葡萄糖在超(近)临界水/甲醇中的稳定性研究

Stabilities of glucose in super/near-critical water or super/ near-critical methanol

在超(近)临界水/甲醇中分别试验考察了温度、压力、停留时间等参数对葡萄糖稳定性的影响。结果表明:无论在水中还是在甲醇中,温度越高,葡萄糖的稳定性越低,降解速率越高;降解产物5-羟甲基糠醛(HMF)和5-甲基(甲氧基)糠醛(MMF)的选择性随温度的变化存在着最大值。压力对葡萄糖在临界水中转化率的影响不明显,但在超临界甲醇中,葡萄糖的转化率随压力升高而增大,当达到临界压力以后基本不变。HMF和MMF的最大收率都出现在临界压力附近。停留时间越长,葡萄糖在超临界水和甲醇中的转化率越高,HMF的收率和选择性越低,而MMF的最大收率和最高选择性却存在着一个适宜的停留时间。

The stabilities of glucose in various temperatures, pressures and residence times were studied. The experimental results indicated that high temperature decreased the stability of glucose. The selectivities of furfural derivatives, which were major byproducts by decomposition of glucose both in water and methanol, presented the maximum values with the increase of temperature. The pressures made little effects on the conversion of glucose in supercritical water at elevated temperature. In methanol, however, the conversion of glucose increased with the pressure and leveled off after the critical pressure. The yields of furfural derivatives both in water and in methanol reach the maxima in the vicinities of the critical pressures. The longer the residence time is, the higher the conversion rate of glucose either in supercritical water or in supercritical methanol. The yield and selectivity of furfural derivative in supercritical water decreased with the extension of residence time, meanwhile, the maximum yield and the selectivity of furfural derivative occurred.