Catalytic processes can be divided into several scales:
1. Atomic Scale: At this level, the focus is on the individual atoms and molecules, including the active sites on the catalyst surface where the chemical reactions occur. Techniques like Density Functional Theory (DFT) are used to study the electronic structure and predict reaction mechanisms.
2. Nanoscopic Scale: This scale involves clusters of atoms or nanoparticles. The catalytic properties can significantly differ from those at the atomic scale due to quantum effects and the high surface-to-volume ratio.
3. Microscopic Scale: Here, we explore the interactions between multiple nanoparticles or the morphology of a catalyst. Microscopy techniques such as TEM and SEM are crucial for visualizing these structures.
4. Mesoscopic Scale: This encompasses the behavior of catalysts at the level of catalyst pellets or grains within a reactor. The focus is on the transport phenomena, such as diffusion of reactants and products, which affect the overall efficiency.
5. Macroscopic Scale: At this level, the entire catalytic reactor is considered, including the flow dynamics, heat transfer, and overall performance metrics. Process engineering tools and computational fluid dynamics (CFD) are often used.
