An ionic liquid, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), was used to dissolve Japanese fir (Abies sachallnensis MAST) wood. Milled woods prepared by planetary ball-milling for 8 h dissolved completely in [Bmim]Cl at 100 °C in 2 h. The dissolved woods were then subjected to in situ acetylation, and the fully acetylated woods were regenerated from [Bmim]Cl. (1)H-(13)C correlation heteronuclear single-quantum coherence (HSQC) nuclear magnetic resonance (NMR) experiments were successfully conducted with the acetylated woods in dimethyl sulfoxide (DMSO)-d(6). The acetylated lignin and polysaccharide signals dispersed reasonably well on the 2D spectra. Characterization of the NMR signals for the whole cell-wall components, including lignin, cellulose, and hemicelluloses, was achieved by comparison with isolated lignin and commercial cellulose and hemicelluloses (arabinoxylan, galactomannan, and glucomannan). The procedure used here is applicable for the characterization of cell-wall components in various plant biomasses.

Changes in the wettability of eight species of tropical woods during artificial weathering up to 600 h are discussed from the aspect of chemical and structural changes in their surfaces: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp., and Tabebuia spp. with relatively high and low specific gravity. On the whole, the wettability of specimens decreased upon irradiation up to 20 h; above that they increased. Changes in wettability during artificial weathering differed according to wood species. The IR spectra suggest that the specimen surfaces after irradiation for 600 h result in a cellulose-rich layer, and therefore the increase in wettability during artificial weathering can be explained in terms of the increase in hydroxyl groups originating from both the exposed cellulose and adsorbed water. However, the difference in wettability exists between species even after the surface develops a cellulose-rich layer. The stereoscopic micrographs showed the development of cracks for all of the specimens after irradiation for 600 h, and differences in their magnitudes according to species. From these results, the differences in wettability between species were estimated to be due to the structural changes on the surface during artificial weathering, whereas the increase in wettability was due to the chemical changes.

This paper describes the change in diffuse reflectance Fourier transform infrared (DRIFT) and ultraviolet-visible (UV-Vis) diffuse reflectance spectra of the following eight tropical woods during artificial weathering up to 600 h in relation to their color changes, especially to yellowing: Amnurana acreana, Acacia auriculiformis, Dipterocarpus spp., Eucalyptus marginata, Eucalyptus robusta, Shorea spp. and Tabebuia spp. with relatively high and low specific gravity. For A. acreana, A. auriculiformis, Dipterocarpus spp. and both Tabebuia spp., Db* (yellowing) increased with exposure up to 50 h, and decreased above 50 h. For E. marginata, E. robusta and Shorea spp., on the other hand, both Da* (shift to red) and Db* decreased with increased exposure time. For woods in which Db* increased, the Db* showed a positive dependence on the difference in relative intensity ratio of a band at 1740 cm y1 to that at 2900 cm y1 (DD 1740 /D 2900 ) in DRIFT spectra of specimens before and after exposure. This result indicated that the increased band at 1740 cm y1 played a significant role in the increased Db*. Then again, also for woods in which Db* decreased, the DD 1740 /D 2900 increased, but was not related to the Db*. The DD 1740 / D 2900 for woods in which Db* decreased had a positive relationship to the difference in remission function at 410 nm (DF(R`) 410 ) in UV-Vis diffuse reflectance spectra for specimens before and after exposure, while woods in which Db* increased were independent of the DF(R`) 410 . Therefore, it is suggested that woods in which Db* increased and decreased differ from one another in the contribution to the increase in the band at 1740 cm y1 , resulting in either an increase or decrease of Db*.

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In this work, pretreatment of wood meals using a recycled ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([Emim] Ac), enhanced glucose liberation by enzymatic saccharification, without dissolution of cellulose and lignin. In contrast, previous studies on IL pretreatment have mostly focused on lignocellulosic dissolution to regenerate cellulose and removing lignin. Softwood (Cryptomeria japonica) was pretreated with [Emim]Ac at 60-100 °C for 2-8 h without collecting regenerated cellulose. The pretreatment did not have a strong effect on wood component dissolution (weight of residues: 91.7-98.8%). The residues contained relatively high amounts of lignin (26.6-32.6%) with low adsorption of [Emim]Ac (0.9-2.7%). Meanwhile, the crystallinity index (C r I) of cellulose in the wood was significantly reduced by pretreatment, from 50.9% to 28.4-37.1%. In spite of the high lignin contents in the residues, their glucose liberation values by enzymatic saccharification using a cellulase mixture were 3-16 times greater than that of untreated wood. A good correlation was found between the saccharification effectiveness of pretreated samples and the C r I. Although lignin dissolved in [Emim]Ac continued to accumulate after repeated use of [Emim]Ac, the pretreatment was found to be effective for three consecutive cycles without the need to remove the dissolved materials.