Lignin-derived Fraction Research Articles

Metal-Based Heterogeneous Catalysts for the Synthesis of Valuable Chemical Blends via Hydrodeoxygenation of Lignin-Derived Fractions

Currently, many research projects are focused on the conversion of renewable raw materials into chemicals and fuels. Lignocellulosic biomass is a raw material used for the production of bio-oils and black liquors. These biomass-derived fractions offer promising paths for the production of valuable chemical products. Various catalytic methods have been investigated for upgrading the biomass-derived fractions. Researchers are interested in the hydrodeoxygenation process (HDO); in this process, the oxygen groups are eliminated by breaking the C-O bonds and water as a product. Incorporating heterogeneous catalysts (i.e., noble metals, transition metals, and metal sulfides) improves this process. Most HDO review articles describe catalytic results for model phenolic compounds. However, there is also a need to investigate the catalytic activity of real biomass-derived fractions. This paper explains research results regarding the upgrading of lignin-derived fractions (i.e., black liquors) by HDO. The paper has been organized according to the type of heterogeneous catalyst and shows compelling results based on different experimental conditions. The final sections present an analysis of the documented results and outline perspectives about integrating lignin into the biorefinery framework.

The in-situ formation of supported hydrous ruthenium oxide in aqueous phase during HDO of lignin-derived fractions

The in-situ formation of supported hydrous ruthenium oxide (HRO) from RuO2 over micro-mesoporous materials is reported for the selective hydrogenation of bio-oil under mild reaction conditions (200 °C, 20 bar H2) in an aqueous medium. For the first time, the phase composition of HRO was determined using a variety of characterization techniques. Using synchrotron radiation and in-situ X-ray absorption spectroscopy (XAS), we demonstrated that HRO was generated during the hydrodeoxygenation process. The hydrodeoxygenation (HDO) of real bio-oil was successfully performed at 200 °C, 20 bar H2 on RuO2-containing catalysts. The approximate composition of HRO after 3 h of catalytic hydrogenation, consisted of in approximately equal ratios metallic Ru, RuO2, and RuOOH phases.

Antifungal activity of simply fractionated organosolv lignin against Trametes versicolor

In an effort to achieve sustainable development goals, a reevaluation of the materials used in wooden buildings must be done, including the preservatives used to treat the materials. Since typical wood preservatives use toxic heavy metals, their handling and use can contaminate the environment. Therefore, substances such as lignin-derived components have been investigated as bio-based preservatives. Organosolv treatment is a promising technique for separating components of lignocellulosic biomass, which enables the utilization of each component. The present report describes components of lignocellulose with antifungal effects that were recovered after organosolv treatment using water and 1-butanol solvent at 473 K for 2 h, followed by simple solvent fractionation. The organosolv lignin was divided into three fractions: n-hexane soluble, ethyl acetate soluble, and ethyl acetate insoluble, yielding 23 wt%, 52 wt% and 13 wt%, respectively. Antifungal activity was determined using an agar plate method. White rot fungi (Trametes versicolor) was dispersed on the agar plate with a cellulose disc containing each lignin-derived fraction obtained from Japanese cedar. Results showed inhibition of fungal growth over the cellulose disc containing the n-hexane soluble fraction. To examine the effect in greater detail, the chemical structure of the n-hexane-soluble fraction on the antifungal activity was investigated. The content of phenolic hydroxyl group in n-hexane-soluble fraction was the highest (4.6 mmol/g), and the results from the chemical modification suggested that the functional group was required for antifungal action. In addition, the n-hexane-soluble fraction imparted some water resistance. The procedures used for cedar as a feedstock were applied to another type of biomass—bagasse—and its fractions showed antifungal activity similar to those of Japanese cedar.

Determination of carbonyl functional groups in lignin-derived fraction using infrared spectroscopy

Carbonyl functional groups contained within lignin-derived fractions were examined using Fourier-transform infrared spectroscopy (FT-IR). The absorption of carbonyl in lignin-derived fractions with and without dimethyl sulfoxide-d6 (DMSO‑d6) was observed at 1707 cm−1. This absorption captured aliphatic ketones, aliphatic carboxylic acids, or aromatic esters because the absorption range of cyclohexanone, heptanoic acid, ethyl benzoate, and butyl benzoate with and without DMSO‑d6 is 1704–1721 cm−1. To estimate the amount of carbonyl in the lignin-derived fraction, DMSO‑d6 solutions of various model carbonyl compounds were analyzed by FT-IR. The FT-IR area ratios of these compounds to carbon-deuterium in DMSO‑d6 at 2250 cm−1 increased proportionally to their mole ratios. The carbonyl oxygen to carbon atomic ratio in the lignin-derived fraction was estimated to be 0.05, indicating that approximately 20% of oxygen in the lignin-derived fraction was from carbonyl functional groups.

Valorization of Pyrolysis Liquids: Ozonation of the Pyrolytic Lignin Fraction and Model Components

Pyrolytic lignin is the collective name of the lignin-derived fraction of pyrolysis liquids. Conversion of this fraction to biobased chemicals is considered an attractive valorization route. Here we report experimental studies on the ozonation of a pine-derived pyrolytic lignin dissolved in methanol (33 wt %). Results show a high reactivity of ozone, and a molecular weight reduction of up to 40% was obtained under mild conditions (0 °C, atmospheric pressure) without the need for catalysts. Detailed analysis of the product mixtures (GC/MS-FID, HPLC, GPC, NMR) showed the presence of low molecular weight (di)acids and esters, along with larger highly oxygenated aliphatics. A reaction network is proposed including the heterolytic cleavage of aromatic rings, followed by secondary reactions. The observations were supported by experimental studies using representative pyrolytic lignin model compounds and a biosynthetic lignin oligomer, which aided further elucidation on the reactivity trends for different chemic...

Pyrolysis–mass spectrometry confirms enrichment of lignin in the faeces of a wood-feeding termite, Zootermopsis nevadensis and depletion of peptides in a soil-feeder, Cubitermes ugandensis

Changes in biopolymer products during transit of the intestine in two termites with contrasting feeding habits were quantified by pyrolysis mass-spectrometry. In Zootermopsis nevadensis, a wood-feeder, native lignin-derived fractions increased in the faeces, with little indication of modification or degradation, but 62% of hexose polymer and 43% of xylan were degraded. In the soil-feeding Cubitermes ugandensis, polysaccharide and alkene-derived mass ions were enriched in faeces while amino acid-derived ions were depleted, consistent with a proposed model of fermentative digestion supported by peptides released from soil organic matter.

Fast Pyrolysis of Forestry Residue and Pine. 4. Improvement of the Product Quality by Solvent Addition

Addition of alcohols was found to improve the homogeneity, decrease the viscosity and density, lower the flash point, and increase the heating value of pyrolysis liquids. Alcohol addition also lowered the viscosity and molecular mass increase during the aging of pyrolysis liquids. The reduction in the viscosity change was primarily due to a stabilizing effect of alcohols on the water-insoluble high molecular mass lignin-derived fraction. Other effects include the formation of acetals in reactions of alcohols with aldehydes, ketones, and anhydrosugars. Low (≤5 wt %) alcohol additions prevented aging reactions by a few months, while the higher (≥10 wt %) ones retarded them by almost a year. Methanol was the most effective alcohol of those tested (methanol, ethanol, isopropanol). By improving solubility, the alcohols also enhanced the separation of the extractive-rich top layer in the pyrolysis of forestry residue by decreasing its volume and increasing the concentration of extractives and solids in the top ...

Hydrogen by Catalytic Steam Reforming of Liquid Byproducts from Biomass Thermoconversion Processes

Biomass, a product of photosynthesis, is a renewable resource that can be used for sustainable production of hydrogen. We propose an approach that combines production of hydrogen with valuable coproducts and shows promising economics. The concept is based on a two-stage process: fast pyrolysis of biomass to generate bio-oil, followed by catalytic steam reforming of the bio-oil, or a fraction thereof, to produce hydrogen. The preferred option is separation of the bio-oil into a lignin-derived fraction, which could be used for producing phenolic resins or fuel-blending components, and a carbohydrate-derived material, which would be reformed to produce hydrogen. The coproduct strategy can also be applied to residual fractions derived from pulping operations or ethanol production and to effluents from other biomass conversion technologies such as transesterification of vegetable oils or food processing residues. In addition, all of the biomass-derived liquids can be coprocessed with natural gas to produce hydrogen from mixed fossil−biomass feedstocks, a strategy similar to cofiring biomass and coal for power generation. This work focuses on the second stage of the process: catalytic steam reforming of various biomass-derived liquids. We have used a commercial nickel-based naphtha reforming catalyst in a fluidized-bed reactor to produce hydrogen from the various biomass-derived liquids. Yields have approached or exceeded 80% of those theoretically possible for stoichiometric conversion.

The Characterization of a Lignin-Derived Organic Matter Fraction in Soils Developed Under Different Vegetation Types

1. Soil profiles developed under beech woodland, spruce woodland, pasture and arable cropping were analysed for total organic C and lignin derivatives extracted by CuO oxidation. This reaction primarily releases lignin-derived phenylpropanoid moieties from soil organic matter(SOM). The amount and composition of the moieties obtained provided a signature that was related to the origin of organic matter from particular soil horizons. 2. There were clear differences between the lignin-derived phenylpropanoid signatures from similar depth horizons of soils developed under beech, spruce and pasture. This was characterized by: equal amounts of syringyl and vanillyl residues; a low syringyl:vanillyl ratio; and high concentration of ferulic acid, respectively, in the surface soil layers. The arable soil profile showed little differentiation in phenylpropanoid signature with depth (0-18 cm), presumably because of annual tillage. 3. Further investigation into the degradation rates of individual phenylpropanoid moieties in soils and their adsorption onto soil fractions is required. A more extensive survey, characterizing the 'lignin'-derived fraction in soils with a well documented land use history is also needed to establish a time scale for the translocation and degradation of the phenylpropanoid signatures of soils. Once calibrated, however, temporal changes in the composition of the lignin-phenylpropanoid SOM fraction will be potentially useful in monitoring the effects of vegetation and land management change on soil C cycling.

Molecular paleobotany ofNyssaendocarps

SUMMARY Fruit endocarps of three recent Nyssa species from southern Georgia and endocarps of three Nyssa species from the late-Oligocene Brandon lignite, VT. are characterized and compared using pyrolysis gas chromatography–mass spectrometry (PYGCMS), pyrolysis-mass spectrometry (PYMS and desorption chemical ionization mass spectrometry DCIMS), and microscopic techniques. PYGCMS and PYMS demonstrated that during the lignitization process almost all of the carbohydrate material is removed from the endocarp fibre walls. Some hexose oligomer residues do survive lignitization as levoglucosan was observed in the PYGCMS trace of the lignitic endocarp N. fissilis and mass peaks indicative for anhydrohexose oligomers were observed in DCIMS spectra of N. fissilis and N. brandoniana. The PYGCMS data on the mixed guaiacyl–syringyl lignin in the recent and fossil endocarp wall have very similar pyrolysis product distributions. The abundance of phenolic pyrolysis products with aliphatic side chains suggest a different less oxygenated lignin in the endocarps compared to the Nyssa xylem cell walls. In spite of the significant chemical changes which occur during the early coalification process considerable microscopic detail can be preserved. Some fibre cell walls even retained an anisotropic character which may be caused by preserved crystalline cellulose. The effect of storage conditions on the chemistry of the paleobotanical samples was investigated by PYMS and multivariate analysis. Fossil endocarps stored in glycerin/ethanol experienced some extraction of a soluble lignin-derived fraction whereas water-stored endocarps did not. The residues of water glycerol/ethanol stored samples have similar polyphenolic polymers.