Using a low melting solvent mixture to extract value from wood biomass

Secondary Amines from Catalytic Amination of Bio-Derived Phenolics over Pd/C and Rh/C: Effect of Operation Parameters

The production of renewable chemicals using lignocellulosic biomass has gained significant attention in green chemistry. Among biomass-derived chemicals, secondary amines have emerged as promising intermediates for synthetic applications. Here, we report a systematic study on the reductive amination of phenolics with cyclohexylamine using Pd/C and Rh/C as catalysts. The catalytic tests were performed in batch reactors under different reaction conditions (various: amine concentration (0.1–0.4 mol/L), hydrogen pressure (0–2.5 bar), temperature (80–160 °C), and substituted phenols (phenol, o-cresol, p-cresol, and methoxyphenol)) and using tert-amyl alcohol as a solvent. The experimental observations were consistent with a multi-step mechanism, where hydrogenation of phenol to cyclohexanone is followed by condensation of the ketone with cyclohexylamine to form an imine, which is finally hydrogenated to produce secondary amines. In addition, there was evidence of parallel self-condensation of the cyclohexylamine. The study also supported a limited dehydrogenation capacity of Rh/C, unlike Pd/C, which increases this capacity at higher temperatures generating a higher yield of cyclohexylaniline (up to 15%). The study of the alkylated phenols demonstrated that the nature and propensity of hydrogenation of the phenolic controls their amination. Kinetic analysis revealed reaction orders between 0.4 and 0.7 for H2, indicating its dissociative adsorption. Meanwhile, phenol’s order (between 1–1.8) suggests a single participation of this compound in the hydrogenation step. The order of 0.4 for cyclohexylamine suggests its participation as a surface-abundant species. The apparent activation energies derived from a power law approximation were of 37 kJ/mol and 10 kJ/mol on Pd/C and Rh/C, respectively.

Closing the Nutrient Loop-The New Approaches to Recovering Biomass Minerals during the Biorefinery Processes

The recovery of plant mineral nutrients from the bio-based value chains is essential for a sustainable, circular bioeconomy, wherein resources are (re)used sustainably. The widest used approach is to recover plant nutrients on the last stage of biomass utilization processes-e.g., from ash, wastewater, or anaerobic digestate. The best approach is to recover mineral nutrients from the initial stages of biomass biorefinery, especially during biomass pre-treatments. Our paper aims to evaluate the nutrient recovery solutions from a trans-sectorial perspective, including biomass processing and the agricultural use of recovered nutrients. Several solutions integrated with the biomass pre-treatment stage, such as leaching/bioleaching, recovery from pre-treatment neoteric solvents, ionic liquids (ILs), and deep eutectic solvents (DESs) or integrated with hydrothermal treatments are discussed. Reducing mineral contents on silicon, phosphorus, and nitrogen biomass before the core biorefinery processes improves processability and yield and reduces corrosion and fouling effects. The recovered minerals are used as bio-based fertilizers or as silica-based plant biostimulants, with economic and environmental benefits.

Quantitative analyses to estimate the bioaccessibility of a hydrolytically degradable cationic flocculant

Poly(lactic acid) choline iodide ester methacrylate, poly(PLA₄ChMA), is a cationic degradable polymer that can flocculate particles and dewater oil sands from tailings ponds. This novel material has yet to be characterized in terms of environmental and human health. If ingested, this substance may become bioaccessible. The bioaccessibility (bioaccessible fraction) of an ingested contaminant is a measure of the portion of an ingested dose that solubilizes and may be available for systemic absorption. In the present study, the partially degraded flocculant and its degradation products, modelled using lactic acid and choline chloride, were subjected to a modified physiologically based extraction test (PBET). Bioaccessible fractions were estimated by proton nuclear magnetic resonance (¹H-NMR) spectroscopy and by high-performance liquid chromatography (HPLC). The measured bioaccessibility of lactic acid in gastric solution containing choline chloride is ∼100% but slightly dropped to 94% in intestinal solution at a solid-to-liquid ratio of 1:200. The partially degraded poly(PLA₄ChMA) did not degrade further during the PBET and is not solubilized (i.e., 0% bioaccessibility) in the gastric phase but is fully solubilized (i.e., 100% bioaccessibility) in the intestinal phase. At the end of PBET intestinal digestion, the molar ratio of lactic acid to choline chloride in the presence of degraded poly(PLA₄ChMA) was 2, approximately the same as in the initial solution. Thus, lactic acid and choline chloride are solubilized to the same extents in both gastric and intestinal solutions. Results suggest that HPLC can be used to directly estimate the bioaccessibility of lactic acid, whereas ¹H - NMR may be used to indirectly quantify the bioaccessibility of both lactic acid and choline chloride by determining their molar ratio in PBET extracts. In future works, these findings may be applied to the estimation of risks from exposure to poly(PLA₄ChMA) as well as to the remediation of contaminants flocculated by poly(PLA₄ChMA) in tailings ponds and in other wastewaters.

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¹H-NMR combined with HPLC are used to quantify poly(PLA₄ChMA) bioaccessibility.

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Poly(PLA₄ChMA) is 100% bioaccessible in intestinal but not in gastric fluids.

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Degradation products lactic acid and choline chloride are solubilized in GI tract.

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Molar ratio of lactic acid to choline chloride remains constant throughout GI tract.

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Degraded poly(PLA₄ChMA) does not degrade further in simulated human GI tract.

Tunable and functional deep eutectic solvents for lignocellulose valorization

Stabilization of reactive intermediates is an enabling concept in biomass fractionation and depolymerization. Deep eutectic solvents (DES) are intriguing green reaction media for biomass processing; however undesired lignin condensation is a typical drawback for most acid-based DES fractionation processes. Here we describe ternary DES systems composed of choline chloride and oxalic acid, additionally incorporating ethylene glycol (or other diols) that provide the desired 'stabilization' function for efficient lignocellulose fractionation, preserving the quality of all lignocellulose constituents. The obtained ethylene-glycol protected lignin displays high β-O-4 content (up to 53 per 100 aromatic units) and can be readily depolymerized to distinct monophenolic products. The cellulose residues, free from condensed lignin particles, deliver up to 95.9 ± 2.12% glucose yield upon enzymatic digestion. The DES can be recovered with high yield and purity and re-used with good efficiency. Notably, we have shown that the reactivity of the β-O-4 linkage in model compounds can be steered towards either cleavage or stabilization, depending on DES composition, demonstrating the advantage of the modular DES composition.

A review of sustainable lignocellulose biorefining applying (natural) deep eutectic solvents (DESs) for separations, catalysis and enzymatic biotransformation processes

Conventional biorefinery processes are complex, engineered and energy-intensive, where biomass fractionation, a key functional step for the production of biomass-derived chemical substances, demands industrial organic solvents and harsh, environmentally harmful reaction conditions. There is a timely, clear and unmet economic need for a systematic, robust and affordable conversion method technology to become greener, sustainable and cost-effective. In this perspective, deep eutectic solvents (DESs) have been envisaged as the most advanced novel polar liquids that are entirely made of natural, molecular compounds that are capable of an association via hydrogen bonding interactions. DES has quickly emerged in various application functions thanks to a formulations’ simple preparation. These molecules themselves are biobased, renewable, biodegradable and eco-friendly. The present experimental review is providing the state of the art topical overview of trends regarding the employment of DESs in investigated biorefinery-related techniques. This review covers DESs for lignocellulosic component isolation, applications as (co)catalysts and their functionality range in biocatalysis. Furthermore, a special section of the DESs recyclability is included. For DESs to unlock numerous new (reactive) possibilities in future biorefineries, the critical estimation of its complexity in the reaction, separation, or fractionation medium should be addressed more in future studies.

Deep eutectic solvent for lignocellulosic biomass fractionation and the subsequent conversion to bio-based products - A review

Since the introduction of deep eutectic solvent (DES) in biomass processing field, the efficiency of DES in lignocellulosic biopolymer model compounds' (cellulose, hemicellulose and lignin) solubilisation and conversion was widely recognized. Nevertheless, DES's potential for biorefinery application can be reflected more accurately through their performance in raw lignocellulosic biomass processing rather than model compound conversion. Therefore, this review examines the studies on raw lignocellulosic biomass fractionation using DES and the subsequent conversion of DES-fractionated products into bio-based products. The review stresses on three key parts: performance of varying types of DESs and pretreatment schemes for biopolymer fractionation, properties and conversion of fractionated saccharides as well as DES-extracted lignin. The prospects and challenges of DES implementation in biomass processing will also be discussed. This review provides a front-to-end view on the DES's performance, starting from pretreatment to DES-fractionated products conversion, which would be helpful in devising a comprehensive biomass utilization process.

Deep eutectic solvents for polysaccharides processing. A review

In the review a new class of green solvents - Deep Eutectic Solvents (DES) as media for polysaccharides treatment has been presented. They are an alternative for ionic liquids, non- or low toxic, biodegradable multipurpose agents obtained via simple and convenient way. Moreover, a large number of composition possibilities allow to tailor their properties. Because of selective solubilization of polysaccharides DES can be used for lignocellulosic biomass delignification, cellulose extraction as well as cellulose nanofibrillation or nanocrystalization. DES have been applied in extraction, separation or purification of some specific biopolymers like chitin, carrageenans and xylans, but also as components of polysaccharide based materials, e.g. plasticizers (mainly for starch, but also for cellulose derivatives, chitosan, agar and agarose), compatibilizers or modifiers. An interest in applying DES as green solvents increased rapidly within last years and it may be expected that their applications in polysaccharides treatment would be developed also on industrial scale.

Alternatives for Chemical and Biochemical Lignin Valorization: Hot Topics from a Bibliometric Analysis of the Research Published During the 2000–2016 Period

A complete bibliometric analysis of the Scopus database was performed to identify the research trends related to lignin valorization from 2000 to 2016. The results from this analysis revealed an exponentially increasing number of publications and a high relevance of interdisciplinary collaboration. The simultaneous valorization of the three main components of lignocellulosic biomass (cellulose, hemicellulose, and lignin) has been revealed as a key aspect and optimal pretreatment is required for the subsequent lignin valorization. Research covers the determination of the lignin structure, isolation, and characterization; depolymerization by thermal and thermochemical methods; chemical, biochemical and biological conversion of depolymerized lignin; and lignin applications. Most methods for lignin depolymerization are focused on the selective cleavage of the β-O-4 linkage. Although many depolymerization methods have been developed, depolymerization with sodium hydroxide is the dominant process at industrial scale. Oxidative conversion of lignin is the most used method for the chemical lignin upgrading. Lignin uses can be classified according to its structure into lignin-derived aromatic compounds, lignin-derived carbon materials and lignin-derived polymeric materials. There are many advances in all approaches, but lignin-derived polymeric materials appear as a promising option.

Green Processing of Lignocellulosic Biomass and Its Derivatives in Deep Eutectic Solvents

The scientific community has been seeking cost-competitive and green solvents with good dissolving capacity for the valorization of lignocellulosic biomass. At this point, deep eutectic solvents (DESs) are currently emerging as a new class of promising solvents that are generally liquid eutectic mixtures formed by self-association (or hydrogen-bonding interaction) of two or three components. DESs are attractive solvents for the fractionation (or pretreatment) of lignocellulose and the valorization of lignin, owing to the high solubility of lignin in DESs. DESs are also employed as effective media for the modification of cellulose to afford functionalized cellulosic materials, such as cellulose nanocrystals. More interestingly, biomassderived carbohydrates, such as fructose, can be used as one of the constituents of DESs and then dehydrated to 5-hydroxymethylfurfural in high yield. In this review, a comprehensive summary of recent contribution of DESs to the processing of lignocellulosic biomass and its derivatives is provided. Moreover, further discussion about the challenges of the application of DESs in biomass processing is presented.

Pretreatment of Lignocellulosic Biomass with Ionic Liquids and Ionic Liquid-Based Solvent Systems

Pretreatment is very important for the efficient production of value-added products from lignocellulosic biomass. However, traditional pretreatment methods have several disadvantages, including low efficiency and high pollution. This article gives an overview on the applications of ionic liquids (ILs) and IL-based solvent systems in the pretreatment of lignocellulosic biomass. It is divided into three parts: the first deals with the dissolution of biomass in ILs and IL-based solvent systems; the second focuses on the fractionation of biomass using ILs and IL-based solvent systems as solvents; the third emphasizes the enzymatic saccharification of biomass after pretreatment with ILs and IL-based solvent systems.