非预置模型计算矿物绝缘油与甲酯热解动力学参数

Investigation of thermal degradation kinetic parameters for mineral insulating oil and methyl ester based on non-preset model method

为了考察脂肪酸甲酯的热稳定性是否满足作为绝缘油的要求,本文以市售大豆油为原料油,通过KOH催化酯交换反应(醇油摩尔比为9,催化剂添加量为2%,反应时间为1 h,反应温度为65℃)制备大豆油甲酯。利用热重分析平台,在不同线性升温速率下,对比分析矿物绝缘油和大豆油甲酯热解特性。并基于等转化率法,采用Flynn-Wall-Ozawa和Kissinger-Akahira-Sunose两种非预置模型分别计算矿物绝缘油和大豆油甲酯的热解活化能。最后,利用Avrami理论计算了二者的热解反应级数。结果表明,甲酯热解起始温度和终止温度均高于矿物绝缘油,同时热解活化能也高于矿物绝缘油,表明甲酯热稳定性优于矿物绝缘油。

Mineral insulating oil has been widely used in oil-filled electrical equipment,however,it would be replaced by green and renewable insulating liquid for its poor biodegradability and non-renewability.To investigate the thermal stability of fatty acid methyl esters for insulating purpose,soybean oil was adopted as raw material in this study.Soybean oil was reacted with methanol to generate soybean oil methyl esters(molar ratio of methanol to oil 9,catalysts addition,reaction time 1 h,and reaction temperature 65 ℃) under KOH catalytic effect.The thermal degradation characteristics of methyl ester and mineral insulating oil was analyzed and compared via thermogravimetry at 10 K/min,20 K/min,30 K/min heating rates.In addition,thermal degradation activation energies for methyl ester and mineral insulating oil were calculated based on two non-preset model,namely,Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose.Finally,the reaction order of thermal degradation was calculated through Avrami theory.The results indicated that the initial and the ending thermal degradation temperatures of methyl ester were higher than that of mineral insulating oil.Meanwhile,the activation energy for methyl ester thermal degradation was also higher than mineral insulating oil revealing the methyl ester owing stronger thermal stability.