UDC 547.992Steam-exploded lignin (SEL) was separated from cornstalk residue, which came from steam-exploded cornstalk after enzymatic hydrolysis. There are two methods to acquire SEL, the alkali solution and the organic solvent method. SEL was analyzed with respect to the elementary composition, molecular weight, IR spectrum, and 13 C NMR spectra. The C 9 -formula of SEL was calculated from the experiment data. According to 13 C NMR, SEL can be classified as a "GSH" type of lignin, and it is composed mainly of β-O-4 ether bonds together with β-5 and β-1 carbon-carbon linkages between the lignin structural units.Key words: enzymatic hydrolysis of cornstalks, steam-exploded lignin (SEL), structure of SEL, separation.Many researchers use cornstalks as raw material for making bioalcohol by transforming the saccharide components through steam explosion to enzymatic hydrolysis [1]. This is an important application for renewable natural resources. There is about 30-35% lignin in cornstalk residue [2]. Steam-exploded lignin (SEL) from cornstalk residue can be obtained by two methods, the aqueous alkali solution and the organic solvent method.Lignin is an amorphous aromatic network polymer made up of phenylpropane (C 6 -C 3 ) units by carbon-carbon bonds and ether linkages, in which the β-aryl ether linkage (48% and 60% in spruce and birch lignin, respectively) is the most dominant [3]. It is a renewable and nontoxic resource, which has potential application as polymer-based products such as lignin-phenol formaldehyde resin, lignin-isocyanate polyurethane adhesives, foam insulation, etc. [2][3][4]. But at present time, lignin is mainly separated from the black liquor of the pulping process, in which the original structure of lignin is destroyed. In spite of many years of development effort, industrial lignin products are limited in number. SEL is used in polymer modification because it preserves the original chemical activity perfectly. Chemical analysis as well as NMR and infrared spectroscopy were used to analyze the structure of lignin, and also to give information on the actual chemical group altered, removed, and/ or added to lignin during the separation process [5]. In this paper, the structural and physical and chemical characterization of SEL was investigated by chemical analysis and infrared and NMR spectroscopy.There are two methods for extracting SEL. An aqueous alkali solution easily reacts with lignin. Sodium hydroxide or ammonia was selected as the alkali solution. According to orthogonal analysis, the reaction temperature is set at 65-70°C. If the pH value is adjusted by H 2 SO 4 , lignin will be precipitated [6]. The second method of separating lignin is by organic solvent extraction. Some solvents such as 1,4-butanediol, glycol, tetrahydrofuran, or dimethyl sulfoxide can be chosen to dissolve the lignin, but the boiling point of tetrahydrofuran or dimethyl sulfoxide is very low, and its toxicity is unfavorable to work with. So 1,4-butanediol and glycol were chosen to dissolve the lignin. The extraction yi...
