Hydrogenation of biomass-derived levulinic acid to γ-valerolactone catalyzed by mesoporous supported dendrimer-derived Ru and Pt catalysts: An alternative method for the production of renewable biofuels

Generation 4 PAMAM-OH dendrimers were employed as templating agent for the synthesis of dendrimer-encapsulated Ru and Pt nanoparticles (Ru- or Pt-DENs). These DEN catalysts were then immobilized onto preformed mesoporous support materials (TiO2 and SiO2) using wet-impregnation method to produce heterogeneous catalysts. Ru- and Pt-DENs were characterized prior to immobilization using UV-vis (UV-vis) spectroscopy and high-resolution transmission microscopy (HRTEM). The average particle sizes for Ru- and Pt-DENs were determined to be 1.4 +/- 0.2 and 1.7 +/- 0.3 nm, respectively. Supported solid catalysts were characterized using various techniques such N-2 adsorption-desorption physisorption, powder X-ray diffraction (PXRD), Fourier transform infrared (FTIR) and HRTEM. Inductive coupled plasma-optical emission spectroscopy (ICP-OES) was used for the determination of metal loading on the support. The catalytic performance of these catalysts was investigated in the selective hydrogenation of levulinic acid (LA) to produce gamma-valerolactone (GVL). The highest conversion was observed when unsupported catalysts (Ru-DENs and Pt-DENS) were used for all systems studied. The Ru catalyst displayed excellent activity as compared to Pt catalysts. All catalysts showed selectivity to gamma-valerolactone up to 100%.