Alkylation: A refining process for chemically combining isobutane with
olefin hydrocarbons (
e.g., propylene, butylene) through the control of temperature and pressure in the presence of anacid catalyst, usually sulfuric acid or hydrofluoric acid.
Hydrotreating includes desulfurization, removal of substances (
e.g., nitrogen compounds) that deactivate catalysts, conversion of
olefins to paraffins to reduce gum formation in gasoline, and other processes to upgrade the quality of the fractions.