Added-value chemicals from lignin oxidation

Lignin is the second most abundant component, next to cellulose, in lignocellulosic biomass. Large amounts of this polymer are produced annually in the pulp and paper industries as a coproduct from the cooking process-most of it burned as fuel for energy. Strategies regarding lignin valorization have attracted significant attention over the recent decades due to lignin’s aromatic structure. Oxidative depolymerization allows converting lignin into added-value compounds, as phenolic monomers and/or dicarboxylic acids, which could be an excellent alternative to aromatic petrochemicals. However, the major challenge is to enhance the reactivity and selectivity of the lignin structure towards depolymerization and prevent condensation reactions. This review includes a comprehensive overview of the main contributions of lignin valorization through oxidative depolymerization to produce added-value compounds (vanillin and syringaldehyde) that have been developed over the recent decades in the LSRE group. An evaluation of the valuable products obtained from oxidation in an alkaline medium with oxygen of lignins and liquors from different sources and delignification processes is also provided. A review of C4 dicarboxylic acids obtained from lignin oxidation is also included, emphasizing catalytic conversion by O2 or H2O2 oxidation.This work was financially supported by Base Funding—UIDB/50020/2020 and Programmatic- UIDP/50020/2020 Funding of the Associate Laboratory LSRE-LCM—funded by national funds through FCT/MCTES (PIDDAC) and Base Funding—UIDB/00690/2020 of CIMO— Centro de Investigação de Montanha—funded by national funds through FCT/MCTES (PIDDAC). COST Action LignoCOST (CA17128). Carlos Vega-Aguilar thanks the Costa Rican Science, Technology and Telecommunications Ministry for the PhD. Scholarship MICITT-PINN-CON-2-1-4-17-1-002.info:eu-repo/semantics/publishedVersio

Microwave-assisted lignin wet peroxide oxidation to C4 dicarboxylic acids

Innovative methodologies, such as microwaveassisted reaction, can help to valorize lignin with higher productivity and better energy efficiency. In this work, microwave heating was tested in the wet peroxide oxidation of three lignins (Indulin AT, Lignol, and Eucalyptus globulus lignins) as a novel methodology to obtain C4 dicarboxylic acids. The effect of temperature, time, and catalyst type (TS-1 or Fe-TS1) was evaluated in the production of these acids. The TS-1 catalyst improved succinic acid yield, achieving up to 9.4 wt % for Lignol lignin. Moreover, the microwave heating specifically enhanced Lignol conversion to malic acid (34 wt %), even without catalyst, showing to be an attractive path for the future valorization of organosolv lignins. Overall, compared to conventional heating, microwave heating originated a rapid lignin conversion. Nevertheless, for prolonged times, conventional heating led to better results for some target products, e.g., malic and succinic acids.This work was financially supported by Base Funding UIDB/50020/2020 of the Associate Laboratory LSRE-LCM funded by national funds through FCT/MCTES (PIDDAC); Base Funding UIDB/00690/2020 of CIMO-Centro de Investigação de Montanha funded by national funds through FCT/MCTES (PIDDAC). COST Action LignoCOST (CA17128). C.A.V.-A. thanks the Costa Rican Science, Technology and Telecommunications Ministry for the Ph.D. Scholarship MICITT-PINN-CON-2-1-4-17-1-002. The authors thank Dr. Maria José Sampaio and Prof. Dr. Joaquim Faria (LA LSRE-LCM) for the help with the FTIR measurements.info:eu-repo/semantics/publishedVersio

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Evaluation of chemical processing impact on E. globulus wood lignin and comparison with bark lignin

In this work a comprehensive characterization of different Eucalyptus globulus lignins was performed in order to evaluate the influence of the industrial process on its structure: LOrg - lignin produced by organosolv process, LKraft - lignin isolated from black liquor (obtained by kraft process) and further purified, taking LEg(wood) - lignin produced by wood mild acidolysis, as representative of wood lignin. Lignin from bark, LEg(bark), also isolated by mild acidolysis, was characterized and compared with LEg(wood). Besides the contaminants content (inorganic material plus carbohydrates - 1-3%), lignins structure were studied with reference to yields obtained by nitrobenzene oxidation (NO), and with reference to functional groups and typical structures/linkages by quantitative C-13, H-1 and P-31 nuclear magnetic resonance (NMR). NO yield order was found to be LKraft (21%) < LOrg (26%) < LEg(wood) (31%) approximate to LEg(bark) (33%), demonstrating that the industrial processing, particularly the kraft one, induced unfavorable changes for a valorization route involving production of functionalized aldehydes by depolymerization. The main changes were the increase of degree of condensation (DC), cleavage of beta-aryl ether linkages, and demethoxylation, in particular for the lignin resulting from the kraft process. The NO yield was successful correlated with DC and Syringyl/Guaiacyl (S/G) ratio from 31P NMR and also a good correlation was obtained between beta-aryl ether content and DC, clearly ascertaining the structural features related with the potential of the E. globulus lignin as source of functionalized aldehydes. LEg(wood) and LEg(bark) have similar structures, whilst the presence of p-hydroxyphenyl (H) detected in the bark lignin leads to a S:G:H (73:23:4) different from wood lignin (80:20:0). The overall results showed that organosolv or a mild delignification process would be a preferable process to obtain lignin from E. globulus wood or bark for production of functionalized aldehydes

Radar Tool for Lignin Classification on the Perspective of Its Valorization

A tool for lignin classification was developed based on radar plots using six descriptors identified as key characteristics for vanillin (V) and syringaldehyde (Sy) production by oxidation in alkaline medium: content on β-<i>O</i>-4 structures, noncondensed structures, syringyl and guaiacyl units, and yield of Sy and V by nitrobenzene oxidation (NO). A set of lignins was classified according to the radar information, simplifying the evaluation and discussion of the impact of the delignification process, wood species, and morphologic part on lignin. Lignin from tobacco stalks was one of the targets, reporting ¹³C NMR and NO characterization data to ascertain the influence of delignification process. Structural data on lignins from different hardwoods (eucalyptus, mimosa, and willow), several parts of the same species (bole, bark, branches, sawdust), and different delignification processes were also used as a basis for the developed methodology. The radar plots of tobacco lignins allow classifying the lignin produced by organosolv process with ethanol as that with the higher aptitude for V and Sy production with O₂. This classification was confirmed by batch oxidation of this lignin as compared with that produced by organosolv process with butanol. In the same way, among the processed hardwood lignins, the one produced by organosolv of eucalyptus bole wood showed the highest intensity in all descriptors, being classified as a privileged source of Sy in comparison to Kraft lignins. The reasons behind the differences on descriptors that gave rise to lignins classification are discussed. The radar classification can be used as a predictive tool for product and process design, for both lignin production and application. The requisite for this is the previous knowledge of the relevant structural parameters. This is a key step to demystify the lignin complexity in key descriptors and consolidation of valorization routes in flexible processing units

Assessment of key features of lignin from lignocellulosic crops: Stalks and roots of corn, cotton, sugarcane, and tobacco

Lignins from industrial crops could be converted into valuable chemicals in the context of a second generation biorefinery, but prior understanding of their structure is required. This work is focused on the characterization of lignins from stalks and roots of corn, cotton, sugarcane and tobacco. Lignin structure was studied through nitrobenzene oxidation, C-13, P-31, and 2D nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). Lignins were isolated by mild acidolysis with a maximum degree of contamination of 10% (carbohydrates plus ashes). Interpretation and quantification of NMR spectra provided consistent data about typical units and structures, such as syringyl:guaiacyl:p-hydroxyphenyl (S:G:H), frequency of beta-aryl ether linkages (beta-O-4) and non-condensed structures (NCS), total hydroxyl phenolic groups and their distribution on different non-condensed units type, and the presence of p-coumaric and ferulic acids. In general, roots lignin contains fewer beta-O-4 and lower S/G ratio than the respective stalks, while NCS content does not follow a perceptible trend. In spite of the similarity between corn and sugarcane lignins, radar plots promptly demonstrate higher differences between species than between morphological parts, confirming the lignin specificity of each species. These results are discussed in a comparative approach, highlighting for each material the characteristic features of its lignin

Effect of film thickness in gelatin hybrid gels for artificial olfaction

Pest-OE/AGR/UI0245/2013 SCENT-ERC-2014-STG-639123 CapTherPV-ERC-2014-CoG-647596 POCI-01-0145-FEDER-007728Artificial olfaction is a fast-growing field aiming to mimic natural olfactory systems. Olfactory systems rely on a first step of molecular recognition in which volatile organic compounds (VOCs) bind to an array of specialized olfactory proteins. This results in electrical signals transduced to the brain where pattern recognition is performed. An efficient approach in artificial olfaction combines gas-sensitive materials with dedicated signal processing and classification tools. In this work, films of gelatin hybrid gels with a single composition that change their optical properties upon binding to VOCs were studied as gas-sensing materials in a custom-built electronic nose. The effect of films thickness was studied by acquiring signals from gelatin hybrid gel films with thicknesses between 15 and 90 μm when exposed to 11 distinct VOCs. Several features were extracted from the signals obtained and then used to implement a dedicated automatic classifier based on support vector machines for data processing. As an optical signature could be associated to each VOC, the developed algorithms classified 11 distinct VOCs with high accuracy and precision (higher than 98%), in particular when using optical signals from a single film composition with 30 μm thickness. This shows an unprecedented example of soft matter in artificial olfaction, in which a single gelatin hybrid gel, and not an array of sensing materials, can provide enough information to accurately classify VOCs with small structural and functional differences.publishersversionpublishe

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved