Solid solution of a zeolite and a framework-bound OSDA-containing molecular sieve.

Area of Science:

• Materials Science
• Crystallography
• Zeolite Chemistry

Background:

• ECR-40C synthesis involves (2-hydroxyethyl)trimethylammonium (HTMA+) ions as an organic structure-directing agent (OSDA) and UZM-22 zeolite seeds.
• Previous understanding suggested ECR-40C might be a pure framework-bound OSDA-containing molecular sieve (FOMS).

Purpose of the Study:

• To determine the precise structure of the as-made, hydrated ECR-40C.
• To elucidate the nature and distribution of organic species within ECR-40C crystals.
• To clarify the classification of ECR-40C as a material.

Main Methods:

• Synchrotron powder X-ray diffraction and Rietveld analyses for structural determination.
• Elemental and thermal analyses, Na+ ion exchange, multinuclear MAS NMR, and IR spectroscopies for chemical and structural characterization.
• Transmission electron microscopy (TEM) elemental mapping for ion distribution.

Main Results:

• ECR-40C contains both encapsulated HTMA+ ions and framework-bound cations.
• A coexistence of zeolite (UZM-22) and FOMS domains in a ~3:2 ratio was confirmed.
• Na+ ions exchanged uniformly, indicating ECR-40C is a solid solution, not pure FOMS.

Conclusions:

• ECR-40C is identified as a novel solid solution of UZM-22 zeolite and an ECR-40-type FOMS.
• This solid solution structure has not been previously recognized.
• The proportion of zeolite in these solid solutions is influenced by the number of hydroxyl groups in the OSDA.