We have developed an environmentally benign large-scale (50 kg wood meal per batch) lignin production plant, operating based on acid-catalyzed polyethylene glycol (PEG) solvolysis of softwood biomass. The motivation for the proposed process was to promote technological innovation in biomass utilization systems in Japanese rural areas based on widely abundant Japanese cedar (sugi) biomass. In this study, the process was evaluated by investigating the effects of the source sugi wood meal size and the solvent PEG molecular mass on the yield, chemical structure, molecular mass, and thermal properties of the resultant PEG-modified lignin derivatives, glycol lignins (GLs). Reducing the source wood meal size and PEG solvent molecular mass not only promoted lignin PEGylation but also the subsequent acid-induced chemical rearrangements of the GLs as demonstrated by chemical analyses, 2D NMR, and size exclusion chromatography (SEC). Reducing the source wood meal size and/or increasing the solvent PEG molecular mass enhanced the thermal properties of GLs as determined by thermomechanical analysis (TMA) and thermogravimetric analysis (TGA). We considered that the proposed process can efficiently produce lignin derivatives with substantial control over the chemical structure and thermal properties to meet commercial and industrial needs for lignin-based advanced material production.

A potential alternative biorefinery platform, in which high quality lignin is the main product of the process, is demonstrated. The polyethylene glycol (PEG)-modified softwood lignin (glycol lignin, GL) was isolated from Japanese cedar by acid-catalyzed PEG solvolysis, where liquid PEG with varying polymer chain length was used as the solvolysis reagent with a small amount of acid catalyst. The isolated glycol lignin had the weight-average molecular weight of 4000–7000 and exhibited a viscous thermal flow property, which is impossible for industrial softwood lignin without further processing steps. Thermal analyses, such as thermomechanical analysis (TMA) and capillary flow tester rheometer (CFT), proved to be sensitive techniques for determination of thermal flow behavior. The lignin yield and solid residue (mostly cellulosic residue), respectively, of 28%–31% and 36%–38% (dry wood basis) were obtained from PEG200 solvolysis with 0.5%–0.7% acid catalyst. The results indicated the effectiveness of the one-step PEG solvolysis process to separate glycol lignin and cellulosic residue. The present approach is promising for the quest of high purity lignin production with specified thermal properties.

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a Acetic acid is one of the major inhibitors of spent sulfite liquor (SSL) fermentation for ethanol production. The objective of this study was to remove acetic acid from hardwood SSL using anion exchange resin in order to achieve effective fermentation with Pichia stipitis CBS6054. Lignosulfonate, as well as sulfate and sulfite ions in the SSL hindered the removal of acetic acid by anion exchange resins. CaO treatment was an effective method for removing these materials from SSL, which facilitated the removal of acetic acid in the subsequent ion exchange resin treatment. A two-stage strong base ion exchange resin (OH -form) treatment removed approximately 90% of the acetic acid from CaOtreated SSL, which decreased the acetic acid concentration to less than 1 g/L. The combined treatment of CaO and ion exchange resin treatments in a relatively short time achieved the selective removal of acetic acid from SSL and significantly increased the ethanol production from SSL.

A large-scale glycol lignin (GL) production process (50 kg wood meal per batch) based on acid-catalyzed polyethylene glycol (PEG) solvolysis of Japanese cedar (JC) was developed at the Forestry and Forest Products Research Institute (FFPRI), Tsukuba, Japan. JC wood meal with various particle size distributions (JC-S < JC-M < JC-L) (average meal size, JC-S (0.4 mm) < JC-M (0.8 mm) < JC-L (1.6 mm)) and liquid PEG with various molecular masses are used as starting materials to produce PEG-modified lignin derivatives, namely, GLs, with various physicochemical and thermal properties. Because GLs are considered a potential feedstock for industrial applications, the effect of heat treatment on GL properties is an important issue for GL-based material production. In this study, GLs obtained from PEG400 solvolysis of JC-S, JC-M, and JC-L were subjected to heating in a constant-temperature drying oven at temperatures ranging from 100 to 220 °C for 1 h. All heat-treated GL series were thermally stable, as determined from the Klason lignin content, TMA, and TGA analyses. SEC analysis suggests the possibility of condensation among lignin fragments during heat treatment. ATR-FTIR spectroscopy, thioacidolysis, and 2D HSQC NMR demonstrated that a structural rearrangement occurs in the heat-treated GL400 samples, in which the content of α–PEG-β–O-4 linkages decreases along with the proportional enrichments of β–5 and β–β linkages, particularly at treatment temperatures above 160 °C.