Biomass Lignin Research Articles

A concerted enzymatic de-structuring of lignocellulosic materials using a compost-derived microbial consortia favoring the consolidated pretreatment and bio-saccharification

The robustness of microbial consortia isolated from compost habitat encompasses the complementary metabolism that aids in consolidated bioprocessing (CBP) of lignocellulosic biomass (LCB) by division of labor across the symbionts. Composting of organic waste is deemed to be an efficient way of carbon recycling, where the syntrophic microbial population exerts a concerted action of lignin and polysaccharide (hemicellulose and cellulose) component of plant biomass. The potential of this interrelated microorganism could be enhanced through adaptive laboratory evolution (ALE) with LCB for its desired functional capabilities. Therefore, in this study, microbial symbionts derived from organic compost was enriched on saw dust (SD) (woody biomass), aloe vera leaf rind (AVLR) (agro-industrial waste) and commercial filter paper (FP) (pure cellulose) through ALE under different conditions. Later, the efficacy of enriched consortium (EC) on consolidated pretreatment and bio-saccharification was determined based on substrate degradation, endo-enzymes profiling and fermentable sugar yield. Among the treatment sets, AVLR biomass treated with EC-5 has resulted in the higher degradation rate of lignin (47.01 ± 0.66%, w/w) and polysaccharides (45.87 ± 1.82%, w/w) with a total sugar yield of about 60.01 ± 4.24 mg/g. In addition, the extent of structural disintegration of substrate after EC-treatment was clearly deciphered by FTIR and XRD analysis. And the factors of Pearson correlation matrix reinforces the potency of EC-5 by exhibiting a strong positive correlation between AVLR degradation and the sugar release. Thus, a consortium based CBP could promote the feasibility of establishing a sustainable second generation biorefinery framework.

Impact of pretreatment with photocatalysis sequential coupling Fenton oxidation on physicochemical properties, pyrolysis behaviors, and product distribution of walnut shell

Naturally occurring alkali and alkaline earth metals (AAEMs) in biomass can adversely affect its pyrolysis behavior and product distribution and contribute to ash deposition in boilers. To address these challenges, we proposed a new idea of photocatalysis sequential coupling Fenton oxidation for biomass pretreatment. Our findings revealed that sequential pretreatment has the optimal moderating effects on biomass relative to individual photocatalysis and Fenton oxidation. The lignin and AAEMs in biomass were effectively reduced via sequential pretreatment, which was accompanied by cellulose content increased by 80.78% relative to untreated. Also, the slagging/fouling inclinations of biomass were successfully alleviated, and the pyrolysis performance was effectively improved. The kinetic parameters obtained based on the Coats-Redfern method can characterize the pyrolysis behavior well. During fast pyrolysis, sequential pretreatment caused the productivity of bio-oil was increased by 30.14% relative to untreated. In particular, the productivity of levoglucosan in bio-oil was increased by 364.71%. This study presented a novel and effective pretreatment strategy to improve the pyrolysis behavior and product distribution of biomass and alleviate ash deposition problems in boilers.

Study on the effect mechanism of Ca and Mg with different anion on lignocellulosic biomass pyrolysis

Alkaline earth metals (AEMs) act an important role on biomass pyrolysis, which is significant to explore its specific mechanism for further understanding biomass pyrolysis. This study analyzed the influence of Ca and Mg with different anion (CaO, CaCO3, CaCl2, MgSO4, MgCl2) on biomass pyrolysis, and explored the influence mechanism on the pyrolytic products. Ca and Mg with different anion had obvious different effect on the pyrolytic products from biomass. CaCO3 had little effect on the distribution of products. And CaO might react with CO2 and acetic acid to form CaCO3, which resulted in that solid yield obviously increased and oil yield decreased. Besides, CaCl2 and MgCl2 intensified the ring-open reaction of pyran ring to generate furan. And the formed acidic condition from CaCl2 and MgCl2 decomposition might be beneficial to C-C fracture, carboxylation to generate linear aliphatic, CO2, and acetic acid, but inhibited the generation of CO. Compared with Ca, Mg had more promotion on the generation of linear aliphatics and cyclopentanones. For biomass, CaCl2 and MgCl2 adding might weaken the connection bond between the hemicellulose and cellulose (HC-C) and hemicellulose and lignin (HC-L) in biomass, and resulted in phenyl and CO2 decreasing but androsugar increasing. However, CaO addition could result in androsurgar decreasing with phenyl increasing.

Continuous flow upgrading of lignin pyrolysis oils to drop-in bio-hydrocarbon fuels over noble metal catalysts

Although there are many studies on the noble metal-based catalysts for the hydrodeoxygenation (HDO) of lignin model compounds such as phenols, HDO studies on lignin biomass pyrolysis oil are relatively scarce. Owing to its complex composition (i.e., a mixture of phenolic monomers and oligomers), the activity and stability of the catalysts for the HDO of pyrolysis oil are significantly different from those for the model compounds. In this study, the catalytic performances of typical HDO catalysts, that is, Ru, Pd, Ru-Re supported on carbon, and the effects of process parameters such as solvent, temperature, and space velocity were investigated for the real lignin pyrolysis oils in a continuous-flow trickle bed reactor system for the first time. We demonstrated that proper tuning of catalyst composition and process parameters allows for producing the deoxygenated hydrocarbon mixtures which can be used for gasoline, jet fuel, and diesel fuels. Specifically, activated carbon promoted the HDO of lignin oil more effectively than acidic supports like HZSM-5 and TiO2 due to the weak adsorption of phenolic molecules. Among the different metals, Ru-Re supported on carbon exhibited the highest deoxygenation activity due to the synergy of the two metals. Tetrahydrofuran was the best solvent for lignin oil processing due to its high solubility and inertness to other side reactions (e.g., excess alkylation with ethanol solvent). The use of low space velocity of 0.2 h−1 and intermediate temperature of 350 °C resulted in the highest yield of the upgrade oil (∼25 wt%) simultaneously with the high level of deoxygenation (O/C < 0.04), mainly consisting of branched cycloalkanes. The causes of the catalyst deactivation and regeneration process are also discussed to provide practical significance.

Solid waste of calcium lignin replaces fossil fuel power by gasification to reduce CO2 emissions

Biomass can partially replace fossil fuels for power to reduce CO2 emissions and save non-renewable resources. In the pulp and paper industry, a waste biomass of calcium lignin was obtained by treating chemo-mechanical pulp (CMP) wastewater with calcium oxide. To investigate waste calcium lignin and its potential use in power generation systems in place of fossil fuels, a basic experiment on calcium lignin gasification was conducted. A model of gasification combined power generation was developed. The results showed that, the gasification temperature was 800 °C, the equivalence ratio (ER) was 0.25, the syngas yield was 78.2 wt%, the lower heating value (LHV) of the syngas was 5.15 MJ/Nm3, and the highest cold gas efficiency (CGE) was 57.84%. In the model, the generated electricity and CO2 emissions were 1.10 kg/kWh and 0.62 kg CO2/kWh, respectively. The use of calcium lignin biomass reduced 35.42% of CO2 emissions compared to a traditional coal-fired power plant. In addition, the product value-added was 1.17 RMB per kWh, and this was 82.81% higher than that of the 0.64 RMB of traditional coal-fired power plant.

Polymerized PEI-modified lignin polyphenolic materials by acid hydrolysis-phase separation for removal of Cr (VI) from industrial wastewater

Cr (VI) accumulates in an aqueous environment and exhibits huge harm to human health and the ecological system. Developed lignin biomass materials are complicated to prepare and have limited properties, and advances in lignin phenolic modification are lacking. Herein, an aminated poplar lignin-pyrogallol (PLP-PEI) with a simple design and adjustable phenolic hydroxyl content was developed using the acid hydrolysis-phase separation (AH-PS) method, and modified by the atom transfer radical polymerization (ATRP) strategy. Through diverse characterization analysis, the structural changes of PLP-PEI in the step-by-step synthesis process were monitored. An effective biomass capture system (Bio-Cap) was shown via systematically investigating the adsorption behaviors of Cr (VI) on PLP-PEI under various environmental conditions. Benefiting from introducing phenolic hydroxyl and amino groups, PLP-PEI demonstrated efficient adsorption capacity (598.80 mg/g for Cr (VI)). Additionally, the material also exhibited advantages, including monomeric chemisorption properties, strong reduction capability, and stable regeneration properties. Multiple driving forces were involved in the capture and removal process of Cr (VI), including complexation and electrostatic interaction. The low-cost natural biomass resources supported the industrial-scale synthesis and practical application of advanced aminated lignin polyphenol material, which showed outstanding advantages and enormous potential in the field of water environmental restoration.

Switchable production of aromatics and alkanes by Ni-ReOx/CeO2-catalyzed wood depolymerization

Complete conversion of lignocellulosic biomass into chemicals and fuels is particularly attractive in biorefinery concept while remains a great challenge due to complicated structure of lignocellulose and its notorious resistance to chemical transformation. Herein, a recyclable multifunctional Ni-ReOx/CeO2 catalyst was designed for switchable conversion of lignocellulose to either aromatics or liquid fuels by simple tuning reaction parameters. Under the condition of 200 °C, 1 MPa H2, lignin in woody biomass was deconstructed via lignin-first manner to produce aromatic oil with the mass yield up to 88.4 %, leaving cellulose and hemicellulose intact. Under harsher condition (260 °C, 4 MPa H2), complete conversion of lignocellulose to alkanes was achieved in 43.8 % carbon yield. The control experiments and characterization of the catalyst revealed that ReOx species of Ni-ReOx/CeO2 enhanced Ni dispersion, the strong electronic interaction and synergic effects of Ni and ReOx species played major roles for the flexible transformation.

Unraveling lignin's structural features for catalytic oxidative depolymerization and enhanced renewable resource utilization

The effective utilization of lignin, a complex and abundant biopolymer in biomass, holds great potential for sustainable biomass conversion and the development of renewable resources. This study focuses on the catalytic oxidative transformation of lignin, aiming to unravel its structural features and their impact on product diversity. The significance of the content of β-O-4 linkages in lignin becomes evident as a crucial factor influencing the yield of phenolic monomer products, emphasizing its utmost importance. Additionally, the presence of S-type structural units in lignin positively influences its catalytic conversion efficiency, as evidenced by higher S/G ratios and increased degradation yields. However, the complex nature of lignin, influenced by growth environment and pretreatment methods, presents challenges for its efficient depolymerization and utilization. Therefore, a comprehensive understanding of lignin's structure is crucial for advancing its effective utilization and the development of renewable resources. This research elucidates the catalytic conversion mechanisms of lignin, providing practical implications for promoting the utilization of renewable resources in relevant fields.

How to Reduce Char Formation in the Lignin Degradation Process: A Review

AbstractAs the most abundant biomass resource in nature, the utilization of renewable aromatic rings contained in lignin has always been the focal point for materials science and chemistry. Many of the current lignin degradation methods need to be carried out under harsh conditions such as extremely high temperatures or high pressures. This leads to the cross‐linking reaction between lignin and depolymerization intermediates to produce solid char. The milder method also requires the use of heating, which may also lead to the polymerization of some intermediates in the reaction to form char. It has been a difficult problem for researchers to find a way to reduce the solid char. This review discusses different methods to avoid or reduce char formation and sedimentation, including thermal degradation, electrochemical catalysis, fungal degradation, and mechanochemical methods. The aim of the review is to help reduce char formation during lignin degradation and to increase the rate of lignin biomass degradation.

Innovative parallel synthesis of 5-nonanone and furfural from lignocellulosic biomass accompanied by deep economic analysis

An integrated strategy is developed to utilize all three primary components (cellulose, hemicellulose, and lignin) of lignocellulosic biomass for the coproduction of hydrocarbon fuel (5-nonanone) and bio-chemicals (furfural and high purity lignin). After biomass fractionation, (1) 5-nonanone is produced with high yield of 89% using cellulose-derived γ-valerolactone (GVL), which can potentially serve as a platform molecule for the production of liquid hydrocarbon fuels for the transportation sector; (2) furfural, a valuable platform chemical, is produced using hemicellulose; and (3) production of high-purity lignin, which can be used to produce carbon foams or battery anodes. Separation subsystems are designed to effectively recover the solvents for reuse in the conversion processes, which ultimately improves the economic feasibility of the integrated process, resulting in achieving lower minimum selling price (MSP) of $5.47 GGE-1 for 5-nonanone compared to market price. Heat pump is introduced to perform heat integration, which reduces utility requirements more than 85%. Finally, a wide range of techno-economic analysis is performed to highlight the major cost and technological drivers of the integrated process.

Bimetallic polyoxometalates catalysts for efficient lignin depolymerization: Unlocking valuable aromatic compounds from renewable feedstock

Lignin, a complex and abundant polymer present in lignocellulosic biomass, holds immense potential as a renewable source for the production of valuable aromatic compounds. However, the efficient depolymerization of lignin into these compounds remains a formidable challenge. Here, we present a promising solution by harnessing polyoxometalates (POMs) catalysts, which exhibit improved catalytic performance and selectivity. We synthesized a series of NixCoy@POMs catalysts (POMs: CsPW or CsPMo) and explored their application in the depolymerization of pine lignin, aiming to investigate the influence of different metal species and doping ratios of POMs on catalytic performance. Through meticulous optimization of reaction conditions, we achieved significant yields of valuable aromatic compounds, including methyl vanillate, vanillin, and 4-hydroxy-3-methoxyacetophenone. Furthermore, the Ni0.75Co0.75@CsPMo catalyst demonstrated exceptional efficacy in catalyzing the cracking process of C-C and/or C-O bonds in a β-O-4 dimer model compound. Notably, our catalyst exhibited outstanding stability over five cycles, underscoring its suitability as an effective heterogeneous catalyst for cyclic lignin depolymerization. This study sheds light on the potential of POMs-based catalysts for advancing lignin valorization and offers new avenues for sustainable biomass conversion into valuable chemicals.

Recent Advances of Lignin Functionalization for High-Performance and Advanced Functional Rubber Composites.

The biomass lignin is the only large-volume renewable feedstock that is composed of aromatics but has been largely underutilized and is sought for valorization as a value-added material. Recent research has highlighted lignin as a promising alternative to traditional petrol-based reinforcements and functional additives for rubber composites. This review summarized the recent advances in the functionalization of lignin for a variety of rubber composites, as well as the compounding techniques for effectively dispersing lignin within the rubber matrix. Significant progress has been achieved in the development of high-performance and advanced functional rubber/lignin composites through carefully designing the structure of lignin-based additives and the optimization of interfacial morphologies. This Review discussed the effect of lignin on composite properties, including mechanical reinforcement, dynamic properties, antiaging performance, and oil resistance, and also the advanced stimuli-responsive performance in detail. A critical analysis for the future development of rubber/lignin composites is presented as concluding remarks.

Full biomass-based multifunctional flocculant from lignin and cationic starch

Flocculation is a common process for wastewater treatment. However, the most commonly used organic synthetic flocculants such as polyacrylamide are petroleum-based. In this work, biomass lignin was grafted with cationic starch to synthesize low-cost, green and fully biomass-based multifunctional flocculants. The cationic polyacrylamide was replaced by cheap industrial cationic starch. Hyperbranched multifunctional lignin-grafted cationic starch flocculant (CS-L) was successfully prepared via ring-opening reaction with epichlorohydrin. The mass content of lignin in the grafted product was between 16.6 % and 70.1 %. With the dosage of CS-L between 4.0 and 7.5 mg/l, the turbidity removal rate for 500 mg/l kaolin suspension reached more than 97 %. When the dosage of CS-L was 24 mg/l, the removal rate of 50 mg/l Cu2+ reached 85.7 %. Importantly, when the mixed solution of kaolin particles and Cu2+ was treated, the synchronous removal rates of kaolin and Cu2+ reached 90 % and 72 % respectively in the range of 8.0–12.0 mg/l flocculant addition. The synthesized lignin-grafted cationic starch flocculant showed an excellent multifunctional flocculation function.

An Overview on Production of Lignocellulose-Derived Platform Chemicals Such as 5-Hydroxymethyl Furfural, Furfural, Protocatechuic Acid

Furan derivatives such as 5-hydroxymethyl furfural (HMF) and furfural (FA) and aromatic acids such as protocatechuic acid (PCA) represent the most essential classes of intermediates derived from lignocellulosic biomass. These bio-based compounds are potential feedstocks for producing bio-based chemicals and fuels. However, the derivatives of these bio-based compounds are useful in their antioxidative, antibacterial, and anti-aging activities. Protocatechuic acid (PCA, 2,3-dihydroxybenzoic acid), derived from lignin biomass, is also one of the essential bio-derived aromatic intermediates with an active acid and hydroxyl group, which can elevate it into an important class of potential platform chemicals for the production of value-added chemicals, such as HMF and furfuryl alcohol (FAL). The platform compounds are indeed the most used furan-based feedstocks since their chemical structure allows the preparation of various high-value-added chemicals. The related catalytic techniques are well known for the upgradation of biomass into these platform chemicals and their conversion into value-added chemicals. In this short review, we aim to briefly discuss biomass conversion into FA, HMF, and PCA and related heterogeneous catalytic processes. In addition, a few potential ongoing research trends are also proposed to provide some ideas for the further preparation of bio-based innovative derivatives in a much more green, simple, efficient, and economical way.

Lignin fractionation towards improved rosin emulsification behavior and advanced liquid packaging board sizing performance

The heterogeneity of lignin, due to its intricate chemical composition and inconsistent molecular weight distribution across various sources, would result in inconsistent materials with unpredictable characteristics, thus presenting a significant obstacle and impeding the advancement of lignin-based products. The need for innovative rosin/lignin-based sizing agents for liquid packaging board (LPB) products has yet to be fulfilled, stimulating ongoing research efforts in this area. Herein, to tackle the urgent challenge posed by the lignin inhomogeneity and its effect on sizing performance, we propose a comprehensive approach for the production of fractionated lignin-modified rosin sizing agents for liquid packaging board (LPB) with improved sizing characteristics. This study first fractionated three lignin components from wheat straw-derived lignin and utilized them as adaptable surfactants in the manufacture of cationic dispersion rosin sizing agents. The resulting agents were analyzed and evaluated for their utilization in LPB sizing process, exhibiting improved homogeneity, molecular weight, and hydrophilic group content. The obtained fractionated lignin-modified rosin sizing agents displayed outstanding sizing performance and desirable stability. Additionally, these agents enhance the mechanical and optical properties of LPB products. This study proposed a novel and valorized approach to apply lignin biomass with a fractionation and sustainable method to prepare series lignin-modified rosin sizing agents and their great potential in liquid packaging board applications.

Fast pyrolysis simulation via kinetic approach and multivariate analysis to assess the effect of biomass properties on product yields, properties, and pyrolyzer performance

Fast pyrolysis (FP) is the thermochemical conversion of biomasses and other carbonaceous materials into bio-oil (liquid), char (solid), and gas products to be used to generate heat, power, chemicals, and fuels of lower greenhouse gas emissions. Considering biomass properties highly affect the FP performance, this work used simulation and multivariate analysis tools to assess the effect of the composition of nine Brazilian biomasses on the FP energy demands, product yields, and bio-oil properties. A simulation, representing a pyrolyzer (480 °C, 1-s residence time), product recovery, and char combustion to meet FP energy demands, was built in Aspen Plus v.10 and validated against experimental data. A dataset correlating biomass compositions from 60 sources and FP outputs was obtained and analyzed, via two statistical methods, to detect similarities between feedstocks and correlate biomass inputs and process outputs. Hierarchical cluster analysis (HCA) separated the feedstocks into two main clusters: agricultural and woody biomasses. The main differences were associated with agricultural feedstocks having higher biomass H/C ratios, lower carbon and volatiles contents, and being of the CHL type (cellulose > hemicellulose > lignin), resulting in lower char and higher gas yields. As for correlations between inputs and outputs, HCA and principal component analysis (PCA) divided the parameters into five main groups: (i) biomass O/C ratio and cellulose content; (ii) bio-oil yield, heating value, and extractives content; (iii) biomass H/C ratio, hemicellulose content, and bio-oil quality metrics; (iv) ash content, char yield, and pyrolyzer heat duty; and (v) biomass lignin, volatiles, and heating value with gas yield and heating value. Several anticorrelations were also detected (e.g., bio-oil yield anticorrelated to bio-oil properties; char yield anticorrelated to gas yield). This work hopes to serve as a simplified roadmap for relationships between biomass properties and FP performance, providing guidelines for biomass selection for different bio-oil downstream applications and perspectives on future works on FP simulation.

Enhancing direct deoxygenation of m-cresol to toluene through inhibiting C-C hydrogenolysis via alloying Ni with Cu

Selective hydrodeoxygenation (HDO) of biomass lignin derived phenolics to aromatics is an attractive approach for utilization of biomass lignin, since minimal H2 is consumed. Herein, bimetallic Ni-Cu/SiO2 catalysts with varying Cu/Ni molar ratios were synthesized by a modified homogeneous precipitation-deposition method and tested for HDO of m-cresol at 350 °C and atmospheric pressure. Characterizations indicate the formation of Ni-Cu alloys with an enrichment of Cu on the surface, which breaks the contiguous surface Ni atoms and reduces the Ni ensemble size. Despite bare Ni/SiO2 favors both C-C hydrogenolysis to CH4 and direct deoxygenation (DDO) to toluene, Ni-Cu/SiO2 makes DDO the dominant pathway (yield of 7.6% at conversion of 9.6% and yield of 90.4% at conversion of 95.2%) while suppresses the C-C hydrogenolysis to a very minor one. Ni-Cu/SiO2 with an optimal Cu/Ni molar ratio of 0.5 produced a turnover frequency (TOF) of 3.09 min−1 for m-cresol conversion. The TOF for toluene formation on Ni-Cu/SiO2 increases by ∼3 times to 2.24 min−1 from that on bare Ni/SiO2 whereas the TOF of CH4 formation is reduced by ∼10 times to 0.16 min−1. This study demonstrates that dilution of Ni by an inert metal such as Cu can effectively enhance DDO through inhibiting C-C hydrogenolysis during HDO of phenolics at atmospheric pressure.

Lignocellulosic Biomass-Based Carbon Dots: Synthesis Processes, Properties, and Applications.

Carbon dots (CDs), a new type of carbon-based fluorescent nanomaterial, have attracted widespread attention because of their numerous excellent properties. Lignocellulosic biomass is the most abundant renewable natural resource and possesses broad potential to manufacture different composite and smart materials. Numerous studies have explored the potential of using the components (such as cellulose, hemicellulose, and lignin) in lignocellulosic biomass to produce CDs. There are few papers systemically aiming in the review of the state-of-the-art works related to lignocellulosic biomass-derived CDs. In this review, the significant advances in synthesis processes, formation mechanisms, structural characteristics, optical properties, and applications of lignocellulosic biomass-based CDs such as cellulose-based CDs, hemicellulose-based CDs and lignin-based CDs in latest research are reviewed. In addition, future research directions on the improvement of the synthesis technology of CDs using lignocellulosic biomass as raw materials to enhance the properties of CDs are proposed. This review will serve as a road map for scientists engaged in research and exploring more applications of CDs in different science fields to achieve the highest material performance goals of CDs.

Heterologous expression, purification and structural features of native Dictyostelium discoideum dye-decolorizing peroxidase bound to a natively incorporated heme.

The Dictyostelium discoideum dye-decolorizing peroxidase (DdDyP) is a newly discovered peroxidase, which belongs to a unique class of heme peroxidase family that lacks homology to the known members of plant peroxidase superfamily. DdDyP catalyzes the H2O2-dependent oxidation of a wide-spectrum of substrates ranging from polycyclic dyes to lignin biomass, holding promise for potential industrial and biotechnological applications. To study the molecular mechanism of DdDyP, highly pure and functional protein with a natively incorporated heme is required, however, obtaining a functional DyP-type peroxidase with a natively bound heme is challenging and often requires addition of expensive biosynthesis precursors. Alternatively, a heme in vitro reconstitution approach followed by a chromatographic purification step to remove the excess heme is often used. Here, we show that expressing the DdDyP peroxidase in ×2 YT enriched medium at low temperature (20°C), without adding heme supplement or biosynthetic precursors, allows for a correct native incorporation of heme into the apo-protein, giving rise to a stable protein with a strong Soret peak at 402nm. Further, we crystallized and determined the native structure of DdDyP at a resolution of 1.95Å, which verifies the correct heme binding and its geometry. The structural analysis also reveals a binding of two water molecules at the distal site of heme plane bridging the catalytic residues (Arg239 and Asp149) of the GXXDG motif to the heme-Fe(III) via hydrogen bonds. Our results provide new insights into the geometry of native DdDyP active site and its implication on DyP catalysis.

Pd-Based Nano-Catalysts Promote Biomass Lignin Conversion into Value-Added Chemicals.

Lignin, as a structurally complex biomaterial, offers a valuable resource for the production of aromatic chemicals; however, its selective conversion into desired products remains a challenging task. In this study, we prepared three types of Pd-based nano-catalysts and explored their application in the depolymerization of alkali lignin, under both H2-free (hydrogen transfer) conditions and H2 atmosphere conditions. The materials were well characterized with TEM, XRD, and XPS and others, and the electronic interactions among Pd, Ni, and P were analyzed. The results of lignin depolymerization experiments revealed that the ternary Pd-Ni-P catalyst exhibited remarkable performance and guaiacols could be produced under H2 atmosphere conditions in 14.2 wt.% yield with a selectivity of 89%. In contrast, Pd-Ni and Pd-P catalysts resulted in a dispersed product distribution. Considering the incorporation of P and the Pd-Ni synergistic effect in the Pd-Ni-P catalyst, a possible water-involved transformation route of lignin depolymerization was proposed. This work indicates that metal phosphides could be promising catalysts for the conversion of lignin and lignin-derived feedstocks into value-added chemicals.