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Article

Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics

by
Zhichang Liu
1,2,3,
Ziwei Wang
1,2,3,
Yichen Li
1,2,3,
Wanxia Wang
1,2,3,
Xiongbin Liu
1,2,3,
Hao Shu
1,2,3 and
Jungang Jiang
4,*
1
China Tobacco Hubei Industrial Co., Ltd., Wuhan 430040, China
2
Hubei Xinye Reconstituted Tobacco Development Co., Ltd., Wuhan 430056, China
3
Applied Technology Research of Reconstituted Tobacco Hubei Province Key Laboratory, Wuhan 430040, China
4
Hubei Provincial Key Laboratory of Green Materials for Light Industry, Hubei University of Technology, Wuhan 430068, China
*
Author to whom correspondence should be addressed.
Catalysts 2024, 14(11), 744; https://doi.org/10.3390/catal14110744
Submission received: 5 September 2024 / Revised: 9 October 2024 / Accepted: 15 October 2024 / Published: 23 October 2024
(This article belongs to the Special Issue Catalytic Conversion and Utilization of Biomass)
Browse Figures
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Abstract

:
Uncovering the structure of lignin from biorefinery has an important effect on lignin catalytic depolymerization and the production of bioenergy. In this study, two biorefinery lignins were isolated from tobacco stalks via alkaline and deep eutectic solvent (DES) catalyzed delignification processes, and the lignin heterogeneity structural characteristics were elucidated by gel permeation chromatography, 2D-HSQC, FT-IR, etc., to understand the relationship between the structure and the thermal characteristics of lignin. It was found that the lignins presented various structural characteristics and components, in which the predominant interunit linkages of black liquor lignin are β-O-4 and β-β linkages, and the β-O-4 linkages disappeared by DES treatment. DES lignins exhibited lower molecular weights and yields than black liquor lignin. Thermogravimetric analysis and fixed-bed pyrolysis were also performed to investigate the lignin thermal behavior. The results show that the DES approach can improve the bio-oil production from lignin and highlight the potential of DES lignin as a promising feedstock in the lignin pyrolysis process. This work provides a valuable example of the conversion of biorefinery lignin into pyrolysis products.

Graphical Abstract

1. Introduction

The growing desire for green energy, materials, and chemicals is strongly promoting the exploration of sustainable bioresources instead of fossil resources [1,2]. In order to tackle the urgent issues of feedstock supplementation and environmental impacts, the utilization of biomass resources is crucial for the sustainable development of green energy conversion [3,4]. Among them, lignocelluloses composed of cellulose, hemicellulose, and lignin are easily available feedstocks that can achieve various value-added products with a low carbon footprint [5]. In particular, lignin, with a unique aromatic structure, is a renewable and abundant source on the earth that possesses a higher energy density than hemicellulose and cellulose. Furthermore, due to its specific aromatic skeleton, lignin can also serve as a promising feedstock for platform chemicals, bioenergy, and biomaterials [6,7,8,9].
Tobacco is widely cultivated in many countries, especially in China. According to the WHO, China has more than 106 hectares of land under tobacco, meaning that it is the largest tobacco plantation country in the world [10]. However, because only tobacco leaves are used, a large amount of tobacco stalks become agricultural waste, which leads to serious environmental concerns. Even burning these residues produces sharp odors, and the chemicals in the smoke harm human health. Presently, many strategies have been used for tobacco stalk fractionation towards its utilization, for example, alkaline extraction, acid pretreatment, hydrothermal or ionic liquid pretreatment, which is based on biomass refining, subcritical water extraction, etc. [11,12]. However, these technologies have not been widely applied owing to their produced manner and environmental issues. Recently, with the increasing desire for green chemistry and sustainability, DES as an emerging green solvent has been selected to extract lignin from lignocelluloses and develop sustainable biorefinery [13,14,15]. DES is synthesized by hydrogen bond donor and hydrogen bond acceptor and shows eco-friendly, economical, and sustainable features, which have been widely used in dissolving and extracting lignin [15,16]. For example, Wang et al. used phosphotungstic acid-assisted DES to isolate tobacco stalk lignin and revealed its structure [17]. Chen et al. used a diol DES system to isolate the bamboo lignin and reveal its structure evolution [18]. Wu et al. used acidic DES to fabricate lignin nanoparticles from Camellia Oleifera shell with in-depth structural characterization [19]. In regard to the methods of isolating lignin after the above treatment, however, most of them are focused on the lignin structure’s characterization; there are less investigations into its utilization. It has been reported that lignin depolymerization is deemed to be an effective and viable strategy for its valorization due to the occurrence of labile linkages within lignin under high temperatures [20]. Among those depolymerization technologies, pyrolysis, an efficient thermochemical process that can depolymerize lignin mainly into bio-oil products, has been regarded as one of the most promising technologies [21,22,23]. The distribution and yield of pyrolysis products are significantly influenced by the macromolecular structures of lignin, which is a non-negligible matter for lignin-tailored utilization. In addition, it has been reported that DES treatment can obtain lignin with a low molecular weight and minor amounts of linkages such as β-O-4, which may improve the subsequent pyrolysis efficiency of lignin [16,24,25]. Based on the sources, isolation methods, and structures of lignin macromolecules, various phenol monomers can be obtained at different pyrolysis conditions [23,26,27,28]. For instance, the methyl, oxypropyl, and acetyl groups in lignin can obviously restrain the adverse effects of lignin oxygen-containing functional groups during the pyrolysis process, improving the bio-oil yield and aromatic monomers’ selectivity [29,30,31]. Researchers have conducted a lot of lignin pyrolysis work; however, scant attention has been paid to exploring the correlation between DES lignin and subsequent lignin pyrolysis behavior, which is directly connected with lignin valorization. Therefore, exploring the pyrolysis properties of lignin which is isolated from viable strategies is necessary for optimizing tobacco stalk fractionation strategies.
Hence, in this study, three typical tobacco lignins were isolated from tobacco stalks via different methods, including the black liquor lignin (BL) from the soda–anthraquinone (AQ) cooking of tobacco stalk and DES-extracted lignin. A previous study by Wang et al. shows that the DES pretreatment with Lewis acids can promote a delignification ratio from 5% to 91%; in this study, AlCl3 as the catalyst was added [32]. The structural characteristics of the isolated lignin were explored by GPC, 2D-HSQC, and FT-IR. The thermal properties and pyrolysis products of the lignin were also analyzed to reveal the correlation between structure and pyrolysis behavior. It is believed that a more detailed elucidation of biorefinery lignin structure will promote the rational design for lignin pyrolysis and conversion into valuable phenolic compounds.

2. Results and Discussion

2.1. Yields and Molecular Weight of Lignin Samples

Figure 1 lists the yields and molecular weight of the lignin fractions. BL showed the highest yield (78.5%) among the isolated lignin samples, which mainly originated from the effective delignification under the given cooking conditions. When it comes to the DES lignin samples, lower lignin yields were observed and varied with the adopted DES systems. The yields of DLE and DLG were 55.4% and 48.6%, respectively. This result is attributed to the limitations in the DES mass transfer, lignin dissolving ability, delignification mechanism, reaction cancelations, etc. However, even the DES lignin showed inferior yields when compared with that of BL from traditional alkaline delignification; as a relatively green solvent, it is still crucial to explore the unique structural and functional characteristics of DES lignin for its conversion.
The relative molecular weights of these lignin samples have been determined by the GPC technique (Figure 1). Comparatively, BL that recovered from the alkaline solvent contained a higher molecular weight and relatively complete structure than those of acidic DES fractioned lignins. In detail, BL showed a relatively higher molecular weight (2420 g/mol) as compared with DES lignin samples; the molecular weight of DLE is 1410 g/mol, which was slightly higher than that of DLG (1320 g/mol). This phenomenon could be ascribed to the fact that an alkaline environment can swell up the cell wall and further facilitate the isolation of lignin from lignocellulose, while the acidic condition would promote the protonation reaction of lignin macromolecules and result in an obvious depolymerization and recondensation reaction [33]. In addition, the PDI of all the recovered DES lignin samples exhibited notably narrow values (1.5 and 1.6) when compared with BL (3.0). This implied that these lignin fractions were more homogenous, which demonstrated great potential to fabricate various lignin-based products, such as lignin-derived functional or nanomaterials [7,34].

D-HSQC NMR Spectra of Lignin Samples

Lignin with well-characterized structures is a vital prerequisite for its value-added conversion in the biorefinery, such as thermochemical conversion and functional materials’ production [35]. In this study, the advanced 2D-HSQC NMR spectra were applied to investigate the chemical structural characteristics of lignin, such as interunit linkages, during different deconstructions [36]. Figure 2 presents the 2D-HSQC spectra of these lignin samples from diverse processes, and the abundances of the main structural units or linkages are listed in Table 1.
The 2D-HSQC NMR spectra of lignins are divided into two regions: the aliphatic-oxygenated region (δC/δH 50–100/2.4–5.5), including the information of lignin side chain linkages, and the aromatic region (δC/δH 100–140/6.0–8.0), including the abundance of lignin units. As shown in Figure 2, BL showed relatively integrated structures compared with the others, which contained β-O-4 (A) and resinol (B, β-β) with different correlations (e.g., Aα, Aβ, Aγ, Bα, Bβ, Bγ). This result is mostly related to the effective swelling and dissolution of lignin in the alkaline solvent that could protect the native structure from destruction under the given conditions [37]. In contrast, lignin from the DES deconstruction of the tobacco stalk exhibited significant depolymerized and condensed structures (Figure 2), in which the main β-O-4 linkages disappeared in the side chain region, indicating that the recalcitrance of the tobacco stalk was effectively disrupted [38,39]. For the aromatic region of lignin, it was found that the main structural units of lignin were syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) and can be clearly identified in the aromatic region. This finding suggested that the tobacco stalk lignin skeleton resembles the gramineous lignin that consists of S, G, and H units [38]. In addition, S and G units resulted in obvious condensed signals occurring in the spectra and presented weakened abundances in the aromatic region of these acidic DES lignins, which was coincidently in line with the findings of the previous study [19]. It was reported that the cleavage of β-O-4 is normally together with the condensation reaction of lignin under acidic conditions, which is mostly owing to the nucleophilic attack by electron-rich aromatic rings [40]. In Table 1, it was also noted that the C-C linkage β-β also presented a decreased tendency after DES treatment, and this could be explained by their depolymerized structures. Furthermore, the acidic DES lignin also contains abundant hydroxyl functional groups and a lower molecular weight that will remarkably promote its valorization [41].

2.2. FT-IR Spectra Element Analysis of Lignin Samples

FT-IR spectra can reflect the molecular structures of lignin, such as the variation in functional groups and relative linkage abundances. The FT-IR spectra of these lignin samples obtained in this study are presented in Figure 3. Evidently, the remarkable peaks that occurred in 3600–3200 cm−1 were assigned to be the -OH stretch, and the obvious signal peaks at 2800–3000 cm−1 were assigned to be for the methyl and methylene groups of the lignins. Next, the absorption peaks at 1603, 1510, and 1465 cm−1 could be attributed to the aromatic ring vibration and methyl deformation of lignin [12,42,43]. Then, the peaks ranging from 1300 cm−1 to 1050 cm−1 were attributed to the vibration absorption of the aromatic ring in lignin, in which the signal absorption peak located around 1150 cm−1 belongs to stretching vibrations of C–C(= O)–O [44]. In practice, lignin was effectively disrupted and would show a lower molecular weight and expose more functional groups, which also facilitated lignin valorization, such as pyrolysis [28]. Diverse chemical reactions occurred in lignin macromolecule under given conditions, in which significant depolymerization and condensation of lignin could be observed in the obtained acidic DES lignin.

2.3. Thermal Stability of Lignin Samples

Structural characteristics have a significant impact on lignin thermal properties, and exploring the thermal stability of lignin is crucial for its subsequent conversion into functional or carbon materials and monomeric phenolic compounds [22,23,45]. Therefore, thermogravimetric analysis (TGA) was applied to analyze all the lignin samples to elucidate the correlation between structural characteristics and thermal stability. Figure 4 shows the TG/DTG curves of the lignins, and Table 2 lists the max degradation temperature (Tmax) and the residual carbon from the lignin samples.
The thermal behavior of different lignins was influenced by their inherent structures, such as the abundance of chemical linkages and functional groups, and the degree of condensation. Firstly, the weight reduction in lignins before 200 °C was observed owing to the dehydration of the lignin. Then, the weak or labile linkages were disrupted in these lignin samples and an obvious decrease in lignin weight was observed [29,30]. It is worth noting that the DES lignin shows Tmax peaks at a temperature of around 260 °C, which is probably from the not-removed DES [46]. When the temperature increased up to 350 °C, severe mass loss of lignins occurred, which could be attributed to the side chain oxidation of lignin under harsh temperatures. Next, the mass loss of lignins was mild, with the temperature being further elevated than the former stages because of the C–C bonds and the fact that the aromatic ring collapsed and sedimented into residual char. It could be found that BL showed a relatively high content of residual char (up to 42%) and Tmax; these results can be explained by the unremoved impurities in the DES lignins, as mentioned above. Another possible reason could be caused by its prominent molecular weight among the DES lignins. The thermostability of lignin is the result of various factors and comprehensive action.

2.4. Pyrolytic Products from Biorefinery Lignin

The internal bonds in the lignin macromolecule were thermally unstable and can be pyrolyzed under high temperatures, such as 600 °C (Figure 4). Therefore, the rapid pyrolysis experiment of these lignin samples was performed at 600 °C, and pyrolysis oil (bio-oil) was also collected [47]. Figure 5a displays the acetone dissolved bio-oil samples, and the effects of different lignin isolation processes on lignin pyrolysis gas, pyrolysis oil, and pyrolysis coke are shown in Figure 5b.
It can be seen that about 33% of the lignin is converted into coke. Compared with BL bio-char, the yield of bio-char from DES-extracted lignin decreased slightly. In addition, the result of the bio-char yield is consistent with the thermogravimetric analysis. The formation of bio-char is because the lignin pyrolysis process is hydrogen-deficient, the aromatic ring-positive ions are generated by pyrolysis, and the lack of hydrogen radical binding leads to the polymerization of lignin to macromolecules between the aromatic rings. The experimental results also display that the bio-oil yield from biorefinery lignin increased from BL to DL lignin, and the choline chloride–glycerol system-extracted lignin has the highest bio-oil yield, which also has the lowest bio-gas production yield. It should be stressed that the estimation of bio-oil production presented here shows that the choline chloride–glycerol DES approach is a preferable method for improving the bio-oil production from lignin, which is of vital importance to the feasibility of lignin valorization.

3. Materials and Method

3.1. Materials

The annual herb tobacco stalks (Flue-cured tobacco, Xuchang, China) were kindly supplied by the Zhengzhou Tobacco Research Institute of CNTC (Zhengzhou, China). Tobacco stalks were ground to 40–60 mesh and extracted in a Soxhlet extractor with ethanol/toluene (1:2, v/v) for 6 h before use. The temperature was set at around 95 °C to ensure that the extraction could be conducted six times per hour. The chemical compositions of the stalk are cellulose (38.1 wt%), hemicelluloses (22.5 wt%), and lignin (23.5 wt%), as we detected before [38]. Choline chloride (ChCl), ethylene glycol (EG), glycerol (Gly), aluminum chloride hexahydrate (AlCl3·6H2O), acetone (analytical grade), and sodium hydroxide (NaOH) were purchased from Sigma Chemical Co., Ltd. (Saint Louis, MO, USA).

3.2. Deep Eutectic Solvents (DESs) Preparation

Two types of DESs were prepared: generally, 1 mol ChCl and 2 mol EG (or Gly) were mixed first to achieve a high delignification ratio, and then 0.1 mol AlCl3·6H2O as a catalyst was added subsequently. Then, the mixtures were continually stirred to be a clear liquid at 80 °C for 1 h, and then the prepared DES was transferred into the dry reagent bottle prior to subsequent use.

3.3. Lignin Isolation by Alkali or DES Extraction

All the lignin isolation procedures from tobacco stalks are presented in Figure 6.
BL lignin: The black liquor lignin from tobacco stalk was extracted by the soda-AQ pulping process in a high-pressure reactor with magnetic stirring: cooking at 160 °C with a solid-to-liquid ratio of 1:5 (weight/volume) for 1 h, and the dosages of NaOH and AQ were 16% and 0.5%, respectively (based on dried tobacco stalks) [48]. The black lignin was precipitated from the black liquor by adjusting the pH to 2 with HCl; after washing three times with acid water (pH = 2 adjusted with HCl), the lignin was freeze-dried for further utilization.
DES lignin: Lignin was extracted by mixing tobacco stalk powder and DES at a weight ratio of 1:10 in a 50 mL round-bottom flask. After the full shake-up of the mixture, the flask was heated in an oil bath at 120 °C and kept for 4 h to obtain raw tobacco stalk. Once the desired time was reached, ethanol/deionized water (50 mL, 1:1 v/v) solvent was poured into the resultant mixture to transfer the mixture into a glass beaker. The mixture was vacuum-filtered and washed with the same ethanol solvent three times to remove the residual DES. After the removal of ethanol by a rotary evaporator, the DES lignins were recovered and subjected to centrifugation and lyophilization, which were named DLE (Lignin isolated by ChCl/EG DES) and DLG (Lignin isolated by ChCl/Gly DES), respectively.
The polysaccharide in the isolated lignin was further detected at 3.7%, 1.6%, and 2.9% for BL, DLE, and DLG, respectively. The lignin yield was calculated based on the weight percentage of the original lignin in the tobacco stalk.

3.4. Structural Characterization

The chemical composition of tobacco stalk powder was determined according to the National Renewable Energy Laboratory (NREL) method [49]. Agilent 1200 gel permeation chromatography, which is equipped with a UV detector and Styragel Column (Waters, Milford, MA, USA, HR 4E DMF, 7.8 mm × 300 mm), was used to measure the lignin molecular weights (without acetylation); the DMF (with 0.1 mol//L LiCl) was used as the mobile phase with a flowthrough of 1 mL/min at a temperature of 50 °C. Fourier-transform infrared spectroscopy (FT-IR, Thermo NICLET 6700, Waltham, MA, USA) and two-dimensional heteronuclear single-quantum coherence (2D-HSQC) NMR spectra were used. Thermal stability analysis was conducted with a thermal analyzer (DTG-60, Shimadzu, Tokyo, Japan); about 5 mg of lignin powder was placed in an alumina crucible in the N2 atmosphere, where the heating rate was 10 °C/min [23].

3.5. Fixed-Bed Pyrolysis of Lignin Samples

First, the temperature of the tube furnace was increased to 600 °C, and the high-purity N2 (99.99%) was aerated with a flow rate of 500 mL/min for 5 min to ensure that the tube was in an oxygen-free atmosphere, and then the flow rate of N2 was reduced to 200 mL/min for 2 min. The sample (0.5 g) was placed in a quartz hanging basket with quartz cotton at the bottom, and the hanging basket was quickly placed in the heating area of the tube furnace. The lower outlet of the tube is connected to the condensing pipe placed in the ice-water bath to collect the bio-oil. The pyrolysis reaction continued for 30 min. After that, the whole quartz tube was taken out and placed at room temperature, and the condensate tube used to collect the bio-oil was removed. The bio-oil was collected by washing the condensate tube with acetone. The bio-char and bio-oil yield were calculated based on their weight ratio to the feedstock. The gas yields were calculated based on the mass balance:
Gas yields = (WR − WC − WO)/WR × 100%
where WR is the weight of the raw stock, WC is the weight of bio-char, and WO is the weight of bio-oil.

4. Conclusions

In this study, different biorefinery lignins were isolated from alkaline cooking and deep eutectic solvent (DES) delignification processes. The lignin structural characteristics were revealed by GPC, FT-IR, and 2D-HSQC analysis and further subjected to pyrolysis. The results showed that these lignins presented depolymerized structures and changed skeleton components, in which DES lignins exhibited lower molecular weights and yields than black liquor lignin (BL). The predominant interunit linkages for black liquor lignin are β-O-4 and β-β linkages; however, the β-O-4 linkages disappeared after DES treatment. Moreover, the lignin thermal behavior results pointed out that the DES approach is a preferable method for improving the bio-oil production from lignin, in which the bio-oil yield is increased by around 22% compared with the BL lignin pyrolysis bio-oil yield.

Author Contributions

Conceptualization and writing: J.J.; resources, formal analysis, and investigation: Z.L., Z.W. and Y.L.; software, visualization, and validation: W.W., X.L. and H.S.; project administration, J.J. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Doctoral Research Start-up Fund from Hubei University of Technology [XJ2021001802]; Hubei Provincial Key Laboratory of Green Materials for Light Industry Open Fund [XJKY20220026].

Data Availability Statement

Data will be made available on request.

Conflicts of Interest

Z.L., Z.W., Y.L., W.W., X.L. and H.S. were employed by China Tobacco Hubei Industrial Co., Ltd. The remaining authors declare that this research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.

References

  1. Sherwood, J. The significance of biomass in a circular economy. Bioresour. Technol. 2020, 300, 122755. [Google Scholar] [CrossRef] [PubMed]
  2. Jiang, J.; Fu, J.; An, N.; Zhang, Y.; Chen, X.; Wang, L. Rapid and effective molten oxalic acid dihydrate pretreatment to enhance enzymatic saccharification for biohydrogen production by efficient coextraction of lignin and hemicellulose in wheat straw. Chem. Eng. J. 2023, 475, 146422. [Google Scholar] [CrossRef]
  3. Ragauskas, A.J.; Williams, C.K.; Davison, B.H.; Britovsek, G.; Cairney, J.; Eckert, C.A.; Frederick Jr, W.J.; Hallett, J.P.; Leak, D.J.; Liotta, C.L. The path forward for biofuels and biomaterials. Science 2006, 311, 484–489. [Google Scholar] [CrossRef] [PubMed]
  4. Wang, B.; Wang, S.-F.; Lam, S.S.; Sonne, C.; Yuan, T.-Q.; Song, G.-Y.; Sun, R.-C. A review on production of lignin-based flocculants: Sustainable feedstock and low carbon footprint applications. Renew. Sustain. Energy Rev. 2020, 134, 110384. [Google Scholar] [CrossRef]
  5. Alonso, D.M.; Hakim, S.H.; Zhou, S.; Won, W.; Hosseinaei, O.; Tao, J.; Garcia-Negron, V.; Motagamwala, A.H.; Mellmer, M.A.; Huang, K. Increasing the revenue from lignocellulosic biomass: Maximizing feedstock utilization. Sci. Adv. 2017, 3, e1603301. [Google Scholar] [CrossRef]
  6. Cui, H.; Jiang, W.; Wang, C.; Ji, X.; Liu, Y.; Yang, G.; Chen, J.; Lyu, G.; Ni, Y. Lignin nanofiller-reinforced composites hydrogels with long-lasting adhesiveness, toughness, excellent self-healing, conducting, ultraviolet-blocking and antibacterial properties. Compos. Part B 2021, 225, 109316. [Google Scholar] [CrossRef]
  7. Wang, H.M.; Yuan, T.Q.; Song, G.Y.; Sun, R.C. Advanced and versatile lignin-derived biodegradable composite film materials toward a sustainable world. Green Chem. 2021, 23, 3790–3817. [Google Scholar] [CrossRef]
  8. Wang, B.; Wang, J.; Hu, Z.; Zhu, A.-L.; Shen, X.; Cao, X.; Wen, J.-L.; Yuan, T.-Q. Harnessing Renewable Lignocellulosic Potential for Sustainable Wastewater Purification. Research 2024, 7, 0347. [Google Scholar] [CrossRef]
  9. Shen, X.; Wen, J.-L.; Huang, C.; Ragauskas, A.J.; Zhang, C. Genetic engineering, pretreatment, thermochemical, and biochemconversion for lignocellulose valorization. Front. Bioeng. Biotechnol. 2023, 11, 1265271. [Google Scholar] [CrossRef]
  10. FAOSTAT. 2021. Available online: https://www.who.int/campaigns/world-no-tobacco-day/2023/top-50-tobacco-growing-countries (accessed on 25 May 2023).
  11. Hu, N.; Liu, X.; Wei, S.; Yao, J.; Wang, W.; Liu, B.; Tang, T.; Jiang, J.; Wang, L. Current status and future prospects of pretreatment for tobacco stalk lignocellulose. Front. Bioeng. Biotechnol. 2024, 12, 1465419. [Google Scholar] [CrossRef]
  12. Jiang, J.; Zhu, Y.; Zargar, S.; Wu, J.; Oguzlu, H.; Baldelli, A.; Yu, Z.; Saddler, J.; Sun, R.; Tu, Q.; et al. Rapid, high-yield production of lignin-containing cellulose nanocrystals using recyclable oxalic acid dihydrate. Ind. Crops Prod. 2021, 173, 114148. [Google Scholar] [CrossRef]
  13. Chen, Z.; Bai, X.; Wan, C. High-solid lignocellulose processing enabled by natural deep eutectic solvent for lignin extraction and industrially relevant production of renewable chemicals. ACS Sustain. Chem. Eng. 2018, 6, 12205–12216. [Google Scholar] [CrossRef]
  14. Ma, C.Y.; Peng, X.P.; Sun, S.; Wen, J.L.; Yuan, T.Q. Short-time deep eutectic solvents pretreatment enhanced production of fermentable sugars and tailored lignin nanoparticles from abaca. Int. J. Biol. Macromol. 2021, 192, 417–425. [Google Scholar] [CrossRef] [PubMed]
  15. Zhou, J.; Wu, S.; Liu, Y. Structural changes of poplar lignin during the ternary deep eutectic solvent (DES) treatment and synergetic alkali-DES treatment. Ind. Crops Prod. 2024, 208, 117782. [Google Scholar] [CrossRef]
  16. Li, T.; Yin, Y.; Wu, S.; Du, X. Effect of deep eutectic solvents-regulated lignin structure on subsequent pyrolysis products selectivity. Bioresour. Technol. 2022, 343, 126120. [Google Scholar] [CrossRef]
  17. Wang, L.; Li, X.; Jiang, J.; Zhang, Y.; Bi, S.; Wang, H.-M. Revealing structural and functional specificity of lignin from tobacco stalk during deep eutectic solvents deconstruction aiming to targeted valorization. Ind. Crops Prod. 2022, 180, 114696. [Google Scholar] [CrossRef]
  18. Cheng, J.; Huang, C.; Zhan, Y.; Han, S.; Wang, J.; Meng, X.; Yoo, C.G.; Fang, G.; Ragauskas, A.J. Effective biomass fractionation and lignin stabilization using a diol DES system. Chem. Eng. J. 2022, 443, 136395. [Google Scholar] [CrossRef]
  19. Wu, Y.; Xie, M.; Liu, X.; Qiu, S.; Zeng, W.; Jiang, Z.; Liu, R.; Xiao, Z.; Li, C.; Zhang, Y. Structural characterization of lignin fractionated by acidic deep eutectic solvents and fabrication of lignin nanoparticles from Camellia Oleifera shell. Ind. Crops Prod. 2024, 210, 118018. [Google Scholar] [CrossRef]
  20. Leng, E.; Guo, Y.; Chen, J.; Liu, S.; Jiaqiang, E.; Xue, Y. A comprehensive review on lignin pyrolysis: Mechanism, modeling and the effects of inherent metals in biomass. Fuel 2022, 309, 122102. [Google Scholar] [CrossRef]
  21. Chen, W.-H.; Wang, C.-W.; Ong, H.C.; Show, P.L.; Hsieh, T.-H. Torrefaction, pyrolysis and two-stage thermodegradation of hemicellulose, cellulose and lignin. Fuel 2019, 258, 116168. [Google Scholar] [CrossRef]
  22. Hu, J.; Wu, S.; Jiang, X.; Xiao, R. Structure-reactivity relationship in fast pyrolysis of lignin into monomeric phenolic compounds. Energy Fuels 2018, 32, 1843–1850. [Google Scholar] [CrossRef]
  23. Wang, H.M.; Sun, Y.C.; Wang, B.; Sun, D.; Shi, Q.; Zheng, L.; Wang, S.F.; Liu, S.-J.; Xia, R.R.; Sun, R.C. Insights into the structural changes and potentials of lignin from bagasse during the integrated delignification process. ACS Sustain. Chem. Eng. 2019, 7, 13886–13897. [Google Scholar] [CrossRef]
  24. Kim, J.-Y.; Choi, J.W. Effect of molecular size of lignin on the formation of aromatic hydrocarbon during zeolite catalyzed pyrolysis. Fuel 2019, 240, 92–100. [Google Scholar] [CrossRef]
  25. Xu, X.; Chen, R.; Pan, R.; Zhang, D. Pyrolysis kinetics, thermodynamics, and volatiles of representative pine wood with thermogravimetry-Fourier transform infrared analysis. Energy Fuels 2020, 34, 1859–1869. [Google Scholar] [CrossRef]
  26. Park, S.; Jae, J.; Farooq, A.; Kwon, E.E.; Park, E.D.; Ha, J.-M.; Jung, S.-C.; Park, Y.-K. Continuous pyrolysis of organosolv lignin and application of biochar on gasification of high density polyethylene. Appl. Energy 2019, 255, 113801. [Google Scholar] [CrossRef]
  27. Yang, H.; Gong, M.; Chen, W.; Fang, Y.; Chen, Y.; Wang, X.; Chen, H. Lignin pyrolysis under NH3 atmosphere for 4-vinylphenol product: An experimental and theoretical study. Fuel 2021, 297, 120776. [Google Scholar] [CrossRef]
  28. Yuan, J.M.; Li, H.; Xiao, L.P.; Wang, T.P.; Ren, W.F.; Lu, Q.; Sun, R.C. Valorization of lignin into phenolic compounds via fast pyrolysis: Impact of lignin structure. Fuel 2022, 319, 123758. [Google Scholar] [CrossRef]
  29. Li, T.; Ma, H.; Wu, S.; Yin, Y. Effect of highly selective oxypropylation of phenolic hydroxyl groups on subsequent lignin pyrolysis: Toward the lignin valorization. Energy Convers. Manage. 2020, 207, 112551. [Google Scholar] [CrossRef]
  30. Li, T.; Yin, Y.; Wu, S.; Ma, H.; Zhang, F. Effect of pre-acetylation of hydroxyl functional groups by choline chloride/acetic anhydride on subsequent lignin pyrolysis. Bioresour. Technol. 2020, 317, 124034. [Google Scholar] [CrossRef]
  31. Kim, J.-Y.; Heo, S.; Choi, J.W. Effects of phenolic hydroxyl functionality on lignin pyrolysis over zeolite catalyst. Fuel 2018, 232, 81–89. [Google Scholar] [CrossRef]
  32. Wang, Z.K.; Hong, S.; Wen, J.L.; Ma, C.Y.; Tang, L.; Jiang, H.; Chen, J.J.; Li, S.; Shen, X.J.; Yuan, T.Q. Lewis acid-facilitated deep eutectic solvent (DES) pretreatment for producing high-purity and antioxidative lignin. ACS Sustain. Chem. Eng. 2020, 8, 1050–1057. [Google Scholar] [CrossRef]
  33. Wen, J.L.; Sun, S.L.; Yuan, T.Q.; Sun, R.C. Structural elucidation of whole lignin from Eucalyptus based on preswelling and enzymatic hydrolysis. Green Chem. 2015, 17, 1589–1596. [Google Scholar] [CrossRef]
  34. Schutyser, W.; Renders, A.T.; Van den Bosch, S.; Koelewijn, S.-F.; Beckham, G.; Sels, B.F. Chemicals from lignin: An interplay of lignocellulose fractionation, depolymerisation, and upgrading. Chem. Soc. Rev. 2018, 47, 852–908. [Google Scholar] [CrossRef] [PubMed]
  35. Svinterikos, E.; Zuburtikudis, I.; Al-Marzouqi, M. Electrospun lignin-derived carbon micro-and nanofibers: A review on precursors, properties, and applications. ACS Sustain. Chem. Eng. 2020, 8, 13868–13893. [Google Scholar] [CrossRef]
  36. Wen, J.L.; Sun, S.L.; Xue, B.L.; Sun, R.C. Recent advances in characterization of lignin polymer by solution-state nuclear magnetic resonance (NMR) methodology. Materials 2013, 6, 359–391. [Google Scholar] [CrossRef]
  37. Sun, D.; Wang, B.; Wang, H.M.; Li, M.F.; Shi, Q.; Zheng, L.; Wang, S.F.; Liu, S.J.; Sun, R.C. Structural elucidation of tobacco stalk lignin isolated by different integrated processes. Ind. Crops Prod. 2019, 140, 111631. [Google Scholar] [CrossRef]
  38. Liu, Z.; Peng, X.; Xu, Y.; Tang, T.; Wei, S.; Liu, B.; Wang, D.; Wang, H.-M.; Jiang, J. Macromolecular structural characteristics and functional potential of tobacco stalk lignin from the phosphotungstic acid-assisted delignification process. Biomass Bioenergy 2023, 170, 106706. [Google Scholar] [CrossRef]
  39. Zhang, C.; Shen, X.; Liu, M.; Wen, J.; Yuan, T.-Q. Uncovering the structure of lignin from moso bamboo with different tissues and growing ages for efficient ambient-pressure lignin depolymerization. ACS Sustain. Chem. Eng. 2023, 11, 13778–13786. [Google Scholar] [CrossRef]
  40. Guo, Y.; Xu, L.; Shen, F.; Hu, J.; Huang, M.; He, J.; Zhang, Y.; Deng, S.; Li, Q.; Tian, D. Insights into lignocellulosic waste fractionation for lignin nanospheres fabrication using acidic/alkaline deep eutectic solvents. Chemosphere 2022, 286, 131798. [Google Scholar] [CrossRef]
  41. Xia, Q.; Chen, C.; Yao, Y.; Li, J.; He, S.; Zhou, Y.; Li, T.; Pan, X.; Yao, Y.; Hu, L. A strong, biodegradable and recyclable lignocellulosic bioplastic. Nat. Sustain. 2021, 4, 627–635. [Google Scholar] [CrossRef]
  42. Wang, N.; Wang, B.; Si, H.; Hu, S.; Chen, L.; Liao, Y.; Wang, L.; Zhang, Y.; Jiang, J. Comparative investigating the structural characteristics of tobacco stalk lignin during the DES and alkaline deconstruction toward sustainable materials. Front. Bioeng. Biotech. 2022, 10, 994760. [Google Scholar]
  43. Jiang, J.; An, N.; Fu, J.; Wan, C.; Zhang, K.; Zhang, Y.; Chen, X.; Wang, L. Ethylene glycol inhibited oxalic acid non-derivatization pretreatment for enhanced wheat straw rapid saccharification and with high efficiency. Ind. Crops Prod. 2024, 216, 118751. [Google Scholar] [CrossRef]
  44. Taverna, M.E.; Bressan, L.B.; Busatto, C.A.; Lescano, M.R.; Estenoz, D.A. Preparation of Lignin/Poly (Lactic Acid) Composite Microspheres as Potential Carriers for Biopesticides Delivery. J. Polym. Environ. 2024, 32, 1811–1820. [Google Scholar] [CrossRef]
  45. Zhang, R.; Du, Q.; Wang, L.; Zheng, Z.; Guo, L.; Zhang, X.; Yang, X.; Yu, H. Unlocking the response of lignin structure for improved carbon fiber production and mechanical strength. Green Chem. 2019, 21, 4981–4987. [Google Scholar] [CrossRef]
  46. Chen, H.; Wang, A.; Yan, C.; Liu, S.; Li, L.; Wu, Q.; Liu, Y.; Liu, Y.; Nie, G.; Nie, S.; et al. Study on the solubility of industrial lignin in choline chloride-based deep eutectic solvents. Sustainability 2023, 15, 7118. [Google Scholar] [CrossRef]
  47. Guo, G.; Liu, X.; Li, R.; Li, Q.; Yu, H.-B.; Li, M.-J. Characterization of tobacco stalk lignin using nuclear magnetic resonance spectrometry and its pyrolysis behavior at different temperatures. J. Anal. Appl. Pyrolysis 2019, 142, 104665. [Google Scholar] [CrossRef]
  48. Jiang, J.; Yuan, T.; Wang, S.; Liu, S.; Shi, X.; Zheng, L.; Sun, R. Upgrading Traditional Pulp Mill into Biorefinery Platform: Wheat Straw as a Feedstock. ACS Sustain. Chem. Eng. 2018, 6, 15284–15291. [Google Scholar] [CrossRef]
  49. Sluiter, A.; Hames, B.; Ruiz, R.; Scarlata, C.; Sluiter, J.; Templeton, D.; Crocker, D. Determination of structural carbohydrates and lignin in biomass. Lab. Anal. Proced. 2008, 1617, 1–16. [Google Scholar]
Catalysts 14 00744 g001
Figure 1. Yield and molecular weights of different lignin samples from tobacco stalk.
Figure 1. Yield and molecular weights of different lignin samples from tobacco stalk.
Catalysts 14 00744 g001
Catalysts 14 00744 g002
Figure 2. Two-dimensional HSQC spectra of different lignin samples from tobacco stalk.
Figure 2. Two-dimensional HSQC spectra of different lignin samples from tobacco stalk.
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Catalysts 14 00744 g003
Figure 3. FT-IR spectra of different lignin samples.
Figure 3. FT-IR spectra of different lignin samples.
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Catalysts 14 00744 g004
Figure 4. (a) TG and (b) DTG curves of the lignin samples.
Figure 4. (a) TG and (b) DTG curves of the lignin samples.
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Catalysts 14 00744 g005
Figure 5. (a) The photograph of the pyrolytic oil dissolved in 5 mL acetone. From left to right: BL, DLE, and DLG. (b) The pyrolytic gas, oil, and char yield of the biorefinery lignins at 600 °C.
Figure 5. (a) The photograph of the pyrolytic oil dissolved in 5 mL acetone. From left to right: BL, DLE, and DLG. (b) The pyrolytic gas, oil, and char yield of the biorefinery lignins at 600 °C.
Catalysts 14 00744 g005
Catalysts 14 00744 g006
Figure 6. Lignin isolated by alkali extraction or DES treatment.
Figure 6. Lignin isolated by alkali extraction or DES treatment.
Catalysts 14 00744 g006
Table 1. The linkage contents and unit abundances in different lignin samples.
Table 1. The linkage contents and unit abundances in different lignin samples.
SamplesS/Gβ-O-4β-β
DEL a0.455.8 b10.2
BL0.846.16.6
DLE1.0ND c2.0
DLG1.0ND4.6
a DEL, double ball-milling and enzymatic hydrolysis lignin; data from our previous research [33]. b Results expressed per 100 Ar based on quantitative 2D-HSQC spectra. c ND, not detected.
Table 2. Thermal properties of the different lignin samples.
Table 2. Thermal properties of the different lignin samples.
SamplesBLDLEDLG
Tmax (°C)330.1262.2255.3
Residual char at 650 °C (wt.%)42.133.239.5
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Liu, Z.; Wang, Z.; Li, Y.; Wang, W.; Liu, X.; Shu, H.; Jiang, J. Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics. Catalysts 2024, 14, 744. https://doi.org/10.3390/catal14110744

AMA Style

Liu Z, Wang Z, Li Y, Wang W, Liu X, Shu H, Jiang J. Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics. Catalysts. 2024; 14(11):744. https://doi.org/10.3390/catal14110744

Chicago/Turabian Style

Liu, Zhichang, Ziwei Wang, Yichen Li, Wanxia Wang, Xiongbin Liu, Hao Shu, and Jungang Jiang. 2024. "Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics" Catalysts 14, no. 11: 744. https://doi.org/10.3390/catal14110744

APA Style

Liu, Z., Wang, Z., Li, Y., Wang, W., Liu, X., Shu, H., & Jiang, J. (2024). Comparison of the Effects of NaOH and Deep Eutectic Solvent Catalyzed Tobacco Stock Lignin Isolation: Chemical Structure and Thermal Characteristics. Catalysts, 14(11), 744. https://doi.org/10.3390/catal14110744

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