Shiho Takahashi

Performance of Softwood Soda-Anthraquinone Lignin as Water-Reducing Chemical Admixture in Concrete

Abstract We have attempted to establish a new process for producing a concrete chemical admixture prepared with by-product lignin of bioethanol production. In our pretreatment process of bioethanol production, soda-anthraquinone (AQ) cooking was applied to remove lignin from softwood chips. Soda-AQ lignin was recovered as precipitate by acidifying the black liquor. Five kinds of soda-AQ lignin were isolated by selecting the pH value of the precipitation. Each of the isolated soda-AQ lignins was used in the mortar fluidity test as concrete admixture. With the exception of the soda-AQ lignin at higher pH (pH 10.5) precipitation, the isolated lignin gave about two times’ higher mortar flow values than that of the widely used commercial lignosulfonate admixture. Size exclusion chromatography (SEC) data showed that the isolated lignin at higher pH value gave higher molecular weight. Functional group chemical analysis suggested that the isolated lignin of lower molecular weight had a higher phenolic hydroxyl group and higher alpha-carbonyl group content.

Differential behavior between acacia and Japanese larch woods in the formation and decomposition of hexenuronic acid during alkaline cooking

The effects of anthraquinone (AQ) and polysulfide (PS) on the hexenuronic acid (HexA) content of pulp during kraft cooking were studied using Acacia mearnsii (acacia) and Larix leptolepis (Japanese larch) sapwood. In contrast to the results of cooking Japanese larch at an H-factor of 1200, the HexA contents of acacia pulp with a kappa number of 20 at an H-factor of 291 did not differ greatly between the kraft, kraft-AQ, and PS-AQ cooking methods, although the hydroxide ion concentration in the acacia cooking liquor decreased on the addition of AQ or sulfur. To explain this difference, we studied the behavior of the formation and degradation of HexA during alkaline cooking of glucuronoxylan from cotton linter, which was cooked with 1.0 and 2.0 mol/l NaOH. The relationship between HexA content and H-factor during alkaline cooking of glucuronoxylan was clarified. The amount of HexA and its rate of decomposition were higher in the 2.0 mol/l solution than in the 1.0 mol/l solution. At a low H-factor similar to that for hardwood cooking, HexA content increased to a maximum level and then started to decrease at high hydroxide ion concentrations such as 2.0 mol/l, whereas it slowly decreased at low hydroxide concentrations such as 1.0 mol/l. At an H-factor of around 450, the HexA formation/degradation curve for 1.0 mol/l of hydroxide crossed the decomposition curve for 2.0 mol/l of hydroxide. Therefore, it was shown that at a low H-factor, a decrease in hydroxide ion concentration during acacia wood cooking had little effect on the HexA content of pulp.

Preparation of flocculant for optimizing glycol lignin manufacturing process by cationization of glycol lignin

Glycol lignin possessing thermoplastic and fusible properties can be a biorefinery platform material; however, glycol lignin is obtained as very small particles in suspension and the low dewatering efficiency is a major difficulty for the mass production. To improve the productivity of glycol lignin in the refinery plant, glycol lignin-based flocculants were prepared and their flocculation performance was examined. The flocculants (cationized glycol lignins) were synthesized by a reaction with glycidyltrimethylammonium chloride (GTA) in various reaction conditions. The prepared flocculants exhibited high flocculation performance and successfully economized the production cost of glycol lignin. Their flocculation efficiency was affected by the precipitation temperature, the length of the glycol chain, the molecular weight and the functional group of the glycol lignin. The flocculation behavior was interpreted by phase separation theory at a lower critical solution temperature (LCST).

Performance of Softwood Soda-Anthraquinone Lignin–Polyethylene Glycol Derivatives as Water-Reducing Admixture for Concrete

We have developed a high-performance lignin-based water-reducing admixture. In this study, softwood soda-anthraquinone lignin was modified with mono-epoxide polyethylene glycols having chain lengths of 10, 25, and 50 mol (the number of repeating units of ethylene oxide). The mortar flow and concrete slump flow tests were used to investigate the performance of the lignin derivatives as a water-reducing admixture. All tested lignin-PEG derivatives performed considerably better than a commercial lignosulfonate water-reducing admixture in the mortar flow test. In particular, the derivative with a PEG chain length of 50 mol performed excellently in both tests. The optimum PEG content for mortar dispersion was approximately 40% for lignin derivatives with a PEG chain length of 50 mol; this content exhibited a dispersing effect that was four times higher than that of the lignosulfonate water-reducing admixture. The strength of concrete containing the lignin derivatives was almost the same strength as that of concrete containing the commercial lignosulfonate water-reducing admixture.