Katalüüt

Katalüüt is a substance that increases the rate of a chemical reaction without being consumed in the overall process. Catalysts work by providing an alternative reaction pathway with a lower activation energy, allowing more reactant molecules to reach the transition state at a given temperature. After the reaction, the catalyst is regenerated and appears unchanged, though it may undergo transient changes during the catalytic cycle.

History and terminology: The concept of catalysis emerged in the 19th century. Jöns Jacob Berzelius introduced the terms catalysis and catalyst in the 1830s, and the word derives from Greek, roughly meaning to loosen or to break down in the context of accelerating reactions.

Types and mechanisms: Catalysts can be classified as homogeneous (same phase as the reactants) or heterogeneous (a different phase, typically a solid catalyst with gases or liquids). Many heterogeneous catalysts function on surfaces, where adsorption, surface reaction, and desorption occur. Enzymes are highly specific biological catalysts, or biocatalysts, that operate under mild physiological conditions and exhibit remarkable selectivity.

Applications and impact: Industrially important catalysts include iron for ammonia synthesis (Haber–Bosch process), noble metals in automotive catalytic converters, and zeolites in petroleum refining. Catalysts also enable polymerization, hydrogenation, and various organic transformations, contributing to energy efficiency and reduced waste. In laboratory settings, catalysts enable otherwise challenging reactions under milder conditions, improving safety and practicality.

Limitations and challenges: Catalysts can be poisoned or deactivated by impurities, sintering, or fouling. They often require regeneration, specific temperatures and pressures, and careful reactor design. Cost and availability of catalytic materials also influence practical use and development.