Tatsuhiko Yamada

A Characteristic Reaction of Lignin in Ionic Liquids; Glycelol Type Enol-Ether as the Primary Decomposition Product of β-O-4 Model Compound

Abstract Guaiacylglycerol-β-guaiacyl ether (GG), which contains a predominant inter-unit linkage of lignin, could be converted into a corresponding glycerol type enol-ether (EE), 3-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-2-propenol, by the heat treatment in ionic liquids. EE is believed to be the unstable intermediate of the lignin decomposition process under acidic and alkaline conditions. By contrast, EE could be isolated as a relatively stable compound from the reaction mixture of ionic liquids. EE was formed as a primary reaction product in all ionic liquids used in this research under the temperature conditions of 120°C, although the decomposition rate and secondary decomposition products of GG varied with the ionic liquid used. NMR data suggested that dehydration reaction of GG progressed stereospecifically and [Z] isomer was predominantly formed (stereoselectivety of [Z] is higher than 90%).

Preparation and Characterization of Amphiphilic Lignin Derivatives as Surfactants

Abstract Acetic acid lignin (AL), one of the organosolv lignins, was modified by polyoxyethylation using commercially available polyethylene glycol diglycidylethers (PEGDE) having various chain lengths in order to generate novel nonionic polymeric surfactants. AL could be converted to the amphiphile by modifying with PEGDE (PEGDE-AL) having more than 9 of the ethylene oxide (EO) repeating units. Although the surface activities of PEG and AL were very limited, PEGDE-AL did strongly depress surface tension of water, and showed clear critical micelle concentrations (CMC). The CMC value of PEGDE-AL could be comparable to a commercial anionic lignin surfactant, lignosulfonate. The surface activity of AL amphiphile was further improved by modification with monoepoxides, ethoxy-(2-hydroxy)-propoxy-polyethylene glycol glycidylether (EPEGGE). The surface tension of water was depressed by the addition of the EPEGGE-AL to the same level as Triton® X-100, which is a commercial PEG-based nonionic surfactant, although there is still room for improvement in CMC value. The hydrophile–lipophile balance (HLB) of these AL amphiphiles was in the range of 11–14, and significant biodegradation was observed. These results suggest that the AL amphiphiles can be used as emulsifier and detergent.

Conversion of Technical Lignins to Amphiphilic Derivatives with High Surface Activity

Abstract To make use of technical lignins as a nonionic polymeric surfactant, we have already reported the modification of acetic acid lignin (AL) to amphiphilic derivatives by polyoxyethylation using two types of polyethylene glycol (PEG) with diglycidyl (PEGDE) and monoglycidyl (EPEG) groups.[ 1 ] Kraft lignin (KL) was converted to amphiphiles in a similar manner. The resultant KL derivatives also indicated high surface activity. Polyethylene glycol with long alkyl chain was introduced to AL, KL, and lignosulfonate (LS) to prepare surfactants of high performance, using dodecyloxy-polyethylene glycol glycidyl ether (DAEO). The resultant DAEO-derivatives showed lower critical micelle concentration by 2–4 orders of magnitude than the corresponding PEGDE- and EPEG-derivatives. The DAEO-derivatives from LS showed better dispersibility for gypsum paste, one of cement components, than LS.

Dissolution of wet wood biomass without heating

Lignocellulose biomass including wood is an abundant, natural, and renewable material, and is a promising fossil fuel substitute. However, there are still no powerful solvents to extract polysaccharides from biomass. Here we report a tetra-n-butylphosphonium hydroxide–water mixture as a potential solvent for wood dissolution without heating. Upon gentle stirring at room temperature, this solution containing 40 wt% water extracted 37% of polysaccharides after stirring for only 1 hour. This excellent dissolution ability was maintained in a wide range of water content.

Almost complete dissolution of woody biomass with tetra-n-butylphosphonium hydroxide aqueous solution at 60 °C

Dissolution of several kinds of woods was examined in tetra-n-butylphosphonium hydroxide ([P4,4,4,4]OH) aqueous solution. Since there is a strong correlation between the dissolution degrees and the Klason lignin contents of the wood, lignin degradation and removal were found to be necessary for efficient dissolution of several woods such as cedar. It was found that moderate heating (60 °C) and addition of H2O2 aqueous solution to 50% [P4,4,4,4]OH aqueous solution are quite effective to dissolve wood. Cedar powder (final concentration of 5.0 wt%) was almost completely dissolved in this aqueous solution at 60 °C under mild stirring for 24 h. This efficient wood dissolution was caused by partial degradation of lignin.

Flexible Electronic Substrate Film Fabricated Using Natural Clay and Wood Components with Cross‐Linking Polymer

Requirements for flexible electronic substrate are successfully accomplished by green nanocomposite film fabricated with two natural components: glycol-modified biomass lignin and Li+ montmorillonite clay. In addition to these major components, a cross-linking polymer between the lignin is incorporated into montmorillonite. Multilayer-assembled structure is formed due to stacking nature of high aspect montmorillonite, resulting in thermal durability up to 573 K, low thermal expansion, and oxygen barrier property below measurable limit. Preannealing for montmorillonite and the cross-linking formation enhance moisture barrier property superior to that of industrial engineering plastics, polyimide. As a result, the film has advantages for electronic film substrate. Furthermore, these properties can be achieved at the drying temperature up to 503 K, while the polyimide films are difficult to fabricate by this temperature. In order to examine its applicability for substrate film, flexible electrodes are finely printed on it and touch sensor device can be constructed with rigid elements on the electrode. In consequence, this nanocomposite film is expected to contribute to production of functional materials, progresses in expansion of biomass usage with low energy consumption, and construction of environmental friendly flexible electronic devices.

Production of 2-hydroxyacetylfuran from lignocellulosics treated with ionic liquid–water mixtures

Japanese cedar (Cryptomeria japonica) was treated with 12 ionic liquid (IL)–water mixtures at 120 °C for 1 h. Production of 5-hydroxymethylfurfural, furfural and 2-hydroxyacetylfuran (2-HAF) was observed by HPLC and GC-MS. This is the first report to identify 2-HAF from lignocellulosics using ILs. The optimal IL–water mixture was found to be a 90% pyridinium chloride and 10% water w/w solution, although any IL–water mixture that contained pyridinium or imidazolium salts produced all three compounds in varying yields.

Molecular weight distributions of polysaccharides and lignin extracted from plant biomass with a polar ionic liquid analysed without a derivatisation process

Polysaccharides and lignin, extracted from wheat bran with 1-ethyl-3-methylimidazolium methylphosphonate, were directly analysed with high-performance liquid chromatography with the aid of ionic liquid as an eluent (HPILC). Polysaccharides and lignin were clearly detected independently with the use of both a refractive index detector and UV detector. Polysaccharides with low molecular weights were obtained at 25 °C in 2 h with an extraction yield of only 4%. High molecular weight polysaccharides were extracted with a yield of 26% at 120 °C and selective extraction of high MW polysaccharides was succeeded with pretreatment at low temperature. Furthermore, a similar extraction was carried out for wood biomass. Characteristics of pine and oak were observed in the molecular weight distributions of the extracted polysaccharides and lignin. We also analysed the extracts from different parts of Prunus × yedoensis ‘Somei-yoshino’. The average molecular weight of polysaccharides from its leaves was determined to be lower than that of its twigs. The present HPILC method has potential to rapidly and easily analyse molecular weight distributions of components of plants.

Reaction behavior of Cryptomeria japonica treated with pyridinium chloride–water mixture

Cryptomeria japonica was treated with 90% pyridinium chloride ([Py]Cl) and 10% water w/w solution at 80 and 120 °C. Most hemicellulose in C. japonica was liquefied and over half the lignin in C. japonica was solubilized after treatments at 80 and 120 °C. However, cellulose was mostly insoluble at 80 °C and partially soluble at 120 °C. The crystal structure of cellulose in the cell walls was retained after treatment at 80 °C for 48 h. The degradation products from the polysaccharides were obtained in different yields. The 90% [Py]Cl and 10% water w/w solution is effective for the treatment of lignocellulosics, such as liquefaction of lignocellulosics and the production of useful low molecular weight compounds.