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Instruments / Technical Area	Publication Details	Published
I13-1-Coherence	New dimensions in catalysis research with hard X-ray tomography Srashtasrita Das , Reihaneh Pashminehazar , Shweta Sharma , Sebastian Weber , Thomas L. Sheppard Chemie Ingenieur Technik DOI: 10.1002/cite.202200082 Diamond Proposal Number(s): [24079] Open Access Show Abstract ▼ Abstract: The structure and function of solid catalysts are inseparably linked at length scales from nm to cm and beyond. Hard X-ray tomography offers unique potential for spatially-resolved characterization by combining flexible spatial resolution with a range of chemical contrasts. However, the full capabilities of hard X-ray tomography have not been widely explored in the catalysis community. This review highlights modern advances in hard X-ray tomography using synchrotron radiation. Case studies from model to technical scale illustrate the bright future of X-ray tomography in catalysis research.	Aug 2022
I13-1-Coherence	Hard x-ray nanotomography for 3D analysis of coking in nickel-based catalysts Sebastian Weber , Darren Batey , Silvia Cipiccia , Matthias Stehle , Ken L. Abel , Roger Gläser , Thomas Lennon Sheppard Angewandte Chemie International Edition DOI: 10.1002/anie.202106380 Diamond Proposal Number(s): [24079] Open Access Show Abstract ▼ Abstract: Understanding catalyst deactivation by coking is crucial for knowledge-based catalyst and process design in reactions with carbonaceous species. Post-mortem analysis of catalyst coking is often performed by bulk characterization methods. Here hard X-ray ptychographic computed tomography (PXCT) was used to study Ni/Al2O3 catalysts for CO2 methanation and CH4 dry reforming after artificial coking treatment. PXCT generated quantitative 3D maps of local electron density at ca. 80 nm resolution, allowing to visualize and evaluate the severity of coking in entire catalyst particles of ca. 40 µm diameter. Coking was primarily revealed in the nanoporous solid, which was not detectable in resolved macropores. Coke formation was independently confirmed by operando Raman spectroscopy. PXCT is highlighted as an emerging characterization tool for nanoscale identification, co-localization, and potentially quantification of deactivation phenomena in 3D space within entire catalyst particles.	Aug 2021
I13-1-Coherence	Porosity and structure of hierarchically porous Ni/Al2O3 catalysts for CO2 methanation Sebastian Weber , Ken L. Abel , Ronny T. Zimmermann , Xiaohui Huang , Jens Bremer , Liisa K. Rihko-Struckmann , Darren Batey , Silvia Cipiccia , Juliane Titus , David Poppitz , Christian Kübel , Kai Sundmacher , Roger Gläser , Thomas L. Sheppard Catalysts 10 DOI: 10.3390/catal10121471 Diamond Proposal Number(s): [24079] Open Access Show Abstract ▼ Abstract: CO2 methanation is often performed on Ni/Al2O3 catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/Al2O3 catalyst for methanation of CO2. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., N2 sorption, Hg porosimetry, and He pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry. Macrokinetic simulations were performed based on the measures obtained by porosity analysis. These show the potential benefit of enhanced mass-transfer properties of the hierarchical pore system compared to a pure mesoporous catalyst at industrially relevant conditions. Besides the investigation of the pore system, the catalyst was studied by Rietveld refinement, diffuse reflectance ultraviolet-visible (DRUV/vis) spectroscopy, and H2-temperature programmed reduction (TPR), showing a high reduction temperature required for activation due to structural incorporation of Ni into the transition alumina. The reduced hierarchically porous Ni/Al2O3 catalyst is highly active in CO2 methanation, showing comparable conversion and selectivity for CH4 to an industrial reference catalyst.	Dec 2020
I18-Microfocus Spectroscopy	In situ multimodal 3D chemical imaging of a hierarchically structured core@shell catalyst Thomas Sheppard , Stephen W. T. Price , Federico Benzi , Sina Baier , Michael Klumpp , Roland Dittmeyer , Wilhelm Schwieger , Jan-Dierk Grunwaldt Journal Of The American Chemical Society DOI: 10.1021/jacs.7b02177 Diamond Proposal Number(s): [13562] Show Abstract ▼ Abstract: A Cu/ZnO/Al2O3@ZSM-5 core@shell catalyst active for one-step conversion of synthesis gas to dimethyl ether was imaged simultaneously and in situ using synchrotron-based X-ray Fluorescence (μ-XRF), X-ray Diffraction (μ-XRD) and Scanning Transmission X-ray Microscopy (STXM) Computed Tomography (CT) with micrometer spatial resolution. An identical sample volume was imaged stepwise, first under oxidizing and reducing atmospheres (imitating calcination and activation processes), and then under model reaction conditions for DME synthesis (H2:CO:CO2 ratio of 16:8:1, up to 250 °C). The multimodal imaging methods offered insights into the active metal structure and speciation within the catalyst, and allowed imaging of both the catalyst core and zeolite shell in a single acquisition. Dispersion of nanosized Cu species was observed in the catalyst core during reduction, with formation of a metastable Cu+ phase at the core-shell interface. Under DME reaction conditions at 1 bar, the coexistence of Cu0 in the active catalyst core together with partially oxidized Cu species was unraveled. The zeolite shell and core-shell interface remained stable under all conditions, preserving the bifunctional nature of the catalyst. These observations are inaccessible using standard bulk techniques like XAS and XRD, demonstrating the potential of multimodal in situ X-ray CT for characterization of hierarchically-designed materials, which stand to benefit tremendously from such 3D spatially-resolved measurements.	May 2017

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