n-Butane transformation on Zn/H-BEA. The effect of different Zn species (Zn2+ and ZnO) on the reaction performance

[Display omitted] •The effect of Zn2+ and ZnO sites on n-butane conversion on Zn-BEA zeolites was established.•n-Butane conversion occurs via same reaction steps on both Zn2+ and ZnO containing zeolites.•Zn2+/H-BEA is more active showing higher rate and lower activation energies for main reaction st...

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Bibliographic Details
Published in:Journal of catalysis 2020-11, Vol.391, p.69-79
Main Authors: Gabrienko, Anton A., Arzumanov, Sergei S., Lashchinskaya, Zoya N., Toktarev, Alexander V., Freude, Dieter, Haase, Jürgen, Stepanov, Alexander G.
Format: Article
Language:English
Subjects:
Aromatization
Hydrogenolysis
Kinetics
Mechanism
n-butane
Solid-state NMR
Zeolite BEA
Zn2+ cations
ZnO clusters
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Summary:[Display omitted] •The effect of Zn2+ and ZnO sites on n-butane conversion on Zn-BEA zeolites was established.•n-Butane conversion occurs via same reaction steps on both Zn2+ and ZnO containing zeolites.•Zn2+/H-BEA is more active showing higher rate and lower activation energies for main reaction steps.•Hydrogenolysis of n-butane occurs differently on Zn2+/H-BEA and ZnO/H-BEA.•Methane co-conversion with n-butane on Zn-BEA zeolite in non-oxidative conditions can be realized. Using solid-state 1H and 13C MAS NMR spectroscopy, the performance of H-BEA zeolite, modified with either Zn2+ cations (Zn2+/H-BEA) or ZnO clusters (ZnO/H-BEA), has been investigated with respect to n-butane transformation by aromatization and hydrogenolysis pathways. 13C-labeled n-butane has been used to follow the main stages of n-butane transformation on both Zn2+/H-BEA and ZnO/H-BEA with 13C MAS NMR at 298–623 K. Similar surface species, including n-butylzinc, n-butene, allyl-like oligomers, are formed as the intermediates on both zeolites. The kinetics of n-butane transformation has been monitored with 1H MAS NMR in situ at 543–573 K. Kinetics modeling reveals that Zn2+/H-BEA is more active for n-butane transformation than ZnO/H-BEA. A remarkable difference in the rates and the pathways of hydrogenolysis for Zn2+/H-BEA and ZnO/H-BEA has also been established. Propane and methane are hydrogenolysis products on ZnO/H-BEA whereas ethane is produced by the reaction on Zn2+/H-BEA. 13C NMR data and the kinetics analysis provide an insight on the occurrence of joint methane and n-butane conversion on Zn-modified zeolites under non-oxidative conditions.
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2020.08.011