Showing papers by "Shiro Saka published in 2002"

A comparative study on chemical conversion of cellulose between the batch-type and flow-type systems in supercritical water

Abstract: Microcrystalline cellulose (avicel) was treated in supercritical waterusing batch-type and flow-type systems. The flow-type system made it possibletoshorten the heating, treating and cooling times, compared with the batch-typesystem. As a result, the flow-type system was able to liquefy avicel withoutproducing any supercritical water-insoluble residue. Although hydrolyzedproducts such as glucose and fructose, and pyrolyzed products such aslevoglucosan, 5-hydroxymethyl furfural, erythrose, methylglyoxal,glycolaldehydeand dihydroxyacetone were found in common from the water-soluble portiontreatedby both systems, the flow-type system gave a water-soluble portion with morehydrolyzed and less pyrolyzed products, together with water-solubleoligosaccharides consisting of cellobiose to cellododecaose and theirdecomposedproducts at their reducing end of glucose, such as[β–glucopyranosyl]1–11 β–levoglucosan,[β–glucopyranosyl]1–11 β–erythrose and[β–glucopyranosyl]1–11 β–glycolaldehyde. Inaddition, the precipitates of polysaccharides were recovered after 12h setting of the water-soluble portion. These results indicatedthat the flow-type system can hydrolyze cellulose with minimizing pyrolyzedproducts. On the other hand, the batch-type system resulted in a higher yieldof the pyrolyzed products due to the longer treatment, but a higher yield ofglucose due possibly to the higher pressure and concomitantly higher ionicproduct of water. Based on these lines of evidence, the process to increase theyield of the sugar is discussed under supercritical water treatment.

Characterization of the lignin-derived products from wood as treated in supercritical water

Abstract: Sugi (Cryptomeria japonica D. Don) and buna (Fugus crenata Blume) woods were treated with supercritical water (>374°C, >22.1 MPa) and fractionated into a water-soluble portion and a water-insoluble residue. The latter was washed with methanol to be fractionated further into a methanol-soluble portion and a methanol-insoluble residue. Whereas the carbohydrate-derived products were in the water-soluble portion, most of the lignin-derived products were found in the methanol-soluble portion and methanol-insoluble residue. The lignin-derived products in the methanol-soluble portion were shown to have more phenolic hydroxyl groups than lignin in original wood. The alkaline nitrobenzene oxidation analyses, however, exhibited much less oxidation product in the methanol-soluble portion and methanol-insoluble residue. These lines of evidence suggest that the ether linkages of lignin are preferentially cleaved during supercritical water treatment. To simulate the reaction of lignin, a study with lignin model compounds was performed;β-O-4-type lignin model compounds were found to be cleaved, whereas biphenyl-type compounds were highly stable during supercritical water treatment. These results clearly indicated that the lignin-derived products, mainly consisting of condensed-type linkages of lignin due to the preferential degradation of the ether linkages of lignin, occurred during supercritical water treatment.

Method for producing glucose and/or water-soluble cellooligosaccharide

Abstract: PROBLEM TO BE SOLVED: To provide a new method for efficiently producing glucose and/or a water-soluble cellooligosaccharide from a cellulosic material. SOLUTION: This method for producing glucose and/or the water-soluble cellooligosaccharide comprises hydrolyzing cellulose ≥100 in mean degree of polymerization by contact reaction with supercritical or subcritical water for 0.01-5 s, cooling and then further contact reaction with subcritical water for 1 s to 10 min. COPYRIGHT: (C)2003,JPO

Method for producing levoglucosan

Abstract: PROBLEM TO BE SOLVED: To provide a method for producing levoglucosan, capable of obtaining the levoglucosan useful as a raw material for an anticancer agent and anti-HIV agent, an optical isomer resolution agent, a raw material for a biodegradable plastic, or the like, from cellulose, or the like, in a high yield (for example, 90% or more based on a charged amount of the raw material). SOLUTION: This method for producing the levoglucosan comprises charging a pressure vessel with a raw material mainly containing polysaccharides (the cellulose is ordinarily used) comprising hexose together with a non-protonic organic solvent, such as tetrahydrothiophene-1,1-dioxide (sulforan) and dioxane, and heating the mixture at a temperature of ≥200°C, preferably not less than 300°C but not higher than a critical temperature of the solvent, for a period of a specified time ((t) (min)), wherein the (t) is in the range of 1-10 min and satisfies: t=(a time in which the levoglucosan is produced in the maximum yield based on the raw material)±1 (when the sulforan is used as the solvent, (t=2). COPYRIGHT: (C)2004,JPO