Identification and quantification of lignin monomers and oligomers from reductive catalytic fractionation of pine wood with GC x GC - FID/MS
Identification and quantification of lignin monomers and oligomers from reductive catalytic fractionation of pine wood with GC x GC - FID/MS
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DOI：
10.1039/d1gc03822b
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发表时间：
2021-12-04
期刊：
影响因子：
9.8
通讯作者：
Van Geem, Kevin M.
中科院分区：
文献类型：
--
作者：
Hang Dao Thi;Van Aelst, Korneel;Van Geem, Kevin M.
彻底的木质素表征对于了解木质素的物理化学性质和评价木质纤维素生物炼制过程至关重要。在这项研究中，从松木的还原催化分馏（RCF）获得的木质素油的深入表征，进行定量GC x GC-FID分析和定性GC x GC-MS。通过在GC x GC系统中利用耐高温柱组和通过应用衍生化步骤，能够明确检测木质素单体，二聚体和三聚体。除了确认对应于34wt%的RCF木质素油的十一种单体的身份之外，通过分析它们的质谱全面鉴定了三十六种二聚体（16wt%）和二十一种三聚体（7wt%），并通过FID定量，包括另外23wt%的RCF木质素油的身份。提出的结构揭示了二聚体和三聚体低聚物中存在的相互连接，含有β-5、β-1、β-β、5-5和少量β-O-4和4-O-5键。此外，二聚体和三聚体分子中的脂肪族末端单元被鉴定，其由先前在RCF衍生的木质素单体中观察到的C4位置处的各种取代基组成。为了降低分析的复杂性，在分析之前将RCF油分离成六个馏分。在不同级分中发现的结构基序（单元间连接和末端单元）显著变化，使得在更极性的溶剂中提取的木质素级分含有更高分子量的片段和更多的含羟基的结构基序。通过GC x GC鉴定的单个二聚体和三聚体分子的结构与H-1-C-13 HSQC NMR光谱的最新发现很好地对齐并进一步补充，证明了两种2D技术之间的互补性，以获得RCF油中分子结构和键和末端单元分布的整体视图。这两种技术的结合为今后的RCF和其他木质素解聚研究提供了强有力的工具。
Thorough lignin characterization is vital to understand the physicochemical properties of lignin and to evaluate lignocellulose biorefinery processes. In this study, an in-depth characterization of lignin oil, obtained from reductive catalytic fractionation (RCF) of pine wood, was performed with quantitative GC x GC - FID analysis and qualitative GC x GC - MS. By utilizing high-temperature resistant column sets in the GC x GC system and by applying a derivatization step, unambiguous detection of lignin monomers, dimers, and trimers is enabled. In addition to confirm the identity of eleven monomers, corresponding to 34 wt% of the RCF lignin oil, thirty-six dimers (16 wt%) and twenty-one trimers (7 wt%) were comprehensively identified by analysis of their mass spectra and quantified by a FID, encompassing the identity of an additional 23 wt% of the RCF lignin oil. The proposed structures reveal the interlinkages present in the dimeric and trimeric oligomers, containing beta-5, beta-1, beta-beta, 5-5, and a minor fraction of beta-O-4 and 4-O-5 bonds. Furthermore, aliphatic end-units in the dimeric and trimeric molecules were identified, consisting of various substituents at the C4 position, that have been previously observed in the RCF-derived lignin monomers. To reduce complexity for analysis, the RCF oil was separated into six fractions, prior to analysis. The structural motifs (inter-unit linkages and end-units) that are found in the different fractions vary significantly, such that the lignin fractions extracted in more polar solvents contained higher molecular weight fragments and more hydroxyl containing structural motifs. The identified structures of individual dimer and trimer molecules by GC x GC align well with and further complement the recent findings from H-1-C-13 HSQC NMR spectroscopy, demonstrating complementarity between both 2D techniques to obtain a holistic view on both the molecular structures and the distribution of bonds and end-units in RCF oil. The combination of these two techniques provides a powerful tool for future RCF and other lignin depolymerization research.