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On route to one-pot synthesis of delaminated Al-SSZ-70 zeolite via partial substitution of OSDA with CTAOH surfactant

Xu, Le and Martinez, Abraham and Hwang, Son-Jong and Chaudhuri, Kaustav and Zones, Stacey I. and Katz, Alexander (2022) On route to one-pot synthesis of delaminated Al-SSZ-70 zeolite via partial substitution of OSDA with CTAOH surfactant. Inorganic Chemistry Frontiers . ISSN 2052-1553. doi:10.1039/d2qi01105k. (In Press)

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Direct one-pot synthesis of delaminated layered zeolitic materials aims to create two-dimensionally confined catalysts for reactions involving sterically bulky reactants, which are too large to benefit from conventional three-dimensional confinement in micropores. As a prototypical system, several efforts have focused on the development of post-synthetic approaches for delamination of silica-rich MWW layered zeolite precursors, but to date this has required either harsh (halide) multi-step conditions, or the need for gemini quaternary ammonium organic surfactants for direct-synthesis routes. The one-pot synthesis of silica-rich delaminated layered zeolites consisting of MWW layers with simple quaternary ammonium surfactants such as those consisting of cetyltrimethyl ammonium (CTA) head groups remains a challenge. In this study, we describe our attempts for one-pot synthesis of delaminated Al-SSZ-70 zeolite via partial replacement of the organic structure-directing agent (OSDA) with a simple surfactant, CTAOH. Leveraging on our prior demonstration of direct one-pot synthesis of delaminated B-SSZ-70, our goal is to use these dual organic additives in Al-SSZ-70 hydrothermal synthesis, to effectively restrain the MWW layer stacking by capping the external surface of the MWW layer with a surfactant. The synthetic approach reported in this work leads to high-silica delaminated MWW-type zeolite Al-SSZ-70, which benefits from postsynthetic high-shear mixing of the layered zeolite precursor for further delamination. The resulting delaminated zeolites exhibit a similar Brønsted/Lewis acid site distributions as characterized by FTIR spectroscopy of adsorbed pyridine at various temperatures, and enhanced acid catalytic properties over a non-delaminated control. However, we observe a minor amorphous-phase impurity when using the high surfactant loading required for optimum delamination, which is observable using TEM imaging and low-angle powder X-ray diffraction. The presence of this amorphous phase highlights the ongoing challenge of synthesizing a fully crystalline MWW-type delaminated material via direct hydrothermal synthesis, when using simple surfactants, which remains a target for future research.

Item Type:Article
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URLURL TypeDescription
Xu, Le0000-0002-9727-7713
Hwang, Son-Jong0000-0002-3210-466X
Zones, Stacey I.0000-0002-3128-6481
Katz, Alexander0000-0003-3487-7049
Additional Information:The authors acknowledge Dr. Dan Xie at Chevron for helpful discussion about PXRD data. The authors are grateful to the Department of Energy, Office of Science, Basic Energy Sciences (DE-FG02-05ER15696) for supporting the catalysis and materials characterization aspects of this work, and the Management and Transfer of Hydrogen via Catalysis Program funded by Chevron Corporation for supporting the materials synthesis work in this manuscript.
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-05ER15696
Chevron CorporationUNSPECIFIED
Record Number:CaltechAUTHORS:20220823-628154700
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116426
Deposited By: Melissa Ray
Deposited On:31 Aug 2022 15:48
Last Modified:31 Aug 2022 15:48

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