Britannica Sources used in this answer

How do conversion refineries produce more gasoline than simple distillation refineries?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Aerial view of an oil refinery complex near New Orleans, Louisiana, with storage tanks, industrial structures, and smoke rising from the facility, surrounded by open land. — petroleum refining Aerial view of an oil refinery near New Orleans.

Simple distillation refineries are limited because they rely solely on the physical separation of naturally occurring components in crude oil, which restricts the total yield of lighter, high-value transportation fuels like gasoline.1

Conversion refineries produce more gasoline by employing chemical processes that alter the molecular structure of heavier, less valuable hydrocarbon fractions. These processes include:1

Cracking: This is the most critical process for gasoline production. It uses heat, pressure, and often catalysts to break down large, heavy molecules into the lighter, smaller molecules that constitute gasoline.23
Hydrocracking: A versatile process that uses hydrogen to convert heavy gas oils into high-quality gasoline or jet fuel.43
Alkylation and Polymerization: These units convert lighter gaseous by-products into liquid components suitable for gasoline blending.53
Coking: A severe form of thermal cracking that converts heavy residual fuels into lighter oils, which then serve as feedstock for further cracking.65

By integrating these units, conversion refineries can transform heavy residues into lighter products, allowing them to produce significantly higher volumes of gasoline compared to distillation-only facilities.15