FT-IR studies on light olefin skeletal isomerization catalysis: I. The interaction of C4 olefins and alcohols with pure {gamma}-alumina

Journal Article · Sun Jun 01 04:00:00 EDT 1997 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1997.1642· OSTI ID:539460

Trombetta, M; Busca, G ^[1]; Rossini, S A ^[2]

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1. Universita de Genova (Italy)
2. Snamprogetti, Milan (Italy); and others

The skeletal isomerization of n-butene to isobutene and the interaction of the four butene isomers and of sec-butanol and tert-butanol with a pure y-alumina sample were investigated. {gamma}-Al{sub 2}O{sub 3} is quite active (>34% conversion) and a selective catalyst for n-butene to isobutene isomerization at 753 K (>80% selectivity). FT-IR spectroscopic experiments show that the C{sub 4} olefins are involved in two different interactions on the alumina surface at room temperature: (I) H-bonding over surface hydroxy groups and (H) reactive adsorption giving rise to allyl species. Both species have been fully characterized spectroscopically for all four butene isomers. At higher temperatures, carboxylates appear, some of which are aromatic. Alcohol adsorption shows that 2-butoxy and tert-butoxy groups decompose to give gaseous n-butene and isobutene, respectively, near 473 K. Moreover, traces of tert-butoxy species are observed starting from 2-butoxides. H-bonded olefin species are assumed to be precursors for carbenium ions that give rise to double-bond and skeletal isomerization at high temperature. Butoxy groups are proposed to act as the unstable intermediate adsorbed forms for carbenium ions. Allyl species are identified as intermediates in double-bond isomerization at low temperature and in the formation of by-products and coking agents (aromatics and carboxylates) at high temperature. 55 refs., 10 figs., 3 tabs.

• OSTI ID: 539460
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 168; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
ADSORPTION
ALUMINIUM OXIDES
AROMATICS
BUTENES
CATALYTIC EFFECTS
COKING
FUELS
ISOMERIZATION
REACTION INTERMEDIATES