Platinum, palladium and nickel supported on Fe3O4 as catalysts for glycerol aqueous-phase hydrogenolysis and reforming

Aqueous-phase hydrogenolysis (APH) and reforming (APR) are intertwined reactions with great interest for biomass valorization, as APR generates hydrogen in situ at preferred APH reaction conditions instead of using external sources. We investigated iron oxide-supported Pt, Pd and Ni as catalysts for these reactions using glycerol as starting material. Catalysts were characterized by ICP, N2 physisorption, H2 chemisorption, XRD, TPR, CO2-TPD, FTIR of pyridine adsorption, XPS and TEM. The catalyst tests were performed in an autoclave extended with an in situ pre-reduction setup. Hydrogen spillover was found from hydrogen chemisorption of Pt catalysts, and after the development of a custom-made methodology, the Pt particle size was found to be 1.8 nm for the 2.5Pt/Fe3O4 catalyst, which agrees with TEM analysis (1.56 nm). Both for hydrogenolysis and APR, the activity order was Pt > Pd > Ni, directly related to the stability of reduced small nanoparticles, which has an impact on acid-base properties of the support. Pt showed the best performance in hydrogenolysis even at a low content (81% conversion, 79% 1,2-propanediol selectivity for 1.0Pt/Fe3O4). The 2.5Pd/Fe3O4 catalyst showed the highest hydrogen yield in APR (69.2% at 513 K and 78.9% conversion). First order kinetic fits were made for 2.5Pt/Fe3O4, from which an apparent activation energy of 61.1 kJ mol(-1) was obtained and an initial turnover frequency (TOF0) of 0.121 s(-1).