Satoshi Kumagai

The Hot Compressed Water Treatment of Solid Waste Material from the Sugar Industry for Valuable Chemical Production

Sugarcane bagasse, the solid waste material produced in the sugar industry, was subjected to treatment in hot compressed water. The experiments were performed in a batch-type reactor containing slurry of 10 ml of water and 1.2 g of solids. The reactor was heated to temperatures ranging between 200°C and 300°C for reaction times of 3 to 30 min. The product was separated into liquid and solid fractions. Each fraction was analyzed to investigate the alteration of the main lignocellulosic polymers by hot compressed water. Results for the liquid fractions showed that increased temperatures and reaction times completely dissolved hemicellulose and cellulose in the water, leaving lignin in the solid product. During treatment, hemicellulose and cellulose gradually decomposed into simple sugars, which were then degraded and decomposed into furfural, 5-(hydroxymethyl)furfural (5-HMF) and organic acids. However, the yield of furans and some organic acids decreased and became undetectable at 300°C and with increasing reaction time. The solid fraction was also characterized before and after treatment. Results showed that the hydrogen and oxygen content of the solids decreased with increased reaction conditions, due to dehydration and decarboxylation reactions. The reactions also increased the carbon content of the treatment products by 1.2–1.6 times that in the raw material, suggesting that the hot compressed water treatment of sugarcane bagasse can be considered for the provision of valuable chemicals for biofuel and high-carbon-content material (biochar).

Effective Utilization of Moso-Bamboo (Phyllostachys heterocycla) with Hot-Compressed Water

In this study, the hydrothermal carbonization behavior of bamboo in hot-compressed water (HCW) using a batch-type reactor at 180–300 °C was observed to investigate the effective utilization of bamboo as a biomass resource. Polysaccharides (hemicellulose and cellulose) in the bamboo were changed to water soluble products. At 180–220 °C, hemicellulose (arabinoxylan) was first hydrolyzed to xylooligosaccharides and then to xylose that was further decomposed to various organic acids and furfural. However, most of the cellulose was not decomposed and was recovered as a solid residue at this temperature range. Cellulose began hydrolyzing to glucose at temperatures above 240 °C. The glucose was further decomposed to various organic acids and 5-HMF. The recovered oligosaccharides and monosaccharides can be used as functional food, food additives, and feedstocks for ethanol and lactic fermentation. Furthermore, organic acids and furans can be used as various chemicals. More hemicellulose and cellulose, which have relatively low carbon content in the bamboo, were decomposed and dissolved in water. As a result, the solid residue consisted mainly of lignin, which has higher carbon content compared to cellulose and hemicellulose. Hence, the heating value of the solid residue increased at higher temperature during treatment and the residue could be considered as a solid fuel.

Application of plasma treated activated carbon to enhancement of phenol removal by ozonation in three-phase fluidized bed reactor

Plasma treatment of activated carbon (AC) was found to be an efficient method to enhance phenol removal by ozonation in a three-phase fluidized-bed reactor. The plasma treatment extended porous structure, changed surface morphologies, and produced oxygen functional groups on the surface of AC. Plasma-treated activated carbon together with O3 gave the best removal result, in which phenol was completely decomposed within 10 min (with pseudo first-order rate constant k = 0.286 min1), while untreated AC without O3 showed the worst result (k = 0.024 min1). Consequently, AC modified by plasma was shown to be a good material for removal of organic pollutants and yield superb performance in an integrated process with ozone in a fluidized-bed reactor.