Spatiotemporal chemical imaging of zeolite deactivation and poisoning phenomena at the extrudate level
Zeolites are solid acid catalysts used in a wide variety of (petro-)chemical processes. Zeolites are often mixed with porous materials, like Al2O3 or SiO2, to ensure a sufficiently high mechanical stability and to give the catalyst material the required shape, so that they can be used in large-scale industrial reactors. This approach of zeolite embedding is illustrated in Figure 1. It is important to note that the added porous material, better known as the binder material, is often assumed inert. However, it is known that binder materials have a large effect on the catalytic activity, both beneficial or detrimental, especially on the deactivation and poisoning of the embedded zeolite material .
Figure 1: Schematic representation of a catalytic reactor with different zoom-in levels, including catalyst extrudates, containing zeolite and binder material, such as silica and alumina. Although active site within the zeolite micropores are most often linked to catalytic performance, also the binder material plays its role.
Within this project, the influence of both zeolite and binder on the deactivation and poisoning of a single catalyst extrudate will be investigated. Multiple characterization methods will be employed to reach a sufficiently high spatiotemporal resolution and to distinguish zeolite and the binder. IR and UV-vis micro-spectroscopy will be explored to follow the deactivation and selectivity of the extrudates. These techniques will be used to identify the species formed within extrudates in time and space. With diagonally offset Raman spectroscopy, we will investigate whether there is a deactivation gradient throughout the extrudate. During the deactivation, polyaromatic species are formed which are fluorescent. These organic species can be made visible with confocal fluorescent microscopy as well as with IR and UV-Vis micro-spectroscopy. 1-hexene will be used as model reactant. Using a zeolite catalyst extrudate, 1-hexene can undergo oligomerization and isomerization reactions. Deactivation of the catalyst will occur due to the formation of long olefins and polyaromatic species, which block the pores of the zeolite . The formation of these species will be followed with the above-mentioned characterization techniques.
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