Hydrogenation of levulinic acid to valeric acid over platinum–tungsten catalysts supported on γ-Al2O3
To address the challenges associated with fossil fuel depletion, exploration of the sustainable energy resources is one of the most pursued research areas in this century. Valeric acid (VA) is considered as a valuable platform molecule for the production of biofuels and chemical intermediates. However, the production of VA from levulinic acid (LA) has become one of the most desirable reactions. The aim of this work was to investigate the amount of acidity, Pt loading and experimental conditions for the hydrogenation of LA into VA operated at 0.1 MPa H2 pressure and to elucidate the relationship between the active sites and the catalytic performance. The Pt–WO3 catalysts supported on γ-Al2O3 were synthesized by a simple wet impregnation method with various Pt loadings from 0.5 to 3 wt% with constant 10 wt% of WO3 and calcination at 500 °C for 4 h under air. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), N2 adsorption–desorption, temperature programmed desorption of ammonia (NH3-TPD), pyridine Fourier transform infrared spectroscopy (Pyr.FT-IR) and CO-chemisorption studies. Under optimized reaction conditions, the 2Pt–10WO3/γ-Al2O3 catalyst exhibited the highest selectivity to VA (58%) with 91% conversion of LA. This is due to the availability of a huge number of acidic and Pt active sites on the catalyst surface. In addition, the catalytic activity, reaction parameters and stability of the catalyst are demonstrated clearly.