木质素催化氢解制备高附加值化学品研究进展

刘菊平; 唐紫玥; 陈应泉; 王贤华; 陈汉平; 杨扬; 杨海平

doi:10.19906/j.cnki.JFCT.2024009

木质素催化氢解制备高附加值化学品研究进展

doi: 10.19906/j.cnki.JFCT.2024009

华中科技大学能源与动力工程学院煤燃烧与低碳利用全国重点实验室, 湖北武汉 430074

基金项目: 国家自然科学基金杰出青年科学基金 ( 52125601) 资助

详细信息

通讯作者:
Haiping Yang, E-mail: yhping2002@163.com (H. Yang)

^#: 共同第一作者
中图分类号: TS6,TQ032
计量
- 文章访问数: 60
- HTML全文浏览量: 7
- PDF下载量: 12
- 被引次数: 0
出版历程
- 收稿日期: 2023-12-31
- 修回日期: 2024-02-20
- 录用日期: 2024-03-06
- 网络出版日期: 2024-03-30

Recent advances in the preparation of high-value-added chemicals by catalytic hydrogenolysis of lignin

State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China

Funds: The project was supported by National Natural Science Foundation of China National Natural Science Funds for Distinguished Young Scholar (52125601).

摘要

摘要: 开发和利用可再生生物质资源是实现二氧化碳减排的有效途径。而生物质结构复杂，整体反应性和利用率较低。木质素是自然界中唯一具有高能量密度的可再生芳香族聚合物，其转化和利用在全球范围内引起了广泛关注。然而，木质素结构的复杂性、连接方式的不确定性、侧链连接的稳定性以及反应片段不可避免的再缩合，使得将木质素解聚成生物燃料或芳香化学品成为一项艰巨的挑战。催化氢解技术可将木质素转化为高选择性、高收率的酚类单体。但是木质素催化解聚过程中化学键的定向剪切，产物与结构之间的转化机理仍不清晰。本工作针对木质素的催化氢解生产高值化学品的最新研究进展，重点总结了木质素的催化氢解过程中催化剂及其高值化学品产物间的耦合关联，着重讨论了不同催化剂体系对木质素解聚产物过程机理的影响，尤其对于金属基催化剂，综述了贵金属基催化剂、过渡基金属催化剂、水滑石催化剂和金属有机框架催化剂对于产物分布影响的最新进展，并进一步总结了不同催化剂存在的问题和转化机制；同时木质素加氢催化裂解过程中溶剂是促进木质素溶解、加速传热传质、促进反应物和催化剂在反应器中均匀分散的关键。本工作并对木质素液化的主要溶剂，例如水、醇类和新型溶剂体系对木质素的解聚效应进行综述。最后，就领域所面临的机遇和挑战进行了总结和展望，为木质素高效定向转化与高值化利用提供了理论参考。
- 木质素 /
- 催化 /
- 氢解 /
- 化学品
Abstract: The development and utilization of renewable biomass resources is an effective way to achieve CO₂ reduction. Biomass, on the other hand, has a complex structure with low overall reactivity and utilization. Lignin is the only renewable aromatic polymer with high energy density in nature, and its conversion and utilization have attracted much attention worldwide. However, the complexity of the lignin structure, the uncertainty of the linkages, the stability of the side-chain connections, and the inevitable recondensation of the reactive fragments make the depolymerization of lignin into biofuels or aromatic chemicals a formidable challenge. Catalytic hydrogenolysis technology converts lignin into highly selective, high-yield phenolic monomers with high heating value, low oxygen content, and high carbon utilization of the product. However, the mechanism of the conversion between products and structures remains unclear with respect to the directed bond shearing during the catalytic depolymerization of lignin. In this paper, in view of the latest research progress on the catalytic hydrogenolysis of lignin for the production of high-value chemicals. We focus on the catalytic hydrogenolysis of lignin to summarize the coupling correlation between the catalysts and their products of high-value chemicals and focus on the influence of different catalyst systems on the process mechanism of lignin depolymerization products. For metal-based catalysts in particular, a detailed review of recent advances in the effects of noble metal-based catalysts, transition metal-based catalysts, hydrotalcite catalysts, and metal-organic framework catalysts on product distribution is presented. And further summarized the problems and conversion mechanisms of different catalysts. Meanwhile, the solvent in the lignin catalytic hydrogenolysis cracking process is the key to promote lignin dissolution, accelerating the heat and mass transfer, and promoting the homogeneous dispersion of reactants and catalysts in the reactor. In this paper, the main solvents for lignin liquefaction, such as water, alcohol, and new solvent systems, are reviewed for their depolymerization impact on lignin. And further, outline the effect of the solvent system on the properties of lignin conversion products. Nevertheless, there are still many difficulties in the catalytic hydrogenolysis of lignin for the preparation of high-value chemicals. The complexity of the macromolecular structure of lignin, the directed depolymerization of the C−O and C−C structures is still difficult, and the preparation of efficient catalysts as well as the mechanism of directional regulation of the products are still to be further investigated. Due to the insolubility of lignin, no solvent system that can completely dissolve lignin has been found yet; secondly, the research on the solvent effect is still only in the preliminary exploration stage. Novel technology for favorable conversion of lignin is still only at the stage of laboratory research. And the efficient conversion of renewable lignin into valuable chemicals and fuels is of great significance in solving the energy crisis and slowing down global warming, and at the same time, it will help our country to realize the energy-dependence transition from oil to renewable biomass. So finally, the opportunities and challenges facing the field are summarized and outlooked, providing a theoretical reference for efficient targeted conversion and high-value utilization of lignin.
- lignin /
- catalytic /
- hydrogenolysis /
- chemicals
注释:

1) ^#: 共同第一作者

HTML全文

图 1 木质素结构示意图^[21]

Figure 1 Schematic representation of lignin structure^[21] (with permission from ACS Publications)

下载: 全尺寸图片幻灯片

图 2 木质素加氢催化过程示意图

Figure 2 Schematic diagram of the catalytic process of lignin hydrogenation

下载: 全尺寸图片幻灯片

图 3 水滑石类催化剂热处理过程

Figure 3 Thermal treatment process of hydrotalcite-based catalysts

下载: 全尺寸图片幻灯片

图 4 （a） Mo₁Al/MgO催化氢解木质素转化示意图；（b）不同条件下木质素解聚性能；（c） DFT计算的能量面^[16,42]

Figure 4 (a) Schematic diagram of Mo₁Al/MgO-catalyzed hydrolytic lignin conversion; (b) Lignin depolymerization performance under different conditions; (c) Energy surfaces calculated by DFT^[16,42] (with permission from Wiley and ACS Publications)

下载: 全尺寸图片幻灯片

图 5 硫酸盐木质素在NiMo@FDC催化剂上的NiMo双金属与载体的协调作用催化解聚机理路线图^[48]

Figure 5 Diagrammatic of the catalytic depolymerisation mechanism of sulphated lignin over NiMo@FDC catalysts by coordinated action of NiMo bimetals and support^[48] (with permission from Royal SOC Chemistry Publications)

下载: 全尺寸图片幻灯片

图 6 硫酸盐木质素在不同酸度和孔结构沸石上催化解聚制备芳烃^[57]

Figure 6 Catalytic depolymerization of Kraft lignin on zeolites of different acidity and pore structure for the preparation of aromatics^[57] (with permission from MDPI Publications)

下载: 全尺寸图片幻灯片

图 7 木质素在活性炭载体上催化氢解示意图^[63]

Figure 7 Schematic diagram of catalytic hydrogenolysis of lignin on activated carbon carriers^[63] (with permission from Elsevier Publications)

下载: 全尺寸图片幻灯片

图 8 咪唑基离子液体协调二元混合物中木质素氧化解聚机理图^[96]

Figure 8 Depolymerization of lignin in cooperative imidazolium-based ionic liquid binary mixtures^[96] (with permission from Elsevier Publications)

下载: 全尺寸图片幻灯片

表 1 生物质提取木质素典型连接键含量

Table 1 Lignin linkage bond content of different biomass extracts

Linkage bond/%	β-O-4	5-5	α-O-4	4-O-5	β-5	β-1	β-β
Softwood	43−50	9.5−11	6−8	3.5−4	9−12	7	2
Hardwood	50−65	4.5	6−8	6.5	6	7	3
Herbaceous plant	40	–	–	–	4	1	6

下载: 导出CSV

表 2 木质素在不同反应条件下产物分布

Table 2 Product distribution of lignin under different reaction conditions

Raw	Reaction condition	Catalyst	Solvent	Major product/%	Reference
Alkali lignin	400 ℃ ，4 h	Lewis acid	Water, methanol	Aromatic compounds 0.1–0.5; monophenol 0.9–5.5, catechol 0.5–3.5	[85]
Alkali lignin	350 ℃ ，28 h	NiMoS/Al₂O₃	Tetrahydronaphthalene	Monomeric phenols and long-chain alkanes 25	[86]
Alkali lignin， Organosolv lignin	250 ℃， 20 h	Ru/Nb₂O₅	Water	Aromatic hydrocarbon 20.4 cycloalkane 8.6	[87]
hydrolysed lignin	250 ℃， 15 min	MgO	Tetrahydrofuran	Monophenol 13.2	[88]
Alkali lignin	300 ℃， 8 h	CuMgAlO_x	Ethanol	Monophenol 23	[39]
Sulfated lignin	350 ℃，4 h	ZrO₂/K₂CO₃	Water/phenol	Monophenol 27	[89]
Sulfated lignin	350 ℃， 4 h	NiMo, ZrO₂	Dimethyl sulfide	Monophenol 26.4	[90]
Organosolv lignin	160 ℃， 24 h	CuZnAl	Propylene glycol	Monophenol 56.1	[91]

下载: 导出CSV

参考文献(102)

[1]	WANG S, RU B, LIN H, et al. Pyrolysis behaviors of four lignin polymers isolated from the same pine wood[J]. Bioresour Technol,2015,182:120−127. doi: 10.1016/j.biortech.2015.01.127
[2]	SHEN D, JIN W, HU J, et al. An overview on fast pyrolysis of the main constituents in lignocellulosic biomass to valued-added chemicals: Structures, pathways and interactions[J]. Renew Sustain Energy Rev,2015,51:761−774. doi: 10.1016/j.rser.2015.06.054
[3]	SHEN D, LIU G, ZHAO J, et al. Thermo-chemical conversion of lignin to aromatic compounds: Effect of lignin source and reaction temperature[J]. J Anal Appl Pyrol,2015,112:56−65. doi: 10.1016/j.jaap.2015.02.022
[4]	ZEVALLOS TORRES L A, LORENCI WOICIECHOWSKI A, DE ANDRADE TANOBE V O, et al. Lignin as a potential source of high-added value compounds: A review[J]. J Clean Prod,2020,263:1−18.
[5]	SETHUPATHY S, MURILLO MORALES G, GAO L, et al. Lignin valorization: Status, challenges and opportunities[J]. Bioresour Technol,2022,347:1−16.
[6]	DONG Z, LIU Z, ZHANG X, et al. Pyrolytic characteristics of hemicellulose, cellulose and lignin under CO₂ atmosphere[J]. Fuel,2019,256:1−9.
[7]	LIU X, BOUXIN F P, FAN J, et al. Recent advances in the catalytic depolymerization of lignin towards phenolic chemicals: A Review[J]. Chem,2020,13(17):4296−4317.
[8]	LIAO Y, KOELEWIJN S-F, VAN DEN BOSSCHE G, et al. A sustainable wood biorefinery for low-carbon footprint chemicals production[J]. Sci,2020,367(6484):1385−1390. doi: 10.1126/science.aau1567
[9]	JIA Z, JI N, DIAO X, et al. Highly selective hydrodeoxygenation of lignin to naphthenes over three-dimensional flower-like Ni₂P derived from hydrotalcite[J]. ACS Catal,2022,12(2):1338−1356. doi: 10.1021/acscatal.1c05495
[10]	WANG M, LIU M, LI H, et al. Dealkylation of lignin to phenol via oxidation–hydrogenation strategy[J]. ACS Catal,2018,8(8):6837−6843. doi: 10.1021/acscatal.8b00886
[11]	ZHAO M, ZHAO L, ZHAO X-Y, et al. Pd-based nano-catalysts promote biomass lignin conversion into value-added chemicals[J]. Mater,2023,16(14):1−13.
[12]	LUO Z, LIU C, RADU A, et al. Carbon–carbon bond cleavage for a lignin refinery[J]. Nat Chem Eng,2024,1(1):61−72. doi: 10.1038/s44286-023-00006-0
[13]	XU Q, WANG Q, XIAO L P, et al. Metal-organic framework-derived CuO catalysts for the efficient hydrogenolysis of hardwood lignin into phenolic monomers[J]. J Mater Chem A,2023,11(44):23809−23820. doi: 10.1039/D3TA04927B
[14]	SHEN Z S, WANG W, PAN L, et al. Ni₅Fe₅/Al₂O₃ catalytic hydrogenolysis of lignin: mechanism investigation and selectivity regulation[J]. Green Chem,2023,25(19):7782−7793. doi: 10.1039/D3GC01988H
[15]	WU Y, DANG Q, WU T, et al. Efficient lignin depolymerization process for phenolic products with lignin-based catalysts and mixed solvents[J]. Energy Fuels,2023,37(7):5206−5219. doi: 10.1021/acs.energyfuels.3c00063
[16]	SHEN Z S, SHI C X, LIU F, et al. Advances in heterogeneous catalysts for lignin hydrogenolysis[J]. Adv Sci,2023,11:1−24.
[17]	WANG Y, WEI L, HOU Q, et al. A Review on catalytic depolymerization of lignin towards high-value chemicals: solvent and catalyst[J]. Fermen Basel,2023,9(4):1−21.
[18]	GALE M, CAI C M, GILLIARD-ABDUL-AZIZ K L. Heterogeneous catalyst design principles for the conversion of lignin into high-value commodity fuels and chemicals[J]. Chem,2020,13(8):1947−66.
[19]	王则祥, 李航, 谢文銮, 等. 木质素基本结构、热解机理及特性研究进展[J]. 新能源进展,2020,8(1):6−14. doi: 10.3969/j.issn.2095-560X.2020.01.002 Wang Zexiang, Li Hang, Xie Wenluan, et al. Progress in the study of the basic structure, pyrolysis mechanism and properties of lignin[J]. New energy progress,2020,8(1):6−14. doi: 10.3969/j.issn.2095-560X.2020.01.002
[20]	DENG J, ZHOU C, YANG Y, et al. Visible-light-driven selective cleavage of C−C bonds in lignin model substrates using carbon nitride-supported ruthenium single-atom catalyst[J]. Chem Eng J,2023,462:1−10.
[21]	GE Y, LI Z. Application of lignin and its derivatives in adsorption of heavy metal ions in water: A Review[J]. ACS Sustain Chem Eng,2018,6(5):7181−7192. doi: 10.1021/acssuschemeng.8b01345
[22]	CHENG C, SHEN D, GU S, et al. State-of-the-art catalytic hydrogenolysis of lignin for the production of aromatic chemicals[J]. Catal Sci & Technol,2018,8(24):6275−6296.
[23]	WANG S, ZHANG K, LI H, et al. Selective hydrogenolysis of catechyl lignin into propenylcatechol over an atomically dispersed ruthenium catalyst[J]. Nat Commun,2021,12(1):1−9. doi: 10.1038/s41467-020-20314-w
[24]	GóMEZ-MONEDERO B, PILAR RUIZ M, BIMBELA F, et al. Selective depolymerization of industrial lignin-containing stillage obtained from cellulosic bioethanol processing[J]. Fuel Process Technol,2018,173:165−172. doi: 10.1016/j.fuproc.2018.01.021
[25]	KARNITSKI A, CHOI J W, SUH D J, et al. Roles of metal and acid sites in the reductive depolymerization of concentrated lignin over supported Pd catalysts[J]. Catal Today,2023,411:1−9.
[26]	CHEN L, PAN L, VAN MUYDEN A P, et al. Anchoring single platinum atoms onto nickel nanoparticles affords highly selective catalysts for lignin conversion[J]. Cell Rep Phys Sci,2021,2(9):1−10.
[27]	CHEN L, XIN J Y, NI L L, et al. Conversion of lignin model compounds under mild conditions in pseudo-homogeneous systems[J]. Green Chem,2016,18(8):2341−2352. doi: 10.1039/C5GC03121D
[28]	DONG L, LIN L, HAN X, et al. Breaking the limit of lignin monomer production via cleavage of interunit carbon-carbon linkages[J]. Chem,2019,5(6):1521−1536. doi: 10.1016/j.chempr.2019.03.007
[29]	ZHANG J, SU Z, WU Z, et al. Basic carrier promoted Pt-catalyzed hydrogenolysis of alkaline lignin[J]. Catal today,2021,365:193−198. doi: 10.1016/j.cattod.2020.06.027
[30]	JIANG M, CHEN X, WANG L, et al. Anchoring single Ni atoms on CeO₂ nanospheres as an efficient catalyst for the hydrogenolysis of lignin to aromatic monomers[J]. Fuel,2022,324:1−11.
[31]	QI Y, ZENG X Z, XIONG L Y Z, et al. Efficient conversion of lignin to alkylphenols over highly stable inverse spinel MnFe₂O₄ catalysts[J]. Fro Chem Sci Eng,2023,17(8):1085−1095. doi: 10.1007/s11705-022-2236-1
[32]	ZHANG J, TEO J, XI C, et al. A series of NiM (M = Ru, Rh, and Pd) bimetallic catalysts for effective lignin hydrogenolysis in water[J]. ACS catal,2014,4(5):1574−1583. doi: 10.1021/cs401199f
[33]	MA D, LU S, LIU X, et al. Depolymerization and hydrodeoxygenation of lignin to aromatic hydrocarbons with a Ru catalyst on a variety of Nb-based supports[J]. J catal,2019,40(4):609−617.
[34]	CHENG C, LI P, YU W, et al. Nonprecious metal/bimetallic catalytic hydrogenolysis of lignin in a mixed-solvent system[J]. ACS Sustain Chem Eng,2020,8(43):16217−16228. doi: 10.1021/acssuschemeng.0c05362
[35]	ZHU J, CHEN F, ZHANG Z, et al. M-gallate (M = Ni, Co) metal-organic framework-derived Ni/C and bimetallic Ni-Co/C catalysts for lignin conversion into monophenols[J]. ACS Sustain Chem Eng,2019,7(15):12955−12963. doi: 10.1021/acssuschemeng.9b02005
[36]	YAN B, LIN X, CHEN Z, et al. Selective production of phenolic monomers via high efficient lignin depolymerization with a carbon based nickel-iron-molybdenum carbide catalyst under mild conditions[J]. Bioresour Technol,2021,321:1−8.
[37]	LONG J X, SHU R Y, YUAN Z Q, et al. Efficient valorization of lignin depolymerization products in the present of NixMg1-xO[J]. Appl Energy,2015,157:540−545. doi: 10.1016/j.apenergy.2015.04.011
[38]	KORANYI T I, HUANG X, COUMANS A E, et al. Synergy in lignin upgrading by a combination of Cu-based mixed oxide and Ni-phosphide catalysts in supercritical ethanol[J]. ACS Sustain Chem Eng,2017,5(4):3535−3543. doi: 10.1021/acssuschemeng.7b00239
[39]	GALEBACH P H, SOEHERMAN J K, GILCHER E, et al. Production of renewable alcohols from maple wood using supercritical methanol hydrodeoxygenation in a semi-continuous flowthrough reactor[J]. Green Chem,2020,22(23):8462−8477. doi: 10.1039/D0GC03218B
[40]	MCCLELLAND D J, GALEBACH P H, MOTAGAMWALA A H, et al. Supercritical methanol depolymerization and hydrodeoxygenation of lignin and biomass over reduced copper porous metal oxides[J]. Green Chem,2019,21(11):2988−3005. doi: 10.1039/C9GC00589G
[41]	汪文静, 刘红缨, 车琳, 等. Ni/镁铝水滑石催化剂解聚木质素[J]. 化学工程,2022,50(12):6−10+16. WANG Wenjing, LIU Hongying, CHE Lin, et al. Depolymerisation of lignin by Ni/magnesium-aluminium hydrotalcite catalyst[J]. Chem Eng,2022,50(12):6−10+16.
[42]	MENG G, LAN W, ZHANG L, et al. Synergy of single atoms and lewis acid sites for efficient and selective lignin disassembly into monolignol derivatives[J]. J Am Chem Soc,2023,145(23):12884−12893. doi: 10.1021/jacs.3c04028
[43]	KIM H U, LIMARTA S O, JAE J. Depolymerization of kraft lignin over a Ru-Mg-Al-oxide catalyst[J]. Clean Technol,2021,27(2):190−197.
[44]	TOTONG S, LAOSIRIPOJANA W, LAOSIRIPOJANA N, et al. Nickel and rhenium mixed oxides-doped graphene oxide (MOs/GO) catalyst for the oxidative depolymerization of fractionated bagasse lignin[J]. Ind Eng Chem Res,2022,61(1):215−223. doi: 10.1021/acs.iecr.1c03848
[45]	ZHOU M, TANG C, XIA H, et al. Ni-based MOFs catalytic oxidative cleavage of lignin models and lignosulfonate under oxygen atmosphere[J]. Fuel,2022,320:1−9.
[46]	CHEN C, LIU P, XIA H, et al. Catalytic conversion of lignin to liquid fuels with an improved H/C-eff value over bimetallic NiMo-MOF-derived catalysts[J]. ACS Sustain chem eng,2021,9(41):13937−13952. doi: 10.1021/acssuschemeng.1c05273
[47]	GUO G, CHEN D, AHMED T, et al. Catalytic depolymerization of Kraft lignin towards liquid fuels over bifunctional molybdenum oxide based supported catalyst[J]. Fuel,2021,306:1−12.
[48]	GUO G, LI W, AHMED T, et al. Production of liquid fuels from Kraft lignin over bimetallic Ni-Mo supported on ZIF-derived porous carbon catalyst[J]. RSC Adv,2021,11(60):37932−37941. doi: 10.1039/D1RA05354J
[49]	KONG L, LIU C, GAO J, et al. Efficient and controllable alcoholysis of Kraft lignin catalyzed by porous zeolite-supported nickel-copper catalyst[J]. Bioresour Telchnol,2019,276:310−317. doi: 10.1016/j.biortech.2019.01.015
[50]	WANG Y, SONG J, BAXTER N C, et al. Synthesis of hierarchical ZSM-5 zeolites by solid-state crystallization and their catalytic properties[J]. J Catal,2017,349:53−65. doi: 10.1016/j.jcat.2017.03.005
[51]	KIM J-Y, PARK S Y, CHOI I-G, et al. Evaluation of RuxNi1-x/SBA-15 catalysts for depolymerization features of lignin macromolecule into monomeric phenols[J]. Chem Eng J,2018,336:640−648. doi: 10.1016/j.cej.2017.11.118
[52]	MENG Q, YAN J, WU R, et al. Sustainable production of benzene from lignin[J]. Nat Commun,2021,12(1):1−12. doi: 10.1038/s41467-020-20314-w
[53]	YAN J, MENG Q, SHEN X, et al. Selective valorization of lignin to phenol by direct transformation of Csp2-Csp3 and C−O bonds[J]. Sci Adv,2020,6(45):1−10.
[54]	ZHANG B, LI W, ZHANG T, et al. Study on the removal and depolymerization of lignin from corn stover through the synergistic effect of Brønsted acid, Lewis acid and hydrogenation sites[J]. Fuel,2021,305:1−9.
[55]	ZENG Z, XIE J, GUO Y, et al. Hydrogenolysis of lignin to produce aromatic monomers over FePd bimetallic catalyst supported on HZSM-5[J]. Fuel Process Technol,2021,213:1−10.
[56]	LI L, CUI M, WANG X, et al. Critical Techniques for Overcoming the Diffusion Limitations in Heterogeneously Catalytic Depolymerization of Lignin[J]. Chem,2023,16:1−13.
[57]	BAXTER N C, WANG Y X, HUANG H J, et al. Kraft lignin ethanolysis over zeolites with different acidity and pore structures for aromatics production[J]. Catal,2021,11(2):1−15.
[58]	HU Y, JIANG G, XU G, et al. Hydrogenolysis of lignin model compounds into aromatics withbimetallic Ru-Ni supported onto nitrogen-doped activated carbon catalyst[J]. Mol Catal,2017,445:316−26.
[59]	MA R, HAO W, MA X, et al. Catalytic ethanolysis of Kraft lignin into high-value small-molecular chemicals over a nanostructured -molybdenum carbide catalyst[J]. Angew Chem Int Ed,2014,53:7310−7315. doi: 10.1002/anie.201402752
[60]	LIU Z, LI H, GAO X, et al. Rational highly dispersed ruthenium for reductive catalytic fractionation of lignocellulose[J]. Nat Commun,2022,13(1):1−11. doi: 10.1038/s41467-021-27699-2
[61]	YAN B, LIN X, CHEN Z, et al. Selective production of phenolic monomers via high efficient lignin depolymerization with a carbon based nickel-iron-molybdenum carbide catalyst under mild conditions[J]. Bioresour Technol,2021,321:1−8.
[62]	XIAO L-P, WANG S, LI H, et al. Catalytic hydrogenolysis of lignins into phenolic compounds over carbon nanotube supported molybdenum oxide[J]. ACS Catal,2017,7(11):7535−7542. doi: 10.1021/acscatal.7b02563
[63]	KUMAR M M, PRABHUDESAI V S, VINU R. Lignin depolymerization to guaiacol and vanillin derivatives via catalytic transfer hydrogenolysis using Pd-Lewis metal oxide supported on activated carbon catalysts[J]. Mol Catal,2023,549:1−13.
[64]	PARK J, OH S, KIM J-Y, et al. Comparison of degradation features of lignin to phenols over Pt catalysts prepared with various forms of carbon supports[J]. RSC Adv,2016,6(21):16917−16924. doi: 10.1039/C5RA21875F
[65]	WAHYUDIONO, SASAKI M, GOTO M. Recovery of phenolic compounds through the decomposition of lignin in near and supercritical water[J]. Chem Eng Process Int,2008,47(9−10):1609−1619. doi: 10.1016/j.cep.2007.09.001
[66]	WANG D, WANG Y, LI X, et al. Lignin Valorization: A novel in situ catalytic hydrogenolysis method in alkaline aqueous solution[J]. Energy Fuels,2018,32(7):7643−7651. doi: 10.1021/acs.energyfuels.8b01032
[67]	WANG H, ZHANG L, DENG T, et al. ZnCl₂ induced catalytic conversion of softwood lignin to aromatics and hydrocarbons[J]. Green Chem,2016,18(9):2802−2810. doi: 10.1039/C5GC02967H
[68]	KHUDOSHIN A G, LUNIN V V, BOGDAN V I. Conversion of veratrole and sodium lignosulfonate in the sub- and supercritical water[J]. J Phys Chem B,2011,5(7):1069−1075.
[69]	SONG Q, WANG F, CAI J, et al. Lignin depolymerization (LDP) in alcohol over nickel-based catalysts via a fragmentation–hydrogenolysis process[J]. Energy Environ Sci,2013,6(3):994−1007. doi: 10.1039/c2ee23741e
[70]	MCVEIGH A, BOUXIN F P, JARVIS M C, et al. Catalytic depolymerisation of isolated lignin to fine chemicals: part 2-process optimisation[J]. Catal Sci Technol,2016,6(12):4142−4150. doi: 10.1039/C5CY01896J
[71]	BARTA K, MATSON T D, FETTIG M L, et al. Catalytic disassembly of an organosolv lignin via hydrogen transfer from supercritical methanol[J]. Green Chem,2010,12(9):1640−1647. doi: 10.1039/c0gc00181c
[72]	SONG Q, WANG F, CAI J, et al. Lignin depolymerization (LDP) in alcohol over nickel-based catalysts via a fragmentation–hydrogenolysis process[J]. Energy Environ Sci,2013,6(3):994−1007. doi: 10.1039/c2ee23741e
[73]	BRAND S, SUSANTI R F, KIM S K, et al. Supercritical ethanol as an enhanced medium for lignocellulosic biomass liquefaction: Influence of physical process parameters[J]. Energy,2013,59:173−82. doi: 10.1016/j.energy.2013.06.049
[74]	HUANG X M, KORáNYI T I, BOOT M D, et al. Catalytic Depolymerization of Lignin in Supercritical Ethanol[J]. Chemsuschem,2014,7(8):2276−2288. doi: 10.1002/cssc.201402094
[75]	LEE H-S, JAE J, HA J-M, et al. Hydro-and solvothermolysis of kraft lignin for maximizing production of monomeric aromatic chemicals[J]. Bioresour Technol,2016,203:142−149. doi: 10.1016/j.biortech.2015.12.022
[76]	KONG X, LIU C, XU W, et al. Catalytic hydroprocessing of stubborn lignin in supercritical methanol with Cu/CuMgAlOx catalyst[J]. Fuel Process Technol,2021,218:1−11.
[77]	KUMAR M M, PRABHUDESAI V S, VINU R. Lignin depolymerization to guaiacol and vanillin derivatives via catalytic transfer hydrogenolysis using Pd-Lewis metal oxide supported on activated carbon catalysts[J]. Mol Catal,2023,549:1−11.
[78]	MCVEIGH A, BOUXIN F P, JARVIS M C, et al. Catalytic depolymerisation of isolated lignin to fine chemicals: part 2 – process optimisation[J]. Catal Sci Technol,2016,6(12):4142−4150. doi: 10.1039/C5CY01896J
[79]	CHEN J, WANG D, LU X, et al. Effect of cobalt(II) on acid-modified attapulgite-supported catalysts on the depolymerization of Alkali lignin[J]. Ind Eng Chem Res,2022,61(4):1675−1683. doi: 10.1021/acs.iecr.1c04695
[80]	YANG Z, FENG J, CHENG H, et al. Directional depolymerization of lignin into high added-value chemical with synergistic effect of binary solvents[J]. Bioresour Technol,2021,321:1−7.
[81]	ZAKZESKI J, JONGERIUS A L, BRUIJNINCX P C A, et al. Catalytic lignin valorization process for the production of aromatic chemicals and hydrogen[J]. Chemsuschem,2012,5(8):1602−1609. doi: 10.1002/cssc.201100699
[82]	WU Y, DANG Q, WU T, et al. Efficient lignin depolymerization process for phenolic products with lignin-based catalysts and mixed solvents[J]. Energy Fuels,2023,37(7):5206−5219 doi: 10.1021/acs.energyfuels.3c00063
[83]	QIN Y, WANG D, CHEN J, et al. Selective depolymerization of lignin into phenolic products over Ni_xZn_{1- x}/ZrO₂-MgO [J]. Biomass Conver Bioref, 2022, 1−17.
[84]	SHEN C, LI W, ZHANG B, et al. Valorization of lignin in native corn stover via fractionation-hydrogenolysis process over cobalt-supported catalyst without external hydrogen[J]. Mol Catal,2021,514:1−11.
[85]	GUVENATAM B, HEERES E H J, PIDKO E A, et al. Lewis acid-catalyzed depolymerization of soda lignin in supercritical ethanol/water mixtures[J]. Catal Today,2016,269:9−20. doi: 10.1016/j.cattod.2015.08.039
[86]	JOFFRES B, NGUYEN M T, LAURENTI D, et al. Lignin hydroconversion on MoS2-based supported catalyst: comprehensive analysis of products and reaction scheme[J]. Appl Catal B-Environ,2016,184:153−162. doi: 10.1016/j.apcatb.2015.11.005
[87]	SHAO Y, XIA Q, DONG L, et al. Selective production of arenes via direct lignin upgrading over a niobium-based catalyst[J]. Nat Commun,2017,8:1−9. doi: 10.1038/s41467-016-0009-6
[88]	LONG J, ZHANG Q, WANG T, et al. An efficient and economical process for lignin depolymerization in biomass-derived solvent tetrahydrofuran[J]. Bioresour Technol,2014,154:10−17. doi: 10.1016/j.biortech.2013.12.020
[89]	THI DIEU HUYEN N, MASCHIETTI M, AMAND L-E, et al. The effect of temperature on the catalytic conversion of Kraft lignin using near-critical water[J]. Bioresour Technol,2014,170:196−203. doi: 10.1016/j.biortech.2014.06.051
[90]	SONG W, LAI W, LIAN Y, et al. Sulfated ZrO₂ supported CoMo sulfide catalyst by surface exsolution for enhanced hydrodeoxygenation of lignin-derived ethers to aromatics[J]. Fuel,2020,263:1−10.
[91]	HUANG Y-B, ZHANG J-L, ZHANG X, et al. Catalytic depolymerization of lignin via transfer hydrogenation strategy over skeletal CuZnAl catalyst[J]. Fuel Process Technol,2022,237:1−13.
[92]	LI Y W, CAI Z P, LIAO M C, et al. Catalytic depolymerization of organosolv sugarcane bagasse lignin in cooperative ionic liquid pairs[J]. Catal Today,2017,298:168−174. doi: 10.1016/j.cattod.2017.04.059
[93]	DIAS R M, PETRIN L C G, H. B. SOSA F, et al. Investigation of Kraft lignin solubility in protic ionic liquids and their aqueous solutions[J]. Ind Eng Chem Res,2020,59(40):18193−18202. doi: 10.1021/acs.iecr.0c02605
[94]	PENG M M, NAKABAYASHI M, KIM K, et al. Lignin depolymerization with alkaline ionic liquids and ethylene glycol in a continuous flow reactor[J]. Fuel,2023,335:1−10.
[95]	LI W, WANG Y, LI D, et al. 1-Ethyl-3-methylimidazolium acetate ionic liquid as simple and efficient catalytic system for the oxidative depolymerization of alkali lignin[J]. Int J Biol Macro,2021,183:285−294. doi: 10.1016/j.ijbiomac.2021.04.118
[96]	GAO H, WANG J, LIU M, et al. Enhanced oxidative depolymerization of lignin in cooperative imidazolium-based ionic liquid binary mixtures[J]. Bioresour Technol,2022,357:1−9.
[97]	JI Q, YU X, CHEN L, et al. Comprehensive depolymerization of lignin from lignocellulosic biomass: A review[J]. Crit Rev Environ Sci Technol,2023,53(21):1866−1887. doi: 10.1080/10643389.2023.2190314
[98]	LI P H, LI X Y, JIANG Z W, et al. Mild depolymerization of alkaline lignin in a formic acid-choline chloride type deep eutectic solvent system[J]. Holzforschung,2023,77(3):149−158. doi: 10.1515/hf-2022-0145
[99]	SOSA F H B, BJELIC A, COUTINHO J A P, et al. Conversion of organosolv and Kraft lignins into value-added compounds assisted by an acidic deep eutectic solvent[J]. Sustain Energy Fuels,2022,6(20):4800−4815. doi: 10.1039/D2SE00859A
[100]	HONG S, SHEN X-J, PANG B, et al. In-depth interpretation of the structural changes of lignin and formation of diketones during acidic deep eutectic solvent pretreatment[J]. Green Chem,2020,22(6):1851−1858. doi: 10.1039/D0GC00006J
[101]	LI Z M, LONG J X, ZENG Q, et al. Production of methyl-hydroxycinnamate by selective tailoring of herbaceous lignin using metal-based deep eutectic solvents (DES) as catalyst[J]. Ind Eng Chem Res,2020,59(39):17328−17337. doi: 10.1021/acs.iecr.0c01307
[102]	YU Q, SONG Z L, CHEN X Y, et al. A methanol-choline chloride based deep eutectic solvent enhances the catalytic oxidation of lignin into acetovanillone and acetic acid[J]. Green Chem,2020,22(19):6415−6423. doi: 10.1039/D0GC02189J