Cobalt nanoparticles embedded in a nitrogen-doped carbon matrix for reductive amination of biomass-derived furfural to furfurylamine

Abstract

The preparation of furfurylamine (FAM) through reductive amination of biomass-derived furfural with liquid ammonia using a heterogeneous catalyst has attracted significant attention. In this work, cobalt nanoparticles encapsulated in a nitrogen-doped carbon matrix were synthesized via pyrolysis of ZIF-67 at various temperatures (400 to 700 °C) under a N₂ atmosphere. The as-prepared catalysts were directly used for the reductive amination of furfural with liquid ammonia at 120 °C using 2 MPa H₂ pressure in methanol. Complete furfural conversion with 99% FAM yield was achieved over the Co/NC-700 catalyst. Different catalyst characterization techniques, TEM, XPS, XRD, BET surface area, H₂-TPD, and Raman spectroscopy, were used to correlate the catalytic activity with the structural properties of the catalyst. The catalyst characterization results showed that the metallic cobalt nanoparticles stabilized by coordination with the nitrogen in the graphitic layers are active centres for reductive amination. The high BET surface area, total pore volume, facile hydrogen desorption and the presence of defect sites on the surface could contribute to the greater catalytic activity and selectivity. In addition, the Co/NC-700 catalyst is heterogeneous, easily recoverable and can be reused for many catalytic cycles without any significant loss of activity. Furthermore, an integrated catalytic process was established for the synthesis of furfurylamine directly from xylose, with a 68.7% overall yield of furfurylamine in a two-step catalytic process. Moreover, the scope of the Co/NC-700 catalyst was also extended to the reductive amination of different aldehydes and ketones, which produced good to excellent yields of primary amines.