两种不同含量β-谷甾醇物质的热解及热动力学研究

摘要

β–sitosterol is widely used in food and medicine,and is ubiquitous in plantage. Thermal decomposition and kinetics of 40%β–sitosterol and 80%β–sitosterol were studied by TG–DTG/DTA. The TG–DTG curve showed the process of mass loss of the substance proceeded in two steps. The first stage could be attributed to the expulsion of water of crystallization. The second stage was corresponding to the devolatilization and decomposition of the molecular structure. Heating rate had a significant effect on the pyrolysis of the two phytosterols. The activation energy E of the second stage of degradation process obtained by Popescu method were 111(for 40%β–sitosterol)and 132 kJ/mol (for 80%β–sitosterol). According to Popescu mechanism functions,the possible kinetic model was estimated to be Reverse Jander Equation(g(α)=[(1+α)1/3–1]2.%β–谷甾醇是食品和医学领域广泛使用，且是植物界最普遍存在的甾醇。用TG–DTG/DTA方法研究了两种含量分别为40%和80%的β–谷甾醇热解过程及热动力学。TG和DTG分析结果表明，该物质的失重过程分两步完成。第一步为结晶水脱出，第二步为甾醇裂解和挥发性物质蒸发。热解过程中，加热速率对两种植物甾醇热解有显著作用。使用Popescu分别计算出40%和80%β–谷甾醇的热解活化能分别为111和132 kJ/mol。对常用41种热解动力学机理函数，确定了两种植物甾醇热解过程均为三维扩散的反Jander方程（g（α）=[（1+α）1/3–1]2。