双季戊四醇酯热氧化性能及氧化动力学分析

Thermal Oxidation Performances and Kinetics Analysis of Dipentaerythritol Ester at High Temperature Oxidation

将恒温氧化、PDSC测试及氧化动力学计算相结合,分析氧化温度与时间对双季戊四醇酯黏度、黏度指数和酸值的影响规律,研究双季戊四醇酯经历恒温氧化后起始氧化温度、活化能及氧化速率常数的变化,探讨其对不同温度耐受能力的差异。结果显示:双季戊四醇酯黏度与酸值的变化符合logistic函数,初始阶段增长缓慢,继而迅速升高并达到最快速率,随后速率逐渐下降;180℃以上的氧化会使黏度、黏度指数和酸值发生显著变化,而低于130℃时其变化趋势十分平缓,能满足冷冻机油的工况要求;180℃以上的高温氧化会使油品起始氧化温度降低,但对活化能、氧化速率常数和氧化半衰期影响较小,因此双季戊四醇酯具备较好的高温氧化安定性。

Isothermal oxidation,pressurized differential scanning calorimetry and oxidation kinetics analysis were combined to study the oxidation performances of dipentaerythritol ester.The ester was oxidized at different temperatures respectively,and the effects of temperature and time on kinematic viscosities,viscosity indexes and acid values were analyzed.In order to compare the endurance of static oxidationat temperatures,the initial oxidation temperature,activation energy and oxidation rate constant of samples oxidized under various conditions were detected respectively.The results show that,the variation trends of kinematic viscosity and acid value are close to logistic function,that is,the kinematic viscosity and acid value increase slowly at the initial stage,then grow rapidly and reach the fastest rate,and finally the rate gradually decreases.High temperature oxidation above 180℃leads to the significant changes of kinematic viscosity,viscosity indexes and acid values,while the variation trends are gentle at the temperature lower than 130℃,therefore,the dipentaerythritol ester can meet the operating requirement of refrigerator oil.High temperature oxidation above 180℃results in the decrease of initial oxidation temperature,while it has less influence on the activation energy and oxidation rate constant.Hence,dipentaerythritol ester possesses good oxidation stability at high temperatures.