Rudzinski Wladyslaw, Panczyk Tomasz, Plazinski Wojciech
Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, ul. Niezapominajek 8, 30-239 Cracow, Poland.
J Phys Chem B. 2005 Nov 24;109(46):21868-78. doi: 10.1021/jp052671v.
Two generalizations of the statistical rate theory (SRT) approach have been developed for the kinetics of adsorption/desorption on/from heterogeneous surfaces and then compared to each other. The first of them is an improved version of the description based on the condensation approximation (CA) used by us. The other one is an exact generalization for the Langmuir model of adsorption. The latter generalization does not lead to simple analytical expressions for the rate of adsorption/desorption as the CA approach does for typical adsorption energy distributions. The comparison of these two approaches suggests, however, that at small and very high surface coverages the CA approach may not be sufficiently accurate. Very intriguing results are obtained when the developed SRT kinetic equations are applied to describe the kinetics of sorption in carbon molecular sieves. It appears that the fit of experimental data is then equally good as that obtained by assuming that the rate of sorption is controlled by surface diffusion in pores. Also, it is shown that the square-root dependence on time of adsorption at small initial coverages cannot be treated as a definite proof for that sorption proceeds via surface diffusion, as is commonly assumed.
针对非均相表面上吸附/脱附动力学，已开发出统计速率理论（SRT）方法的两种推广形式，并对其进行了相互比较。其中第一种是基于我们所使用的凝聚近似（CA）的改进描述版本。另一种是对朗缪尔吸附模型的精确推广。后一种推广不像CA方法那样，对于典型的吸附能分布能得出吸附/脱附速率的简单解析表达式。然而，这两种方法的比较表明，在低表面覆盖率和非常高的表面覆盖率情况下，CA方法可能不够精确。当将所开发的SRT动力学方程应用于描述碳分子筛中的吸附动力学时，会得到非常有趣的结果。结果表明，此时对实验数据的拟合与假设吸附速率由孔内表面扩散控制时得到的拟合效果一样好。此外，研究表明，在低初始覆盖率下吸附对时间的平方根依赖性，不能像通常所假设的那样，被视为吸附通过表面扩散进行的确凿证据。
