Heterogeneous catalysis in chemistry refers to reactions in which the reactants or products are in a different phase from the catalysts. In contrast, homogeneous catalysis involves the presence of the catalyst, reactants, and products in the same phase. Phase makes distinctions between components that are not only made up of solid, liquid, and gas, but also immiscible mixtures and regions where an interface is present. Catalysts in the solid phase and gas phase reactants are typically used in heterogeneous catalysis. At the catalyst surface, a cycle of molecular adsorption, reaction, and desorption is taking place in this instance. Heat transfer, mass transfer, and thermodynamics all affect reaction rate. Due to its ability to speed up large-scale production and allow for the formation of specific products, heterogeneous catalysis is crucial.