杉木纤维素的热稳定性及热分解动力学参数

Thermal Stability and Decomposition Kinetics Parameters of Chinese Fir Cellulose

杉木纤维素的热稳定性和热分解动力学参数是模拟杉木高温热处理的重要参数,研究采用化学方法分离得到木材各主要化学成分的含量,采用热重分析仪在不同升温速率下测试了纤维素的热稳定性,并采用FWO法、Friedman法和ASTM E1641法计算得到纤维素的活化能和指前因子。研究结果表明,杉木纤维素、半纤维素、Klason木质素和苯醇抽提物的含量分别为48.5%、19.9%、33.5%和2.6%。纤维素的热分解峰值在1、5、10、15、20℃/min升温速率下对应的热分解温度分别为293.8、320.4、332.4、340.3℃和346.0℃。杉木纤维素热分解活化能和指前因子随转化率的变化有波动,不同计算方法得到的活化能和指前因子数值具有一定差异,在转化率为0.3至0.6期间时,FWO法、Friedman法和ASTM E1641法计算得到的活化能平均值为167.3、160.9 kJ/mol和164.4 kJ/mol,计算得到的指前因子自然对数平均值为33.2、32.4 min^(-1)和34.5 min^(-1)。

Thermal stability and decomposition kinetics parameters of Chinese fir cellulose are key factors for modeling high-temperature thermal treatment of Chinese fir.Chemical method was employed in this study to separate the main chemical components of Chinese fir,and their thermal stability properties were tested by thermogravimetry analyzer at different heating rates.Furthermore,Flynn-Wall-Ozawa method,Friedman method and ASTM E1641 were used to calculate the activation energy and pre-exponential factor of cellulose.The results show that the content of cellulose,hemicelluloses,Klason lignin and Benzene-alcohol extractives is 48.5%,19.9%,33.5%and 2.6%separately.The temperature peak of thermal decomposition of cellulose at heating rate of 1,5,10,15℃/min and 20℃/min is 293.8,320.4,332.4,340.3℃and 346.0℃separately.The activation energy and pre-exponential factor changes with decomposition rate and calculation methods,the average of activation energy between decomposition rate of 0.3 and 0.6 is 167.3,160.9 kJ/mol and 164.4 kJ/mol for FWO,Friedman and ASTM E1641 method independently,while the average natural logarithm of preexponential factor is 33.2,32.4 min-1and 34.5 min-1 independently.