Heterogeneous catalysis is a process where the catalyst exists in a different phase than the reactants, typically solid catalysts interacting with gaseous or liquid reactants. This type of catalysis is widely used in industrial processes, such as the Haber process for ammonia production, where solid iron serves as the catalyst. In heterogeneous catalysis, the reaction occurs at the surface of the solid catalyst, allowing for efficient interaction with the reactants. The solid catalyst can be easily separated from the products, making it advantageous for recycling and reducing waste in chemical processes.