Search Results (139)

Oxidative catalytic fractionation (OCF) under the lignin-first strategy has emerged as a critical technological approach for biomass refining. To address the inevitable carbohydrate degradation and lignin condensation in conventional OCF, this study designed a cobalt-doped layered double hydroxide oxide (Co-LDO) catalyst compatible with non-alkaline (without Brønsted bases) organic systems, which exhibits excellent performance in poplar biomass OCF. With a straightforward preparation process, the Co-LDO catalyst yields high-content oxidized lignin oligomers while efficiently retaining carbohydrates, providing feedstock rich in carbohydrates (cellulose and hemicellulose) for the subsequent production of bioenergy and biomass-based chemicals. Under optimized conditions screened via systematic reaction condition investigation and metal-doped LDO catalyst evaluation, the process achieved a 94.01 wt% delignification rate, with 72.19 wt% of lignin converted into lignin oligomer oil, supported by detailed product composition and structural characterization. Meanwhile, 74.14 wt% hemicellulose and 98.23 wt% cellulose were recovered in solid residues, with structurally intact hemicellulose retention being 2.3 times higher than in traditional OCF. Mass balance calculation confirmed a total poplar refining yield of 81.58 wt%. In summary, this Co-LDO-catalyzed OCF strategy provides a high-activity non-precious metal system, effectively suppressing lignin condensation while preserving high-yield carbohydrates, realizing the efficient full-component refining of poplar biomass. Full article

The global shift toward carbon-neutral energy systems has renewed interest in biorefineries as integrated platforms for the sustainable production of fuels, chemicals, and materials. In this context, lignin, the second most abundant natural polymer and the only renewable source of aromatic carbon, has gained attention as a promising feedstock for high-value applications. Despite its high energy density and chemically complex structure, lignin is primarily used as a low-value fuel through combustion, a practice that fails to capitalize on its molecular potential and offers minimal energetic and economic benefits to the industry. Unlocking its value requires a fundamental shift toward energy-efficient valorization strategies that minimize external energy input while retaining carbon in marketable products. To enable a comprehensive evaluation of this shift, this perspective introduces a three-criterion framework—operating below 250 °C and 50 bar, achieving a fossil energy ratio above one across all process steps, and retaining more than 40% of lignin carbon in recoverable products—and applies it to critically evaluate four lignin valorization pathways: catalytic depolymerization, solvent-assisted fractionation, biological and electrochemical conversion, and material-based applications. Across all pathways, system-level integration, namely, separation, solvent recycling, and catalyst generation, constantly influences the overall energy balance and represents the field’s unresolved challenge. To address these barriers, this perspective discusses several future research directions spanning advanced catalyst design, biotechnology, computational tools, and process intensification, alongside the policy and economic measures needed to enable the commercial deployment of integrating lignin valorization with existing biorefinery operations. Collectively, these insights aim to elevate lignin from an underutilized by-product to a foundational resource for circular, low-carbon bioeconomy. Full article

Lignin’s complex structure makes it a valuable resource for producing aromatic chemicals, but selectively converting it into specific products remains challenging. This study explores the use of technical hydrolysis lignin as a renewable support for palladium (Pd) and copper (Cu) catalysts in hydrogenation reactions. The materials were characterized using NMR, FTIR, XRF, AAS, XPS, and TEM. The reduction of nitrobenzene to aniline was tested with various Pd/Cu catalysts with different metal contents. The hydrogenation results showed that the Pd-only catalyst (catalyst-1) performed best on most substrates. In contrast, catalysts with only Cu or with Pd-Cu bimetallic showed no catalytic activity. The study discusses the effects of Pd incorporation and the Pd-Cu synergistic effect on catalyst stability, highlighting potential limitations in active-site stability and suggesting ways to enhance catalyst longevity. Overall, this research reveals that lignin is a promising, renewable support for catalysts, offering alternatives to traditional supports. These findings provide valuable insights into improving lignin modification and developing eco-friendly catalytic processes aligned with green chemistry principles. Full article

Ni-based catalysts have been extensively investigated for lignin hydrogenation; however, they often exhibit limited phenol selectivity and poor catalytic stability. To address these challenges, we introduced Cu as a promoter, resulting in the development of NiCu/ZSM-5 catalysts with significantly enhanced phenol selectivity and durability. Characterization studies revealed that Cu species form an alloy structure with Ni, which effectively suppresses the sintering of Ni nanoparticles during the catalytic process, thereby maintaining consistent performance over multiple reaction cycles. Furthermore, the Cu-Ni alloy demonstrated improved hydrogen activation capability while reducing overall H₂ uptake, leading to a marked increase in phenol selectivity compared to the Cu-free Ni/ZSM-5 catalyst. As a result, the Ni₁Cu₁/ZSM-5 (Ni/Cu molar ratio = 1:1) catalyst achieved a lignin conversion of 69.8% and a phenol selectivity of 84.4%, with negligible performance degradation over 8 cycles. The strategy presented in this work may offer an effective approach for enhancing the performance of industrial catalysts in lignin upgrading processes. Full article

Food packaging is the largest segment of the global plastics market, yet its low degradability and limited performance in preserving perishable goods highlight the need for more sustainable alternatives. This study investigates the use of industrial softwood kraft lignin, a renewable polyol, and γ-valerolactone (GVL), an excellent green lignin solvent, to synthesize bio-based polyurethane (PU) coatings for recycled linerboard. PU was synthesized with hexamethylene diisocyanate (HDI), GVL, and 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalyst and applied to recycled linerboard (166.6 g/m²) at three coating weights: 13.5, 16.5, and 23.5 g/m². The coating enhanced water resistance, as shown by the reduced water vapor transmission rate (WVTR) and Cobb₁₈₀₀ values. Oil resistance was also significantly improved, reaching a Kit rating of 11 at the highest coating weight. Mechanical performance was maintained or enhanced, with increases in ring crush strength (RCT) and tensile index. These findings confirm the effectiveness of lignin-based PU in improving both the barrier and mechanical properties of packaging paper. Additionally, this approach presents an environmentally responsible alternative to petroleum-based coatings, adding value to lignin as a byproduct of the pulp and paper industry and supporting the transition toward more circular and sustainable packaging materials. Full article

For the first time, Eriolobus trilobatus bark from Turkey has been characterized in terms of its chemical, extractive, fuel, and ash characteristics using SEM–EDS, wet chemical analysis, phenolic analysis, FT-IR, TGA, XRF, XRD, BET surface area measurement, proximate analysis, and ash fusion temperature (AFT) determination. The results showed that the bark contains 13% ash, dominated by calcium oxalate, and 15% extractives, largely composed of polar phenolic compounds with moderate radical-scavenging potential. Thermal decomposition of bark proceeds in four distinct stages, associated with the sequential degradation of extractives/hemicelluloses, cellulose, lignin/suberin, and inorganic fractions. The higher calorific value of 14.9 MJ/kg indicates moderate fuel quality compared with conventional woody biomass. Ash is mesoporous with a CaO-rich structure highly suitable for catalytic applications in biodiesel production and biomass gasification. Ash fusion analysis revealed a high flow temperature (1452 °C), indicating a very low slagging risk during thermochemical conversion. Overall, E. trilobatus bark is a promising material for value-added biorefinery pathways, enabling processes for the production of biochars, CaO-based catalysts, phenolic extracts, and sustainable energy. The valorization of E. trilobatus bark not only enhances the economic potential of forestry residues but also provides environmental co-benefits through carbon soil amendment and landscape applications. Full article

This study focused on optimising the saccharification of cardoon mixed residues through acid or base-catalysed steam explosion, using a Response Surface Methodology (RSM) to optimise the main process parameters. Despite the increasing interest in cardoon as a lignocellulosic feedstock, its efficient fractionation remains challenging, with limited cellulose hydrolysis and incomplete hemicellulose recovery under non-optimised steam explosion conditions. Therefore, a systematic evaluation of catalytic severity is required to improve biomass valorisation. H₂SO₄-catalysed steam explosion significantly improved glucan hydrolysis in the following enzymatic saccharification process, achieving 78 mol% glucose yield after a pretreatment carried out at 200 °C, 5 min, and 25 mM catalyst concentration. Xylan recovery required a higher catalyst concentration of 50 mM and temperatures lower than 220 °C to avoid the dehydration reaction of xylose to furfural. The optimal conditions for maximising glucose and xylose yields were 196 °C for 5 min with 50 mM H₂SO₄, resulting in 80.5 mol% glucose yield and 70.3 mol% xylose yield. Alkaline-catalysed steam explosion at 200 °C with 25 mM NaOH increased the enzymatic hydrolysis of glucan and favoured the production of lignin with a higher syringyl/guaiacyl ratio, making it more reactive. Overall, this research provides valuable insights into catalytic steam explosion coupled with the enzymatic saccharification step for the complete valorisation of lignocellulosic cardoon residues. Full article

Lignocellulosic biomass—the non-edible fraction of plants composed of cellulose, hemicellulose, and lignin—is the most abundant renewable carbon resource and a key lever for shifting from fossil to bio-based production. Agro-industrial residues (straws, cobs, shells, bagasse, brewery spent grains, etc.) offer low-cost, widely available feedstocks but are difficult to process because their polymers form a tightly integrated, three-dimensional matrix. Within this matrix, lignin provides rigidity, hydrophobicity, and defense, yet its heterogeneity and recalcitrance impede saccharification and upgrading. Today, most technical lignin from pulping and emerging biorefineries is burned for energy, despite growing opportunities to valorize it directly as a macromolecule (e.g., adhesives, foams, carbon precursors, UV/antioxidant additives) or via depolymerization to low-molecular-weight aromatics for fuels and chemicals. Extraction route and severity strongly condition lignin structure linkages (coumaryl-, coniferyl-, and sinapyl-alcohol ratios), determining reactivity, solubility, and product selectivity. Advances in selective fractionation, reductive/oxidative catalysis, and hybrid chemo-biological routes are improving yields while limiting condensation. Remaining barriers include feedstock variability, solvent and catalyst recovery, hydrogen and energy intensity, and market adoption (e.g., low-emission adhesives). Elevating lignin from fuel to product within integrated biorefineries can unlock significant environmental and economic benefits. Full article

The increasing demand for sustainable chemical processes has fostered the development of advanced catalytic systems for biomass valorization. In this work, a series of mono-, bi-, and trimetallic oxides (FeO, FeCuO, FeZnO, and FeCuZnO) were successfully synthesized using MIL-101-based MOFs as sacrificial templates. The obtained materials were thoroughly characterized by N₂ adsorption–desorption, XRD, FTIR, and TEM/STEM-EDX to investigate their structural, morphological, and textural properties. Their catalytic performance was evaluated in the selective oxidation of benzyl alcohol, a lignin-derived platform molecule, into benzaldehyde under microwave irradiation as a sustainable heating strategy. The results demonstrate that MOF-derived oxides exhibit superior activity compared to their parent MOFs, highlighting the beneficial effect of thermal treatment on the exposure of active sites. Among the catalysts, heterometallic oxides showed enhanced performance due to synergistic effects between metals. In particular, FeZnO reached a maximum yield of 62.1% towards benzaldehyde at 150 °C and 30 min, outperforming the monometallic oxide. Recycling tests revealed that FeZnO retained higher overall performance than FeCuO, which suffered from progressive copper leaching. These findings confirm the potential of MOF-derived multimetallic oxides as efficient and reusable heterogeneous catalysts for selective biomass-derived alcohol oxidation. The combination of microwave-assisted processes and the tuneable nature of MOF-derived oxides provides a promising pathway for designing sustainable catalytic systems with industrial relevance. Full article

A versatile, sustainable feedstock pathway to bio-based polymeric materials was developed utilizing lignin biomass and the ring-opening copolymerization (ROCOP) of cyclic anhydrides and epoxides to synthesize functional, lignin-derived, fully bio-based polyester polyols. The initial goal was to make the ROCOP reaction more applicable to bio-derived starting materials and more attractive to commercialization by conducting the polymerization under less constrained and industrially relevant conditions in air and without the extensive purification of reagents, catalysts, or solvents, typically used in the literature. A refined ROCOP system was applied as a powerful tool in lignin valorization by successfully synthesizing the lignin-derived copolyester prepolymers from lignin models and depolymerized native lignin sourced from the reductive catalytic fractionation of Pinus radiata wood biomass. After mechanistic studies based on NMR characterization, an alternative ROCOP-style mechanism was proposed. This was found to be (1) contributing to the acceleration of the observed reaction rates with added [PPNCl] organo-catalyst and (2) ‘self-initiation/self-promoted’ ROCOP without any added external [PPNCl] catalyst, likely due to the presence of inherent [OH] groups/ species in the lignin-derived glycidyl ether monomer promoting reactivity. As a final goal, the potential of these lignin-derived polyesters as intermediate polyols was demonstrated by applying them in the synthesis of polyurethane (PU) film materials with a high biomass content of 75–79%. A dramatic range of thermomechanical properties was observed for the resulting materials, demonstrating how the ROCOP reaction can be used to tailor the properties of the functional polyester and PU material based on the nature of the epoxide and anhydride substrates used. These findings help endeavors towards predicting the relationship between chemical structure and material thermomechanical properties and performance, relevant for industrial applications. Overall, this study demonstrated the proof of concept that PU materials can be prepared from lignocellulosic biomass utilizing industrially feasible ROCOP of bio-derived cyclic anhydrides and epoxides. Full article

Lignin used in this work was isolated from sapele (Entandrophragma cylindricum) wood through a hybrid pulping process using soda/ethanol as pulping liquor and denoted soda-oxyethylated lignin (SOL). SOL was mixed with a polyethylene glycol (PEG)–glycerol mixture (80/20 v/v) as liquefying solvent with 98% wt. sulfur acid as catalyst, and the mixture was taken to boil at 140 °C for 2, 2.5, and 3 h. Three bio-polyols LBP1, LBP2, and LBP3 were obtained, and each of them exhibited a high proportion of -OH groups. Lignin-based polyurethane foams (LBPUFs) were prepared using the bio-polyols obtained with a toluene diisocyanate (TDI) prepolymer by the one-shot method. Gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and carbon-13 nuclear magnetic resonance spectroscopy (¹³C NMR) were used characterize lignin in order to determine viscosity, yield, and composition and to characterize their structure. The PEG-400–glycerol mixture was found to react with the lignin bio-polyols’ phenolic -OHs. The bio-polyols’ viscosity was found to increase as the liquefaction temperature increased, while simultaneously their molecular weights decreased. All the NCO groups were eliminated from the samples, which had high thermal stability as the liquefaction temperature increased, leading to a decrease in cell size, density, and crystallinity and an improvement in mechanical performance. Based on these properties, especially the presence of some aromatic rings in the bio-polyols, the foams produced can be useful in automotive applications and for floor carpets. Full article

Conventional methods for the synthesis of porous carbons are typically time- and energy-consuming and often contribute to the excessive accumulation of waste solvents. An alternative approach is to employ environmentally friendly procedures, such as mechanochemical synthesis, which holds great potential for large-scale production of advanced carbon-based materials in coming years. This review covers mechanochemical syntheses of highly porous carbons, with a particular focus on new adsorbents and catalysts that can be obtained from biomass. Mechanochemically assisted methods are well suited for producing highly porous carbons (e.g., ordered mesoporous carbons, hierarchical porous carbons, porous carbon fibers, and carbon–metal composites) from tannins, lignin, cellulose, coconut shells, nutshells, bamboo waste, dried flowers, and many other low-cost biomass wastes. Most mechanochemically prepared porous carbons are proposed for applications related to adsorption, catalysis, and energy storage. This review aims to offer researchers insights into the potential utilization of biowastes, facilitating the development of cost-effective strategies for the production of porous carbons that meet industrial demands. Full article

The efficient depolymerization of lignin has become a key challenge in the preparation of high-value-added chemicals. Graphitic carbon nitride (g-C₃N₄)-based photocatalytic system shows potential due to its mild and green characteristics over other depolymerization methods. However, its inherent defects, such as a wide band gap and rapid carrier recombination, severely limit its catalytic performance. In this paper, a g-C₃N₄ modification strategy of K⁺ doping and surface alkalinization is proposed, which is firstly applied to the photocatalytic depolymerization of the lignin β-O-4 model compound (2-phenoxy-1-phenylethanol). K⁺ doping is achieved by introducing KCl in the precursor thermal polymerization stage to weaken the edge structure strength of g-C₃N₄, and post-treatment with KOH solution is combined to optimize the surface basic groups. The structural/compositional evolution of the materials was analyzed by XRD, FTIR, and XPS. The morphology/element distribution was visualized by SEM-EDS, and the optoelectronic properties were evaluated by UV–vis DRS, PL, EIS, and transient photocurrent (TPC). K⁺ doping and surface alkalinization synergistically regulate the layered structure of the material, significantly increase the specific surface area, introduce nitrogen vacancies and hydroxyl functional groups, effectively narrow the band gap (optimized to 2.35 eV), and inhibit the recombination of photogenerated carriers by forming electron capture centers. Photocatalytic experiments show that the alkalinized g-C₃N₄ can completely depolymerize 2-phenoxy-1-phenylethanol with tunable product selectivity. By adjusting reaction time and catalyst dosage, the dominant product can be shifted from benzaldehyde (up to 77.28% selectivity) to benzoic acid, demonstrating precise control over oxidation degree. Mechanistic analysis shows that the surface alkaline sites synergistically optimize the C_β-O bond breakage path by enhancing substrate adsorption and promoting the generation of active oxygen species (·OH, ·O₂⁻). This study provides a new idea for the efficient photocatalytic depolymerization of lignin and lays an experimental foundation for the interface engineering and band regulation strategies of g-C₃N₄-based catalysts. Full article

The elevated oxygen content in lignin-derived oil restricts its direct application as a liquid fuel. Ni-based Al₂O₃ catalysts are commonly employed to enhance the quality of lignin-derived oil via the hydrodeoxygenation (HDO) process. In this study, we successfully synthesized Ni-supported Al₂O₃ catalysts with diverse mesopore structural parameters of the Al₂O₃ support. Subsequently, we investigated the impacts of mesoporous size and volume on the HDO of guaiacol, a representative model compound of lignin-derived oil. The results indicate that optimizing the mesoporous size can enhance catalyst stability and significantly boost selectivity for cyclohexane. Moreover, an increase in the mesoporous volume can further improve the selectivity of cycloalkanes in the products. When the Ni/meso-Al₂O₃-F-100 catalyst was utilized, the cycloalkane selectivity reached 98.8%. During the upgrading of lignin-derived oil, the Ni/meso-Al₂O₃-F-200 catalyst, featuring a mesopore size of 4.07 nm and a mesopore volume of 0.286 cm³/g, exhibited outstanding performance. Notably, its selectivity for alkanes reached 65.9%, significantly higher than that of the commercial Ni/c-Al₂O₃ catalyst, which has a mesopore size of 3.83 nm and a mesopore volume of 0.184 cm³/g. This work offers valuable insights into the design of efficient and stable Ni-based Al₂O₃ catalysts for upgrading lignin-derived oil. Full article

In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO₂ atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article