The catalytic oxidation of phenethoxybenzene as a lignin model compound with a β-O-4 bond was conducted using the Keggin-type polyoxometalate nanocatalyst (TBA)sub.5PMosub.10Vsub.2Osub.40. The ...optimization of the process’s operational conditions was carried out using response surface methodology. The statistically significant variables in the process were determined using a fractional factorial design. Based on this selection, a central circumscribed composite experimental design was used to maximize the phenethoxybenzene conversion, varying temperature, reaction time, and catalyst load. The optimal conditions that maximized the phenethoxybenzene conversion were 137 °C, 3.5 h, and 200 mg of catalyst. In addition, under the optimized conditions, the Kraft lignin catalytic depolymerization was carried out to validate the effectiveness of the process. The depolymerization degree was assessed by gel permeation chromatography from which a significant decrease in the molar mass distribution Mw from 7.34 kDa to 1.97 kDa and a reduction in the polydispersity index PDI from 6 to 3 were observed. Furthermore, the successful cleavage of the β-O-4 bond in the Kraft lignin was verified by gas chromatography–mass spectrometry analysis of the reaction products. These results offer a sustainable alternative to efficiently converting lignin into valuable products.
Lignin obtained by hydrogenolysis of lignocellulose biomass is a prospective source of valuable green fuels and chemicals such as monophenols. One of the key factors in the chemical decomposition of ...lignin to monophenols is an efficient catalyst. Inert porous materials such as hypercrosslinked polymers are suitable catalytic supports for the immobilization of noble and transition metal nanoparticles. However, such polymers do not have acidic properties, which are crucial for catalyzing hydrolysis. In this work, we report novel, efficient catalysts for lignin hydrogenolysis to produce valuable monophenolic compounds. The synthesized catalysts contained Ni, Ru, and Ni-Ru nanoparticles supported on SiOsub.2-coated hypercrosslinked polystyrene (SiOsub.2@HPS). Ni-Ru/SiOsub.2@HPS demonstrated remarkable stability without any loss of the metallic phase and a high yield of monophenols (>42 wt.%) at close to full lignin conversion (>95 wt.%). This result was attributed to the synergy between the two metals and the support's surface acidity. All catalysts were fully characterized by a series of physico-chemical methods.
In the present study, the effects of macro- and microclimatic conditions, month of harvest, and leaf age at harvest on the bromatological composition and polyphenol content of Gymnopodium floribundum ...leaves were evaluated. Leaves were harvested in December 2017 and 2018 and March, June, and September 2018. At each harvest, three composite samples of mixed-age leaves were collected from 12 trees (four trees for each sample), and the sampling was repeated on day 90 post-harvest to collect 90-day-old leaves. Fresh and dry matter, crude protein, acid and neutral detergent fibers (ADF and NDF, respectively), lignin, total tannins, condensed tannins (CT), total phenols, in vitro dry matter (IVDMD) and organic matter (IVOMD) digestibility, and metabolizable energy (ME) were estimated. Rainfall, relative humidity, and microhumidity were associated with chemical composition. IVDMD, IVOMD, and ME were highest in leaves sampled in March regardless of age (p < 0.001). Water content, ADF, NDF, and lignin were highest in the leaves sampled in September, regardless of age (p < 0.05), suggesting that leaves require more structural support in the rainy season. CT content was highest in September in the mixed-age leaves and in September and December in the 90-day-old leaves (p < 0.05). A high fiber and CT content during the period of rapid leaf growth could deter herbivory.
Lignin, the term commonly used in literature, represents a group of heterogeneous aromatic compounds of plant origin. Protolignin or lignin in the cell wall is entirely different from the ...commercially available technical lignin due to changes during the delignification process. In this paper, we assess the status of lignin valorization in terms of commercial products. We start with existing knowledge of the lignin/protolignin structure in its native form and move to the technical lignin from various sources. Special attention is given to the patents and lignin-based commercial products. We observed that the technical lignin-based commercial products utilize coarse properties of the technical lignin in marketed formulations. Additionally, the general principles of polymers chemistry and self-assembly are difficult to apply in lignin-based nanotechnology, and lignin-centric investigations must be carried out. The alternate upcoming approach is to develop lignin-centric or lignin first bio-refineries for high-value applications; however, that brings its own technological challenges. The assessment of the gap between lab-scale applications and lignin-based commercial products delineates the challenges lignin nanoparticles-based technologies must meet to be a commercially viable alternative.
Ruthenium-triphos complexes exhibited unprecedented catalytic activity and selectivity in the redox-neutral CC bond cleavage of the beta-O-4 lignin linkage of 1,3-dilignol model compounds. A ...mechanistic pathway involving a dehydrogenation-initiated retro-aldol reaction for the CC bond cleavage was proposed in line with experimental data and DFT calculations.
•Lignin-related factor and its relationships with biomass conversion are reviewed.•Roles of lignin in biological conversion process are discussed.•Most recent lignin-targeting pretreatment strategies ...are summarized.•Change of lignin properties by diverse pretreatment strategies are compared.•Perspectives for future pretreatment in biorefinery process are provided.
Heterogeneity and rigidity of lignocellulose causing resistance to its deconstruction have provided technical and economic challenges in the current biomass conversion processes. Lignin has been considered as a crucial recalcitrance component in biomass utilization. An in-depth understanding of lignin properties and their influences on biomass conversion can provide clues to improve biomass utilization. Also, utilization of lignin can significantly increase the economic viability of biorefinery. Recent lignin-targeting pretreatments have aimed not only to overcome recalcitrance for biomass conversion but also to selectively fractionate lignin for lignin valorization. Numerous studies have been conducted in biomass characteristics and conversion technologies, and the role of lignin is critical for lignin valorization and biomass pretreatment development. This review provides a comprehensive review of lignin-related biomass characteristics, the impact of lignin on the biological conversion of biomass, and recent lignin-targeting pretreatment strategies. The desired lignin properties in biorefinery and future pretreatment directions are also discussed.
•Human history mainly relies on the biopolymers.•Derivatives of lignin like sulfonate, phenolic, organosolv, kraft and sodium sulfonate lignin have good mechanical, chemical and physical ...properties.•Functionalizations by lignin are very appropriate for the development of well-designed materials.•The review sheds a light on lignin derivatives based materials with potential applications.
Lignin and lignin derivatives biopolymers have several properties, such as high thermal stability, antioxidant, biodegradability, antimicrobial actions, adhesive properties, etc., and thus they can be extensively used in wide range of areas. Although human history mostly depend on the biopolymers, however derivatives of lignin such as sulfonate, phenolic, organosolv, Kraft and sodium sulfonate lignin have good mechanical and physicochemical properties. Well-designed materials such as coatings and paints, manufacturing of plastics and resins, for rubber packaging, for fuel production etc., can be obtained by the functionalizations of chemically modified lignin. Considering multi purposes properties of the lignin and lignin derivatives and extensive industrial applications of derivatives, this review sheds a light on lignin derivatives based materials with their prospective applications. All the technical scientific issues have been addressed highlighting the recent advancement.
Lignin is a primary component of lignocellulosic biomass and an underutilized feedstock in the growing pulping and biofuel industries. Currently, over 50 million tons of industrial lignin are ...produced annually from pulping and bioethanol processes in the world. Around 95 % of industrial lignin is burned as fuel in heat and power plants due to its complicated, destructive, and condensed structures hindering direct industrial utilization, while the remaining 5 % of lignin is used for potential applications, such as additives, binders, dispersants, and surfactants, through modification. Meanwhile, different biorefinery processes also produce a considerable amount of lignin with various structural features and properties. The development of technologies for its structural characterization is currently desirable for lignin valorization, which will improve the techno‐economics of applications of lignins in industries.
Sources and structures: Lignin is a primary component of lignocellulosic biomass and an underutilized industrial feedstock. Currently, about 95 % of industrial lignin is burned as fuel in heat and power plants because its structure hinders direct industrial utilization, and 5 % is used for applications after modification. Hence, the development of methods for its structural characterization are desirable for lignin valorization, which will improve the techno‐economics of industrial applications of lignins.
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