fulltext.study @t Gmail

A modulated excitation ED-EXAFS/DRIFTS study of hydrothermal ageing of Rh/Al2O3

Paper ID Volume ID Publish Year Pages File Format Full-Text
54114 46997 2014 8 PDF Available
Title
A modulated excitation ED-EXAFS/DRIFTS study of hydrothermal ageing of Rh/Al2O3
Abstract

•Time-resolved ED-EXAFS and DRIFTS are used to determine structural changes induced by hydrothermal ageing of 2 wt% Rh/Al2O3.•Under CO–NO pulsed conditions CO2 production is maximum at the NO-to-CO switch on all catalysts.•Oxidized Rh species are beneficial to activity but different species form depending on ageing temperature.•On the fresh catalyst, surface oxide species on reduced Rh nano-particles are active.•On the catalyst aged at 1273 K, a RhOAl species is redox active but not for desired chemistry.

The thermal stability of Rh-based catalysts for automotive applications is crucial for NOx emission control. Exposure of Rh/Al2O3 to high temperatures under lean conditions causes the loss of active metal area by reaction of Rh with the Al2O3 support that is detrimental for activity and selectivity. This has been confirmed using X-ray diffraction (XRD) and extended X-ray absorption fine structure spectroscopy (EXAFS) of fresh and hydrothermally aged 2 wt% Rh/Al2O3 at 973 and 1273 K. The nature of the species responsible for the activity of the aged catalysts was investigated by the combination of diffuse reflectance IR spectroscopy (DRIFTS) and energy dispersive EXAFS spectroscopy (ED-EXAFS) with phase-sensitive detection (PSD) in a modulated excitation approach. The observed changes in the IR and ED-EXAFS spectra are correlated with the structural changes induced by ageing. The chemistry of CO and NO on Rh was used to probe such changes. The data reveal that though metallic Rh nano-particles are the base for an active catalyst, a surface oxide species (RhO) is likely necessary for activity. Ageing causes loss of Rh dispersion and formation of different Rh structures, which provide distinct RhO species and therefore different catalytic properties.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (156 K)Download as PowerPoint slide

Keywords
Rh/Al2O3; Ageing; DRIFTS; ED-EXAFS; NO reduction; Modulation excitation
First Page Preview
A modulated excitation ED-EXAFS/DRIFTS study of hydrothermal ageing of Rh/Al2O3
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us
Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 229, 15 June 2014, Pages 80–87
Authors
, , , , , ,
Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us