Kraking

Kraking is a set of processes in petroleum refining that converts heavy, high-boiling hydrocarbon fractions into lighter, more valuable products such as gasoline, diesel, and petrochemical feedstocks. The main forms are thermal cracking, catalytic cracking, and hydrocracking. Thermal cracking uses high temperatures to break carbon–carbon bonds in heavy fractions, producing lighter hydrocarbons. Catalytic cracking uses solid acid catalysts, often zeolites, to lower the energy barrier for bond breaking and to steer product yields toward gasoline and light fuels. Hydrocracking combines hydrogen with a catalyst to produce clean fuels with reduced sulfur and nitrogen and can also improve yields of middle-distillate components.

Development began in the early 20th century with thermal cracking experiments and was transformed by the introduction of catalytic cracking in the 1940s, notably by Houdry’s processes and subsequent commercial fluid catalytic cracking (FCC). This family of processes became a cornerstone of modern refineries, enabling more efficient conversion of crude oil into transportation fuels and petrochemical precursors.

Kraking increases refinery yield by upgrading heavy residues into transport fuels and petrochemical feedstocks. Common feedstocks include vacuum gas oil and residual oils; products include gasoline, diesel, jet fuel, and propylene. In addition to fuels, cracking processes supply light olefins used in downstream petrochemical production.

Operationally, cracking is energy-intensive and may involve high pressures or severe temperatures. Coke formation can deactivate catalysts and requires periodic regeneration in many units. Hydrocracking uses hydrogen, enabling sulfur removal and higher-quality fuels. Environmental considerations include energy use and emissions, with modern units emphasizing efficiency, sulfur control, and feedstock flexibility.