Pyrolysis characteristics and kinetics of five isolated lignins from sugarcane bagasse

doi:10.16085/j.issn.1000-6613.2017-0002

Abstract

Abstract: Lignin is the most abundant natural aromatic polymer on earth. It is also a major byproduct of pulp and papermaking industry and lignocellulose biorefinery. Pyrolysis is one of the most promising ways to utilize lignin for production of fuels and chemicals. However,the pyrolysis characteristics of lignin products are greatly dependent on the isolation methods. In present work,five lignin products were isolated from sugarcane bagasse by organic acid,alkaline,and oxidative pretreatments,respectively,namely acetic acid lignin(AAL),acetosolve lignin(AsL),milox lignin (ML),peracetic acid lignin(PAAL)and alkaline lignin(AL). The pyrolysis of these isolated lignins was investigated using differential scanning calorimetry(DSC)and thermogravimetric analysis(TGA). As indicated by TGA,all of the lignin products showed four stages of weight losses,namely water removal,glass transition,pyrolysis to small molecules and slow coking. The pyrolysis kinetics was analyzed by Coats-Redfern method. The results indicated that the pyrolysis process could be described as a second-order reaction in temperature range of 200-700℃ for PAAL,and 200-700℃ for the other four lignins. The activation energies were determined as 33.33kJ/mol,36.36kJ/mol,31.10kJ/mol, 24.74kJ/mol and 36.93kJ/mol for AAL,AsL,ML,PAAL and AL,respectively.

Key words: sugarcane bagasse, isolated lignin, pyrolysis, kinetics, molecular weight

摘要： 木质素是自然界中最丰富的芳香类化合物，也是制浆造纸和木质纤维素生物炼制过程的主要副产物。热解是将木质素资源化、能源化利用的一个有效途径。但由于分离方法不同，所得的木质素产品具有不同的热解特性。本文通过有机酸处理、碱处理和氧化处理从甘蔗渣中分离得到5种木质素，即乙酸木质素（AAL）、Acetosolv木质素（AsL）、Milox木质素（ML）、过氧乙酸木质素（PAAL）和碱木质素（AL）。采用差示扫描量热（DSC）和热重分析（TGA）对5种木质素的热解性质进行了研究。发现5种木质素的热解过程均可分为水分脱除、玻璃化转变、热解和缓慢结焦4个阶段。采用非等温的Coats-Redfern积分法对热重数据进行动力学拟合。结果表明，PAAL在200~700℃范围内的热解为二级动力学反应，另外4种木质素则在250~700℃范围内为二级动力学反应。5种木质素的热解表观活化能分别为AAL 33.33kJ/mol、AsL 36.36kJ/mol、ML 31.10kJ/mol、PAAL 24.74kJ/mol以及AL 36.93 kJ/mol。

关键词: 甘蔗渣, 分离木质素, 热解, 动力学, 分子量

CLC Number:

O636.2
TQ351

CUI Xingkai, ZHAO Xuebing, LIU Dehua. Pyrolysis characteristics and kinetics of five isolated lignins from sugarcane bagasse[J]. Chemical Industry and Engineering Progress, 2017, 36(08): 2910-2915.

崔兴凯, 赵雪冰, 刘德华. 五种甘蔗渣分离木质素热解特性及动力学[J]. 化工进展, 2017, 36(08): 2910-2915.

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