纤维素超临界水预处理与水解研究

Supercritical Pretreatment and Hydrolyzation of Cellulose

利用超临界水解工艺进行生物质废弃物(秸秆)能源转化,使其主要成分纤维素在超临界水中快速水解为低聚糖,为其进一步葡萄糖转化和乙醇发酵解决技术瓶颈.其中纤维素在超临界水中的溶解是预处理与水解过程的限速步骤.研究表明,反应温度达到380℃及以上时,纤维素可迅速溶解并进行水解,液化比例可达100%;在374～386℃范围内反应温度对纤维素的转化率有明显作用,低聚糖和六碳糖的总产率在临界点附近出现最大值.超临界条件下,低聚糖和六碳糖转化率在较短反应时间内出现峰值,而后随反应时间的延长快速下降,固液比对于纤维素的低聚糖和六碳糖转化也有显著影响.最优水解条件研究显示,在380℃,40mg纤维素/2.5mL水条件下反应16s可获得最大的低聚糖产率,为29.3%,在380℃,80mg纤维素/2.5mL水条件下反应18s可获得最大的六碳糖产率,为39.2%.

A supercritical water pretreatment was applied to cellulose dissolution and hydrolysis. The effects of temperature, residence time, and ratio of solid/liquid phase on the cellulose dissolution and sugar conversion were investigated. The results showed that cellulose could dissolve completely in a short time at 380 ℃ and higher temperature. The reaction temperature has significant effect on consequent hydrolyzation and sugar conversion in the range of 374-386℃, and the highest concentration of oligosaccharides and hexoses was obtained around the critical point. On the other hand, these products were also decomposed rapidly under the supercritical condition with the extending of reaction time. The ratio of initial solid/liquid phase affects the cellulose hydrolyzation markedly as well. The best results were obtained with 40 mg cellulose/2.5 mL water at 380℃ and 16 s, affording oligosaccharide recovery above 29%, or 80 mg cellulose/2.5 mL water at 380 ℃ and 18 s, affording hexose recovery above 39%.