Stable catalysts for ethylene production via ethanol dehydration

IMCN

The dehydration of bio-alcohols is an important catalytic reaction in the perspective of the development of a bio-based industry. Bioethanol, for example, is a major bio-based platform chemical as its production via fermentation processes is now well-established. Its dehydration produces ethylene – a broadly used stock chemical important mainly in polymer industry. In a recent paper, we show that stable and efficient dehydration catalysts can be obtained by non-hydrolytic sol-gel.

Ethanol dehydration is effectively catalyzed by strongly acidic zeolites which, however, exhibit poor stability in a long-term catalytic process. For example, HZSM-5 features strong acid sites, catalyzes unwanted ethylene oligomerization, and is prone to coke deposition, leading to fast catalyst deactivation. Alumina and silica-alumina on the other hand have lower acidity, are relatively stable, but reach only modest activity levels.

To overcome these issues, Ales Styskalik has prepared a series of aluminosilicate catalysts by non-hydrolytic sol-gel (NHSG) – an original synthetic method which is being thoroughly studied in the Debecker lab. Thanks to this peculiar synthesis method, the materials are highly homogeneous on an atomic scale (Si-Al mixing), highly porous (with prevailing mesoporosity), and are shown to feature an intermediate level of acidity (between commercial zeolite and silica-alumina). All these characteristics resulted in intermediate catalytic performance.

Importantly, the best NHSG-made samples exhibited very stable catalytic performance, did not produce ethylene oligomers, did not show any trace of coke formation, and their texture was unaffected. We anticipate that such aluminosilicate materials with a high degree of Si-Al mixing and open mesoporosity could represent an attractive alternative to zeolites for long term operation in (bio)ethanol dehydration.

Mildly Acidic Aluminosilicate Catalysts for Stable Performance in Ethanol Dehydration
Ales Styskalik, Vit Vykoukal, Luca Fusaro, Carmela Aprile, Damien P. Debecker
Applied Catalysis B: Environmental, 2020, 271, 118926

Published on April 20, 2020