Catalysts can be broadly classified into three categories: heterogeneous catalysts, homogeneous catalysts, and biocatalysts. Heterogeneous catalysts are in a different phase than the reactants, typically solid catalysts with liquid or gas reactants. Homogeneous catalysts are in the same phase as the reactants, usually in a liquid state. Biocatalysts, such as enzymes, are natural catalysts that facilitate biochemical reactions.
