- Homogeneous Catalysts: These catalysts exist in the same phase as the reactants, typically in a liquid phase. Examples include acid catalysts like sulfuric acid and base catalysts like sodium hydroxide. - Heterogeneous Catalysts: These catalysts exist in a different phase than the reactants, usually as solids in contact with gaseous or liquid reactants. Examples include metal catalysts like platinum and palladium used in automobile catalytic converters.
