Ru nanoparticles supported graphene oxide catalyst for hydrogenation of bio-based levulinic acid to cyclic ethers

Ruthenium nanoparticles supported on graphene oxide (GO) catalysts have been evaluated for bio-based levulinic acid (LA) hydrogenation to produce vapor-phase cyclic ethers in a fixed-bed reactor. It was found that using the GO supported Ru nanoparticles (Ru/GO) produced additional hydrogenation products cyclic ethers (54%) and gamma-valerolactone (GVL; 41%), while Ru on carbon (Ru/C) catalysts gave only GVL with 100% LA conversion. To improve the yield of cyclic ethers, an additional two-step hydrogenation of LA via GVL was successfully carried out. This provided GVL as a second feedstock from which the Ru/GO catalyst could produce cyclic ethers such as methyltetrahydrofuran (MTHF) and tetrahydrofuran (THF). Ru on GO catalysts showed a 92% selectivity of predominantly cyclic ethers, including a 77% selectivity of MTHF through two steps process. Such a remarkable enhancement in activity and selectivity of LA hydrogenation over Ru/GO can be attributed to the well-dispersion of Ru nanoparticles, as well as favorable interaction with GO in the presence of oxy-functional groups of GO. In order to evaluate the active sites on the catalyst, they were characterized using different characterization techniques such as Raman, XRD, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), temperature-programmed desorption of NH3 (TPD), electron microscopy (TEM and SEM) and H-2-chemisorption and N-2 adsorption. (C) 2015 Elsevier B.V. All rights reserved.