Rational production of highly acidic sulfonated carbons from kraft lignins employing a fractionation process combined with acid-assisted hydrothermal carbonization. (May 2020) - Nunes, Renan S.
Graphical abstract: Highlights: Kraft Lignin was used to produce sulfonated carbons employing the H2 SO4 -HTC method. The acidity of the SCs was correlated with their production method. Fractionation is beneficial for the production of highly acidic sulfonated carbons. Sulfonated carbons were tested in the fructose dehydration reaction to obtain 5-HMF. Abstract: Highly acidic lignin-derived sulfonated carbons (LDSCs) were produced from hardwood and softwood kraft lignins under mild conditions by applying fractionation and/or pre-carbonization treatments combined with acid-assisted hydrothermal carbonization. The use of lignin fraction with higher amount oxygen, obtained from the fractionation process, resulted in carbon with the highest density of surface acid groups and improved catalytic activity. The LDSCs were successful tested in the dehydration reaction of fructose to obtain 5-hydroxymethylfurfural, and the best catalyst can be recycled without loss in its catalytic activity after perform a simple regeneration process. In contrast, the pre-carbonization step, commonly performed in several works, resulted in LDSCs with low acidity. A simple and optimized methodology for obtaining LDSCs under mild conditions was developed, and the correlations between the preparation method and the physicochemical and catalytic properties established in this work may be extendible to other starting materials for rational sulfonated carbons production.