Adding Spectral information to ptychographic imaging of Technical Catalysts – ASTeCa

We've developed an innovative technique called high-resolution X-ray spectral imaging that allows us to see intricate details of catalysts, materials that speed up chemical reactions, without being limited by the size of the X-ray beam. This technique, known as ptychography, involves conducting a series of imaging experiments at different energy levels close to the specific absorption points of the elements we're examining. One of the main benefits of this approach is that it captures data on the X-ray wavefront before and after they interact with the sample. This is particularly useful for studying thick samples and helps us gain important chemical insights without damaging the materials.

Our project focused on several key areas: we created advanced 3D imaging that provides detailed views of catalysts, developed efficient methods to capture images of catalysts near their energy absorption edges, and improved techniques to reconstruct images of thicker samples. We also applied our new imaging methods to real industrial catalysts.

As a result of our work, we've produced high-resolution, non-destructive 3D images that reveal the internal structures of catalysts. This breakthrough allows us to monitor changes in these materials over time, which is crucial for understanding how metals and carbon deposits impact their performance. Our new imaging technology not only displays the physical layout of the catalyst but also maps out the density of different components and identifies any contaminants. Additionally, it provides specific information about the forms and oxidation states of substances that could hinder the catalyst's efficiency, helping us learn how carbon forms and how we can prevent it.

**Development of high-resolution 3D resonant ptychographic imaging**

By performing resonant ptychographic tomography at two photon energies, 3D maps of the refractive index decrease, delta, were obtained at the Ni K-edge energy and at another energy above the edge. These maps allowed the detection of impurities in the Ni wire. The results were published in A. Kulow et al. J. Synchrotron Rad. 31, 867–876 (2024).

**Development of near-edge structure X-ray ptychographic imaging**

A sample of metallic nickel wire was measured using 2D spectral ptychography in XANES mode and resonant ptychographic tomography. From 2D spectral ptychography measurements, the spectra of the complex-valued refractive index components of the sample, delta and beta, were extracted and integrated along the sample thickness. The results were published in A. Kulow et al. J. Synchrotron Rad. 31, 867–876 (2024).

**Development of an open-source software for the spectral ptychography data analysis pipeline**

We have developed ProSPyX, a software with a graphical user interface for processing spectral ptychography datasets. The software facilitates extracting absorption and phase spectral information from spectral ptychography datasets. It also records spectra in file formats compatible with other X-ray absorption spectroscopy data analysis software tools, simplifying integration into existing spectroscopic data analysis pipelines. The results were published in R. Boudjehem et al. J. Synchrotron Rad. 31, 399–408 (2024).

**Development of a 3D reconstruction method for thick catalyst samples using GANs neural networks followed by data post-processing**

The amount of data that must be acquired for spectral ptychographic tomography is too high. Using artificial intelligence, we reduced the number of acquisitions required by a factor of 4 without loss of quality and by a factor of 8 with very little loss. This was done with the help of the TomoGAN, a generative adversarial network. The results have been published on R. Boudjehem's thesis, and another publication is in preparation.

**Applications of the new methodology to technical catalysts relevant to the oil refining industry**

In collaboration with KAUST in Saudi Arabia, we applied the new methodology to samples of extruded hydrocracking catalysts. We could identify their microstructure and the localizations of Ni, rather in oxidized form, as well as other contaminants in their microstructure. The publication is in preparation.

The method's validation led to its adoption by our collaborators at KAUST in Saudi Arabia. In addition, other interested parties, including researchers using different synchrotron sources around the world, have expressed their interest. We anticipate potential collaborations in the near future and that the methods developed will continue to be used by the scientific community.

In addition, the methods created during this project are available to users of the SWING beamline at the SOLEIL synchrotron. We encourage the community to submit beamtime proposals for their research at this experimental station.

In Grenoble, we have been considered for an ANR Equipex+ PIA project to rejuvenate the French CRG beamlines. This includes the establishment of a new beamline, FAMEPIX, which will be dedicated to 3D spectral ptychography, a technique developed during the ASTeCa project. The results obtained in this project have laid the foundation for constructing this new beamline. The design and construction of the FAMEPIX beamline has already started and we hope to have it open to users by spring or summer 2026. Our goal is to build a strong community focused on the characterization of heterogeneous material samples, which will include not only shaped catalysts but also batteries, ceramics for the concrete industry, and essential minerals.

Catalysis is one of the most effective and economic technologies to control air pollution problems. Catalysts reduce pollution by facilitating the conversion of a harmful pollutant to a less-harmful material. The catalysis business is also a growing market in the energy and environmental segments. However, the key issue is the availability of industry-relevant high-performance technical catalysts. The technical catalysts are relatively large multicomponent bodies in which the research catalysts, the small active laboratory-developed catalytic materials, are distributed within their porous microstructure. Despite the tremendous importance in industry, the understanding of the complex structure-property-function of technical catalysts is largely neglected, and the main focus of academic research is still the research catalysts. This is due mainly to industry secrecy and to limitations of the state-of-the-art characterization techniques. To revert this scenario, ASTeCa will develop a novel 3D hyperspectral non-destructive nanoimaging technology capable to simultaneously provide the morphology of the internal microstructure of technical catalysts, the mass density distribution of each sample components, and the chemical information of the catalyst's contaminants or additives. This will be implemented based on a combination of X-ray ptychography, spectroscopic methods and computed tomography. The project objectives are to: develop two 3D hyperspectral nanoimaging modalities, which are (1) the high-resolution 3D resonant ptychographic imaging, and (2) the X-ray near-edge structure ptychographic imaging; (3) implement an innovative 3D reconstruction method for thick samples of catalysts; validate the proposed methodology by (4) application to industry-relevant technical catalysts. In contrast to the classical XAS methods or microscopy methods, this new technology will allow us to correlate for the first time the catalysis activity and morphology of the technical catalyst, at multiple length scales, and to distinguish the different regions within the sample. ASTeCa will deliver an innovative characterization methodology that will assist the design and optimization of technical catalysts that can potentially solve major challenges in energy production and reduction of pollution-related global warming. The anticipated achievements will bring laboratory developments much closer to industry.