Organo-laponites as novel mesoporous supports for manganese(III) salen catalysts

• Type: Article in International Scientific Journal
• Date: 2005

Authors

Kuźniarska-Biernacka, Iwona (Author) Other; Silva, Ana Rosa (Author) REIT; Carvalho, Ana Paula (Author) Other; Pires, João (Author) Other; Freire, Cristina (Author) FCUP

Journal

Title: Langmuir

Vol. 21

Pages: 10825-10834

ISSN: 0743-7463

Publisher: American Chemical Society

Indexing

ISI Web of Knowledge - 23 Citations

Scopus - 32 Citations

Other information

Authenticus ID: P-000-0H7

DOI: 10.1021/la051619n

Abstract (EN): A Mn(III) salen complex was immobilized onto the Laponite surface using three different methodologies: method A, direct immobilization of the complex on the parent Laponite; method B, covalent anchoring through cyanuric chloride (CC); and method C, covalent anchoring through CC into a 3-aminopropyl)-triethoxysilane (APTES) modified Laponite. All of the materials were characterized by FTIR, XPS, thermogravimetry, Y-RD, and nitrogen isotherms at 77 K, to gather information on the modifications introduced by the organo spacers within the Laponite surface, as well as on the anchored complex integrity; the Mn based materials were screened in the heterogeneous epoxidation of styrene. The results have shown that the immobilization of the manganese(III) salen complex by methods B and C have occurred at the edges of the clay particles through the spacers (APTES and CC) that have been anchored onto the Si-OH groups, whereas in method A, the complex is distributed throughout the clay surface, including the interlayer region. Therefore, the manganese loadings on the Laponites were as follows: materials prepared by method A >> method B > method C. All of the heterogeneous catalysts showed high styrene epoxide selectivity, with that prepared by method A showing comparable styrene epoxide selectivity as the homogeneous phase reaction. The styrene epoxide yields decrease in the following order: materials prepared by method A > method B > method C (1st cycles), which parallel the respective support catalytic activity and decreasing of manganese content. The heterogeneous catalysts prepared using methods B and C could be reused at least for four times, with the former exhibiting the most stable catalytic activity, but that prepared by method A showed a significant decrease after two catalytic cycles.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10