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Elucidating the significance of copper and nitrate speciation in Cu-SSZ-13 for N2O formation during NH3-SCR

DOI: 10.1021/acscatal.1c03174 DOI Help

Authors: Leila Negahdar (University College London; UK Catalysis Hub, Research Complex at Harwell; UK Catalysis Hub, Research Complex at Harwell) , Naomi E. Omori (University College London; UK Catalysis Hub, Research Complex at Harwell) , Matthew G. Quesne (Cardiff University; UK Catalysis Hub, Research Complex at Harwell) , Mark D. Frogley (Diamond Light Source) , Fernando Cahco-Nerin (Diamond Light Source) , Wilm Jones (University College of London; Finden Ltd) , Stephen W. T. Price (Finden Ltd) , C. Richard A. Catlow (Cardiff University; University College of London; UK Catalysis Hub, Research Complex at Harwell) , Andrew Beale (University College London; Finden Ltd; UK Catalysis Hub, Research Complex at Harwell)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Catalysis , VOL 38 , PAGES 13091 - 13101

State: Published (Approved)
Published: October 2021
Diamond Proposal Number(s): 22298

Abstract: Unwanted N2O formation is a problem that has been noted in selective catalytic reduction (SCR) where copper zeolite catalysts are utilized. With its immense global warming potential and long-term stability, elevated atmospheric N2O has already been identified as a future challenge in the war on climate change. This paper explores the phenomenon of N2O formation during NH3-SCR over Cu-SSZ-13 catalysts, which are currently commercialized in automotive emissions control systems, and proposes a link between N2O production and the local copper environment found within the zeolite. To achieve this, a comparison is made between two Cu-SSZ-13 samples with different copper co-ordinations produced via different synthesis methods. A combination of synchrotron X-ray absorption near-edge spectroscopy, UV–vis, Raman, and density functional theory (DFT) is used to characterize the nature of copper species present within each sample. Synchrotron IR microspectroscopy is then used to compare their behavior during SCR under operando conditions and monitor the evolution of nitrate intermediates, which, along with further DFT, informs a mechanistic model for nitrate decomposition pathways. Increased N2O production is seen in the Cu-SSZ-13 sample postulated to contain a linear Cu species, providing an important correlation between the catalytic behavior of Cu-zeolites and the nature of their metal ion loading and speciation.

Journal Keywords: Cu-zeolites; NH3-SCR; NOx; operando IR; XAFS; DFT calculation; mechanism

Subject Areas: Chemistry

Instruments: B22-Multimode InfraRed imaging And Microspectroscopy , I14-Hard X-ray Nanoprobe

Added On: 18/10/2021 09:20

Discipline Tags:

Catalysis Physical Chemistry Earth Sciences & Environment Climate Change Zeolites Desertification & Pollution Chemistry

Technical Tags:

Imaging Spectroscopy X-ray Fluorescence (XRF) Infrared Spectroscopy X-ray Absorption Spectroscopy (XAS) Lab-based Fourier Transform Infrared Spectroscopy (FTIR) X-ray Absorption Near Edge Structure (XANES)