catalyse

Catalyse, or catalysis, is the process by which a substance called a catalyst increases the rate of a chemical reaction without being consumed in the overall reaction. Catalysts work by providing an alternative reaction pathway with a lower activation energy, often by stabilizing transition states or by bringing reactants into favorable orientations at active sites.

Most catalysts act by forming temporary bonds with reactants, or by adsorbing them on surfaces in heterogeneous catalysis. In homogeneous catalysis, the catalyst is in the same phase as the reactants, while in biocatalysis, enzymes provide highly selective and efficient catalytic activity under mild conditions.

Common types include heterogeneous catalysis, where solids such as platinum on alumina catalyze gas- and liquid-phase reactions; homogeneous catalysis, using soluble metal complexes; and biocatalysis, using enzymes. Photocatalysis and electrocatalysis use light or electrical energy to drive or enhance reactions.

Industrial importance is extensive. Haber-Bosch ammonia synthesis uses iron catalysts; the contact process uses vanadium oxide catalysts for sulfuric acid; petroleum refining relies on zeolites and metal catalysts; and polymerization often uses catalytic systems such as Ziegler–Natta catalysts.

Key concepts include turnover number and turnover frequency, selectivity, and catalyst lifetime. Catalysts can be deactivated by fouling, poisoning, sintering, or structural changes and may require regeneration.

History: The term catalysis was coined by Jöns Jacob Berzelius in 1835 to describe substances that alter reaction rates without being consumed.