AlCl3催化玉米秸秆中半纤维素的选择性转化

研究了AlCl₃ 催化剂作用下, 水热体系中玉米秸秆中半纤维素组分在温和条件下的选择性转化. 详细考察了反应温度、反应时间和AlCl₃用量对半纤维素选择性转化的影响. 原料及反应后的固体残渣分别采用化学滴定、X射线衍射和扫描电镜进行表征. 结果表明, 140 ℃下反应1 h可转化玉米秸秆中的大部分半纤维素, 转化率为85.1%;而玉米秸秆中的绝大部分纤维素和木质素组分仍保留在固体残渣中, 此时纤维素和木质素的转化率分别为10.7%和23.9%. 半纤维素转化的主要液体产物为木糖, 同时含有一些乙酸和糠醛. 升高温度, 将滤液进行进一步反应可促进木糖的转化. 在水/四氢呋喃反应体系中, 滤液的进一步反应有利于乙酰丙酸、甲酸和糠醛的生成. 固体酸催化剂γ-Al₂O₃/SO₄^2-的加入可进一步提高糠醛的收率.

AlCl3 catalyzed conversion of hemicellulose in corn stover

The selective conversion of the hemicellulose in corn stover (stalk) by AlCl₃ as catalyst under hydrothermal conditions at low temperature was investigated. The effect of reaction temperature, reaction time, and AlCl₃ amount was investigated. The biomass samples before and after reaction were characterized by chemical titration, X-ray diffraction, and scanning electron microscopy. The conversion of the hemicellulose in the corn stover at 140 ℃ for 1 h reached 85.1%, while keeping a high proportion of the cellulose and lignin components unreacted with the conversions of 10.7% and 23.9%, respectively. Xylose and a small amount of acetic acid, and furfural were obtained from the filtrate from the hemicellulose conversion. Further reaction of the filtrate significantly improved the conversion of xylose. This was performed in a H₂O-tetrahydrofuran solvent system, and large amounts of levulinic acid, formic acid, and furfural were obtained. The γ-Al₂O₃/SO₄^2- solid acid catalyst selectively promoted the formation of furfural in the H₂O-tetrahydrofuran solvent system.