Substitution of Cetyltrimethylammonium for OSDA Cations During B-SSZ-70 Zeotype Synthesis and Its Influence on Delamination
| Autor: | Stacey I. Zones, Maya Ramamurthy, Nicolás A. Grosso-Giordano, Alexander Okrut, Dan Xie, Manish Kumar Mishra, Alexander Katz, Son-Jong Hwang, Le Xu |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Olefin fiber
Materials science Intercalation (chemistry) 02 engineering and technology General Chemistry Mesoporous silica 010402 general chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics 01 natural sciences 0104 chemical sciences law.invention Catalysis chemistry.chemical_compound Adsorption chemistry Chemical engineering Mechanics of Materials law Hydroxide General Materials Science Calcination 0210 nano-technology Zeolite |
| Popis: | We investigated the substitution of structure-directing agent diisobutylimidazolium hydroxide with cetyltrimethylammonium hydroxide (CTA+OH−) surfactant in the synthesis gel of layered-zeotype-precursor B-SSZ-70(P). At low substitution levels, CTA+ interacts with the external-zeotype surface, where it assembles. At higher surfactant amounts, CTA+ intercalation occurs, leading to swelling of the precursor material, as evidenced by powder X-ray diffraction. Characterization of adsorbed CTA+ cations by 13C MAS NMR spectroscopy demonstrates unique broad resonances in the intercalated layers, which represent a more rigid environment than in the external-surface assemblies. At still higher CTA+ substitution levels in the synthesis gel, we observe the formation of amorphous mesoporous silica. We attempted to delaminate materials synthesized with varying CTA+ substitution levels using mild conditions, in which the conventional sonication step is replaced with an easy-to-scale high-shear mixing, and in which the use of halide reagents, which are corrosive and have been required in the past, is also avoided. Our data demonstrate that synthesis of a swollen material per se is not essential as an intermediate for delamination, and that layered zeolite precursor swelling can actually undermine zeolite delamination. Our results instead point to the CTA+ external-surface assemblies as facilitating ease of SSZ-70 delamination under these mild conditions. When calcined and functionalized with grafted titanium centers, the delaminated materials are highly active and selective olefin epoxidation catalysts with organic hydroperoxides, showing a 40% higher epoxide conversion than a catalyst prepared from conventional B-SSZ-70. |
| Databáze: | OpenAIRE |
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