What ExxonMobil refineries do

ExxonMobil operates oil refineries that convert crude oil into products you use every day: gasoline, diesel, jet fuel, heating oil, and the base chemicals for plastics, detergents, and pharmaceuticals. A refinery is not a single process but a series of separate units, each doing one job — separating crude oil by weight, removing impurities, breaking large molecules into smaller ones, and blending the results into finished products.

The company runs 16 refineries worldwide, with major facilities in the United States, Europe, and Asia. In the U.S., ExxonMobil's largest refineries are in Baytown, Texas; Baton Rouge, Louisiana; and Torrance, California. Each refinery processes between 200,000 and 550,000 barrels of crude oil per day, depending on its size and design.

Key Takeaways

  • ExxonMobil refineries separate crude oil into gasoline, diesel, jet fuel, and chemical feedstocks through heating, distillation, and chemical reactions.
  • The largest U.S. refineries operated by ExxonMobil are located in Texas, Louisiana, and California, each processing hundreds of thousands of barrels daily.
  • Refining involves multiple stages: crude distillation, conversion units that break down heavy molecules, and treatment processes that remove sulfur and other impurities.
  • Refineries produce not only transportation fuels but also base chemicals used in manufacturing plastics, lubricants, and other industrial products.
  • Environmental and safety regulations govern emissions, wastewater discharge, and worker protection at every stage of the refining process.

The crude distillation unit: separating oil by weight

Refining begins in the crude distillation unit (CDU), where crude oil is heated to about 350 degrees Celsius and fed into a tall fractionating column. The heat vaporizes most of the oil. As the vapor rises through the column, it cools gradually, and different molecules condense at different heights based on their weight.

Light molecules — gasoline-range hydrocarbons — condense near the top of the column where it is coolest. Heavier molecules — diesel and fuel oil — condense lower down. The heaviest material, called residue, settles at the bottom. This single step produces multiple products from one input, but the heavy residue is too thick for most uses and must be processed further.

Conversion units: breaking down heavy molecules

The residue and heavier distillates from the CDU move to conversion units, where chemical reactions break large molecules into smaller, more valuable ones. The two main conversion processes are catalytic cracking and hydrocracking.

In catalytic cracking, heated oil vapor is passed over a catalyst — a material that speeds up chemical reactions without being consumed. The catalyst causes large hydrocarbon chains to break into smaller pieces, producing more gasoline and diesel-range material. Hydrocracking does the same thing but uses hydrogen gas and higher pressure, and it removes sulfur and nitrogen compounds at the same time.

These units are expensive to build and operate but are essential because they convert low-value heavy oil into high-value transportation fuels. A refinery without conversion capacity can only process light crude oil and must sell its heavy residue at a loss.

Treatment and blending: meeting fuel specifications

Gasoline and diesel produced so far contain sulfur, nitrogen, and other impurities that cause air pollution when burned. Hydrotreating units remove these compounds by passing the fuel over a catalyst in the presence of hydrogen. The process converts sulfur into hydrogen sulfide gas, which is then captured and converted to elemental sulfur or sulfuric acid for sale or disposal.

After treatment, different streams — straight-run gasoline, cracked gasoline, alkylate, reformate — are blended together to meet specifications for octane rating, vapor pressure, and other properties. A single gallon of gasoline at the pump may contain material from five or six different process units, blended to meet EPA and state fuel standards.

Chemical production from refinery streams

Refineries produce more than transportation fuels. Certain streams are diverted to petrochemical units where they serve as feedstock for plastics, synthetic rubber, detergents, and other chemicals. Ethylene and propylene — light molecules produced in the cracking units — are the building blocks for polyethylene and polypropylene plastics.

Benzene, toluene, and xylene — aromatic hydrocarbons separated in the refinery — are used to make paints, solvents, and pharmaceutical precursors. Some refineries are integrated with downstream chemical plants, so the chemical feedstock never leaves the site; it moves directly from the refinery to the chemical unit via pipeline.

Environmental controls and emissions management

Refineries are among the largest industrial sources of air and water emissions. ExxonMobil refineries must comply with the Clean Air Act, Clean Water Act, and state-specific regulations that limit sulfur dioxide, nitrogen oxides, volatile organic compounds, and particulate matter.

Wastewater from cooling systems, process condensation, and cleaning operations is treated on-site before discharge to rivers or municipal systems. Sulfur recovered from hydrotreating is either sold as a commodity or converted to sulfuric acid. Refinery gas — hydrogen, methane, and other light gases — is either used as fuel within the refinery or captured and sold.

Refineries also manage flaring, the controlled burning of excess gas when equipment is shut down or during emergencies. Flaring is regulated and reported to state environmental agencies; excessive flaring can trigger fines and operational restrictions.

Refinery capacity and crude oil sourcing

The amount a refinery can process depends on its design capacity, which is set when the facility is built and is difficult to expand significantly. ExxonMobil's U.S. refineries have a combined capacity of roughly 2 million barrels per day, making the company one of the largest refiners in the country.

Refineries source crude oil from multiple suppliers — some domestic, some imported — and can process different crude grades depending on their conversion capacity. A refinery with strong conversion units can handle heavy, sour crude (high in sulfur) that other refineries cannot process profitably. The choice of crude affects product yields, operating costs, and environmental compliance requirements.

Frequently Asked Questions

What is the difference between a refinery and a chemical plant?

A refinery converts crude oil into fuels and base chemicals through physical separation and chemical reactions. A chemical plant takes those base chemicals and transforms them into finished products like plastics, fertilizers, or pharmaceuticals. Many large facilities do both, but they are distinct operations with different equipment and purposes.

Why do refineries produce so much sulfur?

Crude oil naturally contains sulfur compounds. When refined, sulfur must be removed to meet fuel standards and prevent air pollution. Hydrotreating converts sulfur into hydrogen sulfide, which is then captured and converted to elemental sulfur — a byproduct refineries sell to chemical manufacturers or fertilizer producers.

Can a refinery switch between different types of crude oil?

Yes, but not when ready. Switching crude grades requires draining pipelines, adjusting process temperatures and pressures, and recalibrating blending recipes. A major switch can take several days. Refineries plan their crude slate weeks in advance to minimize downtime and optimize product yields.

What happens to refinery waste that cannot be sold?

Most refinery streams have a market — even heavy residue can be sold as bunker fuel for ships or blended into asphalt. Gases are used as fuel within the refinery. Solid waste like spent catalyst is either regenerated on-site or sent to specialized recycling facilities. Wastewater is treated before discharge. Refineries minimize waste because waste represents lost profit.

How much of a barrel of crude oil becomes usable product?

A typical refinery converts 85 to 95 percent of crude oil into saleable products — gasoline, diesel, jet fuel, chemicals, and other goods. The remainder is fuel gas burned within the refinery to power the process, or in some cases, residue that cannot be economically processed further and is sold at a discount or used as bunker fuel.