Synthesis of ternary magnetic nanoparticles for enhanced catalytic conversion of biomass-derived methyl levulinate into γ-valerolactone

Conversion of levulinic acid and its esters into versatile gamma-valerolactone (GVL) is a pivotal and challenging step in biorefineries, limited by high catalyst cost, the use of hydrogen atmosphere, or tedious catalyst preparation and recycling process. Here we have successfully synthesized a ternary magnetic nanoparticle catalyst (Al2O3-ZrO2/Fe3O4(5)), over which biomass-derived methyl levulinate (ML) can be quantitively converted to GVL with an extremely high selectivity of > 99% and yield of similar to 98% in the absence of molecular hydrogen. Al2O3-ZrO2/Fe3O4(5) incorporates simultaneously inexpensive alumina and zirconia onto magnetite support by a facile coprecipitation method, giving rise to a core-shell structure, well-distributed acid-base sites, and strong magnetism, as evidenced by the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning-TEM (HAADF-STEM), SEM-energy dispersive Xray spectroscopy (SEM-EDX), temperature-programmed desorption of ammonia (NH3-TPD), temperature-programmed desorption of carbon dioxide (CO2-TPD), pyridine-adsorption infrared spectra (Py-IR), and vibrating sample magnetometry (VSM). Such characteristics enable it to be highly active and easily recycled by a magnet for at least five cycles with a slight loss of its catalytic activity, avoiding a time-consuming and energy-intensive reactivation process. It is found that there was a synergistic effect among the metal oxides, and the high efficiency and selectivity originating from such synergism are evidenced by kinetic studies. Furthermore, a reaction mechanism regarding the hydrogenation of ML to GVL is proposed by these findings, coupled with gas chromatography-mass spectrometry (GC-MS) analysis. Accordingly, this readily synthesized and recovered magnetic nanocatalyst for conversion of biomass-derived ML into GVL can provide an eco-friendly and safe way for biomass valorization. (C) 2021 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

A ternary magnetic nanoparticle catalyst with high efficiency and extremely high selectivity has been successfully synthesized for the conversion of biomass-derived methyl levulinate into gamma-valerolactone. The catalyst features a core-shell structure, well-distributed acid-base sites, and strong magnetism, enabling easy recycling and reuse.