Interaction mechanism between cellulose and hemicellulose during the hydrothermal carbonization of lignocellulosic biomass

Abstract

The fuel properties of the solid product obtained from hydrothermal carbonization (HTC) are substantially influenced by the interaction reactions of the lignocellulose components. This study focused on the interaction reactions of cellulose and hemicellulose (represented by glucose and xylose, respectively) and the formation mechanism of the hydrochar through experiments and density functional theory methods. Results indicated that furfural was the main intermediate product of xylose and then converted into benzenes, which were seldom produced from the hydrothermal conversion of glucose. When glucose and xylose were co-carbonized hydrothermally, more benzenes were generated because glucose and xylose exhibited a synergistic effect in forming alkenes, which were then cracked remarkably into C 2 H 2 . Furthermore, C 2 H 2 reacted with furan that transformed from furfural and formed benzenes. The aqueous product of co-HTC also contained a high concentration of 5-hydroxymethylfurfural (5-HMF). The 5-HMF could polymerize with benzenes and furfural to form insoluble furan−benzene polymers, gradually aggregating into organic micronucleus. Subsequently, 5-HMF, furfural, and benzenes in the aqueous phase were immobilized on the surface of the organic micronucleus through surface binding sites, eventually causing the growth of organic micronucleus into hydrochar particles. The polymerization between furan−benzene polymers could also increase the aromatization degree of the hydrochar, thereby enhancing the energy density of the hydrochar.

Hydrothermal Treatment of Biomass Feedstocks for Sustainable Production of Chemicals, Fuels, and Materials: Progress and Perspectives

“…The interactions among cellulose, hemicellulose, and lignin during the HTC of lignocellulosic biomass have received considerable attention recently . According to the discussion on comparing mixed model compounds to raw biomass (section ), the HTC of model compounds and raw lignocellulosic biomass produces different products, attributed to the interactions among cellulose, hemicellulose, and lignin. ,, Raw lignocellulosic biomass shows high thermal stability during the HTC processing due to a “protecting shield” offered by the interlinked lignin. ,, Additionally, the morphology and structural difference were observed in comparison to those of model compounds under the same HTC conditions .…”

“…Insoluble furan–benzene polymers and micronucleus were generated from the reaction of HMF and benzene during the HTC processing . Eventually, hydrochar was formed based on the micronucleus immobilized with HMF, furfural, and benzenes …”

“…294 Insoluble furan− benzene polymers and micronucleus were generated from the reaction of HMF and benzene during the HTC processing. 294 Eventually, hydrochar was formed based on the micronucleus immobilized with HMF, furfural, and benzenes. 294 In addition to hydrochar, other high-value-added products could be collected during the HTC of lignocellulosic biomass.…”

“…294 Eventually, hydrochar was formed based on the micronucleus immobilized with HMF, furfural, and benzenes. 294 In addition to hydrochar, other high-value-added products could be collected during the HTC of lignocellulosic biomass. Burguete et al designed a ton-scale HTC process to produce hydrochar as a solid fuel in the form of pellets from orange peel waste.…”

“…According to the discussion on comparing mixed model compounds to raw biomass (section ), the HTC of model compounds and raw lignocellulosic biomass produces different products, attributed to the interactions among cellulose, hemicellulose, and lignin. ,, Raw lignocellulosic biomass shows high thermal stability during the HTC processing due to a “protecting shield” offered by the interlinked lignin. ,, Additionally, the morphology and structural difference were observed in comparison to those of model compounds under the same HTC conditions . Notably, Jia et al investigated the interaction between cellulose and hemicellulose during the HTC of lignocellulosic biomass . A synergistic effect of HTC of cellulose and hemicellulose components in forming alkenes, and subsequently benzene was found due to the remarkable cracking and reaction of C 2 H 2 and furan .…”