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New polymers, properly designed for end-of-life and efficiently formed from renewable carbon, are key to the transition to a more sustainable circular plastics economy. Ring-opening polymerization (ROP) of bicyclic lactones is a promising method for the production of intrinsically recyclable polyesters, but most lactone monomers lack an efficient synthesis route from biobased starting materials, even though this is essential to sustainably account for material loss during the life cycle. Herein, we present the exceptionally rapid and controlled polymerization of a fully biobased tricyclic oxanorbornene-fused γ-butyrolactone monomer ( M1 ). Polyester P( M1 ) was formed in low dispersity (D̵ = 1.2-1.3) and controllable molecular weight up to M n = 76.8 kg mol -1 and exhibits a high glass transition temperature ( T g = 120 °C). The orthogonal olefin and lactone functionalities offer access to a wide range of promising materials, as showcased by postpolymerization modification by hydrogenation of the olefin, which increased polymer thermal stability by over 100 °C. Next to rapid hydrolytic degradation and solvolysis, the poly(oxanorbornene-fused γ-butyrolactone) could be cleanly chemically recycled back to the monomer (CRM), in line with its favorable ceiling temperature ( T c ) of 73 °C. The density functional theory (DFT)-computed Δ H ° of ring-opening with methanol of γ-butyrolactone-based monomers provided a model to predict T c , and the DFT-computed and X-ray crystal structure-derived structural parameters of M1 , hydrogenated analogue M1-H 2 , and regioisomer M2 offered insights into the structural descriptors that cause the high polymerizability of M1 , which is key to establishing structure-property relations.

Recent scientific advances in the valorization of lignin, through e.g., (partial-)catalytic depolymerization, require equally state-of-the-art approaches for the analysis of the obtained depolymerized lignins (DLs) or lignin bio-oils. The use of chemometrics in combination with infrared (IR) spectroscopy is one avenue to provide rapid access to pertinent lignin parameters, such as molecular weight (MW) characteristics, which typically require analysis via time-consuming size-exclusion methods, or diffusion-ordered NMR spectroscopy. Importantly, MW serves as a marker for the degree of depolymerization (or recondensation) that the lignin has undergone, and thus probing this parameter is essential for the optimization of depolymerization conditions to achieve DLs with desired properties. Here, we show that our ATR-IR-based chemometrics approach used previously for technical lignin analysis can be extended to analyze these more processed, lignin-derived samples as well. Remarkably, also at this lower end of the MW scale, the use of partial least-squares (PLS) regression models well-predicted the MW parameters for a sample set of 57 depolymerized lignins, with relative errors of 9.9-11.2%. Furthermore, principal component analysis (PCA) showed good correspondence with features in the regression vectors for each of the biomass classes (hardwood, herbaceous/grass, and softwood) obtained from PLS-discriminant analysis (PLS-DA). Overall, we show that the IR spectra of DLs are still amenable to chemometric analysis and specifically to rapid, predictive characterization of their MW, circumventing the time-consuming, tedious, and not generally accessible methods typically employed., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

To expedite the valorisation of lignin as a sustainable component in materials applications, rapid and generally available analytical methods are essential to overcome the bottleneck of lignin characterisation. Where features of a lignin's chemical structure have previously been found to be predicted by Partial Least Squares (PLS) regression models built on Infrared (IR) data, we now show for the first time that this approach can be extended to prediction of the glass transition temperature (T g ), a key physicochemical property. This methodology is shown to be convenient and more robust for prediction of T g than prediction through empirically derived relationships (e. g., Flory-Fox). The chemometric analysis provided root mean squared errors of prediction (RMSEP) as low as 10.0 °C for a botanically, and a process-diverse set of lignins, and 6.2 °C for kraft-only samples. The PLS models could separately predict both the T g as well as the degree of allylation (% allyl ) for allylated lignin fractions, which were all derived from a single lignin source. The models performed exceptionally well, delivering RMSEP of 6.1 °C, and 5.4 %, respectively, despite the conflicting influences of increasing molecular weight and % allyl on T g . Finally, the method provided accurate determinations of % allyl with RMSEP of 5.2 %., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Humins, (side-)products of the acid-catalysed dehydration of carbohydrates, will be produced in substantial quantities with the development of industrial biorefining processes. Most structural knowledge about such humins is based on synthetic model humins prepared at lab-scale from typical carbohydrate(-derived) compounds. Here, we report the first extensive characterisation study of an industrial humin. The soluble humin was generated from pilot plant-scale methanolic cyclodehydration of D-fructose to 5-methoxymethyl-2-furfural (MMF), as part of the Avantium YXY® process to produce FDCA. Purification of the industrial humin followed by fractionation allowed isolation of a water-insoluble, high molecular weight fraction (WIPIH) and a water-soluble, low-to-middle molecular weight soluble fraction (WES). Characterisation by elemental analysis, thermogravimetry, IR and NMR spectroscopy and size exclusion chromatography provided a detailed picture of the humin structure in both fractions. Aided by a comprehensive NMR spectral library of furanic model compounds, we identified the main furanic building blocks and inter-unit linkages and propose a structure for this industrial humin sample. The WIPIH and WES fractions were found to be composed of furanic rings interconnected by short aliphatic chains containing a wide range of functionalities including alcohols, ethers, carboxylic acids, esters, aldehydes and ketones. The low level of crosslinking and high functional group content of the industrial humin differ from the more extensively studied, (highly over-)condensed synthetic model humins, towards which they can be considered intermediates. The structural and compositional insights into the nature of an actual industrial humin open up a broad spectrum of valorisation opportunities., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Diels-Alder (DA) cycloaddition of furanics is emerging as a key transformation in circular chemistry, providing access to highly versatile, biobased platform molecules. Further development of this technology into viable industrial applications faces major challenges, a notorious one being the lack of reactivity of the most readily available furans, i.e. the furfural derivatives. Herein we describe the remarkably-facile intramolecular DA reaction of allyl acetals of different furfurals to efficiently afford formal DA adducts with the atypical, unreactive dienophile allyl alcohol. Our methodology gives access to unprecedented oxanorbornene derivatives in high chemo-, regio- and stereoselectivity, which can be readily diversified into valuable products. This offers the potential of scalable production of renewable chemical building blocks from cheap, bioderived platform molecules., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

To fully exploit kraft lignin's potential in material applications, we need to achieve tight control over those key physicochemical lignin parameters that ultimately determine, and serve as proxy for, the properties of lignin-derived materials. Here, we show that fractionation combined with systematic (incremental) modification provides a powerful strategy to expand and controllably tailor lignin property space. In particular, the glass transition temperature ( T g ) of a typical kraft lignin could be tuned over a remarkable and unprecedented 213 °C. Remarkably, for all fractions the T g proved to be highly linearly correlated with the degree of derivatisation by allylation, offering such tight control over the T g of the lignin and ultimately the ability to 'dial-in' this key property. Importantly, such control over this proxy parameter indeed translated well to lignin-based thiol-ene thermosetting films, whose T g s thus covered a range from 2-124 °C. This proof of concept suggests this approach to be a powerful and generalisable one, allowing a biorefinery or downstream operation to consciously and reliably tailor lignins to predictable specifications which fit their desired application., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Polyurethane (PU) coatings with high lignin content and tunable properties were made using a combination of fractionation and partial catalytic depolymerization as a novel strategy to tailor lignin molar mass and hydroxyl group reactivity, the key parameters for use in PU coatings. Acetone organosolv lignin obtained from pilot-scale fractionation of beech wood chips was processed at the kilogram scale to produce lignin fractions with specific molar mass ranges ( M w 1000-6000 g/mol) and reduced polydispersity. Aliphatic hydroxyl groups were distributed relatively evenly over the lignin fractions, allowing detailed study of the correlation between lignin molar mass and hydroxyl group reactivity using an aliphatic polyisocyanate linker. As expected, the high molar mass fractions exhibited low cross-linking reactivity, yielding rigid coatings with a high glass transition temperature ( T g ). The lower M w fractions showed increased lignin reactivity, extent of cross-linking, and gave coatings with enhanced flexibility and lower T g . Lignin properties could be further tailored by lignin partial depolymerization by reduction (PDR) of the beech wood lignin and its high molar mass fractions; excellent translation of the PDR process was observed from laboratory to the pilot scale necessary for coating applications in prospective industrial scenarios. Lignin depolymerization significantly improved lignin reactivity, and coatings produced from PDR lignin showed the lowest T g values and highest coating flexibility. Overall, this study provides a powerful strategy for the production of PU coatings with tailored properties and high (>90%) biomass content, paving the path to the development of fully green and circular PU materials., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

A hydrazine-mediated approach towards renewable aromatics production via Diels-Alder aromatization of readily available, biobased furfurals was explored as alterative to the more classical approaches that rely on reactive but uneconomical reduced dienes (e. g., 2,5-dimethylfuran). To enable cycloaddition chemistry with these otherwise unreactive formyl furans, substrate activation by N,N-dimethyl hydrazone formation was investigated. The choice of the reaction partner was key to the success of the transformation, and in this respect acrylic acid showed the most promising results in the synthesis of aromatics. This strategy allowed for selectivities up to 60 % for a complex transformation consisting of Diels-Alder cycloaddition, oxabridge opening, decarboxylation, and dehydration. Exploration of the furfural scope yielded generic structure-reactivity-stability relationships. The proposed methodology enabled the redox-efficient, operationally simple, and mild synthesis of renewable (p-disubstituted) aromatics of commercial importance under remarkably mild conditions., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Feedstock flexibility is highly advantageous for the viability of (solvent-based) biorefineries but comes with the considerable challenge of having to cope with the varying nature and typically high abundance of nonlignocellulose compounds in the most readily available residual biomass streams. Here, we demonstrate that mild aqueous acetone organosolv fractionation of various complex lignocellulosic raw materials (roadside grass, wheat straw, birch branches, almond shells, and a mixed stream thereof) is indeed negatively affected by these compounds and present a versatile strategy to mitigate this bottleneck in biorefining. A biomass pre-extraction approach has been developed to remove the detrimental extractives with (aqueous) acetone prior to fractionation. Pre-extraction removed organic extractives as well as minerals, primarily reducing acid dose requirements for fractionation and loss of hemicellulose sugars by degradation and improved the purity of the isolated lignin. We show how pre-extraction affects the effectiveness of the biorefinery process, including detailed mass balances for pretreatment, downstream processing, and product characteristics, and how it affects solvent and energy use with a first conceptual process design. The integrated biorefining approach allows for the improved compatibility of biorefineries with sustainable feedstock supply chains, enhanced biomass valorization (i.e., isolation of bioactive compounds from the extract), and more effective biomass processing with limited variation in product quality., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Biomass-derived furanic platform molecules have emerged as promising building blocks for renewable chemicals and functional materials. To this aim, the Diels-Alder (DA) cycloaddition stands out as a versatile strategy to convert these renewable resources in highly atom-efficient ways. Despite nearly a century worth of examples of furan DA chemistry, clear structure-reactivity-stability relationships are still to be established. Detailed understanding of the intricate interplay between kinetics and thermodynamics in these very particular [4+2] cycloadditions is essential to push further development and truly expand the scope beyond the ubiquitous addend combinations of electron-rich furans and electron-deficient olefins. Herein, we provide pertinent examples of DA chemistry, taken from various fields, to highlight trends, establish correlations and answer open questions in the field with the aim to support future efforts in the sustainable chemicals and materials production., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Technical lignins are increasingly available at industrial scale, offering opportunities for valorization, such as by (partial) depolymerization. Any downstream lignin application requires careful tailoring of structural properties, such as molecular weight or functional group density, properties that are difficult to control or predict given the structure variability and recalcitrance of technical lignins. Online insight into changes in molecular weight (M w ), to gauge the extent of lignin depolymerization and repolymerization, would be highly desired to improve such control, but cannot be readily provided by the standard ex-situ techniques, such as size exclusion chromatography (SEC). Herein, operando attenuated total reflectance infrared (ATR-IR) spectroscopy combined with chemometrics provided temporal changes in M w during lignin depolymerization with high resolution. More specifically, ex-situ SEC-derived M w and polydispersity data of kraft lignin subjected to aqueous phase reforming conditions could be well correlated with ATR-IR spectra of the reaction mixture as a function of time. The developed method showed excellent regression results and relative error, comparable to the standard SEC method. The method developed has the potential to be translated to other lignin depolymerization processes., (© 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Nature provides much inspiration for the design of multistep conversion processes, with numerous reactions running simultaneously and without interference in cells, for example. A key challenge in mimicking nature's strategies is to compartmentalize incompatible reagents and catalysts, for example, for tandem catalysis. Here, we present a new strategy for antagonistic catalyst compartmentalization. The synthesis of bifunctional Janus catalyst particles carrying acid and base groups on the particle's opposite patches is reported as is their application as acid-base catalysts in oil/water emulsions. The synthesis strategy involved the use of monodisperse, hydrophobic and amine-functionalized silica particles (SiO 2 -NH 2 -OSi(CH 3 ) 3 ) to prepare an oil-in-water Pickering emulsion (PE) with molten paraffin wax. After solidification, the exposed patch of the silica particles was selectively etched and refunctionalized with acid groups to yield acid-base Janus particles (Janus A-B). These materials were successfully applied in biphasic Pickering interfacial catalysis for the tandem dehydration-Knoevenagel condensation of fructose to 5-(hydroxymethyl)furfural-2-diethylmalonate (5-HMF-DEM) in a water/4-propylguaiacol PE. The results demonstrate the advantage of rapid extraction of 5-hydroxymethylfurfural (5-HMF), a prominent platform molecule prone to side product formation in acidic media. A simple strategy to tune the acid/base balance using PE with both Janus A-B and monofunctional SiO 2 -NH 2 -OSi(CH 3 ) 3 base catalysts proved effective for antagonistic tandem catalysis., (© 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Background: The aromatic compounds vanillin and vanillic acid are important fragrances used in the food, beverage, cosmetic and pharmaceutical industries. Currently, most aromatic compounds used in products are chemically synthesized, while only a small percentage is extracted from natural sources. The metabolism of vanillin and vanillic acid has been studied for decades in microorganisms and many studies have been conducted that showed that both can be produced from ferulic acid using bacteria. In contrast, the degradation of vanillin and vanillic acid by fungi is poorly studied and no genes involved in this metabolic pathway have been identified. In this study, we aimed to clarify this metabolic pathway in Aspergillus niger and identify the genes involved., Results: Using whole-genome transcriptome data, four genes involved in vanillin and vanillic acid metabolism were identified. These include vanillin dehydrogenase (vdhA), vanillic acid hydroxylase (vhyA), and two genes encoding novel enzymes, which function as methoxyhydroquinone 1,2-dioxygenase (mhdA) and 4-oxo-monomethyl adipate esterase (omeA). Deletion of these genes in A. niger confirmed their role in aromatic metabolism and the enzymatic activities of these enzymes were verified. In addition, we demonstrated that mhdA and vhyA deletion mutants can be used as fungal cell factories for the accumulation of vanillic acid and methoxyhydroquinone from guaiacyl lignin units and related aromatic compounds., Conclusions: This study provides new insights into the fungal aromatic metabolic pathways involved in the degradation of guaiacyl units and related aromatic compounds. The identification of the involved genes unlocks new potential for engineering aromatic compound-producing fungal cell factories., (© 2021. The Author(s).)

The choice of TiO 2 crystal phase (i. e., anatase, rutile, or brookite) greatly influences catalyst performance in the gas-phase ketonization of small volatile fatty acids, such as acetic acid and propionic acid. Rutile TiO 2 was found to perform best, combining superior activity, as exemplified by an exceptional reaction rate of 141.8 mmol h -1  g cat -1 (at 425 °C and 24 h -1 ) with excellent ketone selectivity when propionic acid was used. Brookite, to the best of our knowledge never reported before as a viable ketonization catalyst, was found to outperform the well-studied anatase phase, but not rutile. Operando Fourier-transform IR spectroscopy measurements combined with on-line mass spectrometry showed that bidentate carboxylates were the most abundant surface species on the rutile and brookite surfaces, while on anatase both monodentate and bidentate carboxylates co-existed. The bidendate carboxylates were thought to be precursors to the active ketonization species, likely monodentate intermediates more prone to C-C coupling. Ketonization activity did not directly correlate with acidity; the observed, strong crystal phase effect did suggest that ketonization activity is influenced strongly by geometrical factors that determine the ease of formation of the relevant surface intermediates., (© 2021 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The furan Diels-Alder (DA) cycloaddition reaction has become an important tool in green chemistry, being central to the sustainable synthesis of many chemical building blocks. The restriction to electron-rich furans is a significant limitation of the scope of suitable dienes, in particular hampering the use of the furans most readily obtained from biomass, furfurals and their oxidized variants, furoic acids. Herein, it is shown that despite their electron-withdrawing substituents, 2-furoic acids and derivatives (esters, amides) are in fact reactive dienes in Diels-Alder couplings with maleimide dienophiles. The reactions benefit from a substantial rate-enhancement when water is used as solvent, and from activation of the 2-furoic acids by conversion to the corresponding carboxylate salts. This approach enables Diels-Alder reactions to be performed under very mild conditions, even with highly unreactive dienes such as 2,5-furandicarboxylic acid. The obtained DA adducts of furoic acids are shown to be versatile synthons in the conversion to various saturated and aromatic carbocyclic products., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A novel route for the production of the versatile chemical building block phthalide from biorenewable furfuryl alcohol and acrylate esters is presented. Two challenges that limit sustainable aromatics production via Diels-Alder (DA) aromatisation-an unfavourable equilibrium position and undesired regioselectivity when using asymmetric addends-were addressed using a dynamic kinetic trapping strategy. Activated acrylates were used to speed up the forward and reverse DA reactions, allowing for one of the four DA adducts to undergo a selective intramolecular lactonisation reaction in the presence of a weak base. The adduct is removed from the equilibrium pool, pulling the system completely to the product with a fixed, desired regiochemistry. A single 1,2-regioisomeric lactone product was formed in up to 86 % yield and the acrylate activating agent liberated for reuse. The lactone was aromatised to give phthalide in almost quantitative yield in the presence of Ac 2 O and a catalytic amount of strong acid, or in 79 % using only catalytic acid., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Pickering emulsions (PEs), emulsions stabilized by solid particles, have shown to be a versatile tool for biphasic catalysis. Here, we report a droplet microfluidic approach for flow PE (FPE) catalysis, further expanding the possibilities for PE catalysis beyond standard batch PE reactions. This microreactor allowed for the inline analysis of the catalytic process with in situ Raman spectroscopy, as demonstrated for the acid-catalyzed deacetalization of benzaldehyde dimethyl acetal to form benzaldehyde. Furthermore, the use of the FPE system showed a nine fold improvement in yield compared to the simple biphasic flow system (FBS), highlighting the advantage of emulsification. Finally, FPE allowed an antagonistic set of reactions, the deacetalization-Knoevenagel condensation, which proved less efficient in FBS due to rapid acid-base quenching. The droplet microfluidic system thus offers a versatile new extension of PE catalysis., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

5-Hydroxymethylfurfural (HMF) is an important biobased platform chemical obtainable in high selectivity by the hydrolysis of fructose (FRC). However, FRC is expensive, making the production of HMF at a competitive market price highly challenging. Here, it is shown that sugar beet thick juice, a crude, sucrose-rich intermediate in sugar refining, is an excellent feedstock for HMF synthesis. Unprecedented high selectivities and yields of >90 % for HMF were achieved in a biphasic reactor setup at 150 °C using salted diluted thick juice with H 2 SO 4 as catalyst and 2-methyltetrahydrofuran as a bioderived extraction solvent. The conversion of glucose, obtained by sucrose inversion, could be limited to <10 mol %, allowing its recovery for further use. Interestingly, purified sucrose led to significantly lower HMF selectivity and yields, showing advantages from both an economic and chemical selectivity perspective. This opens new avenues for more cost-effective HMF production., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Ex situ catalytic biomass pyrolysis was investigated at both laboratory and bench scale by using a zeolite ZSM-5-based catalyst for selectively upgrading the bio-oil vapors. The catalyst consisted of nanocrystalline ZSM-5, modified by incorporation of ZrO 2 and agglomerated with attapulgite (ZrO 2 /n-ZSM-5-ATP). Characterization of this material by means of different techniques, including CO 2 and NH 3 temperature-programmed desorption (TPD), NMR spectroscopy, UV/Vis microspectroscopy, and fluorescence microscopy, showed that it possessed the right combination of accessibility and acid-base properties for promoting the conversion of the bulky molecules formed by lignocellulose pyrolysis and their subsequent deoxygenation to upgraded liquid organic fractions (bio-oil). The results obtained at the laboratory scale by varying the catalyst-to-biomass ratio (C/B) indicated that the ZrO 2 /n-ZSM-5-ATP catalyst was more efficient for bio-oil deoxygenation than the parent zeolite n-ZSM-5, producing upgraded bio-oils with better combinations of mass and energy yields with respect to the oxygen content. The excellent performance of the ZrO 2 /n-ZSM-5-ATP system was confirmed by working with a continuous bench-scale plant. The scale-up of the process, even with different raw biomasses as the feedstock, reaction conditions, and operation modes, was in line with the laboratory-scale results, leading to deoxygenation degrees of approximately 60 % with energy yields of approximately 70 % with respect to those of the thermal bio-oil., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Tandem catalysis combines multiple conversion steps, catalysts, and reagents in one reaction medium, offering the potential to reduce waste and time. In this study, Pickering emulsions-emulsions stabilized by solid particles-are used as easy-to-prepare and bioinspired, compartmentalized reaction media for tandem catalysis. Making use of simple and inexpensive acid and base catalysts, the strategy of compartmentalization of two noncompatible catalysts in both phases of the emulsion is demonstrated by using the deacetalization-Knoevenagel condensation reaction of benzaldehyde dimethyl acetal as a probe reaction. In contrast to simple biphasic systems, which do not allow for tandem catalysis and show instantaneous quenching of the acid and base catalysts, the Pickering emulsions show efficient antagonistic tandem catalysis and give the desired product in high yield, as a result of an increased interfacial area and suppressed mutual destruction of the acid and base catalysts., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lignin is an attractive material for the production of renewable chemicals, materials and energy. However, utilization is hampered by its highly complex and variable chemical structure, which requires an extensive suite of analytical instruments to characterize. Here, we demonstrate that straightforward attenuated total reflection (ATR)-FTIR analysis combined with principle component analysis (PCA) and partial least squares (PLS) modelling can provide remarkable insight into the structure of technical lignins, giving quantitative results that are comparable to standard gel-permeation chromatography (GPC) and 2D heteronuclear single quantum coherence (HSQC) NMR methods. First, a calibration set of 54 different technical (fractionated) lignin samples, covering kraft, soda and organosolv processes, were prepared and analyzed using traditional GPC and NMR methods, as well as by readily accessible ATR-FTIR spectroscopy. PLS models correlating the ATR-FTIR spectra of the broad set of lignins with GPC and NMR measurements were found to have excellent coefficients of determination (R 2 Cal.>0.85) for molecular weight (M n , M w ) and inter-unit abundances (β-O-4, β-5 and β-β), with low relative errors (6.2-14 %) as estimated from cross-validation results. PLS analysis of a second set of 28 samples containing exclusively (fractionated) kraft lignins showed further improved prediction ability, with relative errors of 3.8-13 %, and the resulting model could predict the structural characteristics of an independent validation set of lignins with good accuracy. The results highlight the potential utility of this methodology for streamlining and expediting the often complex and time consuming technical lignin characterization process., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

White-rot fungi, such as Dichomitus squalens, degrade all wood components and inhabit mixed-wood forests containing both soft- and hardwood species. In this study, we evaluated how D. squalens responded to the compositional differences in softwood [guaiacyl (G) lignin and higher mannan content] and hardwood [syringyl/guaiacyl (S/G) lignin and higher xylan content] using semi-natural solid cultures. Spruce (softwood) and birch (hardwood) sticks were degraded by D. squalens as measured by oxidation of the lignins using 2D-NMR. The fungal response as measured by transcriptomics, proteomics and enzyme activities showed a partial tailoring to wood composition. Mannanolytic transcripts and proteins were more abundant in spruce cultures, while a proportionally higher xylanolytic activity was detected in birch cultures. Both wood types induced manganese peroxidases to a much higher level than laccases, but higher transcript and protein levels of the manganese peroxidases were observed on the G-lignin rich spruce. Overall, the molecular responses demonstrated a stronger adaptation to the spruce rather than birch composition, possibly because D. squalens is mainly found degrading softwoods in nature, which supports the ability of the solid wood cultures to reflect the natural environment., (© 2018 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.)

Facile fabrication of well-intergrown, oriented zeolite membranes with tunable chemical properties on commercially proven substrates is crucial to broadening their applications for separation and catalysis. Rationally determined electrostatic adsorption can enable the direct attachment of a b-oriented silicalite-1 monolayer on a commercial porous ceramic substrate. Homoepitaxially oriented, well-intergrown zeolite ZSM-5 membranes with a tunable composition of Si/Al=25-∞ were obtained by secondary growth of the monolayer. Intercrystallite defects can be eliminated by using Na + as the mineralizer to promote lateral crystal growth and suppress surface nucleation in the direction of the straight channels, as evidenced by atomic force microscopy measurements. Water permeation testing shows tunable wettability from hydrophobic to highly hydrophilic, giving the potential for a wide range of applications., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Kraft lignin, the main by-product of the pulping industry, is an abundant, yet highly underutilized renewable aromatic polymer. During kraft pulping, the lignin undergoes extensive structural modification, with many labile native bonds being replaced by new, more recalcitrant ones. Currently little is known about the nature of those bonds and linkages in kraft lignin, information that is essential for its efficient valorization to renewable fuels, materials or chemicals. Here, we provide detailed new insights into the structure of softwood kraft lignin, identifying and quantifying the major native as well as kraft pulping-derived units as a function of molecular weight. De novo synthetic kraft lignins, generated from (isotope labelled) dimeric and advanced polymeric models, provided key mechanistic understanding of kraft lignin formation, revealing different process dependent reaction pathways to be operating. The discovery of a novel kraft-derived lactone condensation product proved diagnostic for the identification of a previously unknown homovanillin based condensation pathway. The lactone marker is found in various different soft- and hardwood kraft lignins, suggesting the general pertinence of this new condensation mechanism for kraft pulping. These novel structural and mechanistic insights will aid the development of future biomass and lignin valorization technologies.

The influence of a highly oxygenated, polar protic reaction medium, that is, levulinic acid in 2-ethylhexanoic acid, on the dealumination of two zeolite-supported ruthenium catalysts, namely Ru/H-β and Ru/H-ZSM-5, has been investigated by 27 Al triple-quantum magic-angle spinning nuclear magnetic resonance spectroscopy (3QMAS NMR). Upon use of these catalysts in the hydrogenation of levulinic acid, the heterogeneity in aluminum speciation is found to increase for both Ru/H-ZSM-5 and Ru/H-β. For Ru/H-ZSM-5, the symmetric, tetrahedral framework aluminum species (FAL) were found to be mainly converted into distorted tetrahedral FAL species, with limited loss of aluminum to the solution by leaching. A severe loss of both FAL and extra-framework aluminum (EFAL) species into the liquid phase was observed for Ru/H-β instead. The large decrease in tetrahedral FAL species, in particular, results in a significant decrease in strong acid sites, as corroborated by Fourier transform infrared spectroscopy (FT-IR). This decrease in acidity, evidence of the inferior stability of the strongly acidic sites in Ru/H-β relative to Ru/H-ZSM-5 under the applied conditions, is considered as the main reason for differences seen in catalyst performance., (©2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Establishing structure-activity relationships in complex, hierarchically structured nanomaterials, such as fluid catalytic cracking (FCC) catalysts, requires characterization with complementary, correlated analysis techniques. An integrated setup has been developed to perform transmission electron microscopy (TEM) and single-molecule fluorescence (SMF) microscopy on such nanostructured samples. Correlated structure-reactivity information was obtained for 100 nm thin, microtomed sections of a single FCC catalyst particle using this novel SMF-TEM high-resolution combination. High reactivity in a thiophene oligomerization probe reaction correlated well with TEM-derived zeolite locations, while matrix components, such as clay and amorphous binder material, were found not to display activity. Differences in fluorescence intensity were also observed within and between distinct zeolite aggregate domains, indicating that not all zeolite domains are equally active., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

We used single-molecule fluorescence microscopy to study self-diffusion of a feedstock-like probe molecule with nanometer accuracy in the macropores of a micrometer-sized, real-life fluid catalytic cracking (FCC) particle. Movies of single fluorescent molecules allowed their movement through the pore network to be reconstructed. The observed tracks were classified into three different states by machine learning and all found to be distributed homogeneously over the particle. Most probe molecules (88%) were immobile, with the molecule most likely being physisorbed or trapped; the remainder was either mobile (8%), with the molecule moving inside the macropores, or showed hybrid behavior (4%). Mobile tracks had an average diffusion coefficient of D = 8 × 10 -14 ± 1 × 10 -13 m 2 s -1 , with the standard deviation thought to be related to the large range of pore sizes found in FCC particles. The developed methodology can be used to evaluate, quantify and map heterogeneities in diffusional properties within complex hierarchically porous materials.

The presence of biogenic or process-derived impurities poses a major problem on the efficient catalytic hydrogenation of biomass-derived levulinic acid to γ-valerolactone; hence, studies on their influence on catalyst stability are now required. Herein, the influence of sulfuric acid as feed impurity on the performance of Ru-based heterogeneous catalysts, including Ru/ZrO 2 and mono- and bimetallic Ru-on-carbon catalysts in dioxane as solvent, was investigated. The carbon-supported Ru catalysts proved to be very sensitive to minor amounts of sulfuric acid. In stark contrast, Ru/ZrO 2 showed a remarkable stability in the presence of the same impurity, which is attributed to the sulfate-ion adsorption capacity of the support. Preferential sulfate adsorption onto the surface of ZrO 2 effectively protects the Ru active phase from deactivation by sulfur poisoning. A simple catalyst regeneration strategy was effective in removing adsorbed impurities, allowing efficient catalyst recycling., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A micro-spectroscopic method has been developed to probe the accessibility of zeolite crystals using a series of fluorescent 4-(4-diethylaminostyryl)-1-methylpyridinium iodide (DAMPI) probes of increasing molecular size. Staining large zeolite crystals with MFI (ZSM-5) topology and subsequent mapping of the resulting fluorescence using confocal fluorescence microscopy reveal differences in structural integrity: the 90° intergrowth sections of MFI crystals are prone to develop structural imperfections, which act as entrance routes for the probes into the zeolite crystal. Polarization-dependent measurements provide evidence for the probe molecule's alignment within the MFI zeolite pore system. The developed method was extended to BEA (Beta) crystals, showing that the previously observed hourglass pattern is a general feature of BEA crystals with this morphology. Furthermore, the probes can accurately identify at which crystal faces of BEA straight or sinusoidal pores open to the surface. The results show this method can spatially resolve the architecture-dependent internal pore structure of microporous materials, which is difficult to assess using other characterization techniques such as X-ray diffraction., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)