Vol.:(0123456789) 1 3 Clean Technologies and Environmental Policy https://doi.org/10.1007/s10098-018-1593-4 ORIGINAL PAPER Glycerol valorization by base‑free oxidation with air using platinum–nickel nanoparticles supported on activated carbon as catalyst prepared by a simple microwave polyol method Thalita S. Galhardo 1  · Maraísa Gonçalves 2  · Dalmo Mandelli 1  · Wagner A. Carvalho 1 Received: 26 April 2018 / Accepted: 2 August 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Biodiesel is one of the most common biofuels, and its production yields a large amount of glycerol as a by-product. It is necessary to develop new technologies for the use of this by-product, adding value to the biodiesel production chain. In this work we investigated glycerol oxidation under mild reaction conditions (air as oxidizing agent and base-free medium) promoted by suitable catalysts. We prepared mono- and bimetallic catalysts of platinum, copper and nickel in the form of nanoparticles by conventional heating and by an alternative method using microwave heating. The nanoparticles were dispersed in activated carbon and tested in glycerol oxidation aiming its valorization into molecules with high added value. Copper and nickel monometallic materials were not active in glycerol oxidation. Platinum monometallic and platinum–cop- per and platinum–nickel bimetallic materials showed catalytic activity, with platinum–nickel prepared by microwave heating being the most active material in reactions tested. This catalyst presented glycerol conversion of approximately 20% with a turnover number of 9465 in a reaction time of 6 h and 58% of selectivity to glyceric acid, the main product obtained. The best performance of platinum–nickel prepared by microwave heating catalyst was attributed to the probable formation of a metallic alloy between Pt and Ni, as evidenced by the decrease in the lattice parameter for PtNi bimetallic nanoparticles. The results showed that it was possible to obtain an active catalyst in glycerol oxidation reaction under mild conditions via a simple methodology using microwave heating, which demands 94% less time in comparison with conventional heating. Keywords Glycerol oxidation · PtNi nanoparticles · Activated carbon · Glyceric acid · Microwave heating · Bimetallic catalyst Introduction Biodiesel production and its use chain have developed enor- mously throughout the world, and today, this biofuel repre- sents one of the main alternatives to petroleum-derived fuels (Gebremariam and Marchetti 2018). Biodiesel is most often produced by a transesterifcation reaction, which consists of the reaction of a vegetable oil with an alcohol (metha- nol or ethanol) catalyzed by an acid or a base. Various raw materials are used to produce biodiesel, such as soybeans, sunfower seeds, castor beans, corn, jatropha, cottonseeds, canola, babassu, buriti, macaúba and peanuts, as well as animal products such as chicken and pork fat (Ambat et al. 2018; Marousek et al. 2012). The increase in biodiesel production in recent years and, consequently, the excess of its main by-product—glycerol, have encouraged the search for alternatives to convert this molecule into another with greater added value via difer- ent processes (Gholami et al. 2014). One way to convert glycerol is its catalytic oxidation (Katryniok et al. 2011), a complex reaction that can generate diferent products such as glyceraldehyde, dihydroxyacetone and several acids, such as glyceric acid, which can be converted into Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10098-018-1593-4) contains supplementary material, which is available to authorized users. * Wagner A. Carvalho wagner.carvalho@ufabc.edu.br 1 Centre of Natural and Human Sciences, Federal University of ABC, Santa Adélia Street, 166, Bangu, Santo André, SP 09210-170, Brazil 2 Science and Technology Institute, Federal University of São Paulo, Talim Street, 330, São José dos Campos, SP 12231-280, Brazil