Cyclopropane reactions over Bronsted, cation, and metal sites in Ni/NaX zeolites

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1190· OSTI ID:6763497

Simon, M W; Suib, S L; Bennett, C O ^[1]

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1. Univ. of Connecticut, Storrs, CT (United States)

The reactions of cyclopropane in helium and hydrogen were investigated over two different loadings (10.7 and 6.0 wt%) of ion-exchanged Ni/NaX zeolites. The effects of reduction temperatures and hydrogen treatment times on catalytic activity and acidity were studied. Apparent activation energies ranged from 35.5 to 95.4 kJ/mol for isomerization reactions over two loadings of Ni/NaX zeolite reduced under different conditions. Rates of isomerization, hydrogenation, and hydrogenolysis are also reported. Deactivation and regeneration of catalysts are discussed. Particle sizes of 8.9 and 17.3 nm were observed in highly reduced Ni zeolites. Sintering of Ni was observed on the surfaces of the zeolite crystallites. Temperature programmed reduction studies show that stoichiometric amounts of H[sub 2] were used to completely reduce reduce all Ni in the samples. Infrared analysis of chemisorbed pyridine on these materials show that higher loadings of Ni result in higher initial acidities. Increased amounts of reduced Ni significantly increase the number of Bronsted sites on the surface of the catalyst. Electron paramagnetic resonance revealed that Ni[sup +] was present in low loaded Ni/NaX samples upon reduction at low temperatures (350[degrees]C), while higher reduction temperatures (450[degrees]C) resulted in a broad EPR signal corresponding to Ni[sup 0] only. Na vapor deposition experiments, designed to selectively poison Bronsted sites on the catalyst, reveal that Ni[sup +] ions are active in cyclopropane isomerization reactions at high temperatures. 59 refs., 11 figs., 5 tabs.

• OSTI ID: 6763497
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 148:1; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

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ACTIVATION ENERGY
ALKANES
AZINES
BROENSTED ACIDS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTIONS
CHEMISORPTION
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HETEROCYCLIC COMPOUNDS
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HYDROGENATION
INORGANIC ACIDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
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MAGNETIC RESONANCE
MATERIALS
METALS
MINERALS
NICKEL
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIDINE
PYRIDINES
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RESONANCE
SEPARATION PROCESSES
SILICATE MINERALS
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TRANSITION ELEMENTS
ZEOLITES