Reaction Mechanism and Deactivation Modes of Heterogeneous Catalytic Systems

解决催化剂释放的问题在过程设计是必要的。做这，有催化剂释放的过程的动力学的各种各样的方面，和他们的不同机制，被讨论。催化剂释放不能经常被避免，但是它的机制上的更多的知识能帮助发现运动工具减少它的有害后果。当释放被焦炭引起时，焦炭先锋的产生是在释放动力学的决定的步。释放的不同类型被区分导致这个过程的不同进化。不一致的 coking 的现象能被连接到催化剂表面不一致。为有活跃地点的超过一种类型的催化剂的班，解释在释放模式为观察趋势被建议。为用工业尺寸的催化剂粒子的催化过程， intraparticle 散开抵抗的影响是重要的。分析证明为很多个过程，反应率的减少由于释放是在散开控制下面的更少。为某些反应机制，在那里存在在散开控制下面的进程的率在运动控制政体超过率的操作条件。一个重要问题是在催化剂释放期间的选择的变化。选择也可以减少或增加，并且在释放期间取决于反应机制。当没有散开抵抗时，变化更大。为乙烯氧化物生产的过程的在催化剂活动和选择的催化剂和它的影响的故意的毒害被讨论。

Solving the problem of catalyst deactivation is essential in process design. To do this, various aspects of the kinetics of processes with catalyst deactivation, and their different mechanisms, are discussed. Catalyst deactivation often cannot be avoided, but more knowledge on its mechanism can help to find kinetic means to reduce its harmful consequences. When deactivation is caused by coke, the generation of coke precursors is the determining step in the deactivation kinetics. Different types of deactivation were distinguished that lead to different evolution of the process. The phenomenon of non-uniform coking can be linked to catalyst surface non-uniformity. For the class of catalysts with more than one type of active sites, an explanation was suggested for the observed trends in the deactivation modes. For catalytic processes using catalyst panicles of industrial size, the influence of intraparticle diffusion resistance is important. The analysis showed that for a number of processes, the decrease of the reaction rate due to deactivation is less under diffusion control. For certain reaction mechanisms,there exist operation conditions where the rate of the process under diffusion control exceeds the rate in the kinetic control regime. A significant problem is the change of selectivity in the course of catalyst deactivation. The selectivity may either decrease or increase, and depends on the reaction mechanism during deactivation. The changes are larger when there is no diffusion resistance. The intentional poisoning of catalysts and its influence on catalyst activity and selectivity for the process of ethylene oxide production was discussed.