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Lignin is among one of the largest natural resources in the world, with aromatic structures that can serve as a raw material in the synthesis of high value-added chemicals, the production of bioenergy, and the development of carbon-based products, among others. A better understanding of the chemical structure of lignin and its valorization methods is necessary to overcome current technological challenges for industrial scale applications. The main challenge found to provide the most abundant source of aromatics in the world is the fractionation of lignin. Current studies propose a way to fractionate lignin to obtain more homogeneous and less complex fractions, because of the fact that aromatic compounds are essential intermediates in the manufacture of polymers, and lignin is the main source of biologically aromatic-based substrates. Numerous review articles have addressed research aimed at understanding the structure of lignin, however, a limited focus has been given to its fractionation methods. This article aims to review papers published in recent years using different lignin fractionation techniques, focusing on the four main types of fractionations: in organic solvents, gel permeation chromatography in preparatory scale, ultrafiltration and precipitation by varying acid gradient. This a Review summarizes the most recent innovations in the area of biorefineries for the chemical valorization of lignin derived from various botanical sources through different fractionation methods.

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This study show influence of alkaline treatment on sisal fiber (SF) in different composites of starch matrices (SM) and cellulose acetate matrices (CAM). SF were modified with an aqueous 0.5M NaOH solution. Composites were prepared in proportion of 3% fiber/matrix (m/m) using casting method. The samples were characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy by Attenuated Total Reflection (FTIR-ATR), Thermogravimetric Analysis (TGA) and Dynamic-mechanical thermal analysis (DMA). Through results obtained in FTIR and TGA, it was possible to verify that alkaline treatment partially removed hemicellulose and SF lignin. With SEM, best fiber/matrix adhesion in composites prepared with modified fiber (TSF) has been proven to change fibre morphology. Through DMA analysis it was possible to observe that after addition of SF and TSF, SM composites showed improvements in mechanical properties, while TGA showed an increase in initial temperature of thermal degradation in CAM composites with addition of fiber.

Environmental friendliness and cost demand the development of lignin-modified phenolic (LPF) resins for application as a binder for carbon-containing refractories (CCRs) production. Moreover, the in-situ graphitization of such resins can produce crystalline carbon, which is an essential component of CCRs. Consequently, this study investigated LPF resins graphitization using ferrocene, boron oxide and boric acid. The modified resins were synthesized using thermally treated kraft lignin based on 1.5 formaldehyde to phenol molar ratio and with up to 30 wt.% lignin as phenol replacement. The resins chemical composition and the structural organization and oxidation resistance of carbons derived from the plain resins and those containing the graphitizing additives were determined. The results showed that ferrocene and the boron compounds could induce graphitic carbon generation when carbonizing LPF resins at 1500 °C for 5 hours. The best graphitization level (73%) was achieved when 10 wt.% boric acid was added to the resin produced with 20 wt.% lignin. Regarding the formulations containing ferrocene, the highest amount of graphitic carbon (48%) was generated when 5 wt.% of this additive was added to the resin synthesized with 10 wt.% lignin. The carbons derived from the formulations containing boron oxide presented the best oxidation resistance.

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The lignin present in the vegetal tissues of the sugarcane bagasse is an interesting material due to its aromatic characteristics. Particularly in Brazil, studies involving the extraction of lignin from sugarcane bagasse have been widely researched due to the high volume of bagasse generated in our country. Recent studies have shown that after isolation, lignin is a raw material that can be used as a pesticide, solution stabilizer and particularly for the production of phenolic resin partially replacing phenol. The present study aimed to isolate and characterize the lignin present in sugarcane bagasse by the acetosolv pulping method. The sugarcane bagasse was pre-treated to remove organic and hot water-soluble extracts, and then acetic (solvent) and hydrochloric (catalyst) acids and water at the temperature were used. boiling point for the isolation of lignin by the acetossolve process. The obtained lignin was characterized by chemical performance analysis, Fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC) and thermogravimetry (TGA). The extraction yield of lignin acetosolv was 19.95 % under total sugarcane bagasse. In the lignin FTIR spectrum the stretch range between 1594 and 1511 cm-1 confirm the preservation of the aromatic structure. GPC analysis demonstrated a low polydispersity of lignin acetosolv. TGA analysis showed no residues above 600°C, indicating high content of organic material, confirming the purity of the extracted sample. It is concluded, therefore, that the acetossolve pulping method for lignin extraction may be an efficient alternative, in view of the processes traditionally employed if fibers, not wood (sugarcane bagasse) are used. The fact that it is a process that does not use pressure combined with the possibility of recovering inputs by simple evaporation, makes the acetosolv competitive and with less environmental damage than other traditional processes. A lignina presente nos tecidos vegetais do bagaço da cana é um material interessante devido às suas características aromáticas. Particularmente no Brasil, estudos envolvendo a extração de lignina do bagaço de cana têm sido amplamente pesquisados devido ao alto volume de bagaço gerado em nosso país. Estudos recentes demonstraram que, após o isolamento, a lignina é uma matéria-prima que pode ser usada como pesticida, estabilizador de solução e particularmente para a produção de resina fenólica, substituindo parcialmente o fenol. O presente estudo teve como objetivo isolar e caracterizar a lignina presente no bagaço de cana-de-açúcar pelo método de polpação acetossolve. O bagaço de cana-de-açúcar foi submetido a um pré-tratamento para a remoção de extrativos orgânicos e extrativos solúveis em água quente, e posteriormente, utilizaram-se os ácidos acético (solvente) e clorídrico (catalisador), e água na temperatura de ebulição, para o isolamento da lignina, pelo processo acetossolve. A lignina obtida foi caracterizada por análise química de rendimento, espectroscopia na região do infravermelho com transforma...