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担载型金属类催化剂表面,在分子层面上往往有些杂质,也许来自使用中的反应物料。这些结构性杂质会影响催化剂的结构与性能,于是本文引入杂质分形结构的概念,通过Monte Carlo模型去分析和探讨担载型金属催化剂表面CO的催化氧化反应行为。模拟结果发现,催化剂活性中心的不均匀分布,在分形杂质所包围的小区域,O_2在催化剂表面活性中心的吸附更加困难。特别是在杂质所占比例较大时,催化剂的活性点在空间被隔离开而形成许多孤立小岛,即使在CO分压较小时,催化剂表面的局部区域也会发生O和CO中毒。随着杂质比例的增加,导致催化剂表面的活性空位分布发生变化,大大减少了CO分子和O原子的接触机会,反应速率随之降低,催化剂活性中心的利用率也降低。
Supported metal catalyst surface, the molecular level is often some impurities, perhaps from the reaction of the use of materials. These structural impurities will affect the structure and properties of the catalyst. Therefore, the concept of impurity fractal structure is introduced in this paper. The Monte Carlo model is used to analyze and discuss the catalytic oxidation reaction of CO on the surface of supported metal catalysts. The simulation results show that the heterogeneous distribution of active sites of catalysts is more difficult to adsorb O_2 on the active sites on the catalyst surface in a small area surrounded by fractal impurities. Especially when the proportion of impurities is large, the active sites of the catalyst are spatially separated to form many isolated islets. O and CO poisoning can occur in the local area of the catalyst surface even when the partial pressure of CO is small. With the increase of the impurity ratio, the active vacancy distribution on the catalyst surface is changed, the contact chance between CO and O atoms is greatly reduced, the reaction rate decreases and the utilization rate of the catalyst active center also decreases.