A combination of experimental and computational methods to study the reactions during a Lignin-First approach

AbstractCurrent pulping technologies only valorize the cellulosic fiber giving total yields from biomass below 50 %. Catalytic fractionation enables valorization of both cellulose, lignin, and, optionally, also the hemicellulose. The process consists of two operations occurring in one pot: (1) solvolysis to separate lignin and hemicellulose from cellulose, and (2) transition metal catalyzed reactions to depolymerize lignin and to stabilized monophenolic products. In this article, new insights into the roles of the solvolysis step as well as the operation of the transition metal catalyst are given. By separating the solvolysis and transition metal catalyzed hydrogen transfer reactions in space and time by applying a flow-through set-up, we have been able to study the solvolysis and transition metal catalyzed reactions separately. Interestingly, the solvolysis generates a high amount of monophenolic compounds by pealing off the end groups from the lignin polymer and the main role of the transition metal catalyst is to stabilize these monomers by transfer hydrogenation/hydrogenolysis reactions. The experimental data from the transition metal catalyzed transfer hydrogenation/hydrogenolysis reactions was supported by molecular dynamics simulations using ReaXFF

Lignin-first biorefining of Nordic poplar to produce cellulose fibers could displace cotton production on agricultural lands

Here, we show that lignin-first biorefining of poplar can enable the production of dissolving cellulose pulp that can produce regenerated cellulose, which could substitute cotton. These results in turn indicate that agricultural land dedicated to cotton could be reclaimed for food production by extending poplar plantations to produce textile fibers. Based on climate-adapted poplar clones capable of growth on marginal lands in the Nordic region, we estimate an environmentally sustainable annual biomass production of similar to 11 tonnes/ha. At scale, lignin-first biorefining of this poplar could annually generate 2.4 tonnes/ha of dissolving pulp for textiles and 1.1 m(3) biofuels. Life cycle assessment indicates that, relative to cotton production, this approach could substantially reduce water consumption and identifies certain areas for further improvement. Overall, this work highlights a new value chain to reduce the environmental footprint of textiles, chemicals, and biofuels while enabling land reclamation and water savings from cotton back to food production

Fractionation of woody biomass : lignin and suberin in focus

This thesis is dedicated to the research of fractionation and valorization of different types of woody biomass. In the first part, oak (Quercus suber) and birch (Betula pendula) barks are considered. Bark is the outer layer of wood and is treated as waste in the current wood processing technologies. The main polymers which form bark are lignin (aromatic polyether) and suberin (aliphatic polyester). In the present study, these compounds have been transformed into monomeric phenols which may serve as a precursors for bio-based polyesters, and hydrocarbon bio-oil of gasoline, diesel, and heavy gas oil ranges. The bio-oil has been studied with GC-MS, 2D GC, and simulated distillation techniques.   The second part concerns birch heartwood. In contrast with bark, wood does not contain suberin but has a higher content of lignin. A variety of fractionation processes are known for wood. The major disadvantages are contamination of pulp with catalyst and irreversible recondensation of lignin which takes place in harsh pulping conditions. For the purpose of solving these problems, a flow process has been developed in which the biomass and the catalyst are separated in time and space and the lignin is stabilized and cleaved into monomers immediately after its extraction. The process has been optimized to obtain monophenolic lignin-derived compounds, while the remaining cellulose pulp was enzymatically converted into glucose. Hemicellulose serves as a hydrogen donor for the lignin reduction, and therefore no external hydrogen source is required. The experimental work was complemented with a theoretical study of the process of lignin cleavage on the Pd surface. Computations under on the ReaxFF approach were used to model the successive steps of the adsorption of the molecules on the catalyst, their fragmentation, reactions, and desorption. The products obtained in the experiment have been also observed in this simulation

Adsorption Isotherms of Lignin-Derived Compounds on a Palladium Catalyst

We have studied the interaction of lignin fragments obtained from catalytic fractionation with a heterogeneous palladium catalyst. By studying the adsorption of verified substrate and product molecules on the palladium surface, understanding of what governs adsorption and desorption dynamics of both substrates and products has been obtained. In addition, we have studied the kinetic isotope effect of hydrogen-transfer reactions occurring on the surface of the catalyst. These studies give insights into the thermodynamics of the process in which species from lignin-derived species adsorb to the catalyst surface, are then transformed by hydrogenation–hydrogenolysis reactions in a slow reaction step, and finally desorbed. It was found that the adsorption dynamics depended on the degree of unsaturation as well as the presence of methoxy groups on the aryl. Thereby, the adsorption is stronger for substrate molecules derived from lignin than for reduced molecules obtained after the rate-determining transfer-hydrogenation and hydrogenolysis transformations.

Valorization of Quercus suber Bark toward Hydrocarbon Bio-Oil and 4-Ethylguaiacol

A reductive fractionation process for the valorization of Quercus suber bark toward hydrocarbons in gasoline and diesel ranges and optionally 4-ethylguaiacol has been developed. The procedure involves three steps: (1) tandem hydrogen-free Pd/C-catalyzed transfer hydrogenolysis of lignin where the carbohydrates serve as an inherent hydrogen donor under slightly alkaline conditions to also facilitate the depolymerization of suberin, (2) optional distillation, to isolate the 4-ethylguaiacol, (3) hydrodeoxygenation of the mixture from the first step by a Pt-MoO3/TiO2 catalyst generated hydrocarbons in gasoline and diesel ranges. The yield of 4-ethylguaiacol (90% purity) is 2.6% of dry bark weight (12% of acid insoluble lignin), and yield of hydrocarbon bio-oil is 42% of dry bark weight. This corresponds to a theoretical maximum yield of 77% for lignin and suberin. The carbon yield of the obtained bio-oil is thereby 64% from the total initial bark

Valorization of <i>Quercus suber</i> Bark toward Hydrocarbon Bio-Oil and 4‑Ethylguaiacol

A reductive fractionation process for the valorization of Quercus suber bark toward hydrocarbons in gasoline and diesel ranges and optionally 4-ethylguaiacol has been developed. The procedure involves three steps: (1) tandem hydrogen-free Pd/C-catalyzed transfer hydrogenolysis of lignin where the carbohydrates serve as an inherent hydrogen donor under slightly alkaline conditions to also facilitate the depolymerization of suberin, (2) optional distillation, to isolate the 4-ethylguaiacol, (3) hydrodeoxygenation of the mixture from the first step by a Pt-MoO₃/TiO₂ catalyst generated hydrocarbons in gasoline and diesel ranges. The yield of 4-ethylguaiacol (90% purity) is 2.6% of dry bark weight (12% of acid insoluble lignin), and yield of hydrocarbon bio-oil is 42% of dry bark weight. This corresponds to a theoretical maximum yield of 77% for lignin and suberin. The carbon yield of the obtained bio-oil is thereby 64% from the total initial bark

Conversion of birch bark to biofuels

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Conversion of birch bark to biofuels

International audienceSubstitution of fossil energy sources for bio-based ones will require development of efficient processes that can convert inedible and preferably low-value fractions that currently are not used into high-value products. It is desirable that such processes are developed so that both current logistics and infrastructure can be used. Bark, which is the outer layer of woody biomass, is currently burnt in a low-value process or left in the forests to decay and is therefore considered waste. In this work, birch (Betula pendula) bark was converted to hydrocarbons suitable for use in both road and aviation fuels in two efficient steps. Development of an efficient, recyclable, salt- and metal-free solvent-based system to solubilize birch bark under benign reaction conditions was a key outcome. The obtained gum was composed of organosolv lignin and suberin oligomers and was fully characterized. This gum had unique properties and could be directly processed in a conventional hydroprocessing unit set-up to afford hydrocarbons in the road and aviation fuel ranges. Life cycle assessment was applied to evaluate different scenarios for implementing this technology. When using bark generated as a forestry by-product and current infrastructure in a pulp mill, the process had a favorable low carbon dioxide footprint for biofuel generation

Lignin-first biorefining of Nordic poplar to produce cellulose fibers could displace cotton production on agricultural lands

Here, we show that lignin-first biorefining of poplar can enable the production of dissolving cellulose pulp that can produce regenerated cellulose, which could substitute cotton. These results in turn indicate that agricultural land dedicated to cotton could be reclaimed for food production by extending poplar plantations to produce textile fibers. Based on climate-adapted poplar clones capable of growth on marginal lands in the Nordic region, we estimate an environmentally sustainable annual biomass production of ∼11 tonnes/ha. At scale, lignin-first biorefining of this poplar could annually generate 2.4 tonnes/ha of dissolving pulp for textiles and 1.1 m3 biofuels. Life cycle assessment indicates that, relative to cotton production, this approach could substantially reduce water consumption and identifies certain areas for further improvement. Overall, this work highlights a new value chain to reduce the environmental footprint of textiles, chemicals, and biofuels while enabling land reclamation and water savings from cotton back to food production

Use of a fully biobased and non-reprotoxic epoxy polymer and woven hemp fabric to prepare environmentally friendly composite materials with excellent physical properties

International audienceIn the future, materials will need to be biobased and produced sustainably without compromising mechanical properties. To date, in many cases, the advantages of the bio-origin of the raw material are overridden by the environmental impact of the process. In the present study, we have developed a novel composite material basedon woven hemp fabric which reinforce a thermoset polymer produced from birch bark, a low-value forestry byproduct. Results show that this fully biobased composite has specific stiffness and strength equivalent to those of flax fibre-reinforced petroleum-based epoxy composites and slightly lower than glass fibre-reinforced petroleum-based epoxy composites. The sustainability of the material was also evaluated by life-cycle assessment from cradle to gate and showedsignificantly superior performance with respect to the potentialglobal warming impact than commercial benchmark materials.Furthermore, toxicology studies showed no endocrine disruptiveactivities. This is an important proof of concept studydemonstrating that biobased structural materials can be producedsustainably