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

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 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 ) 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).