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Selective Oxidation
The selective oxidation of functional groups is an important tool for the synthesis of valuable organic compounds. In general, the oxidation reaction is associated with the loss of hydrogen, the gain of oxygen and even with hydrogen/heteroatom exchanges. The reactivity of the functional group and the oxidation reaction selectivity strongly depend on the functional group stability. The development of solid catalysts that minimize the formation of undesirable products via secondary reactions is therefore crucial to selectively promote the reactant oxidation. Our group is investigating the development of efficient solid catalysts to selectively oxidize carbohydrates to carboxylic acids and 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid.
Reactions
- Oxidation of aromatic alcohols to obtain valuable aldehydes
The selective oxidation of benzyl alcohol (BA) to obtain benzaldehyde (B) is investigated. Benzaldehyde has numerous applications as intermediate in the manufacture of colorants and chemical specialties, but also in the pharmaceutical, food and fragrance industries due to its delicate almond scent. Traditionally, benzaldehyde is obtained as a byproduct of the oxidation of toluene to benzoic acid or by hydrolysis of benzyl chloride. The latter process generates a product with traces of chlorine and a large quantity of polluting residues. For its application in pharmaceutical and fragrance industries, a chlorine-free benzaldehyde is required. In addition, catalytic processes that use clean oxidants (O2, H2O2) are desirable from an environmental point of view. On the other hand, the use of heterogeneous catalysis is preferred, due to the easier separation, recovery and reuse of catalysts. For this reason, at GICIC we address the oxidation of BA to selectively obtain B using O2 as oxidizing agent at atmospheric pressure. We developed catalysts based on Zn-Mn mixtures with different molar ratios, which proved to be active and selective in similar reactions, and are also interesting due to their low cost.
This work is carried out within the framework of a Proyecto de Desarrollo Tecnológico y Social (PDTS) of CONICET and through an agreement between CONICET-UNL and the company Wöhr Química SRL.
- Carbohydrate oxidation to corresponding monocarboxylic acids
Our goal is to obtain active and selective catalysts to oxidize mono and disaccharides to corresponding monocarboxylic acids. In particular, we investigate the oxidation of both glucose to gluconic acid and lactose to lactobionic acid. Mono and bimetallic catalysts of noble metals (Au, Ag, Pt, Pd) supported on Al2O3, CeO2 or TiO2 are employed. Catalysts are used in powder or in monolithic reactors allowing catalyst recovering.
- Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA)We investigate the development of efficient solid catalysts to selectively oxidize HMF, obtained from carbohydrate dehydration, to FDCA under benign operating conditions (65°C, 1 atm). Among others, we employ mono and bimetallic catalysts of Pt, Au, Ag and Pd supported on CeO2 and TiO2. FDCA is a valuable intermediate for the synthesis of pharmaceuticals and is also used as fungicide and corrosion inhibitor. Moreover, it may be employed for the synthesis of biodegradable polyesters that may replace polyethylene terephthalate (PET).
Recent Publications:
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Selective aerobic oxidation of benzyl alcohol on inexpensive and reusable ZnO/MnCO3 catalysts, H.A. Duarte, P. J. Luggren, J. Zelin, M.E. Sad, V.K. Díez and J.I. Di Cosimo, Catalysis Today, doi.org/10.1016/j.cattod.2021.10.013, 2021.
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Monolithic stirrer reactor: The selective lactose oxidation in liquid phase over Au/Al2O3 nanostructured catalysts, S.A. Regenhardt, C.I. Meyer, O. Sanz, V. Sebastian, S. Ivanova, M.A. Centeno, J.A. Odriozola, M. Montes, A.J. Marchi, T.F. Garetto, Molec. Catal., 481,110219 (2020).
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Selective lactose oxidation in aqueous-phase over Ag-Au bimetallic nanoparticles supported on Al2O3 under mild reaction conditions, C.I. Meyer, S.A. Regenhardt, H.A. Duarte, J. Zelin, V. Sebastian, T.F. Garetto, A.J. Marchi, Molec. Catal., 481,110249 (2020).
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A Kinetic modeling of the liquid-phase oxidation of lactose over Pt- and Au-Supported catalysts, C.I. Meyer, S.A. Regenhardt, J. Zelin, V. Sebastian, A.J. Marchi, T.F. Garetto, Topic. Catal., 59, 168-177 (2016)