玉米秸秆在亚/超临界环己烷中的液化过程与机理

    Liquefaction reaction process and mechanism of cornstalk in sub/super critical cyclohexane

    • 摘要: 为了提高玉米秸秆液化收率、研究其液化机理,该文在反应温度260~320℃、反应压力2~4.5 MPa的试验条件下,研究玉米秸秆在亚/超临界环己烷中的液化行为,考察反应温度、环己烷用量和反应停留时间对液化行为的影响。结果表明:反应温度、环己烷量和反应时间对裂解产物的分布均有较显著的影响。温度增加,残渣和重油产率分别降低4.9%和3.34%;环己烷用量增加,残渣量呈现先降低后增加的趋势;反应停留时间的增加有利于残渣产率的降低和气体、轻油产率的增加,但达到40 min以上后呈平稳的趋势。并用GC-MS分析液化产物,探讨液化产物的变化规律,证明秸秆中纤维素、半纤维素和木素在亚/超临界环己烷中发生裂解液化,生成以吡喃衍生物、有机酸为主的轻油,和以酚类及其衍生物为主的重油,同时发现环己烷具有供氢重整作用,液化过程中也存在二次反应,依此建立木素在亚/超临界环己烷中的液化反应路径和集总产物反应网络。

       

      Abstract: The effects of reaction temperature, cyclohexane quantity and reaction time on the liquefaction of cornstalk in sub- and super-critical cyclohexane were investigated by using a batch type reactor. Experiments were carried out over the temperature range of 260-320℃, and pressure range of 2-4.5 MPa. The results showed that the reaction temperature, cyclohexane quantity and reaction time had significant influences on the pyrolysis products. With the temperature increasing from 260 to 320℃, the residue and heavy oil yields decreased by 4.9% and 3.34% respectively. A low residue yields reached to 36.54% with 40 mL cyclohexane at 310℃ for 20 min. The gas and light oil products increased while the residue decreased with the reaction time from 0 to 40 min. The GC/MS measurements for the light oil and heavy oil revealed that the cellulose, hemicellulose and lignin in cornstalk were liquefied in sub/super critical cyclohexane. The components of heave oil were mainly phenol and its derivatives, and pyranoid derivatives and organic acids were dominant in the light oil. Meanwhile the research showed that cyclohexane played the role of hydrogen reforming and a secondary reaction existed in the liquefaction process. The lignin liquefaction reaction paths in sub- and super-critical cyclohexane and the liquefaction reaction network were built based on the results.

       

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