LiBr hydrate as reaction medium for preparation of carbon spheres from wood powders via hydrothermal carbonization

In this work, a suitable solvent (Lithium Bromide Hydrate) was selected and used for the efficient dissolution and carbonization of biomass for the preparation of carbon spheres directly from wood powders by hydrothermal carbonization (HTC), which was so far the first successful attempt of making carbon spheres directly from woody biomass. The impacts of the preparation conditions on the yield and morphology of carbon spheres were carefully studied, and it was found that the yield and degree of carbonization of carbon spheres were positively correlated with the temperature and reaction time. The optimal operation conditions were determined as 170 °C, reaction time 5 h and LiBr concentration 65 wt%. And the produced carbon spheres have an average particle size of 603 nm with a yield of 22.4%. The characterization of carbon spheres revealed that the prepared nanoparticles had excellent spherical morphology and multifunctional groups, which led to a better surface reactivity than the raw material itself. Moreover, levulinic acid (LA) and 5-hydroxymethylfurfural (5-HMF) were found in the liquid phase of the reaction products, indicating the furan derivatives were formed in the HTC process , which demonstrated a great potential of biomass valorisation with this innovative process.