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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Understanding the deactivation phenomena of small-pore Mo/H-SSZ-13 during methane dehydroaromatisation Miren Agote-Aran , Anna B. Kroner , David S. Wragg , Wojciech A. Sławiński , Martha Briceno , Husn U. Islam , Igor V. Sazanovich , María E. Rivas , Andrew W. J. Smith , Paul Collier , Ines Lezcano-Gonzalez , Andrew M. Beale Molecules 25 DOI: 10.3390/molecules25215048 Diamond Proposal Number(s): [11623] Open Access Show Abstract ▼ Abstract: Small pore zeolites have shown great potential in a number of catalytic reactions. While Mo-containing medium pore zeolites have been widely studied for methane dehydroaromatisation (MDA), the use of small pore supports has drawn limited attention due to the fast deactivation of the catalyst. This work investigates the structure of the small pore Mo/H-SSZ-13 during catalyst preparation and reaction by operando X-ray absorption spectroscopy (XAS), in situ synchrotron powder diffraction (SPD), and electron microscopy; then, the results are compared with the medium pore Mo/H-ZSM-5. While SPD suggests that during catalyst preparation, part of the MoOx anchors inside the pores, Mo dispersion and subsequent ion exchange was less effective in the small pore catalyst, resulting in the formation of mesopores and Al2(MOO4)3 particles. Unlike Mo/H-ZSM-5, part of the Mo species in Mo/H-SSZ-13 undergoes full reduction to Mo0 during MDA, whereas characterisation of the spent catalyst indicates that differences also exist in the nature of the formed carbon deposits. Hence, the different Mo speciation and the low performance on small pore zeolites can be attributed to mesopores formation during calcination and the ineffective ion exchange into well dispersed Mo-oxo sites. The results open the scope for the optimisation of synthetic routes to explore the potential of small pore topologies.	Nov 2020
B18-Core EXAFS	Implications of the molybdenum coordination environment in MFI zeolites on methane dehydroaromatisation performance Andrew M. Beale , Miren Agote-Aran , Rachel E. Fletcher , Martha Briceno , Anna B. Kroner , Igor V. Sazanov , Ben Slater , María E. Rivas , Andrew W. J. Smith , Paul Collier , Ines Lezcano-Gonzalez Chemcatchem DOI: 10.1002/cctc.201901166 Diamond Proposal Number(s): [11623] Show Abstract ▼ Abstract: The structure and activity of Mo/Silicalite‐1 (MFI, Si/Al = ∞) were compared to Mo/H‐ZSM‐5 (MFI, Si/Al = 15), a widely studied catalyst for methane dehydroaromatisation (MDA). The anchoring mode of Mo was evaluated by in situ X‐ray absorption spectroscopy (XAS) and density functional theory (DFT). The results showed that in Mo/Silicalite‐1, calcination leads to dispersion of MoO3 precursor into tetrahedral Mo‐oxo species in close proximity to the microporous framework. A weaker interaction of the Mo‐oxo species with the Silicalite‐1 was determined by XAS and DFT. While both catalysts are active for MDA, Mo/Silicalite‐1 undergoes rapid deactivation which was attributed to a faster sintering of Mo species leading to the accumulation of carbon deposits on the zeolite outer surface. The results shed light onto the nature of the Mo structure(s) while evidencing the importance of framework Al in stabilising active Mo species under MDA conditions.	Sep 2019
B18-Core EXAFS I20-EDE-Energy Dispersive EXAFS (EDE)	Combined spatially resolved operando spectroscopy: New insights into kinetic oscillations of CO oxidation on Pd/γ-Al2O3 Ellie K. Dann , Emma K. Gibson , C. Richard A. Catlow , Veronica Celorrio , Paul Collier , Tugce Eralp , Monica Amboage , Christopher Hardacre , Cristina Stere , Anna Kroner , Agnes Raj , Scott Rogers , Alexandre Goguet , Peter P. Wells Journal Of Catalysis 373, 201 - 208 DOI: 10.1016/j.jcat.2019.03.037 Diamond Proposal Number(s): [17340, 17725] Open Access Show Abstract ▼ Abstract: Spatially resolved, combined energy dispersive EXAFS (EDE) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements have been performed over a fixed catalyst bed of Pd/γ-Al2O3 during kinetic oscillations of CO oxidation. The kinetic oscillations of CO oxidation over Pd (or for that matter Pt or Rh) catalysts are a complicated phenomenon that require characterisation techniques with high time resolution and spatial resolution in order to make links between catalyst structure and surface reactivity. By measuring the extent of Pd oxidation at the nanoparticle surface, from Pd K-edge EDE, and matching this with the CO coverage, from DRIFTS spectra, at multiple positions of the fixed bed reactor it is found that the majority of the catalyst undergoes a sharp transition from the CO poisoned catalyst to the highly active, oxidised Pd surface. This transition occurs initially at the end of the catalyst bed, nearest the outlet, and propagates upstream with increasing temperature of the reactor. The oscillations in Pd surface oxide formation and CO coverage are observed only in the first ∼1 mm of the bed, which gives rise to oscillations in CO2 and O2 concentrations observed by end-pipe mass spectrometry after the light-off temperature. The catalyst initially exists as less active, CO poisoned metallic Pd nanoparticles before light-off which transition to a highly active state after light-off when the Pd nanoparticle surface becomes dominated by chemisorbed oxygen. Kinetic oscillations only occur at the front of the catalyst bed where there is sufficient concentration of CO in the gas phase to compete with O2 for adsorption sites at the catalyst surface. We demonstrate the complex nature of the evolving catalyst structure and surface reactivity during catalytic operation and the need for spatially resolved operando methods for understanding and optimising catalyst technologies.	May 2019
B18-Core EXAFS	A versatile liquid-jet/sessile droplet system for operando studies of reactions in liquid dispersions and solutions by X-ray absorption spectroscopy S.-Y. Chang , T. A. Kathyola , E. A. Willneff , C.. J. Willis , P. Wilson , P. J. Dowding , G. Cibin , A. B. Kroner , E. J. Shotton , S. L. M. Schroeder Reaction Chemistry & Engineering 4, 679 - 687 DOI: 10.1039/C8RE00207J Diamond Proposal Number(s): [15850, 14673] Open Access Show Abstract ▼ Abstract: Herein, we designed a versatile cell for operando X-ray absorption spectroscopy (XAS) monitoring of chemical and physical transformations in liquid solutions and dispersions by fluorescence-yield detection. The cell operates under atmospheric pressure, and the composition of the gas phase can be varied, allowing monitoring of gas–liquid reactions. Samples can be examined as a flowing liquid-jet or as a sessile droplet. Both liquid-jet and droplet operations of the cell were demonstrated at the Ca K-edge through time-resolved studies of CaCO3 formation from CO2 and solid Ca(OH)2 in an aqueous suspension. The liquid-jet reaction was performed at 28 °C, and the droplet reaction was performed at ambient temperature, but both configurations had the scope to be modified for operations at higher temperatures. The liquid-jet volumes were recycled, permitting the use of the cell in a continuous sampling loop for process studies in larger reactor vessels. The jet supply tube was interchangeable, permitting adjustment of the jet size through the tubing bore size. Larger bore sizes minimized the pressure drop at the nozzle and thereby the risk of blockage of the liquid supply by the suspended particulates or growth of solid deposits. Sessile droplet operation enabled studies with minimal sample volumes and mechanical disturbances under controlled environmental conditions. The cell is portable and modular and is based on readily available standard vacuum equipment parts. Furthermore, the operation under a He atmosphere allows measurements above 4 keV, covering part of the tender X-ray range, and it is also applicable to the hard X-ray range.	Mar 2019
I20-Scanning-X-ray spectroscopy (XAS/XES)	Operando XAFS studies reveals differences in the activity of Fe-species in MFI and CHA structures for the standard selective catalytic reduction of NO with NH3 Miren Agote-Aran , Ines Lezcano-Gonzalez , Alex G. Greenaway , Shusaku Hayama , Sofia Diaz-Moreno , Anna B. Kroner , Andrew M. Beale Applied Catalysis A: General DOI: 10.1016/j.apcata.2018.11.026 Diamond Proposal Number(s): [9925] Open Access Show Abstract ▼ Abstract: Fe-containing zeolites were studied as catalysts for the standard NH3-SCR reaction with the primary aim of gaining insight into the structure-function relationship of these materials. Catalysts with different Fe nuclearity (i.e. isolated species, clusters, large particles) were synthesised by incipient wetness impregnation, using H-ZSM-5, H-SSZ-13 and Silicalite-1 as supports, and characterised by in situ and operando X-ray emission spectroscopy (XES) and high energy resolution fluorescence detected X-ray absorption near-edge spectroscopy (HERFD-XANES) under NH3-SCR conditions. The combination of these techniques allowed us to obtain a detailed understanding of the changes in Fe coordination, oxidation state and geometry occurring during reaction. The results obtained suggested that isolated octahedral Fe3+ species on H-ZSM-5 are highly active under the conditions studied, undergoing reduction when exposed to NH3 or under SCR conditions. In contrast, isolated tetrahedral Fe3+ sites present in Silicalite-1 exhibited lower redox properties, leading to a reduced NO conversion. Clusters and FexOy particles on H-SSZ-13 exhibited low SCR activity.	Nov 2018
	X-ray Raman scattering: a new in situ probe of molecular structure during nucleation and crystallization from liquid solutions Laila H. Al-madhagi , Sin-yuen Chang , Mahalingam Balasubramanian , Anna B. Kroner , Elizabeth Shotton , Elizabeth A. Willneff , Bhoopesh Mishra , Sven L. M. Schroeder Crystengcomm 52 DOI: 10.1039/C8CE00929E Open Access Show Abstract ▼ Abstract: X-ray Raman scattering (XRS) has been used for in situ probing of solute molecule speciation in solution during cooling crystallization. The C and N K-edges of aqueous imidazole were measured as a function of temperature to monitor the transition from the undersaturated state through supersaturation to crystallization. A new jacketed-vessel crystallizer with internal flow was used, which enables thermal control and minimizes radiation damage. We have demonstrated that the C and N K-edges of imidazole are sensitive to changes in local bonding. In line with this, an abrupt change in the N K-edge fine structure indicates the onset of desolvation and crystallization from the supersaturated solution. In contrast, negligible changes are observed in the C and N K-edge spectra acquired during cooling, indicating that the average solvation structure around imidazole molecules does not change significantly while traversing the thermodynamically metastable supersaturated zone. To the best of our knowledge this is the first time X-ray Raman scattering has been used for studying molecular speciation in organic aqueous solutions during crystallization. Time-dependent density functional theory (TD-DFT) calculations of the near-edge spectra were performed using implicit, explicit and combined solvation models to elucidate the likely binding sites of the water molecules. An explicit solvation model with one water molecule coordinating each nitrogen moiety in the imidazole ring accurately reproduces the peak positions and intensities of the XRS spectra of aqueous imidazole solution.	Sep 2018
B18-Core EXAFS	Determination of molybdenum species evolution during non-oxidative dehydroaromatization of methane and its implications for catalytic performance Miren Agote-aran , Anna B. Kroner , Husn U. Islam , Wojciech A. Slawinski , David S. Wragg , Ines Lezcano-gonzalez , Andrew M. Beale Chemcatchem DOI: 10.1002/cctc.201801299 Show Abstract ▼ Abstract: Mo‐H‐ZSM‐5 has been studied using a combination of operando X‐ray absorption spectroscopy and High Resolution Powder X‐ray diffraction in order to study the evolution of Mo species and their location within the zeolite pores. The results indicate that after calcination the majority of the species present are isolated Mo‐oxo species, attached to the zeolite framework at the straight channels. During reaction, Mo is first partially carburized to intermediate MoCxOy species. At longer reaction times Mo fully carburizes detaching from the zeolite and aggregate forming initial Mo1.6C3 clusters; this is coincident with maximum benzene production. The Mo1.6C3 clusters are then observed to grow, predominantly on the outer zeolite surface and this appears to be the primary cause of catalyst deactivation. The deactivation is not only due to a decrease in the amount of active Mo surface but also due to a loss in shape‐selectivity which leads to an increased carbon deposition at the outer shell of the zeolite crystals and eventually to pore blockage.	Sep 2018
B18-Core EXAFS	Ruthenium stabilized on transition metal-on-transition metal oxide nanoparticles for naphthalene hydrogenation Xiangling Deng , Lihua Zhu , Huan Zhang , Anna Kroner , Jinbao Zheng , Nuowei Zhang , Jun He , Bing Hui Chen International Journal Of Hydrogen Energy DOI: 10.1016/j.ijhydene.2018.05.170 Diamond Proposal Number(s): [12263] Show Abstract ▼ Abstract: The multi-metallic nanocatalysts of ruthenium nanoclusters-on-transition metal/transition metal oxide nanoparticles (TM/TMO NPs) then supported on carbon (Ru/Ni/NiO/C or Ru/Co/Co3O4/C) were designed and synthesized. The Ni/NiO or Co/Co3O4 NPs strongly stabalized the ruthenium nanoclusters by the interfacial interaction among them. These catalysts exhibited high catalytic activity and 100% selectivity to decalin for naphthalene hydrogenation due to the synergy effect of multiple catalytic sites, where naphthalene was absorbed and activated at the TMO sites (NiO or Co3O4), H2 was activated at the Ru sites and it produced the activated H* species, H* was transferred to the surface of NiO or Co3O4 by the hydrogen spillover effect of TM (Ni or Co), reacting with the activated naphthalene and forming decalin. The nanostructures and synergetic effect of the Ru/Ni/NiO/C and Ru/Co/Co3O4/C catalysts were revealed by a series of techniques, such as high-resolution transmission electron microscope (HRTEM), temperature-programmed reduction (TPR), scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) mapping, high-sensitivity low-energy ion scattering (HS-LEIS) and X-ray absorption spectroscopy (XAS). It is promising that the hydrogen storage can proceed at room temperature via catalyzing naphthalene hydrogenation over the Ru/Ni/NiO/C or Ru/Co/Co3O4/C catalyst.	Jun 2018
	QENS study of methane diffusion in Mo/H-ZSM-5 used for the methane dehydroaromatisation reaction Ian P. Silverwood , Miren Agote-aran , Ines Lezcano González , Anna Kroner , Andrew M. Beale Proceedings of the Joint Conference on Quasielastic Neutron Scattering and the Workshop on Inelastic Neutron Spectrometers QENS/WINS 2016 DOI: 10.1063/1.5039294 Show Abstract ▼ Abstract: There is commercial interest in understanding the deactivation of Mo loaded H-ZSM-5 catalyst by coke fouling during the methane dehydroaromatization reaction (MDA). The effect of coke on methane diffusion inside the zeolite pores was studied by quasielastic neutron scattering (QENS) measurements on Mo/H-ZSM-5 samples reacted with methane for 0, 7, 25 and 60 min. Catalytic activity of the samples followed by mass spectrometry indicate that the induction period in which Mo species are carburized lasts for ∼9 min; after this period the material shows selectivity to aromatics. Characterization by TGA and N2 physisorption suggest that practically no carbon is deposited during the induction period. The ∼2 wt % of coke formed after one hour of reaction has a negligible effect in the zeolite crystal structurebut a small effect on the micropore volume. The QENS studies show that the methane transport by jump diffusion is however not measurably affected by the accumulated coke in the samples.	May 2018
B18-Core EXAFS I20-EDE-Energy Dispersive EXAFS (EDE)	X-ray absorption spectroscopy for the chemical and materials sciences Sofia Diaz-moreno , Roberto Boada , Luke Keenan , Anna Kroner , Richard Ilsley Show Abstract ▼ Abstract: X-ray Absorption Spectroscopy is being applied to a widening set of disciplines. Applications started with solid state physics and grew to materials science, chemistry, biochemistry and geology. Now, they cut across engineering materials, environmental science and national heritage — providing very detailed and useful information facilitating understanding and development of materials. This practical guide helps investigators choose the right experiment, carry it out properly and analyze the data to give the best reliable result. It gives readers insights to extract what they need from the world of large-scale experimental facilities like synchrotrons, which seem distant to many laboratory scientists.	Feb 2018

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