Heterogeneous Catalysis

Heterogeneous catalysis is a kind of catalysis in which the catalyst involves a different phase from the reactants and products. This may assign to the physical phase - solid, liquid, or gas - but also to immiscible fluids.

Most heterogeneous catalysts are solids that work within gaseous or liquid reactants. It has active places on its surface onto which the reactants are adsorbed and then associate with the catalyst. This interaction develops the reactivity of the molecules.

Acid catalysis, organometallic catalysis, and enzymatic catalysis are samples of homogeneous catalysis. In such cases, acids and bases are frequently very efficient catalysts, as they can speed up reactions by changing bond polarization.

Heterogeneous catalysis typically includes solid-phase catalysts and gas-phase reactants. In this case, there is a cycle of molecular adsorption, reaction, and desorption happening at the catalyst surface. Thermodynamics, mass transfer, and heat transfer impact the rate of reaction.

Heterogeneous catalysis has at least four steps:

• Adsorption of the reactant onto the surface of the catalyst.
• Activation of the adsorbed reactant
• Reaction of the adsorbed reactant.
• Diffusion of the product from the surface into the gas or liquid phase