木糖在甲酸体系中的糠醛转化及控制

Transformation and control of xylose into furfural in formic acid system

研究木糖在74%甲酸水溶液中的反应途径及控制方式,在不同时间与温度下的反应,并对反应物和产物进行液相色谱分析,分别测定木糖浓度和糠醛浓度。液相色谱分析结果显示,木糖降解在甲酸体系中是不可避免的,且随着温度与时间的延长变得严重。在90℃、1.5h时,木糖从初始浓度199.8mmol/l降低至193.52mmol/l,降解率为3.14%,糠醛浓度达到0.45mmol/l,转化率为0.22%,选择性7.11%,副反应所占比例约为2.92%。为了提高糠醛转化率,应该提高温度并适度延长时间。在130℃、4h时,木糖降解率最高为59.68%,糠醛的转化率最高为25.92%,副反应所占比例为33.76%,糠醛的选择性大约为43.43%。本研究具有两方面的指导意义:对于甲酸溶剂法生物质精炼,为获得木糖最大保留,应选择低温短时间以减少副反应发生;如果是糠醛的生产,应选择高温条件,以弱化副产物的发生。

In this study, 74% formic acid was used to prepare xylose solution, and the mixture was heated and cooked at different times and temperature （90℃, 107℃, 130℃）. The concentration of xylose and furfural were determined by liquid chromatography. The liquid phase analysis of the cooking liquor showed that the degradation of xylose are unavoidable in the formic acid system and became serious as the temperature and time are prolonged. The concentration of xylose decreased by 3.14% from 199.8mmol/l to 193.52mmol/l at 90℃ in 1.5 h reaction time, and the concentration of furfural reached 0.45mmol/l with a yield of 0.22% and a selectivity of 7.11%. The proportion of side reactions was about 2.92%. To improve the conversion of furfural,it should increase the temperature and moderately prolong reaction time. At 130℃, the degradation of xylose was 59.68%, with a furfural yield of 25.92% and side reaction of 33.76%. The selectivity of furfural pathway was about 43.43% at 130℃. It is concluded that low temperature and short time are preferred to avoid xylose loss, while high temperature should be chosen for furfural production.