katalyysis

Katalyisis, commonly spelled catalysis in English, is the acceleration of a chemical reaction by a substance known as a catalyst. The catalyst is not consumed in the overall process; it participates in the reaction mechanism and is regenerated at the end, allowing it to catalyze many cycles.

It works by providing an alternative reaction pathway with lower activation energy, thus increasing the rate of product formation. Although the catalyst can be involved in transient intermediates, the overall composition of reactants changes while the catalyst remains or returns to its original form.

Major types include homogeneous catalysis, where catalyst and reactants share the same phase (usually a solution); heterogeneous catalysis, where the catalyst is in a different phase (commonly a solid surface); and biocatalysis, which uses enzymes or other biological catalysts with high specificity.

Key metrics describe performance, such as turnover number (TON) and turnover frequency (TOF), which quantify how many substrate molecules a catalyst converts and how quickly. Selectivity describes the preferential formation of a desired product; enantioselectivity and regioselectivity are common forms. Catalysts also affect sustainability by enabling lower temperatures or less waste.

Industrial applications include ammonia synthesis by the Haber-Bosch process using iron-based catalysts, the oxidation steps in the contact process with vanadium oxide, and various hydrogenation and polymerization reactions. Enzymes provide biocatalysis in pharmaceuticals and food production. Challenges include catalyst poisoning, deactivation, cost, and stability under operating conditions.