Lõhestus

Lõhestus (in English often rendered as decomposition or cracking) refers to processes in which chemical bonds are broken, yielding smaller molecules or elements from larger ones. In chemistry, lõhestus can describe any process of molecule fragmentation, often driven by heat, light, or catalysts. The term is commonly used in industry to describe cracking processes in petroleum refining, where high-molecular-weight hydrocarbons are split into lighter, more valuable fractions such as gasoline, kerosene, and diesel.

There are several forms: thermal lõhestus, which relies on high temperatures to cleave bonds; catalytic lõhestus, which uses catalysts to lower activation energy and steer products; and hydrocracking, which combines hydrogenation with cracking under high pressure and temperature. Pyrolysis is a related term used in contexts like waste treatment or material analysis, where organic matter is decomposed by heat in the absence of oxygen.

In addition to hydrocarbon processing, lõhestus occurs in polymer science (for example, chain scission in polymers), environmental engineering (degradation of pollutants), and materials science (thermal decomposition of solids). The outcomes can range from desirable product formation to hazardous decomposition products, so reactions are controlled by temperature, pressure, catalysts, and reactor design.

Etymology: the word combines lõhk- meaning "to break" with the suffix -estus, denoting a process or action. See also pyrolysis, decomposition, cracking.