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Acid–base synergistic catalysis of biochar sulfonic acid bearing polyamide for microwave-assisted hydrolysis of cellulose in water

Chen, Zengtian, Li, Qingfeng, Xiao, Yuxue, Zhang, Chao, Fu, Zaihui, Liu, Yachun, Yi, Xianfeng, Zheng, Anmin, Li, Changzhi, Yin, Dulin
Cellulose 2019 v.26 no.2 pp. 751-762
reducing sugars, glucose, cellobiose, microwave treatment, cellulose, biochar, hydroxymethylfurfural, sulfonic acids, hydrolysis, polyamides, fructose, biomass, catalytic activity, adsorption
The development of a highly efficient heterogeneous catalysis process for the hydrolysis of cellulose to reducing sugars (RSs) and especially 5-hydroxymethylfurfural (HMF) in water is highly anticipated for large-scale use of cellulosic biomass in the future. Herein, a bamboo-derived biochar sulfonic acid bearing polyamide (BCSA-PA) designed by us was found to show much higher catalytic activity, better repeatability and especially HMF yield for microwave-assisted such hydrolysis compared to the PA-free BCSA, achieving 25.60% RSs and 23.10% HMF yields with 4.71 turnover number (TON) under optimal conditions. Also, its TON value (2.58) for the conversion of cellulose into HMF was much higher than those obtained from it-catalyzed transformation of glucose (TON, 1.44) and especially fructose (TON, 0.79). The BCSA-PA showing an excellent catalysis performance in cellulose hydrolysis is likely due to the following two reasons: (1) the BCSA and especially BCSA-PA, as supported by glucose and cellobiose adsorption experiments, have a stronger affinity to β-1,4-glycosidic bonds of cellulose than two monosaccharides, thereby leading to the highly-efficient hydrolysis of cellulose on the SO₃H groups. (2) The acid–base synergistic catalysis between the SO₃H and PA groups of BCSA-PA may be responsible for its higher HMF selectivity and excellent repeatability in water medium. The current work highlights new opportunities for the direct production of 5-HMF from glucose and especially cellulose.