Masamitsu Funaoka

A new type of phenolic lignin‐based network polymer with the structure‐variable function composed of 1,1‐diarylpropane units

Phenolic lignin-based network polymers with structure-variable function have been designed, and a reaction process has been developed for synthesizing them directly from native lignins. The process includes a phase-separation reaction system composed of phenol derivatives and concentrated acid. The key point of the process is that lignin and carbohydrates, which form an interpenetrating polymer network within the cell wall, are separated into different phases and their modifications are controlled individually. The resulting lignin-based polymers (lignophenol derivatives) have unique functions, which conventional lignins do not have, in spite of retention of the original interunit linkages: these include highly phenolic property, no conjugated system, light colour comparable with native lignin, structure-variable function and solid-liquid transformation. These original functions are due to the selective hybridization of lignin structural units with monomeric phenol derivatives at C positions, leading to network structures composed mainly of 1,1-diarylpropane-type units. New types of applications of lignophenol derivatives using their original functions are described (biocatalyst system and lignin fibre composites).

The Difference between Guaiacyl and Guaiacyl-Syringyl Lignins in their Responses to Kraft Delignification

On examine les differences entre la cuisson kraft de bois resineux et feuillus du point de vue de la dissolution des noyaux phenyles. En particulier, on demontre quantitativement la difference dans la formulation et la dissolution des unites condensees gaiacyle et gaiacyle-syringyle

The Formation and Quantity of Diphenylmethane Type Structures in Residual Lignin during Kraft Delignification of Douglas-Fir

Kraft delignification of Douglas-fir (Pseudotsuga menziesii) was carried out from 90°C to a final pulping temperature of 170°C at a heating rate of l°C/min. At various stages of delignification the quantity of phenyl nuclei that were Condensed into the diphenylmethane moieties in residual lignins were dctermined directly on delignified wood by a method combining alkaline nitrobenzene oxidation and phenyl nucleus exchange reactions. The results indicate that the formation of diphenylmethane Structures does not occur before the pulping temperature had reached 170°C. As delignification proceeded, the quantity of diphenylmethane moieties in residual lignins increased steadily. After 2 hours at 170°C (~ kappa 30) the residual lignin consisted of 54 mol% phenyl nuclei that were associated with the diphenylmethane structural units, 37 mol% other type of Condensed and 9 mol% noncondensed phenyl nuclei. In this study, the quantity of structural units of the diphenylmethane type in residual lignin was determined for the first time. Further confirmation of the validity of our current results is under investigation using other analytical methods.

Characteristics of lignin structural conversion in a phase-separative reaction system composed of cresol and sulfuric acid

The chemical structures of lignocresols derived from native lignins by the phase-separative treatment with cresol and sulfuric acid were characterized by spectral analyses and chemical degradations. The changes in the structure of lignin during the conversion process were discussed. Lignocresol had few conjugated systems, being pinkish white, its brightness comparable to milled wood lignin. Spruce lignocresol included 0.64 mol/C 9 of cresolic nuclei in the molecule (0.9 mol/C 9 in birch lignocresol), 77% of which were linked to lignin Cα-positions through carbon-carbon linkages, 16% possibly to Cγ-positions, and the remaining 7% etherified to lignin side chains through its phenolic hydroxyl groups. The molecular weight (Mw) of lignocresol was ca. 3500 in spruce, lower in birch. Most of the β- and γ-positions in the side chains of C 9 units remained intact, except the coniferyl alcohol and aldehyde units. These structural features were constant during the reaction time up to 60min. It is concluded that the fragmentation of lignin in the phase-separative reaction system was principally due to the cleavage of benzyl aryl ethers, and the skeleton of lignocresol represents those of lignin subblocks formed by the dehydrogenative polymerization of monolignols.

Enzymatic degradation of highly phenolic lignin-based polymers (lignophenols)

Abstract Enzymatic degradation of two lignin-based polymers (lignophenols), lignocatechol and lignocresol, prepared by selectively grafting catechol and p-cresol to Cα positions of lignin, respectively, were carried out in aqueous organic solvents. Both lignophenols showed high reactivity in the peroxidase-catalyzed oxidation. Structural analyses by NMR spectroscopies revealed that the degraded lignophenols contained aliphatic chain content, which might be mainly formed in the reduction of the intermediate initially generated by the aromatic ring cleavage. Lower amount of aromatic units in the lignophenols after degraded by peroxidase also indicted the cleavage of aromatic rings. Due to the substitution of phenols at Cα positions of lignin, the degraded lignophenols did not have carbonyl structure, which was abundant in the biodegradation products of native lignin. The two lignophenols were also degraded by Rhus vernicifera laccase. But the degree of degradation was lower than that of the degradation by peroxidase, which might be due to the low activity of laccase on the lignin moieties in lignophenols.

Enzymatic synthesis of polyphenols from highly phenolic lignin-based polymers (lignophenols)

Peroxidase-catalyzed polymerization of lignin-based macromonomers (lignophenols), lignocatechol and lignocresol, prepared by phenolation of lignin with catechol or p-cresol, was carried out in aqueous organic solvent mixtures. The two lignophenols were polymerized to give cross-linked polymers. The highest yield of polymerization (83%, w/w) was obtained with lignocatechol, and the maximum yield for the polymerization of lignocresol was 55% (w/w). Pyrolysis GC-MS analysis of polymers indicated that the polymerization of lignophenols involved the oxidative coupling of the introduced phenol derivatives.

Behavior of lignin-binding cellulase in the presence of fresh cellulosic substrate.

A model lignin-binding cellulase was prepared from Trichoderma reesei cellulase and lignocresol, which was synthesized from softwood or hardwood lignin. Filter paper was incubated with the lignocresol-cellulase complex, and it was observed that only a limited amount of cellulase migrated to the filter paper. The cellulase adsorption isotherms for the lignocresols and filter paper were fitted to a Langmuir absorption model, and the determined Langmuir constants were as follows: softwood lignocresol>hardwood lignocresol>>filter paper. The calculations demonstrated that lignin-binding cellulase can potentially be recovered by the addition of a sufficient quantity of cellulosic substrate. As a result, the lignocresol-binding cellulase is highly stable and lignocresol can potentially be used for immobilizing cellulase in the active state.

Lignin isolated from steam-exploded eucalyptus wood chips by phase separation and its affinity to Trichoderma reesei cellulase.

Steam-exploded eucalyptus wood chips were treated with p-cresol and 72% sulfuric acid at ambient temperature. Steam-exploded lignin was isolated as acetone-soluble and diethyl ether-insoluble compounds from the cresol layer. The lignin extraction yield was only 47%, and the amount of cresol grafted to lignin was much less than that in the case of eucalyptus lignin without steam explosion. Clearly, the steam explosion process depolymerized native lignin, and simultaneously, promoted polymerization via labile benzyl positions. The steam-exploded eucalyptus lignin adsorbed more Trichoderma reesei cellulase; however, its enzymatic activity was less than that of eucalyptus lignin that did not undergo steam explosion. It is evident that pretreatment potentially affects the affinity between lignin and cellulase and the resultant saccharification efficiency.

Carbon Molecular Sieving Membranes Derived from Lignin-Based Materials

Carbon molecular sieving membranes were prepared by pyrolysis of lignocresol derived from lignin by the phase-separation method. Lignocresol membranes formed by a dip process on a porous α-alumina tubing were carbonized at 400–800°C under nitrogen atmosphere. The thickness of the membrane formed on the outer surface of the substrate was about 400 nm judging from SEM observation. Gas-evolving behavior of lignocresol was measured using thermogravimetry-mass spectrometry (TG-MS). The gaseous products evolved from lignocresol included a number of fragments with higher molecular weights; whereas those from phenolic resin are mainly due to phenol and methylphenol. These evolved pyrolysis fragments effectively contribute to micropore formation of carbonized lignocresol membranes. Gas permeation rates through the membrane decreased in the order of increasing kinetic molecular diameter of the penetrant gas, and the membrane behaved like a “molecular sieve.” The permeation properties were dependent on heating conditions, and a pyrolysis temperature of 600°C gave the best membrane performance. Gas selectivities of the membrane prepared at 600°C were 50, 8, 290, and 87 for CO2/N2, O2/N2, H2/CH4, and CO2/CH4 at 35°C, respectively.

Adsorption Behavior of Quaternary Amine Types of Lignophenol Compounds for Some Precious Metals

Two kinds of quaternary amine type lignophenol derivatives were prepared and tested for the adsorption behavior of Au(III), Pd(II), Pt(IV), Cu(II), Fe(III), and Zn(II) in hydrochloric acid medium. Both the derivatives were found to exhibit excellent selectivity for precious metals with negligible adsorption for other metal ions. The adsorption isotherm study established the Langmuir type adsorption model, and from the respective adsorption isotherms, the maximum loading capacities for Au(III), Pd(II), and Pt(IV) were evaluated. Ionic interaction between the positive moiety of quaternary amine functional groups and the anionic chloride complexes formed by the precious metal ions in acidic chloride media was concluded as the main adsorption mechanism.