Highly efficient and recyclable chromium/nitrogen-doped carbon nanotube catalysts with unexpected active sites for conversion of fructose into 5-hydroxymethylfurfural

5-Hydroxymethylfurfural (HMF) has great promise as a versatile platform chemical for the synthesis of a wide range of other chemical compounds. The preparation of HMF from carbohydrates for industrial applications, especially fuels and fine chemicals, has received much more attention. In the present study, metal/nitrogen-doped carbon nanotubes (M/N-CNTs) were produced using a one-step carbonization method and used as an exceptional catalyst for converting fructose to HMF. The catalyst structure was determined using Energy-dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), High-resolution X-ray Photoelectron Spectrometer (HRXPS), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), and Fourier-transform Infrared Spectroscopy (FT-IR) techniques. The effects of temperature, catalytic loading, substrate feed concentrations, solvents, reusability, and scalability were carried out. This work achieved an excellent yield of HMF (91 % ± 2) utilizing Cr/N-CNTs as a catalyst for producing HMF at 120 °C for 180 min. Furthermore, the Cr/N-CNTs could be recovered and reused in industrial applications without significant loss of the catalytic activity.