Improving synchrotron methods for advanced characterisation of heterogeneous catalysts

Authors: Eleanor Dann ((University College London)
Co-authored by industrial partner: No

Type: Thesis

State: Published (Approved)
Published: April 2019

Open Access Open Access

Abstract: Heterogeneous catalyst materials, in particular supported metal nanoparticles, are hugely important in industrial processes such as emissions control technology. In order to design new catalyst materials with improved catalytic performance, the catalytic properties and mechanistic pathways must be well understood. The work presented in this thesis makes advances to operando spectroscopy methods for the characterisation of industrial heterogeneous catalyst materials operating in realistic reaction conditions. A multi-technique approach, employing XAFS and DRIFTS simultaneously, has been used to probe the electronic and structural properties of metal nanoparticles as well as the molecular vibrations of reactants and intermediates at the catalyst surface. In this work, the preparation of supported metal nanoparticle catalysts have been investigated using time-resolved XAFS and DRIFTS spectroscopy approach. Structure-activity relationships of the supported Pd nanoparticle catalysts have been identified during their operation for an important reaction used in diesel after-treatment technology; the selective catalytic oxidation of NH3. The selectivity of the reaction towards the different reaction products (N2, N2O and NO), within the relevant temperature window for industrial application, has been linked to the different structural phases of Pd, including a previously unidentified PdNx species. The major challenges for operando measurements, concerning improved time resolution and spatial resolution, have been addressed with the development of a new reactor for combined XAFS and DRIFTS of a catalyst bed operating in plug-flow reaction conditions. The advantage of this reactor design for operando characterisation has been demonstrated in the investigation of a supported Pd nanoparticle catalyst (Pd/γ-Al2O3) during oscillating CO oxidation. This reactor improves on previous designs by allowing spectroscopic measurements to be performed with spatial resolution along the axial length of a catalyst bed. In this way, there is scope for elucidating the structure-function relationships of many other heterogeneous catalysts.

Subject Areas: Chemistry

Instruments: B18-Core EXAFS , I20-EDE-Energy Dispersive EXAFS (EDE)

Other Facilities: Swiss Light Source; ESRF

Added On: 20/06/2019 12:01

EDANN Final thesis 25-04-19.pdf

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