What is Catalysis?
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a
catalyst. The catalyst is not consumed in the reaction and can act repeatedly. Catalysis is crucial in both industrial and biological processes.
What is the Role of Chemical Composition in Catalysis?
The
chemical composition of a catalyst significantly influences its performance. This includes the types of atoms and their spatial arrangement. For example, transition metals like
platinum and
palladium are commonly used in catalytic converters because of their ability to facilitate redox reactions.
Additionally, the presence of
promoters and
inhibitors can modify the activity and selectivity of a catalyst. For instance, adding small amounts of alkali metals can enhance the performance of certain catalysts by modifying their electronic properties.
How do Electronic States Affect Catalysis?
The
electronic states of the atoms in a catalyst play a crucial role in its function. These states determine how the catalyst interacts with reactants. For example, the d-orbitals in transition metals can participate in forming
intermediate complexes with reactants, thereby lowering the activation energy of the reaction.
The
density of states (DOS) near the Fermi level is particularly important. A high DOS can facilitate electron transfer processes, which are essential in many catalytic reactions. This is why materials like
graphene and
carbon nanotubes are being explored as potential catalysts.
Homogeneous Catalysts: These are in the same phase as the reactants, usually a liquid. They offer high selectivity but can be difficult to separate from the reaction mixture.
Heterogeneous Catalysts: These are in a different phase than the reactants, usually a solid in contact with liquid or gas reactants. They are easier to separate and can be reused, making them more industrially viable.
