Conversion of renewable feedstock to bio-carbons dedicated for the production of green fuel additives from glycerol

[Display omitted] •Carbon samples were made from renewable feedstock by a simple and low-cost method.•A high degree of S functionalization (up to 5%) was achieved using one-pot method.•Satisfactory yield of di- and tri-acetins (above 70%) was obtained within 2 h.•A clear dependence between –SO3H density and formation of higher acetins was found.•Some carbon samples showed better performance than other reported catalysts. Sulfonated bio-carbon samples were prepared applying two methodologies: a) sustainable, one-step and low-cost method based on partial carbonization of renewable precursors (common carbohydrates or glycerol) in the presence of sulfuric acid, and b) two-step preparation approach, including template synthesis of carbon followed by its further modification with H2SO4 or diazonium salt. The used characterization techniques revealed significant differences in the chemical composition, surface nature and textural features of the fabricated materials. The synthesized carbons were further applied in simple batch-type, solvent-free esterification of glycerol with acetic acid to produce acetins – valuable fuel additives. The reaction was conducted at 110 °C with glycerol to acetic acid molar ratio of 1:6. The experiments showed that the prepared catalysts can work effectively, giving a very high conversion of glycerol (above 95%) and satisfactory combined selectivity (about 70%) to di- and triacetins (target products) within only 2 h. Moreover, the carbons did not lose their activities in subsequent cycles. The dependence between catalysts’ performance and the concentration of –SO3H groups was found.