Gasoline Hydrogenation & Depentanization

Hydrogenation is important in sulfur removal. When a feedstock with mercaptans and unsaturated hydrocarbons is exposed to high pressure hydrogen and appropriate catalysts, the sulfur is virtually all H2S, which can be washed out with diethanolamine.

The resulting desulfurized naptha is then fed to a reformer unit to restore some double bonds, and the result fractionated so that the various components can be handled separately. Butane and Isobutane feed an alkylation unit along with STRONG sulfuric or hydrofloric acids. Pentane is a valuable component of wintertime gasoline, even in the moderate climate of Los Angeles. Refineries store the stuff all summer, when it would make excessive vapor pressure in a new car's gas tank, or vapor lock old ones. During the winter, pentane is blended in to improve starting and cold weather running.

Refineries are highly interconnected, and the separation of pentane is one of many processes.