指数升温脱附研究

AN INVESTIGATION OF EXPONENTIAL HEATING DESORPTION

本文采用分子筛吸附苯或正已烷,进行指数程序升温脱附。结果表明,活化能与脱附最大速率所对应的温度(T)有线性关系,即E=KT。对指数升温条件下得到的脱附图谱与各个脱附动力学参量之间的关系进行了数学分析,并将分析结果与线性升温所得的结果相比较。各对应的动力学参数的数值基本相同。我们推导得到的指数升温基本方程与目前通用的线性升温基本方程相比较,如果温度的测量精度相同则指数升温计算方法的精度比线性升温高(2T+△T)倍。实验还说明,指数升温的曲线比线性升温容易控制。

Five adsorbed systems have been studied by using exponential heating desorption. Those are benzene/zeolite HZSM-5, benzene/zeolite NaY, benzene/zeolite rare-earthe-Y, benzene/mordenite and n-hexane/mordenite. The experiments proved that the relation between activation energy of desorption and temperature of most desorption rate is linear, i.e.E=KT. The data of exponential temperature programmed were analysed and compared with those of linear temperature programmed. The values of various kinetics parameter are coincided. Their activation energies are shown in Tablel. The following kinetics parameter equation of exponential temperature programmed has been derived: lnT/α=E/RT+lnE/ARnθ, and the equation has been compared with that of linear temperature programmed: ln=E/RT+lnE/(ARnθ. It is found that the effect of temperature deviation, △T, on all parameter is Iess (2T+△T)times by using equation of exponential temperature programmed than that of linear temperature programmed. Through these experiments we found that the temperature control of exponential temperature programmed is easier than that of linear temperature programmed.