Weak-acid biochar catalyst prepared from mechanochemically-activated biomass and humic acid for production of 5-hydroxymethylfurfural

Many types of sustainably-prepared functional biochar catalysts are needed to transform biomass substrates into platform chemicals.In this work,weak-acid biochar catalysts were prepared by mix ball-milled(10 min,isothermal,room temperature)cherry blossom tree leaf biomass(BM)with humic acid(H)prior to carbonization of samples for 1 h under nitrogen gas.Characterization of the as-prepared materials(HBM-carbonization temperature in℃)showed that humic acid activated the biochars and increased their number of oxygen-containing functional(-COOH,OH)groups.The weak-acid biochars were applied as heterogeneous catalysts for dehydration of fructose to 5-hydroxymethylfurfural(5-HMF),where it was found that biochar catalyst,HBM-400,gave 100%fructose conversion and 77.5%5-HMF yields in an ionic liquid(1-butyl-3-methylimidazolium chloride)reaction system(140℃,60 min reaction time).As-prepared HBM-400 biochars exhibited constant catalytic activity for fructose dehydration with repeated use without any type of reactivation treatment and were stable for 5 cycles.Humic acid is an effective additive for preparing weak-acid catalytic materials from waste biomass.