Eiji Minami

Liquefaction of beech wood in various supercritical alcohols

The liquefaction of Japanese beech (Fagus crenata Blume) was studied with various straight-chain alcohols in subcritical and supercritical states using a batch-type reaction vessel to obtain liquid fuel from lignocellulosics. Under the reaction condition of 270°C, beech wood was liquefied to some extent in all alcohols with about 50%–65% insoluble residue left after treatment for 30min. Under the condition of 350°C, however, more than 90% of wood was decomposed and liquefied in all alcohols. Alcohols with longer alkyl chains liquefied lignocellulosics in shorter reaction times. Because many kinds of alcohols, such as methanol and ethanol, can be produced from biomass, 100% biomass-based liquid fuel can be prepared by supercritical alcohol technology when using such bioalcohols.

Comparison of the decomposition behaviors of hardwood and softwood in supercritical methanol

Abstract The chemical conversion of Japanese beech (Fagus crenata Blume) and Japanese cedar (Cryptomeria japonica D. Don) woods in supercritical methanol was studied using the supercritical fluid biomass conversion system with a batch-type reaction vessel. Under conditions of 270°C/27 MPa, beech wood was decomposed and liquefied to a greater extent than cedar wood, and the difference observed was thought to originate mainly from differences in the intrinsic properties of the lignin structures of hardwood and softwood. However, such a difference was not observed at 350°C/43 MPa, and more than 90% of both beech and cedar woods were effectively decomposed and liquefied after 30 min of treatment. This result indicates that the supercritical methanol treatment is expected to be an efficient tool for converting the woody biomass to lower-molecular-weight products, such as liquid fuels and useful chemicals.

Reaction behavior of lignin in supercritical methanol as studied with lignin model compounds

Abstract The reaction behavior and kinetics of lignin model compounds were studied in supercritical methanol with a batch-type supercritical biomass conversion system. Guaiacol, veratrole, 2,6-dimethoxyphenol, and 1,2,3-trimethoxybenzene were used as model compounds for aromatic rings in lignin. In addition, 5-5, β-1, β-O-4, and α-O-4 types of dimeric lignin model compounds were used as representatives of linkages in lignin. As a result, aromatic rings and 5-5 (biphenyl)-type structures were stable in supercritical methanol, and the β-1 linkage was not cleaved in the β-1-type structure but converted rapidly to stilbene. On the other hand, β-ether and α-ether linkages of β-O-4 and α-O-4 lignin model compounds were cleaved rapidly, and these compounds decomposed to some monomeric compounds. Phenolic compounds were found to be more reactive than nonphenolic compounds. These results indicate that cleavages of ether linkages mainly contribute to the depolymerization of lignin, whereas condensed linkages such as the 5-5 and β-1 types are not cleaved in supercritical methanol. Therefore, it is suggested that the supercritical methanol treatment effectively depolymerizes lignin into the lower-molecular-weight products as a methanol-soluble portion mainly by cleavage of the β-ether structure, which is the dominant linkage in lignin.

Decomposition behavior of woody biomass in water-added supercritical methanol

The chemical conversion of Japanese beech (Fagus crenata Blume) in water-added supercritical methanol was studied for a wide range of water content using a batch-type reaction vessel to obtain chemicals from lignocellulosics. It was consequently found that addition of water enhanced the decomposition of wood cell wall components; cellulose, hemicelluloses, and lignin. In cases of high water content, however, it resulted in low solubility of lignin-derived products causing an increase in the mass of the residue. The water content was thus optimized to be around 10% (v/v) for the decomposition of wood. Concomitantly, the yields and selectivity of the chemicals from wood could be regulated by the addition of water, especially for the lignin-derived products. As a result, the monomeric compounds of lignin, coniferyl alcohol and sinapyl alcohol, were recovered as their γ-methyl ethers in the presence of water in higher yields than those obtained without addition of water.

O2 cluster ion-assisted deposition for tin-doped indium oxide films

Abstract In order to realize high throughput for industrial application, a new gas cluster ion-assisted deposition system has been developed. Tin-doped indium-oxide (ITO) films were formed by using the O2 gas cluster ion beam-assisted deposition technique. Large oxygen cluster ions which can transport thousands of atoms in an ion with very low energy per constituent atom were used in this deposition process. The energetic oxygen clusters collapse at the surface and react with the metal atoms. About 10% of atoms are incorporated, when the kinetic energy of the cluster ion is above 5 keV. Interactions between cluster ions and substrate atoms occur in the near-surface region and cluster ions can deposit their energy with a high density in a very localized surface region. The oxidation reaction on the surface can be enhanced by energetic cluster ion bombardment which offers a new technique for ion-assisted thin film formation. Very smooth, highly transparent (>80%) and low resistivity films were obtained by using a 7 keV oxygen cluster ion beam.

Characterization of the precipitated lignin from Japanese beech as treated by semi-flow hot-compressed water

Abstract Japanese beech (Fagus crenata) was decomposed by a semi-flow process in hot-compressed water (HCW) at 150~230°C/10 MPa for 25 min. Mainly hemicelluloses and partly the lignin moiety of the wood was affected and liquefied in water. A part of the liquefied products can be precipitated after 12 h standing at ambient conditions. The precipitates are composed of around 90% of lignin, which was quantified and characterized by various chemical and spectroscopic methods in comparison of milled wood lignin (MWL), which is considered to be a representative compound for the native lignin in wood. The yield of the precipitated lignin (Lprecip) is higher than that of MWL and its syringyl content is also higher as demonstrated by alkaline nitrobenzene oxidation (NBO) giving rise to higher syringaldehyde/vanillin (SA/VA) ratios. Its OHphen group content was also high. The interpretation is that Lprecip is mainly from the secondary wall, and accordingly, the presented semi-flow HCW treatment offers the possibility for an efficient lignin isolation.

Comparative study of the topochemistry on delignification of Japanese beech (Fagus crenata) in subcritical phenol and subcritical water

Abstract The delignification of Japanese beech (Fagus crenata) has been evaluated under conditions of subcritical phenol (230°C/1.2 MPa) and subcritical water (230°C/2.9 MPa). In the former, more than 90% of the original lignin was decomposed and removed, while in subcritical water, around half of the original lignin was left as insoluble residue. Ultraviolet (UV) microscopic images of the insoluble residues showed that the lignin in the secondary walls is decomposed and removed under both conditions. These images also revealed that the lignin in the compound middle lamella (CML) is resistant to subcritical water, but not to subcritical phenol. Results of alkaline nitrobenzene oxidation of the residual lignin confirmed these observations. Lignin in Japanese beech wood was phenolated by subcritical phenol, which was efficiently removed due to its high solubility in the reactant. It is obvious that CML is rich in condensed-type linkages facilitating rapid solvolysis by phenol. The topochemistry of the plant has a pronounced impact on its delignification behavior.