Catalytic dehydrogenation of ethanol over zinc-containing zeolites

Catalytic dehydrogenation of ethanol produces acetaldehyde, an important precursor for several value-added chemicals such as acetic acid and acetate esters. In this paper, we demonstrate that Zn-containing MFI zeo-lites are highly active and selective catalysts for this process. Furthermore, we show that their activity and selectivity depend on the chemical composition and preparation of the catalysts. The best catalyst comprises 5 wt % Zn on Silicalite-1 zeolite and results in 65.2% conversion and 94.5% selectivity towards acetaldehyde at 400 degrees C. We relate the high selectivity to the absence of Bronsted acidic silanol groups, which suppresses the dehy-dration of ethanol into ethylene. Furthermore, while pure HZSM-5 and NaZSM-5 zeolites result in dehydration products, such as ethylene and diethyl ether, Zn on NaZSM-5 zeolite also results in acetaldehyde, which confirms that Zn is the active site. Finally, we compare different preparation procedures to show that several Zn-species may be active for the catalytic reaction.