Acid-Catalyzed Activation and Condensation of the =C5H Bond of Furfural on Aldehydes, an Entry Point to Biobased Monomers

Furfural is an industrially relevant biobased chemical platform. Unlike classical furan, or C-alkylated furans, which have been previously described in the current literature, the =C5H bond of furfural is unreactive. As a result, on a large scale, C=C and C=O bond hydrogenation/hydrogenolysis is mainly performed, with furfuryl alcohol and methyl tetrahydrofuran being the two main downstream chemicals. Here, we show that the derivatization of the -CHO group of furfural restores the reactivity of its =C5H bond, thus permitting its double condensation on various alkyl aldehydes. Overcoming the recalcitrance of the =C5H bond of furfural has opened an access to a biobased monomer, whose potential have been investigated in the fabrication of renewably-sourced poly(silylether). By means of a combined theoretical-experimental study, a reactivity scale for furfural and its protected derivatives against carbonylated compounds has been established using an electrophilicity descriptor, a means to predict the molecular diversity and complexity this pathway may support, and also to de-risk any project related to this topic. Finally, by using performance criteria for industrial operations in the field of fuels and commodities, we discussed the industrial potential of this work in terms of cost, E-factor, reactor productivity and catalyst consumption.

Supramolecular Polymer Network based on Electrophilic Substitution (ES) Adduct of Furan-Triazolinedione

Polymers with furan functionality have been the subject of extensive research on developing sustainable materials applying a limited number of dynamic covalent approaches. Herein, we introduce a facile, dynamic non-covalent approach to make a furan polymer readily accessible for self-healing applications based on its electrophilic substitution (ES) with a commercially available 1,2,4-triazoline-3,5-dione (TAD) derivative, 4-phenyl-TAD (PTAD). A tailor-made furan polymer, poly(furfuryl methacrylate) (PFMA), considering it an initial illustrative example, was rapidly ES modified with PTAD to produce furfuryl-tagged triazolidine that subsequently associated via inter-molecular hydrogen (H-) bonding to produce a thermally reversible supramolecular polymer network under ambient conditions. The H-bonded network was experimentally quantified via ATR-IR analysis and theoretically rationalized via the density functional theory (DFT) study using smaller organic model compounds analogous to the macromolecular system. Thermoreversible feature of the H-bonded triazolidine-derived supramolecular polymer network enabled the solution reprocessing and self-healing of the polymer material.

Bio-based hyperbranched epoxy resins: synthesis and recycling

Epoxy resins (EPs), accounting for about 70% of the thermosetting resin market, have been recognized as the most widely used thermosetting resins in the world. Nowadays, 90% of the world's EPs are obtained from the bisphenol A (BPA)-based epoxide prepolymer. However, certain limitations severely impede further applications of this advanced material, such as limited fossil-based resources, skyrocketing oil prices, nondegradability, and a "seesaw" between toughness and strength. In recent years, more and more research has been devoted to the preparation of novel epoxy materials to overcome the compromise between toughness and strength and solve plastic waste problems. Among them, the development of bio-based hyperbranched epoxy resins (HERs) is unique and attractive. Bio-based HERs synthesized from bio-derived monomers can be used as a matrix resin or a toughener resulting in partially or fully bio-based epoxy thermosets. The introduction of a hyperbranched structure can balance the strength and toughness of epoxy thermosets. Here, we especially focused on the recent progress in the development of bio-based HERs, including the monomer design, synthesis approaches, mechanical properties, degradation, and recycling strategies. In addition, we advance the challenges and perspectives to engineering application of bio-based HERs in the future. Overall, this review presents an up-to-date overview of bio-based HERs and guidance for emerging research on the sustainable development of EPs in versatile high-tech fields.

Supramolecular structure, relaxation behavior and free volume of bio-based poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone) copolyesters

In the present study, a fully plant-based sustainable copolyester series, namely poly(butylene 2,5-furandicarboxylate)-block-poly(caprolactone)s (PBF-block-PCL)s were successfully synthesized by melt polycondensation combining butylene 2,5-furandicarboxylate with polycaprolactone diol (PCL) at different weight ratios. Differential scanning calorimetry (DSC) showed that only PBF underwent melting, crystallization from the melt, and cold crystallization. Thermogravimetric analysis (TGA) revealed outstanding thermal stability, exceeding 305 °C, with further improvement in thermal and thermo-oxidative stability with increasing PCL content. Broadband dielectric spectroscopy (BDS) revealed that at low temperatures, below the glass transition (T_g) all copolyesters exhibited two relaxation processes (β₁ and β₂), whereas the homopolymer PBF exhibited a single β-relaxation, which is associated with local dynamics of the different chemical bonds present in the polymer chain. Additionally, it was proved that an increase in PCL content affected the dynamics of the chain making it more flexible, thus providing an increase in the value of the room temperature free volume fractions (f_v) and the value of elongation at break. These effects are accompanied by a decrease in hardness, Young's modulus, and tensile strength. The described synthesis enables a facile approach to obtain novel fully multiblock biobased copolyesters based on PBF and PCL polyesters with potential industrial implementation capabilities.

High Oxygen Barrier Polyester from 3,3'-Bifuran-5,5'-dicarboxylic Acid

An exceptional oxygen barrier polyester prepared from a new biomass-derived monomer, 3,3'-bifuran-5,5'-dicarboxylic acid, is reported. When exposed to air, the furan-based polyester cross-links and gains O₂ permeability 2 orders of magnitude lower than initially, resulting in performance comparable to the best polymers in this class, such as ethylene-vinyl alcohol copolymers. The cross-links hinder the crystallization of amorphous samples, also rendering them insoluble. The process was observable via UV-vis measurements, which showed a gradual increase of absorbance between wavelengths of 320 and 520 nm in free-standing films. The structural trigger bringing about these changes appears subtle: the polyester containing 5,5'-disubstituted 3,3'-bifuran moieties cross-linked, whereas the polyester with 5,5'-disubstituted 2,2'-bifuran moieties was inert. The 3,3'-bifuran-based polyester is effectively a semicrystalline thermoplastic, which is slowly converted into a cross-linked material with intriguing material properties once sufficiently exposed to ambient air.

Advances in the application of named reactions in polymer synthesis

With the development of polymer science, more and more named reactions have been applied to synthesizing polymers. Introducing new reactions into polymer synthesis is undoubtedly an excellent expansion for monomer and polymer libraries. In this review, the named reactions employed in polymer-chain synthesis were divided into seven types: electrophilic reactions, nucleophilic reactions, transition metal-mediated cross-coupling reactions, free radical reactions, pericyclic reactions, multi-component reactions and rearrangement reactions. The discussion was mainly focused on the progress in the utilization of these named reactions in polymer synthesis, which could be a valuable reference for researchers in the polymer field.

Improving the Wet-Spinning and Drawing Processes of Poly(lactide)/Poly(ethylene furanoate) and Polylactide/Poly(dodecamethylene furanoate) Fiber Blends

This work aims to produce poly(lactic acid) (PLA)/poly(alkylene furanoate)s (PAF)s fiber blends for textile applications and evaluates their microstructural, chemical, thermal, and mechanical properties. The work focuses on two PAFs with very different alkyl chain lengths, i.e., poly(ethylene 2,5−furandicarboxylate) (PEF) and poly(dodecamethylene 2,5−furandicarboxylate) (PDoF), which were blended in solution at various concentrations (in the range 2.5–10 wt %) with PLA, wet spun, and subsequently drawn. Light optical micrographs highlight that PLA/PEF blends present large and concentrate PEF domains, whereas PLA/PDoF blends show small and homogeneously distributed PDoF domains. The blends appear to be immiscible, which is confirmed also by scanning electron microscopy (SEM), Fourier−Transform Infrared (FT−IR) spectroscopy, and differential scanning calorimetry (DSC). Thermogravimetric analysis (TGA) highlights that the addition of the PAFs improves the thermal stability of the fibers. The drawing process, which was carried out at 80 °C with a heat setting step at 95 °C and at three draw ratios, improves the mechanical properties of the fibers upon the addition of the PAFs. The results obtained in this study are promising and may serve as a basis for future investigations on these novel bio−based fiber blends, which can contribute to increase the environmental sustainability of industrial textiles.

Sustainable Catalytic Synthesis of 2,5-Diformylfuran from Various Carbohydrates

Versatile homogeneous and heterogeneous catalysts that convert carbohydrates to 2,5-diformylfuran (DFF) are essential for the development of sustainable processes for producing high-value chemicals from biomass-derived carbohydrates. An efficient catalytic system consisting of Br−, disulfide, and dimethylsulfoxide (DMSO) promoted the sustainable and selective synthesis of DFF in modest-to-good yields from various carbohydrates, such as fructose, glucose, mannose, galactose, and sucrose. Heterogeneous catalysts containing Br− also facilitated this reaction with recyclable high yields.

Renewable Furfural-Based Polyesters Bearing Sulfur-Bridged Difuran Moieties with High Oxygen Barrier Properties

With the goal of achieving high barrier with bio-based materials, for example, for packaging applications, a series of novel furfural-based polyesters bearing sulfide-bridged difuran dicarboxylic acid units with high oxygen barrier properties were synthesized and characterized. For the novel poly(alkylene sulfanediyldifuranoate)s, a 11.2–1.9× higher barrier improvement factor compared to amorphous poly(ethylene terephthalate) was observed which places the novel polyesters in the top class among previously reported 2,5-furandicarboxylic acid (FDCA) and 2,2′-bifuran-based polyesters. Titanium-catalyzed polycondensation reactions between the novel synthesized monomer, dimethyl 5,5′-sulfanediyldi(furan-2-carboxylate), and four different diols, ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol, afforded difuran polyesters with high intrinsic viscosities (0.76–0.90 dL/g). These polyesters had good thermal stability, decomposing at 342–363 and 328–570 °C under nitrogen and air, respectively, which allowed processing them into free-standing films via melt-pressing. In tensile testing of the film specimens, tensile moduli in the range of 0.4–2.6 GPa were recorded, with higher values observed for the polyesters with shorter diol units. Interestingly, besides the low oxygen permeability, the renewable sulfide-bridged furan monomer also endowed the polyesters with slight UV shielding effect, with cutoff wavelengths of ca. 350 nm, in contrast to FDCA-based polyesters, which lack significant UV light absorption at over 300 nm.

Lacerda T. Monomers and Macromolecular Materials from Renewable Resources: State of the Art and Perspectives

A progressively increasing concern about the environmental impacts of the whole polymer industry has boosted the design of less aggressive technologies that allow for the maximum use of carbon atoms, and reduced dependence on the fossil platform. Progresses related to the former approach are mostly based on the concept of the circular economy, which aims at a thorough use of raw materials, from production to disposal. The latter, however, has been considered a priority nowadays, as short-term biological processes can efficiently provide a myriad of chemicals for the polymer industry. Polymers from renewable resources are widely established in research and technology facilities from all over the world, and a broader consolidation of such materials is expected in a near future. Herein, an up-to-date overview of the most recent and relevant contributions dedicated to the production of monomers and polymers from biomass is presented. We provide some basic issues related to the preparation of polymers from renewable resources to discuss ongoing strategies that can be used to achieve original polymers and systems thereof.

Unravelling the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol catalysed by supported RANEY® Ni-Sn alloy catalysts

Bimetallic Ni–Sn alloys have been recognised as promising catalysts for the transformation of furanic compounds and their derivatives into valuable chemicals. Herein, we report the utilisation of a supported bimetallic RANEY® nickel–tin alloy supported on aluminium hydroxide (RNi–Sn(x)/AlOH; x is Ni/Sn molar ratio) catalysts for the one-pot conversion of biomass-derived furfural and levulinic acid to 1,4-pentanediol (1,4-PeD). The as prepared RNi–Sn(1.4)/AlOH catalyst exhibited the highest yield of 1,4-PeD (78%). The reduction of RNi–Sn(x)/AlOH with H₂ at 673–873 K for 1.5 h resulted in the formation of Ni–Sn alloy phases (e.g., Ni₃Sn and Ni₃Sn₂) and caused the transformation of aluminium hydroxide (AlOH) to amorphous alumina (AA). The RNi–Sn(1.4)/AA 673 K/H₂ catalyst contained a Ni₃Sn₂ alloy as the major phase, which exhibited the best yield of 1,4-PeD from furfural (87%) at 433 K, H₂ 3.0 MPa for 12 h and from levulinic acid (up to 90%) at 503 K, H₂ 4.0 MPa, for 12 h. Supported RANEY® Ni–Sn(1.5)/AC and three types of supported Ni–Sn(1.5) alloy (e.g., Ni–Sn(1.5)/AC, Ni–Sn(1.5)/c-AlOH, and Ni–Sn(1.5)/γ-Al₂O₃) catalysts afforded high yields of 1,4-PeD (65–87%) both from furfural and levulinic acid under the optimised reaction conditions.

The RANEY® Ni–Sn(x) alloy catalysed the one-pot conversion of biomass-derived furfural and levulinic acid to allow remarkable yield of 1,4-pentanediol (up to 90%) under the mild reaction conditions.

Production of Copolyester Monomers from Plant-Based Acrylate and Acetaldehyde

PCTA is an important copolyester that has been widely used in our daily necessities. Currently, its monomers are industrially produced from petroleum-derived xylene. To reduce the reliance on fossil energy, we herein disclose an alternative route to access PCTA monomer (terephthalate/isophthalate=2.4/1) in 61 % overall yield using plant-based acrylate and acetaldehyde as the feedstocks. The process includes Morita-Baylis-Hillman (MBH) reaction of acetaldehyde with acrylate, subsequent one-step dehydration/Diels-Alder reaction with acrylate over H₂ SO₄ /SiO₂ catalyst, and final Pd/C-catalyzed dehydrogenation. Besides, when varying the final step to hydrogenation, another important monomer UNOXOL™ diol (1,4-trans/1,4-cis/1,3-trans/1,3-cis=5.2/2/2.5/1) can be produced in 67 % overall yield.

Selective Hydrogenation of the Carbonyls in Furfural and 5-Hydroxymethylfurfural Catalyzed by PtNi Alloy Supported on SBA-15 in Aqueous Solution Under Mild Conditions

Valuable furfuryl alcohol (FFA) and 2,5-dihydroxymethylfuran (DHMF) could be produced by selective hydrogenation of biomass-derived furfural (FF) and 5-hydroxymethylfurfural (HMF) with high atom economy. In this study, SBA-15 (a kind of mesoporous silica molecular sieve)-supported low metal loading (3 wt% total metal content) PtNi alloy catalyst (PtNi/SBA-15) was synthesized via two steps, including the generation of PtNi alloy by hydrothermal method, and the immobilization of PtNi alloy on SBA-15. PtNi/SBA-15 has ordered mesoporous structure with high surface area, and high dispersion of the PtNi alloy with the formation of Pt^δ--Ni^δ+ surface pairs on SBA-15, which benefit hydrogen activation and selective carbonyl hydrogenation. The selective hydrogenation of FF and HMF over PtNi/SBA-15 in water solvent at 303 K with 1.5 MPa H₂ within 2 h, could respectively yield 64.6% FFA with 77.0% selectivity, and 68.2% DHMF with 81.9% selectivity. Besides, PtNi/SBA-15 exhibited a satisfactory water resistance and stability after recycling at least five runs.

Conversion of inulin-rich raw plant biomass to 2,5-furandicarboxylic acid (FDCA): Progress and challenge towards biorenewable plastics

The current commercial plastic manufactures have been produced using petroleum-based resource. However, due to concerns over the resource depletion and the environmental sustainability, bioresource-based manufacturing processes have been developed to cope against these concerns. Bioresource-derived 2,5-furandicarboxylic acid (FDCA) can be utilized as a building block material for plastic manufactures. To date, numerous technologies have been developed for the production of FDCA using various types of bio-based feedstocks such as hydroxymethylfurfural (HMF), 6-C sugars, and polysaccharides. The commercial companies produce FDCA using HMF-based production processes due to their high production efficiency, but the high price of HMF is a problem bottleneck. Our review affords important information on breakthrough approaches for the cost-efficient and sustainable production of FDCA using raw plant feedstocks rich in inulin. These approaches include bioprocessing technology based on the direct use of raw plant feedstocks and biomodification of the target plant sources. For the former, an ionic liquid-based processing system is proposed for efficient pretreatment of raw plant feedstocks. For the latter, the genes encoding the key enzymes; sucrose:sucrose 1-fructoyltransferase (1-SST), fructan:fructan 1-fryuctosyltransferase (1-FFT), fructan 1-exohydrolase (1-FEH), and microbe-derived endoinulinase, are introduced for biomodification conducive to facilitating bioprocess and improving inulin content. These approaches would contribute to cost-efficiently and sustainably producing bio-based FDCA.

The Promotion Effect of Cu on the Pd/C Catalyst in the Chemoselective Hydrogenation of Unsaturated Carbonyl Compounds

Highly efficient and selective hydrogenation of a,b-unsaturated carbonyl compounds to unsaturated alcohol using bimetallic palladium-copper supported on carbon (denoted as Pd-Cu(3.0)/C; 3.0 is Pd/Cu molar ratio) catalyst is demonstrated. Pd-Cu(3.0)/C catalyst was prepared via a simple hydrothermal route under air atmosphere at 150 °C for 24 h followed by reduction with hydrogen at 400°C for 1.5 h. The chemoselective hydrogenation of typical a,b-unsaturated carbonyl ketone (2-cyclohexene-1-one) and aldehyde (trans-2-hexenaldehyde), and chemoselective hydrogenation of FFald and (E)-non-3-en-2-one mixture demonstrated high productivity, leading to high selectivity of unsaturated alcohols. The presence of bimetallic Pd-Cu alloy phase with relatively high H2 uptakes was observed, enabling to preferentially hydrogenate C=O rather than to C=C bonds under mild reaction conditions. Pd-Cu(3.0)/C catalyst was found to stable and reusable for at least four reaction runs and the activity and selectivity of the catalyst can be restored to the original after rejuvenation with H2 at 400 °C for 1.5 h. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

A guide towards safe, functional and renewable BPA alternatives by rational molecular design: structure–property and structure–toxicity relationships

Putting the pieces together: a guide for rational molecular design of safe, functional and renewable BPA alternatives.

Current Situation of the Challenging Scale-Up Development of Hydroxymethylfurfural Production

Hydroxymethylfurfural (HMF) is a high-value platform chemical derived from renewable resources. In recent years, considerable efforts have been made to produce HMF also at industrial scale, which still faces some challenges regarding yield as well as sustainable and economic process designs. This critical Review evaluates the industrial process development of sustainable biomass conversion to HMF. Qualitative and quantitative guidelines are defined for the technological assessment of the processes described in patent literature. The formation of side products, difficulties in the separation and purification of HMF as well as catalyst regeneration were identified as major challenges in the HMF production. A first small-scale, commercial HMF production plant with a capacity of 300 tHMF per year has been operating in Switzerland since 2014.

Tuning the Properties of Furandicarboxylic Acid-Based Polyesters with Copolymerization: A Review

Polyesters based on 2,5-furandicarboxylic acid (FDCA) are a new class of biobased polymers with enormous interest, both from a scientific and industrial perspective. The commercialization of these polymers is imminent as the pressure for a sustainable economy grows, and extensive worldwide research currently takes place on developing cost-competitive, renewable plastics. The most prevalent method for imparting these polymers with new properties is copolymerization, as many studies have been published over the last few years. This present review aims to summarize the trends in the synthesis of FDCA-based copolymers and to investigate the effectiveness of this approach in transforming them to a more versatile class of materials that could potentially be appropriate for a number of high-end and conventional applications.

Base-Assisted Conversion of Protonated d-Fructose to 5-HMF: Searching for Gas-Phase Green Models

A gas-phase investigation of the d-fructose dehydration reaction in the presence of base has been performed by the joint application of mass spectrometric techniques and theoretical calculations. Protonated addition products of d-fructose and base were generated in the gas phase by electrospray ionization using several bases of different proton affinity. The intermediates, products and decomposition channels were investigated by ion trap mass spectrometry. Electronic structure calculations allowed the identification of the ionic intermediates and products of a selected system containing NH₃, helping to rationalize the observed reaction pathways. The obtained results show that the final product, the protonated 5-hydroxymethyl-2-furaldheyde [5-HMF]H⁺, is better formed using selected bases and only if these remain clustered until the end of the dehydration process.

Preparation and Single Crystal Structure Determination of the First Biobased Furan-Polydiacetylene Using Topochemical Polymerization

Crystal structure elucidations of bio-based polymers provide invaluable data regarding structure–property relationships. In this work, we achieved synthesis and Single Crystal X-ray Diffraction (SCXRD) structural determination of a new furan-based polydiacetylene (PDA) derivative with carbamate (urethane) functionality. Firstly, diacetylene (DA) monomers were found to self-assemble in the crystalline state in such a way that the polymerization theoretically occurred in two different directions. Indeed, for both directions, geometrical parameters for the reactive alignment of DA are satisfied and closely related with the optimal geometrical parameters for DA topochemical polymerization (d(1) = 4.7–5.2 Å, d(2) ≤ 3.8 Å, θ ≈ 45°). However, within the axis of hydrogen bonds (HB), the self-assembling monomers display distances and angles (d(1) = 4.816 Å, d(2) = 3.822 Å, θ = 51°) that deviate more from the ideal values than those in the perpendicular direction (d(1) = 4.915Å, d(2) = 3.499Å, θ ≈ 45°). As expected from these observations, the thermal topochemical polymerization occurs in the direction perpendicular to the HB and the resulting PDA was characterized by SCXRD.

Ugi reaction-derived prolyl peptide catalysts grafted on the renewable polymer polyfurfuryl alcohol for applications in heterogeneous enamine catalysis

The multicomponent synthesis of prolyl pseudo-peptide catalysts using the Ugi reaction with furfurylamines or isocyanides is described. The incorporation of such a polymerizable furan handle enabled the subsequent polymerization of the peptide catalyst with furfuryl alcohol, thus rendering polyfurfuryl alcohol-supported catalysts for applications in heterogeneous enamine catalysis. The utilization of the polymer-supported catalysts in both batch and continuous-flow organocatalytic procedures proved moderate catalytic efficacy and enantioselectivity, but excellent diastereoselectivity in the asymmetric Michael addition of n-butanal to β-nitrostyrene that was used as a model reaction. This work supports the potential of multicomponent reactions towards the assembly of catalysts and their simultaneous functionalization for immobilization.

Biobased Poly(ethylene furanoate) Polyester/TiO₂ Supported Nanocomposites as Effective Photocatalysts for Anti-inflammatory/Analgesic Drugs

In the present study, polymer supported nanocomposites, consisting of bio-based poly(ethylene furanoate) polyester and TiO₂ nanoparticles, were prepared and evaluated as effective photocatalysts for anti-inflammatory/analgesic drug removal. Nanocomposites were prepared by the solvent evaporation method containing 5, 10, 15, and 20 wt% TiO₂ and characterized using Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Thin films of them have been prepared by the melt press and optimization of the photocatalytic procedure was conducted for the most efficient synthesized photocatalyst. Finally, mineralization was evaluated by means of Total organic carbon (TOC) reduction and ion release, while the transformation products (TPs) generated during the photocatalytic procedure were identified by high-resolution mass spectrometry.

Living (co)polymerization of ethylene and bio-based furfuryl acrylate using dibenzobarrelene derived α-diimine palladium catalysts

Living (co)polymerizations of petroleum-based ethylene and bio-based furfuryl acrylate were realized using dibenzobarrelene-derived α-diimine palladium catalysts.

Electrocatalytic Upgrading of Biomass-Derived Intermediate Compounds to Value-Added Products

The continuous advance in exploring renewable energy resources such as solar and wind will certainly alleviate our reliance on limited fossil reserves. However, the sustainable development of mankind demands not only energy but also carbon-based chemical goods. Unfortunately, exploitation of renewable energy resources like solar and wind will not lead to any carbon-based chemicals. The only sustainable and green carbon source is biomass, the scale of annual production of which has an immense potential to complement that of fossil-derived carbons. To utilize biomass in economically effective ways, many catalytic processes have been investigated. Among various strategies of biomass refinery, electrocatalytic upgrading stands out as an attractive option because of its benign operation conditions, high energy efficiency, and convenient control on production rate and selectivity using electrochemical parameters. This Minireview showcases several electrocatalytic systems for both reductive and oxidative upgrading of representative biomass-derived intermediate compounds, including 5-hydroxymethylfurfural, furfural, levulinic acid, glycerol, and sorbitol to different value-added products. The catalytic routes and mechanisms of each biomass-derived platform compound are discussed and compared. In order to be feasible for large-scale applications, low-cost composition and preparation of electrocatalysts are mandatory and will be emphasized. Finally, our personal perspective on the current challenges and future directions of electrocatalytic biomass upgrading is presented.

A Review of Recent Research on Bio-Based Epoxy Systems for Engineering Applications and Potentialities in the Aviation Sector

Epoxy resins are one of the most widely used thermosets in different engineering fields, due to their chemical resistance and thermo-mechanical properties. Recently, bio-based thermoset resin systems have attracted significant attention given their environmental benefits related to the wide variety of available natural resources, as well as the resulting reduction in the use of petroleum feedstocks. During the last two decades, considerable improvement on the properties of bio-sourced resins has been achieved to obtain performances comparable to petroleum-based systems. This paper reviews recent advances on new bio-based epoxy resins, derived from natural oils, natural polyphenols, saccharides, natural rubber and rosin. Particular focus has been given to novel chemical formulations and resulting mechanical properties of natural derived- epoxies, curing agents or entire systems, constituting an interesting alternative for a large variety of engineering applications, including the aviation sector. The present work is within the scope of the ECO-COMPASS project, where new bio-sourced epoxy matrixes for green composites are under investigation.

Recent advances in the application of carbohydrates as renewable feedstocks for the synthesis of nitrogen-containing compounds

Carbohydrates, in the form of chitin, chitosan and cellulose, are one of the most available, renewable, and sustainable chemical feedstocks. Their conversion to biofuels, fine chemicals, and industrially-relevant monomers is becoming increasingly viable and promising as innovation decreases the price of this technology, and climate change and the price of fossil fuels increases the social and economic costs of using traditional feedstocks. In recent years, carbohydrates have been increasingly used as sources for nitrogen-containing fine chemicals. This chapter, with 86 references, provides a brief overview of the conversion of carbohydrate biomass to the standard hydrocarbon and oxygen-containing derivatives, and then provides a survey of recent progress in converting the biopolymers, and the derived mono and di-saccharides, into nitrogen-containing molecules with a special focus on N-heterocycle synthesis for medicinal applications.

One-Step Lignocellulose Fractionation by using 2,5-Furandicarboxylic Acid as a Biogenic and Recyclable Catalyst

To develop novel biorefinery concepts, the use of bio-based catalysts and solvents must be aligned with the principles of green chemistry. In this context, biogenic 2,5-furandicarboxylic acid (FDCA) is a very promising yet underused molecule with high potential for application as an acid catalyst, combining feasibility and sustainability with efficient and straightforward recovery. In this study, FDCA was evaluated as a catalyst in the recently developed OrganoCat pretreatment, a biphasic lignocellulose fractionation system. The catalyst was investigated for the efficient fractionation of the three main components-lignin, cellulose and noncellulosic sugars-with particular focus on the lignin quality, on the effect on enzymatic hydrolysis of the cellulosic residue, and on the noncellulosic sugar extraction. To address recovery of FDCA from the OrganoCat system, a method was developed, leading to the recovery of >97 % of FDCA with a spectroscopic purity of >99 %, maintaining full activity in consecutive runs.