高温液态水中甜高粱渣半纤维素水解及其机理

为了回收甜高粱渣中的半纤维素衍生糖并了解其水解机理，在自行设计的Flowthrough反应器中对甜高粱渣进行了高温液态水水解，分别考察了不同反应温度和反应液流量下水解液中产物的生成情况。研究表明，相对葡萄糖和阿拉伯糖而言，木糖的生成受反应温度和反应液流量影响更大。温度高于195 ℃时糖降解加剧，总木糖浓度不断降低；低流量（5 ml?min-1）条件下生成的木糖不能被及时排出而进一步降解。通过产物分析可知，甜高粱渣半纤维素中含有典型的O-乙酰基-4-O-甲基葡萄糖醛酸基阿拉伯糖基木聚糖结构，木糖、葡萄糖、阿拉伯糖、各种低聚糖、乙酸和葡萄糖醛酸等是半纤维素水解的直接产物，糠醛和5-羟甲基糠醛等是糖类的降解产物， 甲酸等小分子酸是它们的进一步降解产物。

Hydrolysis of sweet sorghum bagasse hemicellulose with liquid hot water and its mechanism

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.