Preparation Of Biomass Carbon Microbead And Application In Catalytic Conversion Of Biomass

The efficient conversion of renewable biomass has been gained much attention in recent decades due to the increasing energy crisis and global warming problem. Particularly, the preparation of the platform chemical5-hydroxymethylfurfural (5-HMF) from biomass is attracting wide attentions around the world.5-HMF is the acid-catalyzed dehydration product of fructose.5-HMF can be transformed to various down-stream products by hydrogenation, oxo-dehydrogenation, esterification, halogenation, polymerization or hydrolyzation.5-HMF is considered to be a key intermediate that combines biomass chemistry with petroleum-based industrial organic chemistry. Therefore, transformation of carbohydrates such as fructose, glucose and cellulose has attracted widespread attentions. However, it is a challenge for the conversion of lignocellulosic biomass to chemical products due to the structural recalcitrance of the lignocellulosic biomass. Particularly, bio-based chemicals have been suffered a severe issue that the start point of the biorefinery schemes of hydrolysis of biomass is hard.In this work, firstly, a sulfonated carbon material was prepared by incompletely hydrothermal carbonization of glucose followed by sulfonation. The carbon material contained-SO3H,-COOH, and phenolic-OH groups, and exhibited high catalytic performance for the hydrolysis of cellulose. A total reducing sugar (TRS) yield of72.7%was obtained in ionic liquid1-butyl-3-methyl imidazolium chloride at110℃in240min reaction time. The effect of water on the hydrolysis of cellulose in the catalytic system was studied. A water content of less than2%in the ionic liquid promoted the formation of TRS, whereas a water content of greater than2%lead to a decrease in TRS. The sulfonated carbon material catalyst was demonstrated to be stable for five cycles with minimal loss in catalytic activity. The use of an ionic liquid with functionalized carbon catalyst derived from glucose provides a green and efficient process for cellulose conversion.Then, we synthesized a novel carbon-based solid acid by eco-friendly approach from cellulose, sulfosalicylic acid and sulfuric acid, offering a stable solid containing a high density of actives sites. Carbonaceous solid (CS) catalysts with-SO3H,-COOH, and phenolic-OH groups, were prepared by incompletely hydrothermal carbonization of cellulose followed by either sulfonation with H2SO4to give carbonaceous sulfonated solid (CSS) material or by both chemical activation with KOH and sulfonation to give activated carbonaceous sulfonated solid (a-CSS) material. The obtained carbon products (CS, CSS, and a-CSS) were amorphous; the CSS material had a small surface area (<0.5m2g-1) and a high-SO3H group concentration (0.953mmol g-1), whereas the a-CSS material had a large surface area (514m2g-1) and a low-SO3H group concentration (0.172mmolg-1). The prepared materials were evaluated as catalysts for the dehydration of fructose to5-hydroxymethylfurfural (5-HMF) in the ionic liquid1-butyl-3-methylimidazolim chloride ([BMIM][Cl]). High5-HMF yield (83%) could be obtained (80℃and10min reaction time). CSS and a-CSS catalysts had similar catalytic activities and efficiencies for the conversion of fructose to5-HMF in [BMIM][C1]; this could be explained by the trade-off between-SO3H group concentration (high for CSS) and surface area (high for a-CSS). The cellulose-derived catalysts and ionic liquid exhibited constant activity for five successive recycles, and thus, the methods provide a renewable strategy for biomass conversion.Moreover, in order to solve the problem that the solid acid catalyst is difficult to recover from the reaction solution by filtration or sedimentation, we prepared a novel magnetic amorphous carbon solid acid bearing-SO3H,-COOH and phenolic-OH groups. The prepared magnetic catalyst was used as catalyst for the hydrolysis of cellulose in the ionic liquid [BMIM][Cl] and can be easily separated from the reaction mixture by external magnet field and can be reused for subsequent reactions, which is essential part of principles of green engineering.