Pore tuned activated carbons as supports for an enantioselective molecular catalyst

• Type: Article in International Scientific Journal
• Date: 2008

Authors

Frederico Maia (Author) Other; Rui Silva (Author) Other; Bruno Jarrais (Author) Other; Ana R Silva (Author) Other; Cristina Freire (Author) FCUP; Manuel F R Pereira (Author) FEUP; Jose L Figueiredo (Author) FEUP

Journal

Title: Journal of Colloid and Interface Science

Vol. 328

Pages: 314-323

ISSN: 0021-9797

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 19 Citations

Scopus - 23 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-003-T7K

DOI: 10.1016/j.jcis.2008.09.030

Abstract (EN): The Jacobsen catalyst was immobilized onto four activated carbons with different average pore sizes, achieved by a gasification process followed by molecular oxygen oxidation. The influence of the textural properties of the activated carbon in the immobilization process and in the catalytic performance of the Mn(III) heterogeneous catalysts was investigated in detail. Three different catalytic systems were studied: styrene epoxidation using m-chloroperoxybenzoic acid; 6-CN-2,2-diMeChromene epoxiclation using NaOCl and iodosylbenzene (PhIO) as oxidants. The catalysts tested were active and enantioselective in the three systems studied. Selectivity towards the desired epoxide only decreases in the case of the material with smaller pores, remaining identical to that of the homogeneous phase in all the other materials. The enantiomeric excess values (%ee) for alkene epoxidation increase with the pore size of the heterogeneous catalysts, and these values are even higher than the homogeneous counterparts in the styrene epoxiclation reaction. Total Mn(III) loadings increase with the pore size, as well as their distribution within the carbon porous matrix. Characterization of the activated carbons bearing the immobilized manganese(III) complexes by TPD and XPS point to reaction between carbon surface phenolate groups and the manganese(III) complexes through axial coordination of the metal centers to these groups.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 10