Optimisation of lignin liquefaction with polyethylene glycol/ glycerol through response surface methodology modelling

In order to diminish the dependence on oil lignin, which is the most abundant biopolymer of phenolic origin on Earth and can be utilised in different industrial endeavours, such as, the production of polyurethanes. In this study, hardwood (Eucalyptus globulus) and softwood (Pinus radiata) organosolv lignins were employed to produce bio-polyols trough microwave-assisted liquefaction. The resulting bio-polyols possessed specific properties to be employed in the synthesis of rigid and elastic polyurethanes. The values of the reaction parameter were optimized using response surface methodology to determine the most effective conditions for producing bio-polyols from both types of lignins for the purpose of rigid and elastic polyurethane formulation. The effect of catalyst concentration (%wt.), temperature (ºC) and Polyethylene glycol/Glycerol weight ratio on the molecular weight (Mw) and hydroxyl number (IOH) of bio-polyols was evaluated. The optimum reaction conditions of bio-polyols production for rigid polyurethanes were virtually equal for the two lignins, 159–161 ºC, Polyethylene glycol/Glycerol ratio of 3 without catalyst. On the contrary, the bio-polyols for elastic polyurethanes required different reaction parameters depending on the lignin used. For hardwood lignin the optimised conditions were 180 ºC, 7.57 (Polyethylene glycol/Glycerol ratio) and 5.00% of catalyst while for softwood lignin were 160 ºC, 7.34 (Polyethylene glycol/Glycerol) and 3.85% of catalyst. Additionally, the bio-polyols obtained at optimised conditions were fully characterised and acid number, polydispersity index, functionality and the rheological behaviour was studied.The authors would like to acknowledge the financial support of the University of the Basque Country (project COLAB20/04). F.Hernández-Ramos would like to acknowledge the Grant received from the Environmental Department of the Diputación Foral de Gipuzkoa. The authors thank SGIker (UPV/EHU/ERDF, EU) for their technical and human support

Valorisation of crude glycerol in the production of liquefied lignin bio-polyols for polyurethane formulations

Bio-polyols, produced by liquefying lignin with polyhydric alcohols, offer a promising alternative to conventional polyols for polyurethane production. To enhance the sustainability on the production of these bio-polyols, this study proposes the use of crude glycerol and microwave-assisted liquefaction as substitutes for conventional methods and commercial glycerol. This approach reduces the energy requirements of the reaction while also adding value to this by-product. The synthesis of bio-polyols with suitable properties to produce elastic and rigid polyurethane was carried out using previously optimised reaction conditions. Organosolv lignins obtained from Eucalyptus globulus and Pinus radiata were employed, using polyethylene glycol and crude glycerol as solvents and sulphuric acid as a catalyst. Several parameters of the bio-polyols were analysed, including hydroxyl number (IOH), acid number (An), and functionality (f), suggesting that the bio-polyols were suitable for polyurethane synthesis. Bio-polyols formulated to produce rigid polyurethanes exhibited IOH values of 554 and 383 (mg KOH/g), An values of 1.91 and 4.21 (mg KOH/g), and functionalities of 4.16 and 3.14 for Eucalyptus globulus and Pinus radiata lignin. In the case of bio-polyols for elastic polyurethanes, the values were 228 and 173 (mg KOH/g) (IOH), 20.94 and 25.09 (mg KOH/g) (An), and functionalities of 3.51 and 2.08.The authors would like to acknowledge the financial support of the University of the Basque Country (project COLAB20/04). F. Hernández-Ramos would like to acknowledge the Grant received from the Environmental Department of the Diputación Foral de Gipuzkoa. The authors thank SGIker (UPV/EHU/ERDF, EU) for their technical and human support

Fine-tune of lignin properties by its fractionation with a sequential organic solvent extraction

[EN] In this work, different lignins were obtained from two different extraction methods (kraft and organosolv) but from the same raw material (Eucalyptus globulus sp.). They were subsequently fractionated to determine the differences of each extraction method and their corresponding physicochemical properties found in fractionation sequence and obtained fractions. The goal of the fractionation was to obtain lignin fractions with narrower molecular weight distribution and lower polydispersity index (PI). The solvent sequence was designed based on the environmental friendly properties, health and safety assessments of the selected organic solvents: (methanol (MeOH), ethanol (EtOH), propan-2-one (DMK), ethyl acetate (EtOAc), propan-1-ol (nPrOH), propan-2-ol (iPrOH), butan-2-one (MEK), and butan-1-ol (tBuOH)). The different fractions obtained were characterised to determine their chemical structure by several analytical techniques, such as Fourier Transformed Infrared Spectroscopy (FTIR), Ultraviolet (UV), Phosphorus-31 Nuclear Magnetic Resonance (P-31 NMR), Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC). In addition, Gel Permeation Chromatography (GPC) was used to obtain the molecular weight distribution. This study showed an effective method for obtaining homogeneous lignins with specific structures and properties depending on the solvent and molecular weight attained. Moreover, the method designed was found to be effective regardless of the lignin extraction process employed; besides, various lignin fractions were obtained which were different from each other, having specific target applications depending on their structure and chemical properties, ranging from small molecules with abundant reactive sites to act as active materials or copolymer reagents for many applications, to larger and more inactive molecules with higher thermal resistivity.The authors would like to acknowledge the Basque Government for the financial support of this research through project IT1008-16 and grant PIF19-183. Furthermore, E. R. wants to acknowledge the tenure track position "BOIS" part of E2S UPPA supported by the "Investisse-ments d'Avenir" French program managed by ANR (ANR-16-IDEX-0002)

Life Cycle Assessment of various biorefinery approaches for the valorisation of almond shells

In the near future, sustainable and efficient biorefineries would be essential for the production of commodity chemicals and high-added value compounds. Therefore, in this work, six scenarios differing on the delignification steps and cellulose conversion routes were assessed via Life Cycle Assessment methodology in order to study the environmental impacts derived from the conversion of an abundant agricultural residue (almond shells) into high added-value products and select the most suitable one for large-scale valorisation. The assessments were conducted employing experimental results and processing them by SimaPro software. The main conclusion achieved suggested that the enzymatic hydrolysis of the solid from any delignification step entailed the highest environmental impacts and had the highest relative contribution in all the studied impact categories with a maximum of 74%, which was ascribed to Scenario 5. It was also concluded that the organosolv delignification process affected overall more negatively than the alkaline treatment having bigger impacts especially in abiotic depletion (ADP) and photochemical oxidation (POP) categories. Finally, it can be stated that the best route for valorising the almond shell in a biorefinery facility is composed of autohydrolysis (common for every scenario), alkaline delignification, bleaching and acid hydrolysis steps for the obtaining of oligosaccharides, lignin and nanocrystals as products.Authors want to acknowledge the University of the Basque Country UPV/EHU, as well as the Spanish Ministry of Science and Innovation (CTQ2016-78689-R) for supporting financially this research. L.S. and R.F. would like to acknowledge the Departmentof Economic Development and Infrastructures of the Basque Government (scholarship of young researchers training) . A.M. and I.D, would like to thank the University of the Basque Country (Training of Researcher Staff, PIF17/207 and grant reference DOCREC19/47, respectively)

Effect of the photocatalytic activity of TiO2 on lignin depolymerization

Lignin is a good candidate for photocatalytic cracking due to the presence of hydroxyl groups. The photocatalytic cracking reaction involves TiO2 as heterogeneous catalyst. In the present work lignin obtained by two different pulping methods is treated under photocatalytic conditions to be depolimerized. Different exposure times to UV radiation were carried out. The results of GS–MS revealed the degradation products of the hemicelluloses contained in the lignin samples. 1 h of exposure to UV radiation shows the best yield in the obtaining of lignin degradation derived compounds; the main products obtained are syringaldehyde, pyrocatechol and raspberryketone, the concentration of syringaldehyde increases 20% and vanillin 30%.Departments of Agriculture, Fishing and Food and Department of Education, Universities and Investigation of the Basque Government (scholarship of young researchers training) and the Saiotek progra

Study of the influence of reutilization ionic liquid on lignin extraction

The development of green techniques for biomass processing and fractionation is crucial from the point of view of sustainability and environmental protection. Lignin is the second most abundant bio-renewable material on Earth and ionic liquids are developed as green solvents because of their reutilization possibility and low vapour pressure. In this work the recyclability of methylsulphate 1-butyl-3-methylimidazoliumionic liquid on the obtaining of lignin from biomass was studied. The experimental results showed that the obtained lignins were similar until the third cycle and the extraction process showed good performances, whereas in the fourth cycle it appeared ionic liquid contamination on the lignin and the performance decreased dramatically.Authors would like to thank the Department of Education, Universities and Investigation of the Basque Government (IT672-13) and the Spanish Ministry of Economy and Competitiveness (CTQ2013-41246-R)

Exploring chemical reactions to enhance thermal and dispersion stability of kraft and organosolv lignin

Lignin has been overlooked and used as a waste for long due to its complex and partially hydrophobic structure. Many efforts have been carried out to overcome these deficiencies and apply it as a high-value product, which are insufficient to reach the full potential of lignin in various advanced applications, since they require with procedures for the obtaining of more specific and fine-tuned chemical structures. This work focuses on the obtaining of differently structured hydrophilic lignins derived both from Kraft and organosolv isolation processes. The chemical structures of the different lignin types were studied, and the effect of the structural differences in the modification processes and their subsequent properties analyzed, valorizing their potential application for diverse purposes. The carboxymethylation and sulfomethylation reactions were carried out with the aim of enhancing the polarity of the lignin samples, while the methylation reaction aimed to obtain lignins with higher stability. The physicochemical analyses of the samples, carried out by FTIR, GPC, 31P NMR, 13C NMR, and HSQC NMR, verified the effectiveness of the chemical reactions and conditions selected, obtaining lignins with lower hydroxyl content, due to their substitution and insertion of carboxymetyl, sulfomethyl and methyl groups, therefore obtaining more condensed, aromatic and oxygenated aromatic carbon structures. While the methylation reaction was the most efficient in substituting the OH groups, due to its non-selectivity, OL showed higher modification yields than KL. In terms of the thermal and morphological properties, analyzed by DLS and TGA respectively, it was observed that the modified samples showed lower Z potential values, along with higher conductivity, being the sulfomethylated organosolv lignin the one showing the best results, which was also the one with the smallest particle size and polydispersity index. Finally, all the modified samples showed higher T50% values, suggesting a better stability towards degradation.The authors would like to acknowledge the financial support of the Basque Government for (grant PIF19-183) and Diputación de Gipuzkoa (EZAGUTZ-11/2022). The authors thank for the technical and human support provided by SGIker (UPV/EHU/ ERDF, EU)

Techno-economic analysis of different integrated biorefinery scenarios using lignocellulosic waste streams as source for phenolic alcohols production

The whole process of lignin extraction from a lignocellulosic waste streams (almond shell) by sulfur-free methods and its depolymerization by base catalyzed or solvolysis reactions have been addressed in this work. In addition, the influence of avoiding the lignin isolation stage prior to its depolymerization reaction has been studied based on the final product yields (phenolic monomers compounds, such as catechol derivatives), energy requirements and production costs. As summary, four different scenarios were approached using experimental data values from previous works and compared by the help of a simulation software (AspenTech®). The direct lignin depolymerization from black liquors equalized the phenolic monomer yields of the precipitated lignin depolymerization for the organosolv process (0.08 wt%), and increased in the soda process (0.05 wt% against 0.03 wt%). However, the bigger volume to be treated in the depolymerization reaction and downstream stages significantly increased the production costs (chemicals consumptions, energetic duties and waste stream disposal), as well as the investment cost. Regarding the depolymerization from the precipitated lignin, despite the loss of lignin during the isolation stage, the reduction of the volume to be treated led to hugely reduce the production costs and the environmental impact. Among these last two mentioned scenarios, the organosolv process presented better indicators. Even though the lignin extraction yield was poorer for the organosolv process, the depolymerization performance was improved in such level, that the most desirable product (phenolic oil) was obtained in higher amount.Spanish Ministerio de Economía y Competitividad (CTQ2016-78689-R) and Department of Education of the Basque Country (IT1008-16

Economic analysis of a biorefinery process for catechol production from lignin

Recently, the valorization of the lignin fraction in the biorefinery scheme is getting more and more attention as the use of this component for the production of bio-based chemicals is crucial for the success of the integral development of lignocellulosic biorefinery processes. The present work includes the exergy performance and the economic analysis of a process for catechols production using lignin extracted from olive tree pruning. Energy and exergy calculations were obtained from the process simulation with Aspen Plus®. The exergy analysis was applied to identify the units associated with the main irreversibilities and exergy losses. The process investment and operating costs were determined as well as the derived catechol market price. The calculated total plant capital investment was about 4.9 M$for a plant capacity of 2,544 kg feedstock /day. The estimated catechol price was 1100$/t with a valorization ratio of 3.02. These results place the product in a competitive position in the market.Basque Government (project IT1008-16) and Spanish Ministry of Economy, Industry and Competitiveness (CTQ2016-78689-R