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
“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.
“Normally a lab-based diffractometer has quite a large beam profile of a few millimetres in size and the sample here is much less than one millimetre,” says Price, explaining that even if a lab-based X-ray source could identify the phases there would be no spatial information as to whether those phases were at the surface, middle or right by the canvas. “Further to that a lab-based source just doesn’t have the flux to image such a small volume,” he adds.
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.
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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