used in refining, the chemical reaction of a low-molecular-weight olefin with an isoparaffin to form a liquid product, alkylate, that has a high octane number and is used to improve the antiknock properties of gasoline. The reaction takes place in the presence of a strong acid catalyst, and at controlled temperature and pressure. Alkylation less commonly describes certain other reactions, such as that of an olefin with an aromatic hydrocarbon.