The treatment in NH4OH of Fe-Silicalite (Fe-MFI)catalysts creates mesopores with a different mechanism with respect to the conventional desilication treatment. A reassembling of Fe-MFI nanocrystals is induced by the creation of isolated defects on the surface of these nanocrystals, as well as a change in the amorphous layer between nanocrystals acting as “glue” to assemble them into larger round-shaped particles occurs. The reassembling process induces also changes in the acidity and hydrophobic character, leading to an enhanced reactivity, and influences the relatives rate constants in the HMF (5-hydroxymethylfurfural)etherification to 5-(ethoxymethyl)furan-2-carbaldehyde (EMF)via acetalization. Moreover, for treatment times with NH4OH longer than 6 h, there is an effective, although minimal, desilication process which leads to a loss of crystallinity, microporous surface area, mesoporosity and acidity characteristics with consequent worsening of the catalytic performances.

Reassembly mechanism in Fe-Silicalite during NH4OH post-treatment and relation with the acidity and catalytic reactivity

Centi G.;Catizzone E.;
2019

Abstract

The treatment in NH4OH of Fe-Silicalite (Fe-MFI)catalysts creates mesopores with a different mechanism with respect to the conventional desilication treatment. A reassembling of Fe-MFI nanocrystals is induced by the creation of isolated defects on the surface of these nanocrystals, as well as a change in the amorphous layer between nanocrystals acting as “glue” to assemble them into larger round-shaped particles occurs. The reassembling process induces also changes in the acidity and hydrophobic character, leading to an enhanced reactivity, and influences the relatives rate constants in the HMF (5-hydroxymethylfurfural)etherification to 5-(ethoxymethyl)furan-2-carbaldehyde (EMF)via acetalization. Moreover, for treatment times with NH4OH longer than 6 h, there is an effective, although minimal, desilication process which leads to a loss of crystallinity, microporous surface area, mesoporosity and acidity characteristics with consequent worsening of the catalytic performances.
Desilication in mild conditions; Fe-MFI; Fe-Silicalite; HMF etherification; NH; 4; OH treatment
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/20.500.12079/52359
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