Alkylation is a chemical reaction that involves the transfer of an alkyl group from one molecule to another. The alkyl group can be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene. Alkylating agents are reagents used to effect alkylation. Alkylation is used in a variety of applications, including:

• In organic chemistry, alkylation reactions are common. One of the frequently employed alkylation reactions is the Friedel-Crafts reaction, which involves the use of a Lewis acid catalyst such as AlCl3, an alkyl halide, and an aryl compound to form a substituted aromatic ring structure.

• In the petroleum industry, alkylation units are large chemical reaction vessels and associated technology. The alkylation process produces alkylate from propylene, butylene, and isobutane, which are alkylating olefins that form longer branched-chain hydrocarbons. The alkylate is a mixture of high-octane hydrocarbons that is blended into gasoline to improve performance and drivability.

• Electron-rich species such as phenols are also commonly alkylated to produce a variety of products, including linear alkylbenzenes used in the production of surfactants like LAS, or butylated phenols like BHT, which are used as antioxidants.

Alkylate is high in octane, low in sulfur, and has zero aromatics, which all help to lower vehicle emissions and tailpipe pollution. It also has low measures of fuel volatility and evaporative emissions, a requirement in parts of the country where smog is a concern. Alkylate is produced at nearly 90% of U.S. refineries in appropriately titled “alkylation units” . Refineries use different technologies to produce alkylate, depending on their facility configurations and a number of other factors. Today, nearly all alkylate produced in refinery settings is made using one of two catalysts: hydrofluoric acid (HF) and sulfuric acid.