detected extra-framework aluminum species via characteristic charge transfer transitions.
• Acetylacetone treatment shifted the DRS band from 260-280 nm to a distinct 285 nm band.
• This spectral shift indicates a transformation of aluminum coordination to a highly ordered octahedral symmetry.

Conclusions:

• DRS is effective in monitoring structural alterations and extra-framework aluminum species in mazzite zeolite.
• Acetylacetone treatment induces significant changes in aluminum coordination within the zeolite.
• A dual approach combining DRS and UV-Visible spectrophotometry is suitable for studying such complex material transformations.