3 D Chemical Distribution of Titania–Alumina Catalyst Supports Prepared by the Swing‐pH Method

Abstract

Analytical electron tomography combined with more classical techniques such as X‐ray fluorescence and X‐ray photoelectron spectroscopy were performed with a series of titania–alumina catalyst supports prepared by using the swing‐pH method. The bulk proportion of titania and alumina was varied along the sample series. It was observed that, independently of this bulk proportion, only 30 % of the surface of the grains of the resulting catalysts was titania covered. It was also shown that the porosity of the material was driven by alumina, and for low titania contents, alumina formed a layer close the surface of the grains. At concentrations higher than 30 % titania, the layer was broken and aggregates covered by alumina were formed, which may have an impact on catalysis if these materials are used as supports for an active phase.

Three‐Dimensional Analytical Surface Quantification of Heterogeneous Silica‐Alumina Catalyst Supports

“…The same phenomenon was observedo ntitani-um oxide-alumina catalysts upports;i ft he proportion of titanium oxide was more than 30 wt %a lumina embedded the titanium oxide. [34] The PSB AS2 sample shows ab etter homogeneityt han the MM AS1 sample, which is expected from the smaller size of the silica precursor used to prepareA S2 (silicic acid oligomers) than that of the precursor used for AS1 (silica colloidal particles). Surprisingly, AS1 shows an asymmetric Al 2p XPS peak, which is compatible with an aluminosilicate phase and provides direct evidence for the intimate contact between silica and alumina at the surface of the grains.…”

“…In this context, a combination of the energy‐filtered transmission electron microscopy (EFTEM) and electron tomography approaches can provide a real 3 D chemical map of a material with a complex morphology, which offers new perspectives for the analysis of catalyst supports and catalytic process modelling. EFTEM tomography could, in principle, give valuable information on both the surface chemistry and reactant accessibility for catalysis applications . Moreover, this technique has the advantage to visualise the analysed grains directly, which is often helpful to explain synthesis mechanisms or the microscopic modelling of macroscopic properties.…”

“…EFTEM tomography could, in principle, give valuable information on both the surface chemistry and reactanta ccessibility for catalysis applications. [34] Moreover,t his technique has the advantage to visualise the analysed grains directly,w hich is often helpful to explain synthesis mechanismso rt he microscopic modelling of macroscopicp roperties.…”

“…The micropores are provided mainly by silica and the mesopores by alumina, which seems less compacted and embeds the silica as a core. The same phenomenon was observed on titanium oxide‐alumina catalyst supports; if the proportion of titanium oxide was more than 30 wt % alumina embedded the titanium oxide …”

Uncovering the 3 D Structure of Combustion‐Synthesized Noble Metal‐Ceria Nanocatalysts

“…The previous conventional TEM analysis provides only 2 D projections of the Pt‐CeO 2 sample, which can hide important 3 D information . In our case, from TEM and STEM it was impossible to determine the actual positions of the Pt particles with respect to their support.…”