Heterogeneous catalysis

In chemistry, heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reactants or products. Contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. Phase distinguishes between not only solid, liquid, and gascomponents, but also immiscible mixtures (e.g. oil and water), or anywhere an interface is present. Catalysts are useful because they increase the rate of a reaction[2] without themselves being consumed and are therefore reusable.