Humins with Efficient Electromagnetic Wave Absorption: A By-Product of Furfural Conversion to Isopropyl Levulinate via a Tandem Catalytic Reaction in One-Pot

Graphical The by-product (called humins) is accompanied by a one-pot catalytic conversion reaction of furfural (FAL) to isopropyl levulinate (PL), which is carbonized (Humins-700) and applied to a new experiment of electromagnetic wave absorption, showing superior electromagnetic wave absorption performance. The minimum reflection loss (RLmin) value is −47.3 dB at 13.0 GHz with a thickness of 2.0 mm. This provides inspiration that humins can be applied to electromagnetic wave absorption. Both one-pot catalytic conversion of furfural (FAL) to isopropyl levulinate (PL) and carbonization of by-product (humins) for electromagnetic wave absorption are discussed, which provides inspiration that humins can be applied to electromagnetic wave absorption. In the former, phosphotungstic acid (PW) is employed as a homogeneous catalyst to convert FAL to PL via a tandem reaction in one pot, with the formation of a vast amount of humins. With FAL and various intermediates as substrates, it was found that humins was a polymerization product of FAL, furfuryl alcohol (FOL) and furfuryl ester (FE) with furan rings. In addition, the in situ attenuated total reflection infrared (ATR-IR) spectra also provided a basis for the proposed reaction route. In the latter, with the humins as raw material, P species and WO 3 doped nano-porous carbon (Humins-700) platform formed after high-temperature annealing is used for electromagnetic wave absorption and manifests desirable absorption performance. The minimum reflection loss (RL min ) value is −47.3 dB at 13.0 GHz with a thickness of 2.0 mm and the effective absorption bandwidth reaches 4.5 GHz (11.2–5.7 GHz).