Conversion of phoenix tree leaves into hydro-char by microwave-assisted hydrothermal carbonization

This study provided a detailed observation on microwave-assisted hydrothermal carbonization of phoenix tree leaves. The effect of microwave and the influence of different factors on the product were analyzed by comparison and experiment separately. As the reaction severity increased, higher heating value of hydro-char increased (17.70–22.42 MJ/kg), but mass yield had the opposite trend. It was found microwave-assisted heating can economize more than 50% in time. Elemental analysis showed the highest energy rentation rate of hydro-char was obtained at 220 °C, 60 min, and pH = 7, whose higher heating value was about 27.7% higher than that of feedstock. Based on the analysis of the properties and van Krevelen diagrams of hydro-char, the reaction process was proposed. Morphological change analysis showed the surface morphology of hydro-char was partially destructed suggesting OH- can effectively promote the destruction of wood structure, and make cellulose components contact with reaction medium faster. © 2019 Elsevier Ltd