Diffusion, Sorption and Reactions in Micro- and Mesopores

在许多情况下，微孔和中孔的扩散限制了多孔天然或合成材料的传质和反应速率。微孔和中孔结构域的可及性和反应性应是孔径和孔隙极性的函数。在天然多孔介质中，根据多孔材料的类型，可以假设这两个参数显示出一种分布。此外，反应的产物和产物可能表现出不同的极性，从而导致扩散系数的分布，从而影响总体反应速率。本工作的目的是合成和表征具有不同孔径和极性的具有催化活性位点的多孔材料，并通过各种方法研究其可及性。氯化烃（三氯乙烯和氯苯）的催化加氢脱卤和苯的加氢反应作为模型反应，导致产物在极性和分子大小方面的不同分布。使用表征良好的模型固体应该允许将不同材料的扩散速率和反应性与孔隙大小和孔隙极性联系起来。该结果将有助于更好地理解水饱和天然多孔介质中自然发生的非生物降解过程。研究结果也可能对开发用于清除地下水中有机碳氢化合物污染的多孔催化活性材料产生影响。

Diffusion in micro- and mesopores is in many cases limiting for mass transfer and reaction rates in porous natural or synthetic materials. Accessibility and reactivity of micro- and mesopore domains should be a function of the pore sizes as well as pore polarities. In natural porous media both parameters can be assumed to show a distribution, depending on the type of the porous material. Moreover, educts and products of a reaction may show different polarities resulting in a distribution of diffusivities with an impact on overall reaction rates. The objective of this work is the synthesis and characterization of well-defined porous materials with different pore sizes and polarities containing catalytically active sites, and study their accessibility with various methods. The catalytic hydrodehalogenation of chlorinated hydrocarbons (trichloroethylene (TCE) and chlorobenzene) and the hydrogenation of benzene serve as model reactions resulting in different product distributions in terms of polarity and molecular size. The use of well-characterized model solids should allow to relate diffusion rates and reactivities of the different materials to pore sizes and pore polarities. It is expected that the results will lead to a better understanding of naturally occurring abiotic degradation processes in water saturated natural porous media. Results could also have an impact on the development of tailired porous catalytic acti materials for the clean up of ground water contaminated with organic hydrcarbon compunds.