Styrene oxidation by manganese Schiff base complexes in zeolite structures

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Silva, M (Author) Other; Freire, C (Author) FCUP; de Castro, B (Author) FCUP; Figueiredo, JL (Author) FEUP

Journal

Title: Journal of Molecular Catalysis A: Chemical

Vol. 258

Pages: 327-333

ISSN: 1381-1169

Publisher: Elsevier B.V.

Indexing

ISI Web of Knowledge - 63 Citations

Scopus - 65 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-004-GNK

DOI: 10.1016/j.molcata.2006.05.070

Abstract (EN): Styrene oxidation was investigated using manganese(III) salen complexes as catalysts in homogeneous media and encapsulated in NaX and NaY zeolites using tert-butylhydroperoxide as the oxygen source. The oxidation of styrene led to formation of benzaldehyde, styrene oxide and phenylacetaldehyde, with minor amounts of phenyl-1,2-ethane-diol; some polymer formation was also observed. In homogeneous media, both complexes with ligands functionalized with methoxyl groups showed similar styrene conversions and chemoselectivities in styrene epoxide and benzaldehyde. Upon immobilization, [Nln(3-MeOsalen)]@X showed the highest catalytic activity at 60 degrees C and atmospheric pressure, and the highest chemoselectivities in styrene epoxide and benzaldehyde. No leaching of the encapsulated metal complexes was observed during the catalytic reactions and support for the entrapment of metal complexes inside the zeolite cages and not on their external surfaces was provided by nitrogen adsorption analyses and SEM micrographs. The reaction mechanism was investigated using the most active heterogeneous catalyst, [Mn(3-MeOsalen)]@X, and the influence of various reaction parameters, such as substrate, catalyst concentration and temperature, on alkene conversion and styrene epoxide yield have been studied. Furthermore, the homogeneous oxidation of styrene using [Mn(3-MeOsalen)CH3COO] was monitored by electronic spectroscopy, the results suggesting a free radical mechanism involving a peroxomanganese species as the catalyst active intermediate.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 7