Vol.:(0123456789) 1 3 Catal Lett DOI 10.1007/s10562-017-2191-5 Aqueous-Phase Oxidation of Furfural to Maleic Acid Catalyzed by Copper Phosphate Catalysts Tomáš Soták 1  · Milan Hronec 1  · Miroslav Gál 2  · Edmund Dobročka 3  · Jaroslava Škriniarová 4   Received: 19 July 2017 / Accepted: 13 September 2017 © Springer Science+Business Media, LLC 2017 Graphical Abstract Keywords Furfural · Oxidation · Metal pyrophosphates · Maleic acid · Furoic acid 1 Introduction The major challenge today is to convert biomass as feedstock into useful chemicals for the chemical and pharmaceutical industries in an economically viable fashion. Furfural is a renewable resource coming from agricultural byproducts, hemicelluloses, by dehydration in acidic media. Currently it is used as a solvent and as a platform compound for syn- thesis of variety of chemicals and engine fuels [1, 2]. Selec- tive oxidation of biomass-based furfural to maleic acid or anhydride which is currently manufactured from benzene and/or butane is an alternative route to the on-going fossil based processes. Maleic acid is applied in the synthesis of plasticizers, copolymers, resins, surface coatings, lubricants and agricultural chemicals. In literature is described oxidation of furfural in both vapor and liquid phases using various types of metal cata- lysts [3, 4]. In spite of oxidation of furfural in vapor phase where the main products are maleic anhydride and carbon dioxide, the oxidation in the liquid phase, depending on the catalyst and solvent, can produce 2-furancarboxylic acid (furoic acid) eventually its esters or furan-ring opening Abstract This work describes catalytic aqueous-phase oxidation of furfural to maleic acid. The heterogeneous Cu- phosphate catalysts were prepared by coprecipitation method at diferent atomic ratios of precursors and characterized by various techniques. The CaCu-phosphate catalyst showed the best catalytic performance. Using this catalyst under reaction conditions (115 °C and 0.8 MPa of O 2 ) 37.3 mol% yield and 54.8% selectivity of maleic acid were achieved. This catalyst can be recycled more than four times producing practically the same selectivity as fresh one by 13% decrease in furfural conversion. The proposed mechanism involves furoic acid as an intermediate in the formation of maleic acid. Electronic Supplementary Material The online version of this article (doi:10.1007/s10562-017-2191-5) contains supplementary material, which is available to authorized users. * Tomáš Soták tomas.sotak@stuba.sk * Milan Hronec milan.hronec@stuba.sk 1 Department of Organic Technology, Catalysis and Petroleum Chemistry, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia 2 Department of Inorganic Technology, Slovak University of Technology, Radlinského 9, 812 37 Bratislava, Slovakia 3 Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 845 41 Bratislava, Slovakia 4 Institute of Electronics and Fotonics, Slovak University of Technology, Ilkovičova 3, 812 19 Bratislava, Slovakia