Characterization of isolated lignin from eucalyptus wood chip obtained by liquid hot water process

In this study, we propose a novel optimization for lignin isolation from the eucalyptus wood chip (EWC) under hydrothermal liquid hot water (LWH) process in the presence of alkaline catalyst (NaOH). The optimal conditions were obtained employing response surface methodology (RSM). The optimal condition was 160°C for 30 min in the presence of alkaline catalyst of 0.020 M. This condition demonstrated the highest lignin extraction with solid fraction of 77.3% and 76.1%. In addition, the physicochemical structure of isolated lignin was characterized with diverse techniques. The lignin recovery from liquid phase’s GPC analysis illustrated a high average Mw/Mn (17500/7450 g/mol) while polydispersity index (2.34) was lower in comparison with the commercial organosolv lignin. The TGA analysis showed the maximum decomposition of lignin recovery at 140 to 350oC. Furthermore, the Py/GCMS analysis showed a predominance of 57.63% of syringyl units (S) over 37.37% of guaiacyl units (G) under optimal conditions. The results revealed that the integrated process was a potential approach to add more value in the employment of the agricultural waste material.

Probing the molecular weights of sweetgum and pine kraft lignin fractions

The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter- mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.

An extensive parameter study of hydrotropic extraction of steam-pretreated birch

Efficient fractionation of lignocellulosic biomass is an important step toward the replacement of fossil-based products. However, the utilisation of all of the components in biomass requires various fractionation techniques. One promising process configuration is to apply steam explosion for the recovery of hemicelluloses and a subsequent hydrotropic extraction step for the delignification of the remaining solids. In this work, the influence of residence time, temperature and biomass loading on lignin recovery from birch using sodium xylene sulphonate as a hydrotrope was investigated. Our results show that residence time, temperature and biomass loading correlate positively with lignin extraction, but the effects of these parameters were limited. Furthermore, when steam explosion was implemented as the initial step, hydrotropic extraction could be performed even at room temperature, yielding a lignin extraction of 50%. Also, hydrothermal degradation of the material was necessary for efficient delignification with sodium xylene sulphonate, regardless of whether it occurs during steam explosion pretreatment or is achieved at high temperatures during the hydrotropic extraction.

A Review on the Lignin Biopolymer and Its Integration in the Elaboration of Sustainable Materials

Lignin is one of the wood and plant cell wall components that is available in large quantities in nature. Its polyphenolic chemical structure has been of interest for valorization and industrial application studies. Lignin can be obtained from wood by various delignification chemical processes, which give it a structure and specific properties that will depend on the plant species. Due to the versatility and chemical diversity of lignin, the chemical industry has focused on its use as a viable alternative of renewable raw material for the synthesis of new and sustainable biomaterials. However, its structure is complex and difficult to characterize, presenting some obstacles to be integrated into mixtures for the development of polymers, fibers, and other materials. The objective of this review is to present a background of the structure, biosynthesis, and the main mechanisms of lignin recovery from chemical processes (sulfite and kraft) and sulfur-free processes (organosolv) and describe the different forms of integration of this biopolymer in the synthesis of sustainable materials. Among these applications are phenolic adhesive resins, formaldehyde-free resins, epoxy resins, polyurethane foams, carbon fibers, hydrogels, and 3D printed composites.

Determination of Alpha-, Beta- and Gamma- Cellulose in Bagasse and Wheat Straw: Lignin Recovery, Characterization and Depolymerization

Lignocellulosic biomass is an abundantly available byproduct obtained after the separation of edible parts from various crops that is a potential source to produce renewable and sustainable biofuels, chemicals, materials, and polymers, without altering the greenhouse gas emissions relative to fossil feedstocks. Valorisation of lignocellulosic biomass focuses on polysaccharides conversion to value-added chemicals and polymers. However, lignin rich of high carbon burned to generate energy and chemicals. For the development of an effective lignocellulosic biomass conversion technology to biofuels and chemicals, biomass composition analysis and their properties need to be characterized prior to biomass reactions, including polysaccharide hydrolysis and lignin depolymerization. In this work, we have determined alpha-, beta- and gamma- cellulose, pentosan, lignin, and silica percentages of wheat straw (WS) and two bagasse (BG I and II) samples. The impact of different types of biomass samples on composition, and lignin recovery by applying two-stage concentrated and dilute sulphuric acid treatment, has been discussed. Subsequent studies extended to the correlation of lignin properties and their susceptibility to depolymerization using homogeneous (1-methyl-3-(3-sulphopropyl)-imidazolium hydrogen sulphate) and heterogeneous (immobilized Brønsted acidic ionic liquid) catalysts to lower molar mass aromatic fractions. Thermal, physical, and chemical properties of WS, BG, and recovered lignin samples were characterized by using UV-visible, ATR, 13 C CP-MAS NMR, CHNS, XRD, and TGA techniques showed substantial differences in lignin structure and properties.