摘要
沥青纤维在不熔化过程中,同时伴着氧的增加和脱除,含氧量的变化又会体现在沥青纤维的增重及失重上。使用热重分析仪(TG)研究沥青纤维在空气中的热氧化行为,考察了从120℃升温到410℃的质量变化,以及分别在230和290℃恒温过程中的质量变化。将氧化过程中含氧官能团的生成和脱除视为同时发生的两个连串反应,用连串反应动力学模拟计算了氧化过程中的纤维重量变化并计算了反应速率常数。结果表明:氧化和脱氧反应均为一级反应,用连串反应可以很好地拟合沥青纤维的氧化增重过程。用恒速升温的非等温动力学可以分别计算出氧化反应和脱氧反应的频率因子和活化能,并据此可以计算不同温度下两种反应的表观速率常数随温度的变化。低温时氧化反应速率常数k1明显大于脱氧反应速率常数k2,随着温度的升高,k1和k2均增大,但k2增加的速率>k1,达到290℃时k1和k2相等,290℃后k2>k1,与实验结果先增重后失重相吻合。同样用连串反应动力学模拟了恒温过程中纤维的质量变化,也具有很好的拟合度,但所得到的反应速率常数k1和k2与恒速升温反应相比明显要小,并对其原因进行了分析。
There is significant increase and removal of oxygen during oxidative stabilization process of pitch fibers. Meanwhile, the change of oxygen content can be reflected on the weight gain and loss of the fibers. In this paper, thermogravimetry（TG） was used to investigate the oxidative stabilization of pitch fibers, the weight change of pitch fibers from 120 to 410 ℃ and that of heated thermostatically at two temperatures of 230 and 290 ℃. The generation and removal of oxygen containing functional groups occurred simultaneously during oxidation process can be treated as two consecutive reactions. According to the kinetics simulation of consecutive reaction, we calculated the weight change of pitch fibers and reaction rate constant during oxidative stabilization. The results are shown as follows： both oxidation and deoxygenation reactions obey first order reaction, the weight gain process of pitch fibers can be fitted well with consecutive reaction. Frequency factor and activation energy of oxidation and deoxygenation can be calculated by non-isothermal kinetics with a constant heating rate, thus the changes of apparent frequency factor at different temperatures can be calculated. Oxidation reaction rate constant（k1） has a higher value than deoxygenation reaction rate constant（k2） at lower temperature, k1 and k2 increase with increasing temperature and k2 increases faster than k1, k1 and k2 are equal at 290 ℃, while k2 is higher than k1 at temperature higher than 290 ℃, which is consistent with the experimental results of firstly weight gain and loss afterwards. The weight change of pitch fibers during isothermal process can be simulated by kinetics of consecutive reaction as well, and fitted well, but k1 and k2 is smaller than oxidation reaction with a constant heating rate, and the reasons are shown in this article.
出处
《高科技纤维与应用》
CAS
2016年第1期40-44,58,共6页
Hi-Tech Fiber and Application
基金
国家自然科学基金(51372037)
关键词
不熔化
氧化动力学
连串反应
反应速率常数
stabilization
oxidation kinetics
consecutive reaction
reaction rate constant
