Lignin-based carbon solid acid catalyst prepared for selectively converting fructose to 5-hydroxymethylfurfural

Lignin-based activated carbon solid (LCS) was prepared by simultaneous carbonization and activation at different temperatures. Lignin-based carbon solid acid (LCSA) was synthesized from LCS via sulfonation by sulfuric acid and used as a catalyst for converting fructose to 5-hydroxymethylfurfural (HMF). The physicochemical properties of LCS and LCSA were determined by scanning electron microscopy, N-2 adsorption-desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and element analysis. Owing to the microporous structure, LCSA possessed high specific area and could selectively and effectively convert fructose to HMF. Under the optimal conditions, the yield of HMF was 75.7% when dimethyl sulfoxide was used as the solvent. The recovery rate of the LCSA catalyst was nearly 95%, and the catalytic ability was more than 70% after five recycles. The preparation of microporous LCSA and its use as a catalyst are not only a value addition to lignin but are also environmentally friendly strategies for converting carbohydrates into HMF, as LCSA can prevent the pollution caused by the use of conventional mineral acid catalysts.