katalisis

Katalisis is the process by which the rate of a chemical reaction is increased by a substance called a catalyst, which remains chemically unchanged at the end of the reaction. The term comes from Greek, meaning “to loosen” or “to dissolve.”

Catalysts work by providing an alternative reaction pathway with a lower activation energy, enabling more reactant molecules to convert to products at a given temperature. They are not consumed in the overall reaction, though some catalysts may be temporary intermediates.

Types include homogeneous catalysis, where the catalyst is in the same phase as the reactants; heterogeneous catalysis, where the catalyst is in a different phase (often a solid) and surfaces are involved; enzymatic catalysis, catalyzed by biological enzymes; and photocatalysis, where light energy drives the catalytic cycle.

Everyday and industrial applications include catalytic cracking in petroleum refining, the Haber-Bosch synthesis of ammonia using iron catalysts, and automotive catalytic converters that reduce emissions using metal catalysts such as platinum group metals. In organic synthesis, catalysts control reaction rate and selectivity, enabling enantioselective and regioselective transformations.

Key concepts include turnover number and turnover frequency, which quantify catalytic efficiency, and catalyst deactivation or poisoning, by impurities that block active sites. Catalysis supports greener chemistry by allowing lower temperatures and shorter reaction times.