Elucidaton of the formation mechanism and characteristics of acid-soluble lignin, and conversion of lignin into functional material

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This research studied on (1) elucidaton of the formation mechanism and characteristics of acid-soluble lignin, and (2) conversion of lignin into functional material. Sulfuric acid lignin (SAL) with highly condensed structures was selected as a lignin sample.( 1 ) Elucidaton of the formation mechanism and characteristics of acid-soluble lligninAcid soluble lignin (ASL) prepared from beech was composed of about half the amount of chloroform-soluble ASL and the rest half the amount of water-soluble ASL. Reaction of guaiacyl and syringyl lignin model compounds with carbohydrates iin 72% sulfuric acid (SA) suggested that water-soluble ASL is formed by condensation of syringyl lignin with hemicellulose. Furthermore, degradation reaction of syringyl lignin model compounds in 72% SA indicated that syringyl alkyl ether linkages are hydrolyzed to form chloroform-soluble low molecular weight degradation products of SAL.( 2 ) Conversion of lignin into functional materialTo develop new methods for effective utilization of acid hydrlysis lignin, chemical conversion of SAL as a typical acid hydrolysis lignin into funcrional material was investigated. at first, preparation of neutral surfactant with carbohydrate component as a gydrophilic group from SAL and phenolized SAL (p-SAL) in 72% SAL on the model of water-soluble ASL was tried. However, reaction of condensed-type lignin model compounds with monosaccharides in 72% SA gave the expected C-glycosides only in low yields. Attempts to introduce carboxymethyl and dimethylaminomethyl groups into SAL and/or P-SAL were successful to prepare soluble acidic and cationic surfactants from P-SAL, respetively, in quantitative yields. The content of the groups was 1.4 and 1.3 per C_9-C_6 unit (p-hydroxypheny) guaiacyl methyl unit), respectively.