Low temperature pretreatment of poplar using deep eutectic solvent and the structural evolution of three components of poplar
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摘要: 本研究考察了不同 ChCl/羧酸、氢键供受体比例,处理温度和时间对杨木木质素脱除效果的影响;并采用XRD、FT-IR、GPC、HSQC表征手段对固体残渣和提取木质素进行结构表征,研究木质纤维素三组分的结构演变规律。结果表明,低温下(90 ℃),ChCl/FA木质素脱除率高于90%,木质素提取率和纯度高达63%和90%。纤维素保留率 > 98%,纤维素晶型不变(Iβ型),固体残渣结晶度高达70%。提取木质素平均相对分子质量为1400,β−O−4保留率高达71%,占所有连接键的84.8%,是制备单酚的理想原料。Abstract: In this work, the impacts of ChCl/carboxylic acids, molar ratios of hydrogen bond acceptors to donors, pretreatment temperature and time on the delignification of poplar were investigated. Characteristic methods including XRD, FT-IR, GPC, and HSQC were used to analyze the solid residue and extracted lignin for the study of the structural evolution of the three components. The results showed that under low temperature of 90 ℃, the delignification of poplar wood was 91% with ChCl/FA pretreatment. About 63% of lignin was collected and the purity of lignin was 90%. Over 98% cellulose remained intact with Iβ type crystal form, and the crystallinity was 70%. The β−O−4 bond content of extracted lignin was 84.8% (71% of the original β−O−4 bond), and Mn of the lignin was 1400, suggesting the extracted lignin to be an ideal raw material for monophenlics production.
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Key words:
- deep eutectic solvent /
- pretreatment /
- lignin /
- structural evolution /
- β−O−4
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图 2 ChCl/羧酸组合及ChCl:FA比例对对杨木预处理的作用
Figure 2 Effects of different DES combinations and molar ratios of ChCl to FA on poplar pretreatment
reaction conditions: 0.5 g poplar wood powder, 10 g DES (HBA:ChCl); (a) molar ratio of ChCl to HBD is 1∶1, 90 ℃, 8 h; (b) the molar ratio of ChCl to HBD is 1:2, 90 ℃, 8 h
表 1 不同温度和处理时间下木质素的GPC分析
Table 1 GPC analysis of lignin extracted at different temperatures and treatment times
t/℃ t/h Mn Mw D = Mw/Mn 90 8 954 1400 1.46 120 8 991 1352 1.48 150 8 873 1006 1.37 90 12 702 1039 1.48 90 16 655 750 1.16 90 24 580 865 1.49 表 2 木质素中的主要连接键及结构单元
Table 2 Main interlinkages and units in lignin
Connection key MWL DESL 100Ar % 100Ar % β–O–4 (A) 43.3 77.6 18 48 β–O–4 (A′) 0.1 0.3 12.6 34 β–O–4 (A′′) 0 0 1 2.8 β–O–4 in total 43.4 77.9 30.6 84.8 β–β 8.6 15.4 2.9 7.7 β–5 3.7 6.7 2.8 7.5 Total 55.8 100 37.1 100 G/S/PB 43∶47∶10 39∶53∶8 -
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