Ji Liu,Hao Fu,Bin Hu,Guan-zheng Zhou,Shou-gang Wei,Zhen-xi Zhang,Qiang Lu
Pyrolysis, a promising thermochemical conversion technique, can convert lignocellulosic biomass into various value-added products. Herein, the selective production of 1,4:3,6-dianhydro-α- d -glucopyranose (DGP) was achieved through fast pyrolysis of cellulose based on oxalic acid-assisted torrefaction (OAT) pretreatment. The mixture of cellulose and oxalic acid first underwent torrefaction, followed by fast pyrolysis to yield DGP. Simultaneously, the air atmosphere was considered to facilitate the formation of esterification intermediates, thereby promoting the formation of DGP. The effects of torrefaction temperature, oxalic acid amount, as well as pyrolysis temperature were carefully explored for DGP production. A yield of 9.6 wt% and a selectivity of 57.5 % for DGP were achieved from the micro-scale pyrolysis of cellulose under the optimized conditions. In lab-scale tests, the DGP yield reached 12.5 wt% from cellulose. The OAT-based pyrolysis was confirmed to be applicable to the waste cellulose-rich materials, with a DGP yield of 8.2 wt% from waste cotton and 6.0 wt% from spent paper in lab-scale experiments. Additionally, the OAT-based pyrolysis also showed the potential for poly-generation of DGP and formic acid at different stages.
Bin Hu,An-shuai Cheng,Yang Li,Yao-bing Huang,Ji Liu,Bing Zhang,Kai Li,Li Zhao,Ti-peng Wang,Qiang Lu
Selective preparation of value-added products via fast pyrolysis is a sustainable way for biomass utilization. We developed a novel strategy, oxalic acid-assisted fast pyrolysis (OAFP) of cellulose, which achieved the selective production of a promising anhydrosugar, 1,4:3,6-dianhydro-α- d -glucopyranose (DGP), for the first time. Effects of temperature and the mass ratio of cellulose-to-oxalic acid (Cell/OA) in their solid mixture were explored. The yield of DGP could be up to 14.0 wt% (based on cellulose) at 400 °C and the Cell/OA mass ratio of 1:9 with a lab-scale setup, about 200 times higher than that from fast pyrolysis of pure cellulose. According to the experiments and density functional theory (DFT) calculations, it was OA rather than its pyrolysis vapors (mainly formic acid) that played the predominant role in the selective generation of DGP, where OA acted as a reactant and a catalyst-like material at the same time. The formation of DGP competed with that of levoglucosan (LG), the most typical product in the fast pyrolysis of pure cellulose, and a small amount of DGP came from the secondary conversion of LG. The esterification of free hydroxyl at C3 or C6 position with OA determined the selective generation of DGP by promoting the formation of the C1 = C2 bond and the 3,6-acetal ring, and the generation of the 1,6-acetal ring was inhibited correspondingly which led to the decrease of LG. In addition, the OAFP process also showed the potential for poly-generation of value-added chemicals, syngas, and char.
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