Diamond Publications - Search Results

Search Again...

These results only include publications that have been reviewed and processed by Diamond Light Source. To also view papers that have not yet been processed click here.

You can use the folder icon under Actions to collate papers as required. You can then click on View Folder in the left-hand navigation to review and/or download your folder.

2 items found (0 items not approved), displaying all items.

Instruments / Technical Area	Publication Details	Published	Actions
B18-Core EXAFS	Operando potassium K-edge X-ray absorption spectroscopy: investigating potassium catalysts during soot oxidation Catherine J. Davies , Alexander Mayer , Jess Gabb , Jake M. Walls , Volkan Degirmenci , Paul B. J. Thompson , Giannantonio Cibin , Stan Golunski , Simon Kondrat Physical Chemistry Chemical Physics 173 DOI: 10.1039/D0CP01227K Diamond Proposal Number(s): [19850] Open Access Show Abstract ▼ Abstract: The chemical and structural nature of potassium compounds involved in catalytic soot oxidation have been studied by a combination of temperature programmed oxidation and operando potassium K-edge X-ray absorption spectroscopy experiments. These experiments are the first known operando studies using tender X-rays (∼3.6 keV) under high temperature oxidation reaction conditions. X-ray absorption near edge structure analysis of K2CO3/Al2O3 catalysts during heating shows that, at temperatures between 100 and 200 °C, potassium species undergo a structural change from an initial hydrated K2CO3·xH2O and KHCO3 mixture to well-defined K2CO3. As the catalyst is heated from 200 °C to 600 °C, a feature associated with multiple scattering shifts to lower energy, indicating increased K2CO3 dispersion, due to its mobility at high reaction temperature. This shift was noted to be greater in samples containing soot than in control experiments without soot and can be attributed to enhanced mobility of the K2CO3, due to the interaction between soot and potassium species. No potassium species except K2CO3 could be defined during reactions, which excludes a potential reaction mechanism in which carbonate ions are the active soot-oxidising species. Simulations of K-edge absorption near edge structures were performed to rationalise the observed changes seen. Findings showed that cluster size, unit cell distortions and variation in the distribution of potassium crystallographic sites influenced the simulated spectra of K2CO3. While further simulation studies are required for a more complete understanding, the current results support the hypothesis that changes in the local structure on dispersion can influence the observed spectra. Ex situ characterisation was carried out on the fresh and used catalyst, by X-ray diffraction and X-ray photoelectron spectroscopy, which indicated changes to the carbonate species, in line with the X-ray absorption spectroscopy experiments.	Jul 2020
I11-High Resolution Powder Diffraction	A hydrothermally stable ytterbium metal–organic framework as a bifunctional solid-acid catalyst for glucose conversion David Burnett , Ryan Oozeerally , Ralentri Pertiwi , Thomas W. Chamberlain , Nikolay Cherkasov , Guy J. Clarkson , Yuni K. Krisnandi , Volkan Degirmenci , Richard I. Walton Chemical Communications 316 DOI: 10.1039/C9CC05364F Diamond Proposal Number(s): [13284] Open Access Show Abstract ▼ Abstract: Yb6(BDC)7(OH)4(H2O)4 contains both bridging hydroxyls and metal-coordinated waters, possessing Brønsted and Lewis acid sites. The material crystallises from water at 200 °C. Using the solid as a heterogenous catalyst, glucose is converted into 5-hydroxymethylfurfural, via fructose, with a total selectivity of ∼70% after 24 hours at 140 °C in water alone: the material is recyclable with no loss of crystallinity.	Sep 2019

Instruments / Technical Area

Publication Details

Published

Actions

B18-Core EXAFS

Operando potassium K-edge X-ray absorption spectroscopy: investigating potassium catalysts during soot oxidation

Catherine J. Davies , Alexander Mayer , Jess Gabb , Jake M. Walls , Volkan Degirmenci , Paul B. J. Thompson , Giannantonio Cibin , Stan Golunski , Simon Kondrat

Physical Chemistry Chemical Physics 173

DOI: 10.1039/D0CP01227K

Diamond Proposal Number(s): [19850]

Open Access

Show Abstract ▼

Abstract: The chemical and structural nature of potassium compounds involved in catalytic soot oxidation have been studied by a combination of temperature programmed oxidation and operando potassium K-edge X-ray absorption spectroscopy experiments. These experiments are the first known operando studies using tender X-rays (∼3.6 keV) under high temperature oxidation reaction conditions. X-ray absorption near edge structure analysis of K2CO3/Al2O3 catalysts during heating shows that, at temperatures between 100 and 200 °C, potassium species undergo a structural change from an initial hydrated K2CO3·xH2O and KHCO3 mixture to well-defined K2CO3. As the catalyst is heated from 200 °C to 600 °C, a feature associated with multiple scattering shifts to lower energy, indicating increased K2CO3 dispersion, due to its mobility at high reaction temperature. This shift was noted to be greater in samples containing soot than in control experiments without soot and can be attributed to enhanced mobility of the K2CO3, due to the interaction between soot and potassium species. No potassium species except K2CO3 could be defined during reactions, which excludes a potential reaction mechanism in which carbonate ions are the active soot-oxidising species. Simulations of K-edge absorption near edge structures were performed to rationalise the observed changes seen. Findings showed that cluster size, unit cell distortions and variation in the distribution of potassium crystallographic sites influenced the simulated spectra of K2CO3. While further simulation studies are required for a more complete understanding, the current results support the hypothesis that changes in the local structure on dispersion can influence the observed spectra. Ex situ characterisation was carried out on the fresh and used catalyst, by X-ray diffraction and X-ray photoelectron spectroscopy, which indicated changes to the carbonate species, in line with the X-ray absorption spectroscopy experiments.

Jul 2020

I11-High Resolution Powder Diffraction

A hydrothermally stable ytterbium metal–organic framework as a bifunctional solid-acid catalyst for glucose conversion

David Burnett , Ryan Oozeerally , Ralentri Pertiwi , Thomas W. Chamberlain , Nikolay Cherkasov , Guy J. Clarkson , Yuni K. Krisnandi , Volkan Degirmenci , Richard I. Walton

Chemical Communications 316

DOI: 10.1039/C9CC05364F

Diamond Proposal Number(s): [13284]

Open Access

Show Abstract ▼

Sep 2019