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Highly Loaded Fe-MCM-41 Materials: Synthesis and Reducibility Studies
Department of Chemistry, University of Limpopo, P/Bag X1106, Sovenga, 0727, Polokwane, South Africa
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, P/Bag 3, WITS 2050, Johannesburg, South Africa
* Author to whom correspondence should be addressed.
Received: 4 November 2009; in revised form: 30 November 2009 / Accepted: 14 December 2009 / Published: 15 December 2009
Abstract: Fe-MCM-41 materials were prepared by different methods. The Fe was both incorporated into the structure and formed crystallites attached to the silica. High Fe content MCM-41 (~16 wt%) with retention of mesoporosity and long-range order was achieved by a range of new synthetic methodologies: (i) by delaying the addition of Fe3+(aq) to the stirred synthesis gel by 2 h, (ii) by addition of Fe3+ precursor as a freshlyprecipitated aqueous slurry, (iii) by exploiting a secondary synthesis with Si-MCM-41 as SiO2 source. For comparative purposes the MCM-41 was also prepared by incipient wetness impregnation (IWI). Although all these synthesis methods preserved mesoporosity and long-range order of the SiO2 matrix, the hydrothermally-fabricated Fe materials prepared via the secondary synthesis route has the most useful properties for exploitation as a catalyst, in terms of hydrothermal stability of the resulting support. Temperatureprogrammed reduction (TPR) studies revealed a three-peak reduction pattern for this material instead of the commonly observed two-peak reduction pattern. The three peaks showed variable intensity that related to the presence of two components: crystalline Fe2O3 and Fe embedded in the SiO2 matrix (on the basis of ESR studies). The role of secondary synthesis of Si-MCM-41 on the iron reducibility was also demonstrated in IWI of sec-Si-MCM-41.
Keywords: Fe-MCM-41; secondary synthesis; temperature programmed reduction; wustite (FeO); incipient wetness impregnation
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MDPI and ACS Style
Mokhonoana, M.P.; Coville, N.J. Highly Loaded Fe-MCM-41 Materials: Synthesis and Reducibility Studies. Materials 2009, 2, 2337-2359.
Mokhonoana MP, Coville NJ. Highly Loaded Fe-MCM-41 Materials: Synthesis and Reducibility Studies. Materials. 2009; 2(4):2337-2359.
Mokhonoana, Malose P.; Coville, Neil J. 2009. "Highly Loaded Fe-MCM-41 Materials: Synthesis and Reducibility Studies." Materials 2, no. 4: 2337-2359.