Our paper on Operando and Postreaction Diffraction Imaging of the La–Sr/CaO Catalyst in the Oxidative Coupling of Methane Reaction has been published online by The Journal of Physical Chemistry.
A La–Sr/CaO catalyst was studied operando during the oxidative coupling of methane (OCM) reaction using the X-ray diffraction computed tomography technique. Full-pattern Rietveld analysis was performed in order to track the evolving solid-state chemistry during the temperature ramp, OCM reaction, as well as after cooling to room temperature. We observed a uniform distribution of the catalyst main components: La2O3, CaO–SrO mixed oxide, and the high-temperature rhombohedral polymorph of SrCO3. These were stable initially in the reaction; however, doubling the gas hourly space velocity resulted in the decomposition of SrCO3 to SrO, which subsequently led to the formation of a second CaO–SrO mixed oxide. These two mixed CaO–SrO oxides differed in terms of the extent of Sr incorporation into their unit cell. By applying Vegard’s law during the Rietveld refinement, it was possible to create maps showing the spatial variation of Sr occupancy in the mixed CaO–SrO oxides. The formation of the Sr-doped CaO species is expected to have an important role in this system through the enhancement of the lattice oxygen diffusion as well as increased catalyst basicity.
Read the full article at https://pubs.acs.org/doi/10.1021/acs.jpcc.8b09018
The nDTomo software is now publicly available for download. Developed by our research scientist Dr. Antony Vamvakeros and primarily designed for processing XRD-CT data, it can be used for other tomographic techniques as well. The software suite contains GUIs for the acquisition, pre-processing and analysis of X-ray chemical tomography data. Download it at https://github.com/antonyvam/ndtomo
Finden Ltd’s work with microfocus X-ray beams at Diamond Light Source recently appeared in an article in The Telegraph, “Old Master paintings shown to be ‘crusting over’ by microscope 10 billion times brighter than the Sun.” Dr. Stephen Price explains in the article,
“We were able to plot the different chemistry from the surface down to the base layer where the canvas would be.
“Knowing some of the more eventful history of the painting, such as fire damage, led us to work out what had caused the chemistry change.”
Excerpt from article. Read the full article at https://www.telegraph.co.uk/news/2019/01/26/old-master-paintings-shown-crusting-microscope-10-billion-times/
His work has also appeared on the Physics World website, “Diamond Light Source – when a tool becomes a gem”.
“Stephen Price, a researcher at Finden and formerly a Diamond Light Source scientist, is currently working with the Rijksmuseum in Amsterdam on a sample of Rembrandt’s painting “Homer”, which dates back to 1663. As he explains, the sample is of a white bloom or crust that forms on the painting despite the best efforts of conservationists. His aim has been to identify the chemistry of the crust and hopefully determine how to prevent such crusts forming.
Using the microfocus X-ray beam at Diamond to scan the sample at different angles, they were able to show how the lead paint had reacted with atmospheric pollutants including sulphur dioxide, which was forming the white crust disfiguring the painting. “Using this information the conservation team at the Rijks can investigate further how to prevent and reverse this degradation process,” says Price.”
Excerpt from article. Read the full article at Physics World.
We have just published an article relating to the Homer painting – Unravelling the spatial dependency of the complex solid-state chemistry of Pb in a paint micro-sample from Rembrandt’s Homer using XRD-CT – Chemical Communications (RSC Publishing). Read more about this exciting work at https://pubs.rsc.org/en/content/articlehtml/2019/cc/c8cc09705d
Solid catalysts are used in almost every field of the chemical industry, ranging from pharmaceuticals to petrochemicals as well as the automotive industry, to produce the desired products. These catalytic solids usually comprise complex 3D structures which can be inhomogeneous. In recent years, it has been realised that it is crucial to investigate these materials using characterisation techniques that provide spatially-resolved information as these heterogeneities can play a crucial role in the catalyst performance.
In our recent paper in Nature Communications we show that synchrotron X-ray diffraction computed tomography (XRD-CT) can be used to study the evolution in solid-state composition in complex materials in 3D under real process conditions and as a function of time; specifically a complex multi-component Ni-Pd/CeO2-ZrO2/Al2O3 solid catalyst under operating conditions.
Read the full article at https://chemistrycommunity.nature.com/channels/1465-behind-the-paper/posts/40955-5d-chemical-imaging
Our paper on 5D operando tomographic diffraction imaging of a catalyst bed has been published online by Nature Communications, volume 9, Article number: 4751 (2018)
We report the results from the first 5D tomographic diffraction imaging experiment of a complex Ni–Pd/CeO2–ZrO2/Al2O3 catalyst used for methane reforming. This five-dimensional (three spatial, one scattering and one dimension to denote time/imposed state) approach enabled us to track the chemical evolution of many particles across the catalyst bed and relate these changes to the gas environment that the particles experience. Rietveld analysis of some 2 × 106 diffraction patterns allowed us to extract heterogeneities in the catalyst from the Å to the nm and to the μm scale (3D maps corresponding to unit cell lattice parameters, crystallite sizes and phase distribution maps respectively) under different chemical environments. We are able to capture the evolution of the Ni-containing species and gain a more complete insight into the multiple roles of the CeO2-ZrO2 promoters and the reasons behind the partial deactivation of the catalyst during partial oxidation of methane.
Read the full article at https://doi.org/10.1038/s41467-018-07046-8
Finden Ltd’s techniques for 3D imaging computed tomography appeared in the September 2017 edition of Chemistry World, in the article titled, “Diamonds are forever” which can be found at Chemistry World:
Here is an extract from the article which explains the techniques Professor Andrew Beale, Chief Scientific Officer at Finden Ltd uses,
“Principal beamline scientist Fred Mosselmans has been a synchrotron scientist for 20 years, and a resident of the spectroscopy village since Diamond first opened, where he now runs the I18 beamline … ‘One of the best things [about Diamond] is you see a lot of different science. [Users] have an enormous range of science problems, and the techniques that we have can hopefully address them,’ Mosselmans modestly explains.
‘In the last three or four years, we’ve gone from 2D imaging to 3D imaging computed tomography. We’re doing two different techniques: x-ray diffraction tomography, where we can look at the distribution of the species on the micron scale, and XRF to get distribution of the elements in the sample itself.’ This setup allows him to construct a 3D picture of a sample and watch reactions as they happen, which is just what Andy Beale from University College London is doing.
Beale is exploring how 3D-printing customised supports for different catalysts can improve their performance, specifically nickel nanoparticles on a carbon support. Mosselmans points to one of the screens behind him where a greyish cylinder is displayed: ‘Effectively, we’re probing inside that rod while it’s under operating conditions, without having to cut it open.’
On another screen the results are coming in. ‘[The printing method] isn’t producing the nanoparticles we’re interested in yet,’ Beale explains, ‘but this is a great illustration of how this beamline is giving novel insight into a catalyst … getting spatial and chemical composition information together. We’re calling [this technique] chemical tomography of catalysis.’”
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