Disentangling Reaction Processes of Zeolites within Single-Oriented Channels.

Donglong Fu,Onno Van Der Heijden,Bert M Weckhuysen,Katarina Stanciakova,Joel E Schmidt

doi:10.1002/anie.201916596

Donglong Fu, Onno Van Der Heijden + Show 3 more

Open Access

https://doi.org/10.1002/anie.201916596

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Abstract

Establishing structure–reactivity relationships for specific channel orientations of zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, a well‐defined model system was developed to build structure–reactivity relationships for specific zeolite‐channel orientations during various catalytic reaction processes, for example, the methanol‐ and ethanol‐to‐hydrocarbons (MTH and ETH) process as well as oligomerization reactions. The entrapped and effluent hydrocarbons from single‐oriented zeolite ZSM‐5 channels during the MTH process were monitored by using operando UV/Vis diffuse reflectance spectroscopy (DRS) and on‐line mass spectrometry (MS), respectively. The results reveal that the straight channels favor the formation of internal coke, promoting the aromatic cycle. Furthermore, the sinusoidal channels produce aromatics, (e.g., toluene) that further grow into larger polyaromatics (e.g., graphitic coke) leading to deactivation of the zeolites. This underscores the importance of careful engineering of materials to suppress coke formation and tune product distribution by rational control of the location of zeolite acid sites and crystallographic orientations.

Highlights

Establishing structure–reactivity relationships for specific channel orientations of zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes
One of the most important microporous materials (MMs) is zeolite ZSM-5 (MFI framework topology) with two different types of channels, namely, sinusoidal and straight channels (Figure 1 a). This unique channel structure and resulting performance have made zeolite ZSM-5 ubiquitous in petroleum refining and chemical manufacturing
ZSM-5 coking in the MTH process has long been studied,[13] and it is known that the deactivation is caused by the coking of aromatic species, and that the deactivation heavily depends on the location of the coke.[13,19,20,21,22,23,24]