Adsorption of reactant molecules onto a heterogeneous catalyst surface promotes chemical reactions by increasing the concentration of reactants at the catalyst surface, facilitating the formation of reactive intermediates, and lowering the activation energy required for the reaction to occur. Heterogeneous catalysis involves catalysts that are in a different phase usually solid than the reactants usually gas or liquid . The different mechanisms involved in heterogeneous catalysis include:1. Adsorption: Reactant molecules are adsorbed onto the catalyst surface, which is typically composed of a solid material with high surface area and active sites. Adsorption can be physical physisorption or chemical chemisorption . In physisorption, weak van der Waals forces hold the reactant molecules onto the surface, while in chemisorption, stronger chemical bonds are formed between the reactant molecules and the surface.2. Surface reaction: Once the reactant molecules are adsorbed onto the catalyst surface, they can undergo various surface reactions. These reactions can involve the breaking of existing chemical bonds, the formation of new bonds, or the rearrangement of atoms within the reactant molecules. The catalyst surface provides a platform for these reactions to occur more easily by stabilizing reactive intermediates and lowering the activation energy required for the reaction.3. Desorption: After the surface reaction has occurred, the product molecules are released from the catalyst surface through a process called desorption. This can occur through the breaking of chemical bonds between the product molecules and the surface or through the weakening of van der Waals forces in the case of physisorption.4. Catalyst regeneration: In some cases, the catalyst surface may become deactivated due to the accumulation of reaction products or other impurities. Regeneration processes, such as thermal or chemical treatments, can be employed to restore the catalyst's activity.The overall effectiveness of a heterogeneous catalyst depends on factors such as the nature of the catalyst material, the size and shape of the catalyst particles, the availability of active sites, and the strength of the adsorption and desorption processes. By understanding these mechanisms, chemists can design more efficient and selective catalysts for various chemical reactions.