关键词: 高温液态水, 甜高粱渣, 水解, 半纤维素, 机理

Abstract: Sweet sorghum bagasse（SSB）was hydrolyzed with liquid hot water in a flowthrough reactor with the objective of achieving complete saccharification of hemicellulose of SSB and understanding the hydrolysis mechanismThe effect of reaction temperature (155—235℃)and flow rate (5—30 ml·min-1)on the concentration of xylose, glucose, arabinose, their total sugars and their degradation products (furfural, 5HMF, acetic acid, glucuronic acid, formic acid and glycolic acid)in the liquid fractions was investigatedThe experimental results indicated that xylose was more sensitive to temperature and flow rate than arabinose and glucoseThe concentration of total xylose including xylose monomer and xylose oligomer dropped dramatically when temperature was higher than 195℃A lower flow rate (5 ml·min-1）resulted in a higher furfural yield due to longer residence time for xylose in the reactorIn contrast, a higher flow rate (30 ml·min-1）would reduce the thickness of stagnant fluid layer surrounding the solid particles and lower resistance to penetration of water into the solids for hydrolysis and diffusion of oligomers into solutionIt was hypothesized that the major xylan in SSB hemicellulose was O-acetyl4-O-methylglucuronoarabinoxylanXylose, arabinose, glucose and their oligosaccharides could be considered as the primary productsGlucuronic acid and acetic acid were produced from the decomposition of glucuronic and Oacetyl groups in the branched chain of hemicelluloseFurfural and 5hydroxymethyl2-furaldehyde (5-HMF)were the direct degradation products of sugarsMoreover, glucuronic acid would be further oxidatively degraded into glycolic acidLow molecular weight organic acids, such as formic acid were the further degradation products.

Key words: liquid hot water, sweet sorghum bagasse, hydrolysis, hemicellulose, mechanism