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

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–copper 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.