Catalysis: Active Sites

Study Notes

The active site is the region on the catalyst surface where chemical reactions occur.
It is a specific location on the catalyst surface where reactants adsorb and react to form products.
Active sites are typically associated with defects or irregularities on the surface, such as steps, kinks, or adatoms.
The properties of active sites, such as their geometry, electronic structure, and chemical composition, influence the catalytic activity and selectivity.

Adsorption is the process by which reactants bind to the catalyst surface.
It is a critical step in heterogeneous catalysis, as it brings reactants in close proximity to each other and to the active site.
Adsorption can occur through physisorption (weak van der Waals forces) or chemisorption (strong covalent bonds).
The strength of adsorption affects the reaction rate, with stronger adsorption often leading to higher activity.

Desorption is the process by which products detach from the catalyst surface.
It is an essential step in heterogeneous catalysis, as it allows the catalyst to recover its active sites and continue catalyzing reactions.
Desorption can occur through thermal, kinetic, or chemical means.
The rate of desorption affects the overall reaction rate and product yield.

Reactant diffusion refers to the movement of reactants from the bulk phase to the catalyst surface.
It is an important step in heterogeneous catalysis, as it affects the availability of reactants at the active site.
Reactant diffusion can occur through bulk diffusion, Knudsen diffusion, or surface diffusion.
The rate of reactant diffusion affects the reaction rate and can influence the selectivity of the reaction.

Surface chemistry refers to the chemical properties and reactions that occur on the catalyst surface.
It plays a crucial role in heterogeneous catalysis, as it influences the adsorption, desorption, and reaction of reactants.
Surface chemistry is affected by factors such as surface composition, roughness, and defects.
Understanding surface chemistry is essential for designing and optimizing heterogeneous catalysts.

Active sites are specific regions on the catalyst surface where chemical reactions occur, associated with defects or irregularities such as steps, kinks, or adatoms.
The properties of active sites, including geometry, electronic structure, and chemical composition, influence catalytic activity and selectivity.

Adsorption is the process by which reactants bind to the catalyst surface, bringing them in close proximity to each other and the active site.
Adsorption can occur through physisorption (weak van der Waals forces) or chemisorption (strong covalent bonds).
The strength of adsorption affects the reaction rate, with stronger adsorption often leading to higher activity.

Desorption is the process by which products detach from the catalyst surface, allowing the catalyst to recover its active sites and continue catalyzing reactions.
Desorption can occur through thermal, kinetic, or chemical means.
The rate of desorption affects the overall reaction rate and product yield.

Reactant diffusion is the movement of reactants from the bulk phase to the catalyst surface, affecting the availability of reactants at the active site.
Reactant diffusion can occur through bulk diffusion, Knudsen diffusion, or surface diffusion.
The rate of reactant diffusion affects the reaction rate and can influence the selectivity of the reaction.

Surface chemistry refers to the chemical properties and reactions that occur on the catalyst surface, influencing adsorption, desorption, and reaction of reactants.
Surface chemistry is affected by factors such as surface composition, roughness, and defects.
Understanding surface chemistry is essential for designing and optimizing heterogeneous catalysts.