In situ {sup 13}C MAS NMR study of n-hexane conversion on Pt and Pd supported on basic materials
- Facultes Universitaires N.D. de la Paix, Namur (Belgium); and others
n-Hexane conversion was studied in situ on Pt and Pd supported on aluminum-stabilized magnesium oxide and Pt on Zeolite KL catalysts (Pt/Mg(Al)O, Pd/Mg(Al)O and Pt/KL) by means of {sup 13}C MAS NMR spectroscopy. n-Hexane 1-{sup 13}C was used as a labelled reactant. Forty NMR lines corresponding to 14 different products were resolved and identified. The NMR line assignments were confirmed by adsorption of model compounds. The NMR results were further quantified and compared with continuous flow microreactor tests. Four parallel reaction pathways were identified under flow conditions: isomerization, cracking, dehydrocyclization, and dehydrogenation. Aromatization occurs via two reaction routes: (1) n-hexane dehydrogenation towards hexadienes and hexatrienes, followed by dehydrogenation of a cyclic intermediate. The former reaction pathway is prevented under NMR batch conditions. High pressures induced in the NMR cells at high reaction temperatures (573, 653 K) shift the reaction equilibrium towards hydrogenation. NMR experiments showed that on Pt catalysts aromatization occurs via a cyclohexane intermediate, whereas on Pd it takes place via methylcyclopentane ring enlargement. 54 refs., 15 figs., 3 tabs.
- OSTI ID:
- 263705
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 158; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
40 CHEMISTRY
AROMATIZATION
CATALYST SUPPORTS
CATALYTIC CRACKING
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CYCLIZATION
DEHYDROGENATION
ELECTROLYTIC CELLS
HETEROGENEOUS CATALYSIS
HEXANE
ISOMERIZATION
MAGNESIUM OXIDES
NUCLEAR MAGNETIC RESONANCE
PALLADIUM
PLATINUM
REACTION INTERMEDIATES
ZEOLITES