Alkylation unit

Alkylation unit, is one of the conversion processes used in the petroleum refineries. It is used to convert isobutane and low-molecular-weight alkenes (primarily a mixture of propene and butene) into an alkylate, a high octane gasoline component. The process occurs in presence of a strong acting acid as catalyst. The acid can be either sulfuric acid or hydrofluoric acid (HF). Depending on the acid used as catalyst the unit takes the name of SAAU (Sulphuric Acid Alkylation Unit) or HFAU (Hydrofluoric Acid Alkylation Unit). Since crude oil generally contains only 10 to 40 percent of hydrocarbon constituents in the gasoline range, refineries use a fluid catalytic cracking unit (FCCU) process to convert high molecular weight hydrocarbons into smaller and more volatile compounds, which are then converted into liquid gasoline-size hydrocarbons. Alkylation processes transform low molecular-weight alkenes and iso-paraffin molecules into larger iso-paraffins with a high octane number. FCCU is a very common unit in a modern oil refinery, but it is not uncommon for a refinery not to have an alkylation unit. Indeed, by 2010 there are some countries in the world without any installed alkylation unit.