Katalysator

A katalysator is a substance that increases the rate of a chemical reaction without being consumed in the overall process. It provides an alternative reaction pathway with lower activation energy, allowing the reaction to proceed more rapidly under given conditions.

Catalysts are commonly categorized by phase. Heterogeneous catalysts are solids that interact with reactants in a different phase, typically a gas or liquid. Homogeneous catalysts are in the same phase as the reactants and often operate in solution. Enzymes are biological catalysts that accelerate biochemical reactions under mild conditions. Some catalysts function under light (photocatalysts) or electricity (electrocatalysts).

In industry, catalysts are essential for efficiency and selectivity. Examples include iron catalysts for ammonia synthesis in the Haber-Bosch process, vanadium oxide in the contact process for sulfuric acid production, and zeolites or other solids in catalytic cracking of hydrocarbons. Hydrogenation, oxidation, and various reforming and purification steps also rely on catalysts. While catalysts are not consumed overall, they can be poisoned or deactivated by impurities, and some catalysts involve expensive or scarce metals that require recovery and recycling.

Key properties used to evaluate catalysts include activity (rate enhancement), selectivity (preference for a specific product), stability (resistance to deactivation), and turnover metrics such as turnover frequency and turnover number, which quantify how many substrate molecules a site converts per unit time or per lifetime. The study and design of catalysts combine surface chemistry, reaction mechanisms, and reactor engineering.

In summary, a katalysator enables and controls chemical transformations more efficiently, with wide-ranging applications in industry, energy, environment, and biology, while remaining unchanged in overall composition.