We report here about the results of a study on the oxidation of cyclohexanone to adipic acid with air, catalysed by Keggin-type polyoxometalates of composition H3+xPMo12-xVxO40 (x=1 and 2), which was carried out in a semi-continuous stirred-tank reactor. It was found that when conducted in the presence of a water-only solvent, the reaction proceeds with a redox mechanism, in which the step of reoxidation of the reduced POM by oxygen is rate-limiting. When, however, the reaction was carried out with an acetic acid co-solvent, a radical-chain autoxidation mechanism prevailed, especially when very low amounts of catalyst were used. Autoxidation overlapped with the redox mechanism when the catalyst-to-cyclohexanone ratio was increased. Moreover, the composition of the polyoxometalate, that is, the number of V atoms per Keggin unit, affected the relative importance of the two mechanisms. The selectivity to adipic acid achieved was a function of the reaction mechanism, but also was affected by cyclohexanone conversion, due to the presence of a complex reaction network.

F. Cavani, A. Frattini, A. Mazzini, K. Raabova, S. Alini, P. Accorinti, et al. (2010). Evidence for the presence of alternative mechanisms in the oxidation of cyclohexanone to adipic acid with oxygen, catalysed by Keggin polyoxometalates. s.l : SCI-GIC.

Evidence for the presence of alternative mechanisms in the oxidation of cyclohexanone to adipic acid with oxygen, catalysed by Keggin polyoxometalates

CAVANI, FABRIZIO;FRATTINI, ALESSANDRA;MAZZINI, ANDREA;RAABOVÁ, KATERINA;
2010

Abstract

We report here about the results of a study on the oxidation of cyclohexanone to adipic acid with air, catalysed by Keggin-type polyoxometalates of composition H3+xPMo12-xVxO40 (x=1 and 2), which was carried out in a semi-continuous stirred-tank reactor. It was found that when conducted in the presence of a water-only solvent, the reaction proceeds with a redox mechanism, in which the step of reoxidation of the reduced POM by oxygen is rate-limiting. When, however, the reaction was carried out with an acetic acid co-solvent, a radical-chain autoxidation mechanism prevailed, especially when very low amounts of catalyst were used. Autoxidation overlapped with the redox mechanism when the catalyst-to-cyclohexanone ratio was increased. Moreover, the composition of the polyoxometalate, that is, the number of V atoms per Keggin unit, affected the relative importance of the two mechanisms. The selectivity to adipic acid achieved was a function of the reaction mechanism, but also was affected by cyclohexanone conversion, due to the presence of a complex reaction network.
2010
XVI Congresso nazionale di catalisi GIC 2010 "Catalysis between Innovation and atrdition: new challenges and new opportunities for University and Industry"
O16
O16
F. Cavani, A. Frattini, A. Mazzini, K. Raabova, S. Alini, P. Accorinti, et al. (2010). Evidence for the presence of alternative mechanisms in the oxidation of cyclohexanone to adipic acid with oxygen, catalysed by Keggin polyoxometalates. s.l : SCI-GIC.
F. Cavani; A. Frattini; A. Mazzini; K. Raabova; S. Alini; P. Accorinti; P. Babini
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/97772
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