Sustainable synthesis of biomass-derived sulfonated hydrochars and pyrochars for the production of 5-(hydroxymethyl)furfural

Lignocellulosic biomass is one of the most important renewable bioresources containing cellulose, hemicellulose and lignin and represents a valid feedstock for producing renewable fuels and platform chemicals. Various processes can cause the biomass deconstruction and among them, the hydrothermal carbonization treatment plays a crucial role to synthesize “high-quality” carbon-based materials, named hydrochar. The obtained hydrochars show potential applications and in the catalysis field, within the project PRIN 2020 LEVANTE "LEvulinic acid Valorization through Advanced Novel Technologies", different hydrochars have been synthesized starting from model compounds (glucose and xylose), cellulose and hazelnut shells as real lignocellulosic biomass to be used as precursors for the preparation of biomass-derived catalysts. Subsequently, pyrochars resulting from the pyrolysis of the obtained hydrochars have been synthesized and all the produced chars, hydrochars and pyrochars, were sulfonated with sulfuric acid and tested in the acid-catalyzed hydrothermal synthesis of 5-(hydroxymethyl)furfural, adopting microwave irradiation. The achieved high yields of about 40 mol% are in agreement with the best data obtained for the same reaction in the literature with sulfonated biochars and with commercial resins, thus confirming their promising potential as heterogeneous green acid catalysts.