Intermediates in the Methanol-to-hydrocarbons (MTH) Reaction: A Gas Phase Study of the Unimolecular Reactivity of Multiply Methylated Benzenium Cations |
| |
Authors: | Stian Svelle Morten Bjørgen Stein Kolboe Dietmar Kuck Matthias Letzel Unni Olsbye Osamu Sekiguchi Einar Uggerud |
| |
Affiliation: | 1. Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315, Oslo, Norway 2. Fakult?t für Chemie, Universit?t Bielefeld, Postfach, 10 01 31, D-33501, Bielefeld, Germany
|
| |
Abstract: | In order to reach a deeper insight into the reaction mechanism of the zeolite catalyzed methanol to hydrocarbons reaction
(MTH), the proposed reaction intermediates, i.e., a series of multiply methyl-substituted benzenium ions has been generated
in the gas phase by chemical ionization. The fragmentations of the corresponding long-lived (metastable) ions have been investigated.
While expulsion of H2 dominates for the lower homologues, elimination of methane dominates for the higher homologues, accompanied by increasing
amounts CH3·. Loss of larger fragments relevant to the MTH-reaction, in particular ethene, propene and even butene, is also observed in
minor amounts. This latter finding is consistent with a proposed reaction cycle in the MTH reaction known as the paring mechanism, and the feasibility of this mechanism has thus been demonstrated. The metastable gas-phase ions studied here are considerably
more energetic than those residing in a zeolite catalyst, but they were found to decompose with markedly higher selectivity
towards alkenes as compared to those activated by collision-induced dissociation (CID). |
| |
Keywords: | gas phase ion chemistry mass spectrometry methylbenzene methanol-to-hydrocarbons zeolite heptamethylbenzenium |
本文献已被 SpringerLink 等数据库收录! |
|