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C−C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM‐5 Zeolite
Author(s) -
Chen Yuxiang,
Gong Ke,
Jiao Feng,
Pan Xiulian,
Hou Guangjin,
Si Rui,
Bao Xinhe
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201912869
Subject(s) - syngas , chemistry , zeolite , zsm 5 , catalysis , selectivity , inorganic chemistry , molecular sieve , hydrocarbon , photochemistry , organic chemistry
Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn 2+ ‐ion exchanged ZSM‐5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO 2 ) at 20 % CO conversion. NMR spectroscopy, X‐ray absorption spectroscopy, and X‐ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM‐5. Quasi‐in‐situ solid‐state NMR, obtained by quenching the reaction in liquid N 2 , detects C 2 species such as acetyl (‐COCH 3 ) bonding with an oxygen, ethyl (‐CH 2 CH 3 ) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C−C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn 2+ ‐ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ‐13, MCM‐22, and ZSM‐12) all give ethane predominantly. By contrast, a physical mixture of ZnO‐ZSM‐5 favors formation of hydrocarbons beyond C 3+ . These results provide an important guide for tuning the product selectivity in syngas conversion.