Abstract
AbstractThe performance of zeolite‐based catalyst extrudates can be largely influenced by the choice of binder material. To investigate these binder effects in zeolite‐based catalyst extrudates in more detail, high spatiotemporal resolution techniques need to be further developed and employed. In this work, we present a new methodology to investigate binder effects in catalyst extrudates at different reaction pressures using operando UV‐vis diffuse reflectance (DR) micro‐spectroscopy coupled with on‐line gas chromatography. We have studied mm‐sized zeolite H‐ZSM‐5‐containing extrudates with either Al2O3 or SiO2 binder material, during the transalkylation of toluene with 1,2,4‐trimethylbenzene at 450 °C and at a pressure of either 1 or 5 bar. Using this technique, it was revealed that the binder material significantly influenced catalyst deactivation at different reaction pressures. By subsequent mapping of the cross sections of the cylindrical catalyst extrudates using UV‐vis micro‐spectroscopy, it was shown that the SiO2‐bound extrudate formed poly‐aromatic coke molecules homogeneously throughout the entire extrudate, whereas for the Al2O3‐bound extrudate a coke ring formed that moved inwards with increasing reaction time. Notably, the developed methodology is not limited to the transalkylation reaction, and can also be used to gain more insight into binder effects during a variety of important catalytic reactions.
Highlights
The performance of zeolite-based catalyst extrudates can be largely influenced by the choice of binder material
To overcome these differences in dimensions, advanced characterization techniques have been explored that can Zeolite-containing catalyst extrudates are widely used in chemical processing, such as fluid catalytic cracking (FCC), alkane isomerization and aromatics alkylation reactions.[1,2,3]
ChemCatChem investigate both μm-sized FCC particles and mm-sized catalyst extrudates non-invasively. Examples of these techniques are UV-vis diffuse reflectance micro-spectroscopy and confocal fluorescence microscopy, [13,14,15,16] focused-ion-beam scanning electron microscopy (FIB-SEM), [17] X-ray tomography (XRM), [18]
Summary
The performance of zeolite-based catalyst extrudates can be largely influenced by the choice of binder material. Whiting et al.[13] investigated the oligomerization of thiophene on either Al2O3- or SiO2-bound zeolite H-ZSM-5containing extrudates They showed that the reaction mechanism was dependent on the choice of binder. Both materials are inert during the thiophene reaction, the combination of materials forms thiol-like species due to the creation of extra acid sites These examples illustrate the large impact of the binder material on the performance of catalyst extrudates, showing the importance of a thorough understanding of these complex interactions. Catalyst extrudates are employed in large industrial reactors, as they can achieve high catalytic activity and selectivity, whilst maintaining high mechanical, chemical and thermal stability To achieve these properties, zeolites are often mixed with different materials, such as a binder Examples of these techniques are UV-vis diffuse reflectance micro-spectroscopy and confocal fluorescence microscopy, [13,14,15,16] focused-ion-beam scanning electron microscopy (FIB-SEM), [17] X-ray tomography (XRM), [18]
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