N-doped carbon supported Pt catalyst for base-free oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

A new kind of N-doped carbon supported Pt catalyst (Pt/C) has been prepared for the selective oxidation of 5-Hydroxymethylfurfural (HMF) to 2,5-Furandicarboxylic Acid (FDCA) in base-free conditions. The catalyst (Pt/C-EDA-x) prepared by using ethylenediamine (EDA) as nitrogen source showed higher activity than those prepared by N,N-dimethylaniline (DMA), ammonia (NH3) or acetonitrile (ACN) as nitrogen sources. The Pt/C-EDA-4.1 catalyst showed the highest activity in the oxidation of HMF to FDCA and as high as 96.0% FDCA was obtained under optimal reaction conditions (110 °C, 1.0 MPa O2, 12 h). The samples were characterized by XRD, XPS, CO2-TPD, TEM, SEM, and elemental analysis. XPS results showed that the pyridine-type nitrogen (N-6) played a key role in the selective oxidation of HMF, which can be attributed to the basicity of N-6 site. CO2-TPD measurements also showed that the involving of N elements in catalyst preparation introduced a new kind of medium basic site on the support surface. The influence of reaction time, catalyst dosage, and temperature on the HMF oxidation to FDCA catalyzed by Pt/C-EDA-4.1 was studied.