Key Laboratory of Air-driven Equipment of Zhejiang Province, College of Mechanical Engineering, Quzhou University, Quzhou 324000, China.
Molecules. 2023 Dec 30;29(1):219. doi: 10.3390/molecules29010219.
Understanding the pyrolysis product distributions of deep eutectic solvent (DES)-isolated lignins (DESLs) from different types of biomass is of great significance for lignin valorization. The structure and pyrolysis properties of DESLs obtained from eucalyptus (E-DESL), pine (P-DESL), and rice straw (R-DESL) were studied through the use of various methods such as elemental analysis, GPC, HS-GC, and NMR techniques, and the pyrolysis characteristics and product distributions of the DESLs were also further investigated through the use of TGA, Py-GC/MS, and tubular furnace pyrolysis. DESLs with high purity (88.5-92.7%) can be efficiently separated from biomass while cellulose is retained. E-DESL has a relatively low molecular weight, and P-DESL has a relatively higher hydrogen-carbon effective ratio and a lower number of condensation structures. The Py-GC/MS results show that, during DESL pyrolysis, the monomeric aromatic hydrocarbons, -hydroxyphenyl-type phenols, and catechol-type phenols are gradually released when the guaiacyl-type phenols and syringyl-type phenols decrease with the rising temperature. 4-methylguaiacol and 4-methylcatechol, derived from the guaiacyl-type structural units, are positively correlated with temperature, which causes a significant increase in products with a side-chain carbon number of 1 from P-DESL pyrolysis. 4-vinylphenol, as a representative product of the R-DESL, derived from -hydroxyphenyl-type structural units, also gradually increased. In addition, the P-DESL produces more bio-oil during pyrolysis, while gases have the highest distribution in E-DESL pyrolysis. It is of great significance to study the characteristic product distribution of lignin isolated through the use of DES for lignin directional conversion into specific high-value aromatic compounds.
理解不同类型生物质来源的深共熔溶剂（DES）分离木质素（DESL）的热解产物分布对于木质素的增值利用具有重要意义。通过元素分析、GPC、HS-GC 和 NMR 等方法研究了从桉树（E-DESL）、松树（P-DESL）和稻草（R-DESL）中获得的 DESL 的结构和热解性质，并通过 TGA、Py-GC/MS 和管式炉热解进一步研究了 DESL 的热解特性和产物分布。DESL 可以从生物质中高效分离出高纯度（88.5-92.7%）的纤维素。E-DESL 的分子量相对较低，P-DESL 的氢碳有效比相对较高，缩合结构数量较少。Py-GC/MS 结果表明，在 DESL 热解过程中，当愈创木型酚和丁香型酚随着温度的升高而减少时，单体芳烃、-羟苯基型酚和邻苯二酚型酚逐渐释放。来源于愈创木型结构单元的 4-甲基愈创木酚和 4-甲基邻苯二酚与温度呈正相关，导致 P-DESL 热解产物中侧链碳原子数为 1 的产物显著增加。来源于 -羟苯基型结构单元的 R-DESL 的代表性产物 4-乙烯基苯酚也逐渐增加。此外，P-DESL 在热解过程中产生更多的生物油，而 E-DESL 热解中气体的分布最高。研究通过 DES 分离木质素的特征产物分布对于木质素定向转化为特定高价值芳香化合物具有重要意义。
