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Sr SSZ-13 Al pair Oct 2020.pdf (642.54 kB)

Increasing Al-Pair Abundance in SSZ-13 Zeolite via Zeolite Synthesis in the Presence of Alkaline Earth Metal Hydroxide Produces Hydro-Thermally Stable Cobalt and Pd-SSZ-13 Materials for Pollutant Abatement Applications

preprint
submitted on 16.02.2021, 07:11 and posted on 17.02.2021, 04:51 by Konstantin Khivantsev, Miroslaw A. Derewinski, Nicholas R. Jaegers, Daria Boglaienko, Xavier Isidro Pereira Hernandez, Carolyn Pearce, Yong Wang, János Szanyi

We show that replacing alkaline (NaOH) for alkaline-earth metal (Sr(OH)2 as an example) in the synthesis of SSZ-13 zeolite with Si/Al~10 produces SSZ-13 zeolite material with novel, advantageous properties. Its NH4-form ion-exchanges higher amount of Co(II) ions than the conventional one: this is the consequence of increased number of Al pairs in the structure induced by the +2 charge of Sr(II) cations in the synthesis gel that force two charge-compensating AlO4- motives to be closer together. We characterize the +2 state of Co(II) ions in these materials with infra-red spectroscopy and XANES measurements. They can be used for NOx pollutant adsorption from ambient air: the ones derived from SSZ-13 with higher Al pair content contain more cobalt(II) and thus, perform better as ambient-air NOx adsorbers before reaching full saturation capacity. Notably, Co(II)/SSZ-13 material with increased number of Al pairs is significantly more hydrothermally stable than its NaOH-derived analogue. Loading 1.7 wt% Pd into Co-SSZ-13 synthesized in the presence of Sr(II) produces a passive NOx adsorber (PNA) material that can be used for NOx adsorption from simulated diesel engine exhaust. The critical issue for these applications is hydrothermal stability of Pd-zeolites. Pd/SSZ-13 synthesized in NaOH media loses most of its PNA capacity after ~800 ⁰C hydrothermal aging in the flow of air and steam (10 hours in 10% H2O/air flow). The 1.7 wt% Pd/Co/SSZ-13 material with Si/Al ~10 does not lose its PNA capacity after extremely harsh aging at 850 and 900 ⁰C (10 hours in 10% H2O/Air flow) and loses only ~55% capacity after hydrothermal aging at 930 ⁰C. It shows considerably enhanced stability compared with previous record for Pd/FER, Pd/SSZ-39 and Pd/BEA materials that could survive hydrothermal aging no higher than 820 ⁰C. We herein reveal a new, simple, and scalable strategy for making remarkably (hydro)thermally stable metal-zeolite materials/catalysts with a number of useful applications.

Funding

We would like to thank the financial support by Crosscut Lean Exhaust Emissions Reduction Simula-tions (CLEERS), which is an initiative funded by the U.S. Department of Energy (DOE) Vehicle Tech-nologies Office to support the development of accurate tools for use in the design, calibration, and con-trol of next generation engine/emissions control systems that maximize efficiency while complying with emissions regulations. M.A.D. was supported by the Materials Synthesis and Simulation Across Scales (MS3) Initiative conducted under the Laboratory Directed Research & Development Program at PNNL. Most experiments were conducted in the Environmental Molecular Sciences Laboratory (EMSL), a na-tional scientific user facility sponsored by the Department of Energy’s Office of Biological and Envi-ronmental Research at Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for the DOE by Battelle Memorial Institute under Contract DE-AC06- 76RL01830.

History

Email Address of Submitting Author

Konstantin.Khivantsev@pnnl.gov

Institution

Pacific Northwest National Laboratory

Country

United States

ORCID For Submitting Author

0000-0002-4810-586X

Declaration of Conflict of Interest

No conflicts to decalre

Version Notes

Version 1.0

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