Since its commercial introduction three-quarters of a century ago, fluid catalytic cracking has been one of the most important conversion processes in the petroleum industry. In this process, porous composites composed of zeolite and clay crack the heavy fractions in crude oil into transportation fuel and petrochemical feedstocks. Yet, over time the catalytic activity of these composite particles decreases. Here, we report on ptychographic tomography, diffraction, and fluorescence tomography, as well as electron microscopy measurements, which elucidate the structural changes that lead to catalyst deactivation. In combination, these measurements reveal zeolite amorphization and distinct structural changes on the particle exterior as the driving forces behind catalyst deactivation. Amorphization of zeolites, in particular, close to the particle exterior, results in a reduction of catalytic capacity. A concretion of the outermost particle layer into a dense amorphous silica–alumina shell further reduces the mass transport to the active sites within the composite.

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The discovery of Li-containing transition-metal (TM) oxides has attracted broad interest and triggered intensive studies on these oxides as cathodes for lithium-ion batteries over decades.Unfortunately, a clear picture of how Li/TM/O ions are transported and electrons are transferred during synthesis of these compounds is still missing, especially when cubic close-packed (ccp) anion sublattices are involved, as it is the case for spinel, layered, or rock-salt systems. In the present study, a series of layered Li(Ni,Co,Mn)O 2 oxides was chosen as target materials to elucidate the underlying formation mechanism of these compounds during high-temperature lithiation reaction. The consistent experimental results demonstrate that, as lithium ions are inserted from surface to bulk, some transition metal cations located within the bulk of crystallites are able to diffuse to the near-surface region. They create cation vacancies for the inserted lithium ions, the mass transport behavior of these elements is driven by chemical potential gradient. Concurrently, oxygen anions from lithium oxides and/or ambient oxygen are adsorbed and incorporated into the ccp oxygen lattice on the surface structure, connecting the relocated transition metal cations and the incorporated lithium ions by forming ionic bonds. This process is concomitant with crystal growth, surface reorganization caused by phase transformation, occurrence and disappearance of pores.

NOx emissions are a major source of pollution, demanding ever improving performance from catalytic aftertreatment systems. However, catalyst development is often hindered by limited understanding of the catalyst at work, exacerbated by widespread use of model rather than technical catalysts, and global rather than spatially-resolved characterisation tools. Here we combine operando X-ray absorption spectroscopy with microtomography to perform 3D chemical imaging of the chemical state of copper species in a Cu-SSZ-13 washcoated monolith catalyst during NOx reduction. Gradients in copper oxidation state and coordination environment, resulting from an interplay of NOx reduction with adsorption-desorption of NH3 and mass transport phenomena, were revealed with micrometre spatial resolution while simultaneously determining catalytic performance. Crucially, direct 3D visualisation of complex reactions on nonmodel catalysts is only feasible using operando X-ray spectrotomography, which can improve our understanding of structure-activity relationships including the observation of mass and heat transport effects.Due to health and environmental concerns, there is currently a strong societal demand for improved air quality, driving strict emission limits for CO, NOx, unburnt hydrocarbons and particulates. The primary means of mitigating such pollutants is through more efficient catalytic converters. Highly effective Cu-zeolite catalysts such as Cu-SSZ-13 (chabazite) are among the prominent recent examples of active materials for selective catalytic reduction of NOx with ammonia (NH3-SCR) 1,2 .

The ion beam synthesis of Pb nanoparticles (NPs) in silica is studied in terms of a two step thermal annealing process consisting of a low temperature long time aging treatment followed by a high temperature short time one. The samples are investigated by Rutherford backscattering spectrometry and transmission electron microscopy. The results obtained show that highly stable Pb trapping structures are formed during the aging treatment. These structures only dissociate at high temperatures, inhibiting the nucleation of NPs in the metallic phase and causing an atomic redistribution that renders the exclusive formation of a two dimensional, uniform and dense array of Pb NPs at the silica–silicon interface. The results are discussed on the basis of classic thermodynamic concepts.

Fluid catalytic cracking is a chemical conversion process of industrial scale. This process, utilizing porous catalysts composed of clay and zeolite, converts heavy crude-oil fractions into transportation fuel and petrochemical feedstocks. Among other factors iron-rich reactor and feedstream impurities cause these catalyst particles to permanently deactivate. Herein, we report tomographic X-ray absorption spectroscopy measurements that reveal the presence of dissimilar iron impurities of specific localization within a single deactivated particle. Whereas the iron natural to clay in the composite seems to be unaffected by operation, exterior-facing and feedstream-introduced iron was found in two forms. Those being minute quantities of ferrous oxide, located near regions of increased porosity, and impurities rich in Fe , preferentially located in the outer dense part of the particle and suggested to contribute to the formation of an isolating amorphous silica alumina envelope.

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We present combined in situ X-ray diffraction and high-speed imaging to monitor the phase evolution upon cyclic rapid laser heating and cooling mimicking the direct energy deposition of Ti-6Al-4V in real time. Additive manufacturing of the industrially relevant alloy Ti-6Al-4V is known to create a multitude of phases and microstructures depending on processing technology and parameters. Current setups are limited by an averaged measurement through the solid and liquid parts. In this work the combination of a micro-focused intense X-ray beam, a fast detector and unidirectional cooling provide the spatial and temporal resolution to separate contributions from solid and liquid phases in limited volumes. Upon rapid heating and cooling, the β ↔ α′ phase transformation is observed repeatedly. At room temperature, single phase α′ is observed. Secondary β-formation upon formation of α′ is attributed to V partitioning to the β-phase leading to temporary stabilization. Lattice strains in the α′-phase are found to be sensitive to the α′ → β phase transformation. Based on lattice strain of the β-phase, the martensite start temperature is estimated at 923 K in these experiments. Off-axis high speed imaging confirms a technically relevant solidification front velocity and cooling rate of 10.3 mm/s and 4500 K/s, respectively.