葡萄糖水溶液环境对麦秆水热产物特性的影响

Effects of Glucose Solution on Characteristics of Products from Hydrothermal Treated Wheat Straw

为了研究葡萄糖对水热炭化反应过程和水热焦形成的影响,以麦秆为原料,利用高温高压反应釜,对麦秆在葡萄糖水溶液环境中的炭化反应过程和水热焦理化结构演变及液相产物主要组分浓度分布的变化进行了分析。研究发现,在反应温度220℃,停留时间120 min条件下,随着葡萄糖添加量的增加,水热焦产率和碳质量分数有所增加,而氢和氧质量分数未发生明显改变,当葡萄糖添加量为麦秆质量的0.4倍时,水热焦产率达68.56%;葡萄糖分子阻碍了麦秆中主要化学组分的分解与炭化反应,使得水热焦炭聚合物的红外吸收特征峰减弱,同时XRD衍射峰强度降低,热稳定性下降,如选择水热炭化过程水循环利用,可进行可溶性糖分离;在麦秆与葡萄糖共同水热炭化过程中,葡萄糖以分解反应为主,同未添加葡萄糖的麦秆水热炭化液相产物相比,糠醛、5-HMF和乙酸的质量浓度均有所增加,其中5-HMF增加最为显著,至葡萄糖添加量为4 g时,达20.21 g/L。

Glucose is one of main intermediate components and final aqueous product from biomass hydrothermal carbonization （HTC）. To explore the effects of glucose on reaction processing and hydrochars formation, wheat straw was hydrothermally treated in different concentrations of glucose solution, and the process and products were analyzed. All the experiments were carried out in a 2 L autoclave at temperature of 220℃ for residence time of 120 min. The results show that with increasing concentration of glucose, the yields and carbon content of hydrochars increase slightly. However, the hydrogen and oxygen contents of hydrochars are not substantial. When the added glucose mass is 0.4 times as much as the wheat straw mass, the yield of hydrochars reaches 68.56%. Glucose could cause an increase of mass transfer resistance for sugar monomers produced from hemicelluloses and cellulose degradation to enter the liquid phase. The precipation of glucose could impede the degradation and carbonization reaction of biomass during the HTC process. Thus, the aromatic characteristic peaks of hydroehars in Fourier transform infrared （FTIR） spectra weaken, and the diffraction peak intensity of cellulose in X-ray diffraction （XRD） spectra decreases. Moreover, the thermal stability of hydrochars also decreases. During reutilization of the HTC processing water, the dissolvable sugars could be extracted. When the wheat straw is co-treated with glucose under hydrothermal conditions, degradation of glucose is possible the main pathway. When compared with liquid products from the wheat straw HTC using pure water, the concentrations of furfural, 5-hydroxymethyl-furfural （5-HMF） and acetic acid increase. The concentration of 5-HMF increases to 20. 21 g/L when the ratio of glucose to wheat straw is 0. 4.