Highly efficient 5-hydroxymethylfurfural production from fructose over S, N-doped lignin carbon solid acids

The production of 5-hydroxymethylfurfural (HMF) by traditional liquid acid catalysis has the problems of high equipment requirements and high pollution, which can be overcame by using environmentally friendly solid acid catalysts. In this paper, the lignin-based carbon solid acid (LBCS) co-doped with S, N elements was synthesized for the efficient catalysis of fructose conversion to HMF. The ammonium sulphate and sodium lignosulfonate (LS) were served as carbon-containing precursors via ice templates, and lignin-based carbon solid acids were prepared after one-step carbonization activation and sulfonation. Ammonium sulfate enhances the weak acid sites of the solid acids, while bringing high S, N contents of 3.75 % and 3.35 %. The total acidity of the solid acid was as high as 8.123 mmol/g. Following the optimization of the catalytic reaction conditions, the conversion of fructose to HMF was successfully catalyzed within a DMSO and water system, resulting in a fructose conversion rate exceeding 99 % and achieving an HMF yield of up to 91.91 %. In addition, there was no significant deactivation after 5 cycles of reuse. The efficient catalysis of LBCS represents both a value-added use of woody biomass resources and an environmentally friendly alternative to liquid acid catalysts for HMF production.