环戊烷在Silicalite-1分子筛上吸附的动力学研究

为了探究环戊烷在Silicalite—1分子筛上扩散过程的动力学特性,以及温度、压力等环境因素和吸附质的性质是如何对动力学过程的影响,实验采用重量法测定了环戊烷不同压力下扩散的动力学数据,绘制其在Silicalite—1上的吸附等温线,计算了扩散系数、扩散活化能和活化熵变等动力学参数。结果表明,环戊烷在Silicalite—1上的扩散过程符合Fick第二定律,吸附剂Silicalite—1的特殊孔道结构和吸附质分子的尺寸大小、及分子间的作用,影响着扩散的动力学过程。扩散的活化能、活化熵变和吸附热的变化决定了扩散系数的变化。随着吸附质在沸石上的吸附量增大,吸附热增大,而环戊烷的扩散速率随之降低,并且温度越高,扩散速率越大。

Kinetics of Adsorption for Cyclopentane in Silicalite-1

The adsorption and adsorption kinetics of cyclopentane in silicalite - 1 has been studied by using intelligent gravimetric analyze technology. From experiments, curves were obtained which give the amount of the adsorbed sorbate as a function of the square root of time. Such curves were measured for various pressure jumps and, correspondingly, different coverages as well as for different temperatures. The result shows that the diffusion of cyclopentane in silicalite- 1 can well be derived from the second Fick law, and the diffusivity D increases with temperature. A tendency, meanwhile, could be noticed that the diffusivity decreases with increasing coverage under the constant temperature. In addition to the particular pore system of silicalite- 1 zeolite with the straight channel, the sinusoidal channel and the intersection between them affecting the diffusion of sorbate, the feature of sorbate cyclopentane also influences the process, such as the molecular dimension. Moreover, the change of activation energy, activation entropies and the heat of sorption for cyclopentane with various sorption coverages determined the change of diffusion coefficients for cyclopentane. The isotherms shows that the bigger activation energy, the smaller activation entropies and the sorption heats determined the diffusion coefficients for cyclopentane are a little bit more than that for benzene. The interactions between the cyclopentane molecules increase with increasing sorption coverage. The data and relevant graph in this study show believable values and detailed explanations.