katalyse

Katalyse, or catalysis, is the acceleration of a chemical reaction by a substance called a catalyst, which is not consumed in the overall reaction. Catalysts work by providing an alternative reaction pathway with lower activation energy, enabling more molecules to react per unit time and often improving selectivity toward desired products.

Catalysis is classified by the phase of the reactants and catalyst. In homogeneous catalysis, all species are in the same phase, typically a solution. In heterogeneous catalysis, the catalyst is in a different phase, usually a solid surface against reacting gases or liquids, where the reaction occurs at active sites on the surface. Biocatalysis uses enzymes as highly specific biological catalysts.

Industrially important examples include the Haber-Bosch synthesis of ammonia on iron catalysts, the contact process for sulfuric acid using vanadium(V) oxide, and catalytic cracking using acidic zeolites. Enzymes enable many biological reactions under mild conditions and are central to biotechnological applications. Catalysis is also essential for environmental technologies, for example catalytic converters in automobiles reduce emissions of carbon monoxide, hydrocarbons, and nitrogen oxides.

Key concepts in catalysis include turnover frequency (activity), catalyst specificity and selectivity, catalyst lifetime and deactivation, and poisoning by impurities. Catalysis underpins a large portion of chemical manufacturing and energy conversion, making it a cornerstone of modern chemistry.