Hydrogenation of Levulinic Acid to gamma-Valerolactone in Water Using Millimeter Sized Supported Ru Catalysts in a Packed Bed Reactor

gamma-Valerolactone (GVL) has been identified as a sustainable platform chemical for the production of carbon-based chemicals. We here report an experimental study on the catalytic hydrogenation of levulinic acid (LA) in water to GVL in a packed bed reactor using supported Ru catalysts (carbon, alumina, and titania) with particle sizes in the millimeter range (C-LA,C-0 = 1.2 mol/L, LA feed = 1 mL/min, H-2 feed = 30 mL/min, 90 degrees C, 45 bar, and WHSV = 30 of g(feed)/g(cat).h). Intraparticle diffusion limitations for hydrogen and LA were confirmed by performing LA hydrogenation experiments with different catalyst particle sizes (0.5 wt % Ru/C) and supported by calculations. The best performance was obtained with Ru/C, showing high LA conversion during 6 h on stream with negligible deactivation. Ru/Al2O3 was found to be less active, and stability was also considerably reduced due to the reactivity of the support. Ru/TiO2 was considerably less reactive, though stability was better than that for the alumina based counterpart. A long duration test (52 h) for Ru/C (0.5 wt % of Ru) showed a small though significant reduction in LA conversion (from 95 to 82 mol %). Catalyst characterization studies showed a significant decrease in the specific surface area of the catalyst (from 1110 m(2)/g to 390 m(2)/g) and sintering of the Ru particles (TEM-HAADF).