Effect of the Nature and Location of Copper Species on the Catalytic Nitric Oxide Selective Catalytic Reduction Performance of the Copper/SSZ‐13 Zeolite

Abstract

. (2014). Effect of the nature and location of copper species on catalytic nitric oxide selective catalytic reduction performance of the copper/SSZ-13 zeolite. ChemCatChem, 6(2), 634-639. DOI: 10.1002/cctc.201300775 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. [b] Guanna Li, [a, b] Zhaochi Feng, [a] Emiel J. M. Hensen,* [b] and Can Li*[a] IntroductionThe selective catalytic reduction (SCR) of nitrogen oxides (NO x ) with ammonia (NH 3 -SCR) is an efficient way for NO x abatement. [1][2][3] Copper-containing zeolites are one of the most active catalyst systems for the related reactions. [3][4][5][6][7][8] The most extensive studies have been performed on Cu/ZSM-5 and Cu/ BEA zeolites. Cu/BEA demonstrates excellent activity with better hydrothermal stability than does Cu/ZSM-5. [7,[9][10][11] The ion-exchanged copper-containing SSZ-13 zeolite, based on the small-pore chabazite (CHA) zeolite topology, recently demonstrated higher activity and selectivity to N 2 over a wide temperature range and better hydrothermal stability than did Cu/ ZSM-5 and Cu/BEA zeolites. [12][13][14][15][16][17] Typically, the catalytic SCR performance of the copper-containing zeolite greatly depends on the location and nature of copper species. The existence of various types of copper species in the zeolite has been proposed: Cu 2 + and Cu + monomers, [CuÀOÀCu] 2 + dimers, and CuO x clusters. [17][18][19] Isolated Cu 2 + species are usually postulated as the active sites in the SCR reaction. [20][21][22] The preparation method strongly affects the nature and speciation of the copper phase. In general, monomeric copper ions located at the cation-exchange sites dominate in ion-exchanged samples, with the fraction of [CuÀOÀ Cu] 2 + dimers typically becoming more important with increasing Cu content. [18] In contrast, precipitation usually results in the formation of a separate CuO phase located at the external zeolite surface. [17][18][19] Lobo et al. suggested that Cu 2 + ions are located in the six-membered rings of the CHA structure. [23] Combining extended X-ray absorption fine structure and in situ UV/Vis spectroscopy, Beale et al. proposed that isolated mononuclear Cu 2 + species slightly shifted toward the edge of the six-membered rings.[20] Kwak et al. reported that the location of ...

Cu-CHA – a model system for applied selective redox catalysis

“…As discussed in Section 2.1.2, there are evidences for the formation of mono-and multi-nuclear Cu(II) species other than Z[Cu(II)OH] under high-temperature oxidative treatment of high-loading Cu-SSZ-13 materials with Si/Al ratio in the 13-20 range. 25,27,29,58,145,146 In this respect, the most sensitive techniques are UV-Vis-NIR and Raman spectroscopy, whereas FTIR in the υ(OH) region can be employed indirectly to track the temperature-dependent dynamics of Z[Cu(II)OH] 27 through its fingerprint band at ca. 3650 cm 1 .…”

The dynamic nature of Cu sites in Cu-SSZ-13 and the origin of the seagull NOx conversion profile during NH3-SCR

“…63 Furthermore, Guo et al also observed by Raman spectroscopy the formation of Cu-O-Cu dimers upon dehydration of Cu-chabazite. 64 However, since Cu sites seem to be very mobile, 50,61,65 one has to follow their structural dynamics under realistic reaction conditions, i.e. operando.…”

Synthesis and evaluation of Cu/SAPO-34 catalysts for NH3-SCR 2: Solid-state ion exchange and one-pot synthesis

“…This difference is expected to greatly influence Cu 2+ positioning and Cu 2+ /Cu + redox processes. Besides isolated Cu ions, more recent spectroscopic studies seem to suggest that oxygen-bridged dicopper species (dimers) can also exist in Cu-CHA, especially at high Cu loadings and in the presence of oxygen [32,33]. In any case, it is important to realize that: ) [34].…”