Monomer Yield Research Articles

Task-Specific Deep Eutectic Solvent for Efficient Dissolution and Further Accelerating Alkaline Hydrolysis of Polyesters Into Their Monomers.

Polyester plastics have brought great convenience to modern society. However, the continuous accumulation of their production increasingly threatens human health. Polyethylene terephthalate (PET) is one of the largest type of polyester plastics and its recycling is a major challenge. In this work, deep eutectic solvent (DES) composed of thenyl alcohol and choline chloride (ChCl) was designed for efficient dissolution of PET at 165 °C for 20 min, and further accelerating complete alkaline hydrolysis of PET into its monomer terephthalic acid (TPA) and ethylene glycol (EG) with a high TPA monomer yield (98.2 %) in 25 min at 100 °C. Moreover, the designed DES is also efficient for dissolution and alkaline hydrolysis of other polyester plastics, including poly(trimethylene terephthalate) (PTT) and poly(ethylene furanoate) (PEF) into their monomers. This work provides a feasible and sustainable solution for the recycling of polyester wastes.

Tetravalent metals modulated Zn-based layered double hydroxides and their mixed metal oxides for catalytic depolymerization of carbonyl-coordinating plastic waste

Plastic waste generation has become a global issue and presents a significant challenge concerning degradability in the environment. This poses a serious threat and adverse impact on the health of living creature and the environment ecosystem. The up-/re-cycling of plastic waste through catalytic depolymerization is becoming a sustainable way to reduce economic concerns about production and serious environmental impacts. Here, in the present study an effort has been made for the development of catalysts for efficient recycling of carbonyl group containing polymer waste [Polyethylene terephthalate (PET) and polycarbonate (PC)]. The sequential preparation of ZnMIV- and ZnAlMIV- LDHs (layered double hydroxides) (MIV= Zr and Ti) and their respective mixed metal oxide (MMOs) based catalytic materials, has been carried out by one-pot co-precipitation and calcination methods. The structural parameters were examined through the various characterisation techniques including XRD, FTIR, TEM, SEM, and EDS. The layered structure, high crystalline nature and hexagonal 2D-sheet/flakes like morphology with average particle size ranging from ~14 to 51nm [for LDHs] and ~6 to 21nm [for MMOs] were observed. Depolymerization of PET and PC using LDHs/MMOs catalyst in ethylene glycols (EG) produced bis(2-hydroxyethyl terephthalate) (BHET) and bisphenol A (BPA) monomers as main products, respectively. The catalyst quantity, concentration of solvent, recyclability of catalysts, reaction duration, and crystallization time have also been further investigated for better yield during catalytic glycolysis. The isolated monomers were further characterized by using melting point, mass spectroscopy, 1H-NMR, 13C-NMR and FTIR analysis. The order of catalytic activities of prepared samples as ZnTi-LDH˃ ZnAlTi-LDH ˃ ZnTi-MMO˃ ZnAlZr-LDH˃ ZnAlTi-MMO˃ ZnZr-LDH in PET depolymerization while in case of PC, the order as ZnTi-LDH˃ ZnAlTi-LDH ˃ ZnZr-LDH˃ ZnAlZr-LDH˃ ZnZr-MMO˃ ZnAlZr-MMO˃ ZnTi-MMO˃ ZnAlTi-MMO were observed. LDH samples showed higher catalytic conversion than their respective MMOs during PET and PC depolymerization into monomers BHET and BPA with % yield of ~76-83% and ~81-89%, respectively. ZnTi-LDH shows high catalytic efficacy in depolymerization of PET and PC with yield of (~82%) BHET monomer and (89%) BPA. This catalyst displayed good recyclability more than eight cycles during this catalytic glycolysis study.

Accessing monomers from lignin through carbon-carbon bond cleavage.

Lignin, the heterogeneous aromatic macromolecule found in the cell walls of vascular plants, is an abundant feedstock for the production of biochemicals and biofuels. Many valorization schemes rely on lignin depolymerization, with decades of research focused on accessing monomers through C-O bond cleavage, given the abundance of β-O-4 bonds in lignin and the large number of available C-O bond cleavage strategies. Monomer yields are, however, invariably lower than desired, owing to the presence of recalcitrant C-C bonds whose selective cleavage remains a major challenge in catalysis. In this Review, we highlight lignin C-C cleavage reactions, including those of linkages arising from biosynthesis (β-1, β-5, β-β and 5-5) and industrial processing (5-CH2-5 and α-5). We examine multiple approaches to C-C cleavage, including homogeneous and heterogeneous catalysis, photocatalysis and biocatalysis, to identify promising strategies for further research and provide guidelines for definitive measurements of lignin C-C bond cleavage.

Efficient biodegradation of poly(butylene adipate-co-terephthalate) in mild temperature by cutinases derived from a marine fungus

Poly(butylene adipate-co-terephthalate) (PBAT) waste gradually accumulates in the environment, posing ecological risks. Enzymatic hydrolysis holds great potential in the end-of-life management of PBAT, but reported enzymes require high reaction temperatures, limiting their practical industrial applications. In this study, we discovered that the marine fungus Alternaria alternata FB1 can efficiently degrade PBAT at 28 °C. Two cutinases designated as AaCut4 and AaCut10, were identified and verified as key enzymes responsible for this degradation process. Notably, the recombinant AaCut10 was able to depolymerize 82.14 % PBAT within 24 h and fully decompose it within 48 h at 37 °C. Through protein engineering, the yield of terephthalic acid monomer was increased to 96.01 %, highlighting its potential for facilitating PBAT upcycling. Furthermore, based on the investigation of the distribution patterns of PBAT hydrolases, novel degradative agents have been identified within unique ecological niches, leading to the establishment of a comprehensive screening repository of PBAT hydrolases. Overall, our study provides new candidates for enzymatic PBAT recycling with low energy consumption and offers insights into the PBAT degradation manner in ecosystems.

Mechanochemically accelerated deconstruction of chemically recyclable plastics.

Plastics redesign for circularity has primarily focused on monomer chemistries enabling faster deconstruction rates concomitant with high monomer yields. Yet, during deconstruction, polymer chains interact with their reaction medium, which remains underexplored in polymer reactivity. Here, we show that, when plastics are deconstructed in reaction media that promote swelling, initial rates are accelerated by over sixfold beyond those in small-molecule analogs. This unexpected acceleration is primarily tied to mechanochemical activation of strained polymer chains; however, changes in the activity of water under polymer confinement and bond activation in solvent-separated ion pairs are also important. Together, deconstruction times can be shortened by seven times by codesigning plastics and their deconstruction processes.

Pd catalysts in the mild reductive depolymerization of Soda lignin: Support and Cu addition effects

This study pioneers the exploration of the structure-performance relationship of 5 wt% Pd and PdCu catalysts on 3 supports (γ-Al2O3, SiO2, and activated carbon (AC)) in the mild reductive depolymerization (MRD) of Soda lignin. While all catalysts achieve similar final weight average molecular weight (Mw) reduction (≈ 85 %), Pd/AC and PdCu/AC show significant differentiation from solvolysis already after 2 h and 3 h, compared to 6 h and 20 h for Pd and PdCu on oxide supports. This study also highlights the importance of hydrogenation of C=C bonds in monomer side-chains for maximizing monomer yields. Particularly PdCu/SiO2 is characterized by the lowest monomer yields (7 wt%) due to its low hydrogenation activity, while catalysts like Pd(Cu)/Al2O3, Pd/SiO2, and Pd/AC, with more expressed hydrogenation, achieve a total monomer yield of up to 14 wt%. Additional findings confirm that on γ-Al2O3, the co-impregnation of Cu and Pd leads to the formation of a chemical bond between Pd2+ and Cu1+, resulting in a new mixed metal oxide Pd-Cu–O phase. On SiO2, Pd2+ and Cu1+ do not form a chemical bond, however, the presence of Cu1+ in close proximity to Pd2+ significantly alters the selectivity of the PdCu/SiO2 catalyst due to synergetic effects. PdCu/AC maintains similar selectivity to Pd/AC, except for reduced hydrogenation over time, due to the lack of interaction between Pd and Cu on the AC surface. This research also delves into the MRD mechanism of Soda lignin over Pd and PdCu catalysts, focusing on the β-O-4 linkage cleavage and the subtle differences in reaction pathways depending on the catalyst. These findings bridge gaps in understanding the MRD of actual lignin feedstocks, offering valuable insights for catalyst development and process optimization.

Highly efficient lignin depolymerization and enhanced bio-oil upgrading via in-situ hydrogenation: Impact of lignin structure

The inherent structural rigidity of lignin poses a significant challenge to its direct hydrogenation to produce aromatic compounds, requiring harsh reaction conditions. In this study, microwave-assisted hydrothermal liquefication was employed to rapidly generate raw bio-oil under mild conditions, coupled with an in-situ hydrogenation strategy to upgrade its quality. A series of lignin substrates were characterized to establish the relationship between lignin characteristics and aromatic products. Grass lignin can produce low molecular weight bio-oil in high yields (50.4–60.7 %) within 30 min at 180 °C, which is attributed to the abundance of cleavable β-O-4 linkages in its uniform structure. In contrast, softwood lignin with abundant guaiacyl (G) units possessed a robust thermal stability, resulting in a low monomer yield, but a high selectivity to G-type products (97 %). The raw bio-oil was further upgraded through in-situ hydrogenation with Pd catalysts. Low reaction temperatures (60–100 °C) favored the hydrogenation of aromatic aldehydes and ketones to their alcohol products, while high temperatures (100–220 °C) promoted the deep hydrogenation of aromatic side chains to alkyl products. Besides, an upgraded bio-oil with a higher heating value (29.8 MJ/kg) was obtained. Furthermore, the hydrogenation mechanism was investigated through the kinetics of simulated bio-oils. The activation energy follows the order: dimer β-O-4 linkage < monomer aldehyde group < ketone group < CC linkage, which is consistent with the hydrogenation kinetics observed in real lignin bio-oil. Overall, this study highlights the impact of lignin characteristics on subsequent conversion and alsoenhances our understanding of the complex depolymerization/hydrogenation mechanisms during lignin upgrading.

Investigating structural disparities and catalytic depolymerization of larch lignin for high-value biomass conversion

Understanding the structural diversity of lignin is crucial for its efficient conversion into high-value aromatic compounds. However, the impact of lignin's structural characteristics from artificial forests on catalytic depolymerization is not well understood. This study investigates the structural differences in lignin from larch trees of varying ages (10, 20, and 40 years) and anatomical parts (heartwood, sapwood, canopy, bark) to understand how these variations influence catalytic depolymerization. Polyoxometalates (POMs) were selected as catalysts due to their high efficiency in facilitating the conversion of lignin into valuable chemical products. By utilizing POMs for catalytic oxidation, we explore the relationship between lignin structure and depolymerized products, providing insights into the structural features of larch lignin. Our findings reveal that the β-O-4 content of heartwood lignin is as high as 78.7 %, while that of the canopy is lower at 67.1 %. Additionally, the unique lignin structure significantly impacted the yield and selectivity of aromatic monomers, with the highest monomer yield from heartwood lignin reaching 15.64 %, compared to the lowest yield of 7.46 % from canopy lignin. These results lay a theoretical foundation for developing efficient biomass conversion technologies and offer novel strategies for sustainable biomass utilization and environmentally friendly production.

Furandicarboxylic Acid (FDCA): Electrosynthesis and Its Facile Recovery From Polyethylene Furanoate (PEF) via Depolymerization.

Replacing fossil fuels with renewable, bio-based alternatives is inevitable for the modern chemical industry, in line with the 12 principles of green chemistry. 2,5-Furandicarboxylic acid (FDCA) is a promising platform molecule that can be derived from 5-hydroxymethyl furfural (HMF) via sustainable electrochemical oxidation. Herein, we demonstrate TEMPO-mediated electrooxidation of HMF to FDCA in ElectraSyn 2.0 using inexpensive commercially available electrodes: graphite anode and stainless-steel cathode, thereby avoiding the often cumbersome electrode preparation. Key parameters such as concentration of HMF, KOH, and catalyst loading were optimized by experimental design. Under the optimized conditions, using only a low amount of TEMPO (5 mol%), high yield and Faradaic efficiency of 96% were achieved within 2.5 hours. Moreover, since FDCA is a monomer of the bio-based poly(ethylene furanoate), PEF, we aimed to investigate its recovery by depolymerization, which could be of paramount importance in the circular economy of the FDCA. For this, a new polar aprotic solvent, methyl sesamol (MeSesamol), was used, allowing the facile depolymerization of PEF at room temperature with high monomer yields (up to 85%), while the cosolvent MeSesamol was recycled with high efficiency (95-100%) over five reaction cycles.

Catalytic depolymerization of Camellia oleifera shell lignin to phenolic monomers: Insights into the effects of solvent, catalyst and atmosphere

Camellia oleifera shell (COS) is a renewable biomass resource abundant in lignin with significant potential for producing phenolic monomers. However, the dearth of research has led to considerable resource wastage and environmental pollution. Herein, reductive catalytic fractionation (RCF) of COS was performed using noble metal catalysts in different solvents. An 11.1 wt% yield of phenolic monomers was achieved with 91% selectivity toward propylene-substituted monomers in H2O/EtOH (3:7, v/v) cosolvent under N2 atmosphere. Notably, the highest phenolic monomer yield of 17.0 wt% was obtained with impressive selectivity (86.9%) toward propanol-substituted monomers in the presence of H2. The GPC analysis and 2D HSQC NMR spectra indicated the effective depolymerization of lignin oligomers with catalysts. Phenolic monomers with ethyl, propyl, or propanol side chain could be produced from lignin-derived oligomers through hydrogenolysis, hydrogenation, and decarboxylation reactions. Overall, this study has paved the way for the valorization of COS lignin through the RCF strategy.

Efficient cleavage of C-C bond in lignin adopting Z-scheme heterojunction photocatalyst by g-C3N4/CQDs/WO3

It is a practical approach to overcome the shortage of energy and environmental pollution simultaneously if obtaining useful products from biomass through chemical decomposition. Photocatalytic depolymerization of lignin to generate high value-added chemicals has received extensive attention for decades. The low yield of aromatic monomers is still one of the urgent problems to be solved. Selective breakage of Cα-Cβ bonds in lignin is of importance to improve the yield of aromatic monomers. Herein, Z-scheme heterojunction g-C3N4/CQDs/WO3 was constructed by combining graphite-like carbon nitride (g-C3N4), tungsten oxide (WO3) with carbon quantum dots (CQDs) to break the C-C bond selectively in β-O-4 model compounds. Both the efficiencies of substrate conversion and selectivity of C-C bond cleavage reached to 99 %. As a result, the total yield of benzaldehyde and benzoic acid attained to 83.92 %. Furthermore, the photocatalyst has satisfactory effect on depolymerization of four types of lignin, while the heterojunction can validly reduce the recombination rate of photogenerated carriers. Additionally, CQDs broadens the light absorption range and enhances the mobility of photogenerated carriers. Consequently, this study provides a feasible idea for highly selective cleavage of lignin C-C bonds through heterojunction engineering.

Development of an Effective Au : Pd Bimetallic Heterogeneous Catalyst for Oxidative Lignin Depolymerization to Low Molecular Weight Aromatics

AbstractLignin, a phenolic‐rich biomass component, holds promise for producing value‐added products. However, its complex structure and recalcitrance present challenges for its effective utilization. To overcome this, a AuPd/Li−Al layered double hydroxide (LDH) catalyst was developed to facilitate lignin depolymerization. Various AuPd bimetallic nanoparticle compositions were supported on a basic Li−Al LDH support via a sol‐immobilization method and characterized using N2‐physisorption, X‐ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The catalysts were then evaluated in the oxidation of several benzylic alcohols using O2 as the oxidant, from which Au7Pd3/Li−Al LDH and Au1Pd1/Li−Al LDH were identified as possessing promising catalytic activity. Further investigations focused on the aerobic oxidation of β‐O‐4 linked lignin model dimers under atmospheric pressure. The tested catalysts demonstrated sequential oxidation of the model compounds, leading to cleavage of the β‐O‐4 linkage. Finally, the catalysts were applied to the oxidative deconstruction of γ‐valerolactone (GVL) extracted maple lignin at 120 °C. Au1Pd1/Li−Al LDH emerged as the most effective catalyst, yielding a range of aromatic monomers with a total monomer yield of 27 %. These results highlight the potential of the Au1Pd1/Li−Al LDH catalyst system as an eco‐friendly approach for lignin depolymerization under mild conditions.

Activity and product distribution in Ni-Co and Ni-Cu catalyst-mediated lignin depolymerization into phenolic substances with isopropanol H-donating solvent.

Lignin, a vital renewable biopolymer, serves as the Earth's primary source of aromatics and carbon. Its depolymerization presents significant potential for producing phenolic fine chemicals. This study assesses promoted Ni-based bimetallic catalysts (Ni-Co/C and Ni-Cu/C) supported on activated carbon in isopropanol for lignin depolymerization, compared to monometallic counterparts. BET, SEM, EDX, and XPS analyses highlight their physicochemical properties and promotional effects, enhancing hydrogenolysis activity and hydrogen transformation. Reaction parameter exploration elucidates the influence on lignin depolymerization, with cobalt and copper as promoters notably increasing conversion and monomer yield. Ni-Co/C exhibits the highest lignin conversion (94.2%) and maximum monomer yield (53.1 wt%) under specified conditions, with lower activation energy (36.1kJ/mol) and higher turnover frequency (31.6h-1) compared to Ni/C. FT-IR, GPC, GC-FID, and GC-MS analyses confirm effective depolymerization, identifying 20 monomer products. Proposed reaction mechanisms underscore the potential of Ni-based bimetallic catalysts for lignin valorization, offering insights into developing efficient catalytic systems for lignin hydrogenolysis. This research enhances understanding and facilitates the development of selective catalytic processes for lignin valorization.

Asymmetric Ru-In atomic pairs promote highly active and stable acetylene hydrochlorination

Ru single-atom catalysts have great potential to replace toxic mercuric chloride in acetylene hydrochlorination. However, long-term catalytic stability remains a grand challenge due to the aggregation of Ru atoms caused by over-chlorination. Herein, we synthesize an asymmetric Ru-In atomic pair with vinyl chloride monomer yield (>99.5%) and stability (>600 h) at a gas hourly space velocity of 180 h−1, far surpassing those of the Ru single-atom counterparts. A combination of experimental and theoretical techniques reveals that there is a strong d-p orbital interaction between Ru and In atoms, which not only enables the selective adsorption of acetylene and hydrogen chloride at different atomic sites but also optimizes the electron configuration of Ru. As a result, the intrinsic energy barrier for vinyl chloride generation is lowered, and the thermodynamics of the chlorination process at the Ru site is switched from exothermal to endothermal due to the change of orbital couplings. This work provides a strategy to prevent the deactivation and depletion of active Ru centers during acetylene hydrochlorination.

Enhanced reductive catalytic fractionation of lignocellulose using a water-resistant RuNiZnOx/Nb2O5 catalyst with synergistic hydrogen spillover and acidic properties

Eco-friendly lignin depolymerization into monomeric phenols in an aqueous system is essential for the sustainable and green valorization of lignocellulosic biomass. However, a major challenge in this process is the development of efficient and stable catalysts for aqueous reductive catalytic fractionation (RCF), as water can cause catalyst deactivation and reduce monomer yields. In this study, a water-resistant RuNiZnOx/Nb2O5 catalyst is developed that demonstrates excellent catalytic activity and stability in aqueous systems, achieving a near-theoretical monomeric phenol yield of 40.1 wt% under reaction conditions of 240℃ and 3 MPa H2 for 4 h. The excellent performance of this catalyst is attributed to the synergistic hydrogen spillover effect between Ni and Ru and the strong acidic properties of ZnO, as revealed by in-situ XPS analysis and NH3-TPD, respectively. This hydrogen spillover effect significantly alters the product composition, promoting the generation of POH-S/G from lignin model compounds. Additionally, screening of the catalyst support materials revealed that Nb2O5 not only enhances Ru dispersion but also improves its stability, resulting in a minor decrease in lignin monomer yield observed after three cycles.

Sustainable depolymerization of lignin into aromatic compounds using amphiphilic Anderson-type polyoxometalate catalysts

Lignin serves as a primary abundant source of renewable aromatic compounds. Achieving efficient breakdown of lignin and retaining its aromatic properties is highly desirable but remains a challenging task. To address this challenge, we synthesized Anderson-type polyoxometalate (POM) catalysts, particularly [CTAC]2[CoMo6]. We then investigated the effectiveness of the POM catalysts in the oxidative depolymerization of larch lignin. Under conditions of 160 °C, 1.0 MPa oxygen atmosphere, and a catalyst-to-substrate ratio of 1:5, we achieved a monomer yield of phenolic compounds at 12.43 wt%. The unsaturated coordination sites of Mo5+ within the catalysts were identified as active sites, facilitating enhanced O2 adsorption and activation. The enhanced O2 adsorption significantly influenced the production of aromatic monomers from lignin. We observed that the catalysts effectively cleaved CC bonds in β-O-4 dimer compounds using lignin dimer model compounds. Notably, the [CTAC]2[CoMo6] catalyst exhibited excellent stability across five cycles, maintaining its high efficiency in lignin depolymerization. This indicates that Anderson-type POM-based catalysts exhibit potential for sustainable conversion of biomass into valuable compounds and for enhancing lignin valorization processes.

High‐throughput in silico workflow for optimization and characterization of multimodal chromatographic processes

AbstractWhile high‐throughput (HT) experimentation and mechanistic modeling have long been employed in chromatographic process development, it remains unclear how these techniques should be used in concert within development workflows. In this work, a process development workflow based on HT experiments and mechanistic modeling was constructed. The integration of HT and modeling approaches offers improved workflow efficiency and speed. This high‐throughput in silico (HT‐IS) workflow was employed to develop a Capto MMC polishing step for mAb aggregate removal. High‐throughput batch isotherm data was first generated over a range of mobile phase conditions and a suite of analytics were employed. Parameters for the extended steric mass action (SMA) isotherm were regressed for the multicomponent system. Model validation was performed using the extended SMA isotherm in concert with the general rate model of chromatography using the CADET modeling software. Here, step elution profiles were predicted for eight RoboColumn runs across a range of ionic strength, pH, and load density. Optimized processes were generated through minimization of a complex objective function based on key process metrics. Processes were evaluated at lab‐scale using two feedstocks, differing in composition. The results confirmed that both processes obtained high monomer yield (&gt;85%) and removed of aggregate species. Column simulations were then carried out to determine sensitivity to a wide range of process inputs. Elution buffer pH was found to be the most critical process parameter, followed by resin ionic capacity. Overall, this study demonstrated the utility of the HT‐IS workflow for rapid process development and characterization.

Modeling Mechanochemical Depolymerization of PET in Ball-Mill Reactors Using DEM Simulations.

Developing efficient and sustainable chemical recycling pathways for consumer plastics is critical for mitigating the negative environmental implications associated with their end-of-life management. Mechanochemical depolymerization reactions have recently garnered great attention, as they are recognized as a promising solution for solvent-free transformation of polymers to monomers in the solid state. To this end, physics-based models that accurately describe the phenomena within ball mills are necessary to facilitate the exploration of operating conditions that would lead to optimal performance. Motivated by this, in this paper we develop a mathematical model that couples results from discrete element method (DEM) simulations and experiments to study mechanically-induced depolymerization. The DEM model was calibrated and validated via video experimental data and computer vision algorithms. A systematic study on the influence of the ball-mill operating parameters revealed a direct relationship between the operating conditions of the vibrating milling vessel and the total energy supplied to the system. Moreover, we propose a linear correlation between the high-fidelity DEM simulation results and experimental monomer yield data for poly(ethylene terephthalate) depolymerization, linking mechanical and energetic variables. Finally, we train a reduced-order model to address the high computational cost associated with DEM simulations. The predicted working variables are used as inputs to the proposed mathematical expression which allows for the fast estimation of monomer yields.

Improved Lignin Conversion to High-Value Aromatic Monomers through Phase Junction CdS with Coexposed Hexagonal (100) and Cubic (220) Facets.

Photocatalysis has the potential for lignin valorization to generate functionalized aromatic monomers, but its application has been limited by the slow conversion rate and the low selectivity to desirable aromatic products. In this work, we designed the phase junction CdS with coexposed hexagonal (100) and cubic (220) facets to improve the photogenerated charge carriers' transfer efficiency from (100) facet to (220) facet and the hydrogen transfer efficiency for an enhanced conversion rate of lignin to aromatic monomers. Water is found as a sufficient external hydrogen supplier to increase the yields of aromatic monomers. These innovative designs in the reaction system promoted complete conversion of PP-ol to around 94% of aromatic monomers after 1 h of visible light irradiation, which shows the highest reaction rate and selectivity of target products in comparison with previous works. PP-one is a byproduct from the overoxidation of PP-ol and is usually difficult to be further cleaved to acetophenone and phenol as the desirable aromatic monomers. TEA was first identified in this study as a sacrificial electron donor, a hydrogen source, and a mediator to enhance the cleavage of the Cβ-O bonds in PP-one. With the assistance of TEA, PP-one can be completely cleaved to desirable aromatic monomer products, and the reaction time is reduced from several hours to 10 min of visible light irradiation.

Promotion of lignin depolymerization and cellulose utilization via the coupling effects of DDQ pre-oxidation and HCOOH extraction

The full utilization of biomass plays an important role in the environment and energy. In this study, the coupling pretreatment of DDQ pre-oxidation and HCOOH extraction was employed to realize the separation and modification of three components of sugarcane bagasse for full utilization. Especially, the modified lignin was depolymerized to obtain aromatic monomers, and cellulose-rich residue was used to prepare lignocellulose straws. Furthermore, the coupling effects between DDQ pre-oxidation and HCOOH extraction on chemical and physical properties of modified lignin and lignocellulose straws were studied. In addition, the mechanism of lignin depolymerization and lignocellulose straw synthesis were explored as well as the mass balance of the biorefinery process. The results showed that the total yield of aromatic monomers increased by nearly 2 times and the conversion of lignin was 95.1 % after DDQ pre-oxidation. The mechanism showed that DDQ selectively oxidized Cα-OH bond of lignin to Cα = O bond, which not only avoided the formation of carbocation, but also reduced the bond dissociation energy of β-O-4 bond. Moreover, the tensile strength of hydrophobic lignocellulose straw increased by nearly 2 times and its flexural strength was 10.36 MPa. Modified lignin and modified cellulose were connected via hydrogen bonds, which enhanced the intermolecular crosslinking of molecules, thus improving the mechanical properties of lignocellulose straws. Besides, the maximum xylose relative content and concentration of xylose were 61.16 % and 17.57 g/L, respectively. This study provides a method for high-value and green utilization of sugarcane bagasse.