Journal Article10.1021/JACS.6B02651
Catalysis in a Cage: Condition-Dependent Speciation and Dynamics of Exchanged Cu Cations in SSZ-13 Zeolites
Christopher Paolucci,Atish A. Parekh,Ishant Khurana,John R. Di Iorio,Hui Li,Jonatan D. Albarracin Caballero,Arthur J. Shih,Trunojoyo Anggara,W. Nicholas Delgass,Jeffrey T. Miller,Fabio H. Ribeiro,Rajamani Gounder,William F. Schneider +12 more
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TL;DR: Experimental and theory together reveal that the Cu sites respond sensitively to exposure conditions, and in particular that Cu species are solvated and mobilized by NH3 under SCR conditions.
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Abstract: The relationships among the macroscopic compositional parameters of a Cu-exchanged SSZ-13 zeolite catalyst, the types and numbers of Cu active sites, and activity for the selective catalytic reduction (SCR) of NOx with NH3 are established through experimental interrogation and computational analysis of materials across the catalyst composition space. Density functional theory, stochastic models, and experimental characterizations demonstrate that within the synthesis protocols applied here and across Si:Al ratios, the volumetric density of six-membered-rings (6MR) containing two Al (2Al sites) is consistent with a random Al siting in the SSZ-13 lattice subject to Lowenstein’s rule. Further, exchanged CuII ions first populate these 2Al sites before populating remaining unpaired, or 1Al, sites as CuIIOH. These sites are distinguished and enumerated ex situ through vibrational and X-ray absorption spectroscopies (XAS) and chemical titrations. In situ and operando XAS follow Cu oxidation state and coordinatio...
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Citations
Single-Atom Catalysts across the Periodic Table.
TL;DR: A compositional encyclopedia of SACs is provided, celebrating the 10th anniversary of the introduction of this term, and examines the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis.
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Dynamic multinuclear sites formed by mobilized copper ions in NO x selective catalytic reduction.
Christopher Paolucci,Ishant Khurana,Atish A. Parekh,Sichi Li,Arthur J. Shih,Hui Li,John R. Di Iorio,Jonatan D. Albarracin-Caballero,Aleksey Yezerets,Jeffrey T. Miller,W. Nicholas Delgass,Fabio H. Ribeiro,William F. Schneider,Rajamani Gounder +13 more
TL;DR: It is demonstrated that under reaction conditions, mobilized Cu ions can travel through zeolite windows and form transient ion pairs that participate in an oxygen (O2)–mediated CuI→CuII redox step integral to SCR.
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Small-Pore Zeolites: Synthesis and Catalysis
Michiel Dusselier,Mark E. Davis +1 more
TL;DR: This review first focuses on the relevant synthesis details of all 8MR zeolites and provides some generalized findings and related insights, and catalytic applications where 8MRZeolites either have been commercialized or have dominated investigations are presented, with the aim of providing structure-activity relationships.
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Selective Catalytic Reduction over Cu/SSZ-13: Linking Homo- and Heterogeneous Catalysis.
TL;DR: Detailed reaction kinetics are reported on low-temperature standard NH3-SCR, supplemented by DFT calculations, as strong evidence that the low-Temperature oxidation half-cycle occurs with the participation of two isolated CuI ions via formation of a transient [CuI(NH3)2]+-O2-[CuI (NH3]2]+ intermediate.
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References
Role of Hydrated Cu Ion Complexes and Aluminum Distribution in the Framework on the Cu Ion Siting in ZSM-5
TL;DR: In this paper, a series of CuNa−ZSM-5 zeolites with different Cu/Al and Si/Al ratios were prepared by Cu2+ ion exchange from Cu acetate and Cu chloride solutions in order to investigate the complexation of the Cu ions in hydrated and dehydrated zeolite.
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Reaction-driven Ion Exchange of Copper into Zeolite SSZ-13
Anna Clemens,Alexander Shishkin,Per-Anders Carlsson,Magnus Skoglundh,Francisco Javier Martinez-Casado,Z. Matĕj,Olivier Balmes,Hanna Härelind +7 more
TL;DR: In this paper, the authors used several techniques to characterize Cu-SSZ-13 before and after exposure to reaction conditions relevant for NO reduction by NH3-SCR to address the increase in NH3SCR activity observed as a function of time on stream.
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Incorporation of Al at ZSM-5 hydrothermal synthesis. Tuning of Al pairs in the framework
TL;DR: In this article, the authors investigated the effect of TPAOH ion on the networking of Si and Al atoms in gels and incorporation of Al atoms and their distribution in the hydrothermally synthesized ZSM-5 framework.
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Identification of adsorbed species on Cu-ZSM-5 under NH3 SCR conditions
TL;DR: In this paper, the selective catalytic reduction of nitrogen oxides with ammonia as the reducing agent was studied using Fourier transform infrared (FTIR) spectroscopy, and the results indicated that the formation of nitrites or nitrates decreased as surface coverage of ammonia increased.
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Cluster Model Studies of Oxygen-Bridged Cu Pairs in Cu−ZSM-5 Catalysts
TL;DR: In this article, the effect of the support environment on the existence of Cu ion pairs in Cu-exchanged ZSM-5 catalysts using density functional theory was examined using a variety of cluster models, including a previously established single T-site model and larger multi-T-site models specific to particular binding sites.
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