Multifunctional properties of alumina-based graphene nanocomposites as catalysts for esters of glycerol production

Abstract

The properties of alumina-based graphene nanocomposites were fine-tuned using a directed self-assembly of graphene oxide and metal oxides mediated by a surfactant approach. The resultant nanostructured metal oxides were evaluated in the esterification of glycerol with acetic acid as catalysts for the esters of glycerol production. X-Ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy measurements of the self-assembled nanocomposites revealed the nanocrystalline γ-Al2O3 phase between the separated graphene lamellar nanostructures. A crumpled monolayered graphene sheet along with well dispersed Ni and Co entities on solid surface appeared by Scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDS) analyses. Electron paramagnetic resonance spectroscopy (EPR) and X-ray photoelectron spectroscopy (XPS) showed Ni2+, Co3+/Co2+and Al3+species and a more reduced surface oxygen species in the self-assembled solids. The addition of basic promoters such as La, Mg or Zn to the composites did not improve the catalytic properties of the solids, but combined with NiCo-alumina-based graphene nanocomposites, they had shown good activities for triacetin production.