Shape‐Selective Zeolites Promote Ethylene Formation from Syngas via a Ketene Intermediate

다국어 초록 (Multilingual Abstract)

Syngas conversion by Fischer–Tropsch synthesis (FTS) is characterized by a wide distribution of hydrocarbon products ranging from one to a few carbon atoms. Reported here is that the product selectivity is effectively steered toward ethylene by employing the oxide‐zeolite (OX‐ZEO) catalyst concept with ZnCrOx‐mordenite (MOR). The selectivity of ethylene alone reaches as high as 73 % among other hydrocarbons at a 26 % CO conversion. This selectivity is significantly higher than those obtained in any other direct syngas conversion or the multistep process methanol‐to‐olefin conversion. This highly selective pathway is realized over the catalytic sites within the 8‐membered ring (8MR) side pockets of MOR via a ketene intermediate rather than methanol in the 8MR or 12MR channels. This study provides substantive evidence for a new type of syngas chemistry with ketene as the key reaction intermediate and enables extraordinary ethylene selectivity within the OX‐ZEO catalyst framework.
Deep pockets: The eight‐membered‐ring side pockets of mordenite can effectively steer the conversion of ketene intermediates, formed over ZnCrOx during syngas conversion, toward ethylene with a selectivity of 73 % at a CO conversion of 26 %. By comparison, methanol intermediates are mainly converted over the 12‐membered‐ring sites of MOR and result in a remarkably different product distribution dominated by longer‐chain hydrocarbons.