大豆秸秆乙醇预处理脱木素动力学研究

Delignification Kinetics of Ethanol Pretreatment of Soybean Stalk

中文关键词:  大豆秸秆  乙醇预处理  脱木素  动力学

Key Words:soybean stalk  ethanol pretreatment  delignification  kinetics

中文摘要:

      在保温温度170℃、保温时间90 min、乙醇浓度50%的条件下对大豆秸秆进行乙醇预处理,并对预处理后大豆秸秆进行成分分析,发现乙醇预处理主要脱除了大豆秸秆中的半纤维素和木素(脱除率分别为82.9%和62.0%)。动力学研究发现,乙醇预处理脱木素反应为一级反应,脱木素过程由大量脱木素段和补充脱木素段组成,且预处理反应进入补充脱木素段的温度要高于160℃。在保温温度为170℃时,大量脱木素段和补充脱木素段的木素脱除率分别为87.9%和12.1%。大量脱木素段主要脱除的是小分子木素(相对分子质量为9101)；而补充脱木素段脱除的木素的相对分子质量较大,达到12961。对比2个阶段的木素脱除速率发现,大量脱木素段的脱除速率(k大=4×10-4 s-1)高于补充脱木素段(k补=4×10-5 s-1),说明大量脱木素段木素脱除速率较快。

Abstract:

      It is an essential step to destroy the structure of the cell wall by pretreatment before enzymatic hydrolysis for the conversion of lignocellulose to ethanol. Ethanol pretreatment has many advantages, and is a hot research topic in recent years. In this experiment, soybean stalk was pretreated under the following condition: heat preservation temperature 170℃, holding time 90 min, ethanol concentration 50%. The component analysis of pretreated material indicated that the hemicellulose and lignin in soybean stalk were mainly removed by ethanol pretreatment (The removal ratio reached 82.9% and 62.0% respectively). Delignification reaction during ethanol pretreatment was a first order reaction. The kinetics study showed that there were two delignification stages i.e. bulk delignification and supplement delignification when the temperature was above 160℃. Lignin was removed 87.9% and 12.1% respectively in the two steps when the temperature was 170℃. The removed lignin in the two stages had different molecular weight (Mw=9101 and 12961). In these two delignification stages, lignin removal rate in bulk delignification stage was higher (kbulk=4×10-4 s-1>ksupplement=4×10-5 s-1)．