The profitability and sustainability of future biorefineries are dependent on efficient feedstock use. Therefore, it is essential to valorize lignin when using wood. We have developed an integrated biorefinery that converts 78 weight % (wt %) of birch into xylochemicals. Reductive catalytic fractionation of the wood produces a carbohydrate pulp amenable to bioethanol production and a lignin oil. After extraction of the lignin oil, the crude, unseparated mixture of phenolic monomers is catalytically funneled into 20 wt % of phenol and 9 wt % of propylene (on the basis of lignin weight) by gas-phase hydroprocessing and dealkylation; the residual phenolic oligomers (30 wt %) are used in printing ink as replacements for controversial para-nonylphenol. A techno-economic analysis predicts an economically competitive production process, and a life-cycle assessment estimates a lower carbon dioxide footprint relative to that of fossil-based production.

/pdf/a-sustainable-wood-biorefinery-for-low-carbon-footprint-zp3p92lahc.pdf

A sustainable wood biorefinery for low–carbon footprint chemicals production

The valorisation of the plant biopolymer lignin is now recognised as essential to enabling the economic viability of the lignocellulosic biorefining industry. In this context, the “lignin-first” biorefining approach, in which lignin valorisation is considered in the design phase, has demonstrated the fullest utilisation of lignocellulose. We define lignin-first methods as active stabilisation approaches that solubilise lignin from native lignocellulosic biomass while avoiding condensation reactions that lead to more recalcitrant lignin polymers. This active stabilisation can be accomplished by solvolysis and catalytic conversion of reactive intermediates to stable products or by protection-group chemistry of lignin oligomers or reactive monomers. Across the growing body of literature in this field, there are disparate approaches to report and analyse the results from lignin-first approaches, thus making quantitative comparisons between studies challenging. To that end, we present herein a set of guidelines for analysing critical data from lignin-first approaches, including feedstock analysis and process parameters, with the ambition of uniting the lignin-first research community around a common set of reportable metrics. These guidelines comprise standards and best practices or minimum requirements for feedstock analysis, stressing reporting of the fractionation efficiency, product yields, solvent mass balances, catalyst efficiency, and the requirements for additional reagents such as reducing, oxidising, or capping agents. Our goal is to establish best practices for the research community at large primarily to enable direct comparisons between studies from different laboratories. The use of these guidelines will be helpful for the newcomers to this field and pivotal for further progress in this exciting research area.

/pdf/guidelines-for-performing-lignin-first-biorefining-47ujskqy2i.pdf

Guidelines for performing lignin-first biorefining

Bacterial cellulose as a material for wound treatment: Properties and modifications. A review

The analysis of chemical structural characteristics of biorefinery product streams (such as lignin and tannin) has advanced substantially over the past decade, with traditional wet-chemical techniques being replaced or supplemented by NMR methodologies. Quantitative 31P NMR spectroscopy is a promising technique for the analysis of hydroxyl groups because of its unique characterization capability and broad potential applicability across the biorefinery research community. This protocol describes procedures for (i) the preparation/solubilization of lignin and tannin, (ii) the phosphitylation of their hydroxyl groups, (iii) NMR acquisition details, and (iv) the ensuing data analyses and means to precisely calculate the content of the different types of hydroxyl groups. Compared with traditional wet-chemical techniques, the technique of quantitative 31P NMR spectroscopy offers unique advantages in measuring hydroxyl groups in a single spectrum with high signal resolution. The method provides complete quantitative information about the hydroxyl groups with small amounts of sample (~30 mg) within a relatively short experimental time (~30–120 min). This protocol describes a quantitative 31P NMR spectroscopy approach for the analysis and determination of hydroxyl groups on biorefinery resources such as lignins and tannins.

/pdf/determination-of-hydroxyl-groups-in-biorefinery-resources-5gi7u2qcvb.pdf

Determination of hydroxyl groups in biorefinery resources via quantitative 31P NMR spectroscopy

Surface chemical functionalization of cellulose nanocrystals by 3-aminopropyltriethoxysilane

Determination of molecular weight parameters of native and, in particular, technical lignins are based on size exclusion chromatography (SEC) approaches. However, no matter which approach is used, either conventional SEC with a refractive index detector and calibration with standards or multi-angle light scattering (MALS) detection at 488 nm, 633 nm, 658 nm, or 690 nm, all variants can be severely erroneous. The lack of calibration standards with high structural similarity to lignin impairs the quality of the molar masses determined by conventional SEC, and the typical fluorescence of (technical) lignins renders the corresponding MALS data rather questionable. Application of MALS detection at 785 nm by using an infrared laser largely overcomes those problems and allows for a reliable and reproducible determination of the molar mass distributions of all types of lignins, which has been demonstrated in this study for various and structurally different analytes, such as kraft lignins, milled-wood lignin, lignosulfonates, and biorefinery lignins. The topics of calibration, lignin fluorescence, and lignin UV absorption in connection with MALS detection are critically discussed in detail, and a reliable protocol is presented. Correction factors based on MALS measurements have been determined for commercially available calibration standards, such as pullulan and polystyrene sulfonate, so that now more reliable mass data can be obtained also if no MALS system is available and these conventional calibration standards have to be resorted to.

https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.1002/cssc.201801177

Getting Closer to Absolute Molar Masses of Technical Lignins.

³¹P nuclear magnetic resonance (NMR) based on the derivatization reagent 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane is a common approach for the hydroxyl group determination of lignins, but the results are sometimes less reproducible compared to other methods. In the present work, common pitfalls in ³¹P NMR analysis of kraft lignin (KL) and lignosulfonates (LS) are addressed and the results are compared to those obtained by ¹H NMR spectroscopy. Several experimental parameters are revisited in terms of the reliability of the obtained data, such as the choice of relaxation delay, internal standards, and the best solution technique for the ³¹P NMR analysis of LS. For the first time, ³¹P NMR data of LS are presented based on a new dissolution protocol. The analytical data of a set of lignins consisting of three KLs, one LS, and one milled wood lignin are presented based on the optimized ³¹P NMR approach.

Characterization of technical lignins by NMR spectroscopy: optimization of functional group analysis by 31P NMR spectroscopy

The modification of cellulosic materials is of great interest in materials research. Wet bacterial cellulose sheets were modified by an alkoxysilane under mild conditions to make them accessible to click chemistry derivatization. For this purpose (3-azidopropyl)triethoxysilane was grafted covalently onto the cellulosic surface. The silanized bacterial cellulose sheets were characterized comprehensively by attenuated total reflectance FTIR spectroscopy, solid-state NMR spectroscopy, thermogravimetric analysis, SEM with energy-dispersive X-ray spectroscopy, and elemental analysis. To demonstrate subsequent click chemistry functionalization, a new fluorophore based on fluorescein was synthesized and clicked to the silane-modified bacterial cellulose. The new method renders bacterial cellulose and other never-dried cellulosic materials susceptible to direct and facile functionalization in an aqueous medium without the need to work in water-free organic phases or to employ extensive protecting group chemistry and functional group interconversion.

Silane meets click chemistry: towards the functionalization of wet bacterial cellulose sheets.

In this study, a novel approach for isolation and purification of lignosulfonates from spent sulfite liquor was established. This approach involves sorption onto macroreticular non-ionic poly(methyl methacrylate) beads (XAD-7 resin) and subsequent desorption with organic solvents to obtain lignosulfonates of high purity. The method was optimized, verified and tested on four industrial lignosulfonate liquors from different processes and compared with an established ultrafiltration protocol. The method proved to be reproducible, robust and significantly faster than ultrafiltration.

Fast track for quantitative isolation of lignosulfonates from spent sulfite liquors

Technical lignins (waste products obtained from wood pulping or biorefinery processes) have so far required lengthy analysis procedures and different eluents for molar-mass analysis by gel permeation chromatography (GPC). This challenge has become more pressing recently since attempts to utilize lignins have increased, leading to skyrocketing numbers of samples to be analyzed. A new approach, which uses the eluent DMSO/LiBr (0.5 % w/v) and converts lignosulfonate salts into their acidic form before analysis, overcomes these limitations by enabling measurement of all kinds of lignins (kraft, organosolv, soda, lignosulfonates) in the same size-exclusion chromatography (SEC) system without the necessity of prior time-consuming derivatization steps. In combination with ultra-performance liquid chromatography (UPLC), analysis times are shortened to one tenth of classical lignin GPC. The new approach is presented, along with a comparison of GPC and UPLC methods and a critical discussion of the analytical parameters.

Ivan Sumerskii

Papers

Getting Closer to Absolute Molar Masses of Technical Lignins.

Characterization of technical lignins by NMR spectroscopy: optimization of functional group analysis by 31P NMR spectroscopy

Silane meets click chemistry: towards the functionalization of wet bacterial cellulose sheets.

Fast track for quantitative isolation of lignosulfonates from spent sulfite liquors

Fast Track to Molar-Mass Distributions of Technical Lignins