Science And Environment: How Gasoline Works

A brief overview of where gasoline comes from and how it works.

Gasoline is initiated in an engine by an ignition system that fires a high voltage spark through an air gap or sparkplug. The carburetor inside most engines mixes the gasoline with air in precise proportions. Most modern engines use electronics to control this process because it increase efficiency and reduces air pollution. It is very light in color and very flammable. Care should be taken very seriously when working with gasoline or storing it.

Gasoline is manufactured from crude oil inside a refinery. It contains more than 150 chemicals. First, it is run through a distillation tower, which is similar to a distillery for alcohol. Intense heat vaporizes most of the crude oil and the vapors rise. Compounds inside the vapor rise at different heights and are collected as they cool into liquids. These collection trays at the various levels and capture the liquids.

The first gasoline created was made from the lightest liquids. Kerosene was the middle liquid and industrial fuels came from the heaviest liquids. Anything left over was burned off. To make more gasoline, more crude oil was burned.



As automobile engines, airplanes and other modern machines needed cleaner gasoline, the refineries had to create better ways of distilling products.

Right before World War II, ExxonMobil developed a chemical engineering process called catalytic cracking or 'cat cracking'. The process breaks apart the heavier hydrocarbon molecules. This forces them into lighter components for gasoline. As the process was improved, it allows for higher quality gasoline and for more gallons to be retrieved from a barrel of crude oil. This process was hailed as the most revolutionalizing feat in 50 years.

Even today, newer and better technologies are allowing refineries to create highly useful and cleaner products. Gasoline for today's engines needs to allow fast start-ups, smooth acceleration in all weather and run cleanly to prevent engine sticking. Each state has various requirements for gasoline as well. Automobiles in higher elevations need a different formulation than ones in lower elevations. Some states have strict limits on the amounts of volatile organic compounds (VOCs) in exhaust fumes because they contribute to air pollution.

Over the years, improvements to gasoline have ranged from having lead removed to lowering sulfur levels. The federal government has added restrictions as well through the U.S. Clean Air Act Amendments of 1990. Gasoline is being reformulated by adding oxygenates to the fuel and reducing emissions of nitrogen compounds (NOx) and VOCs. Vapor pressure reduction was made a requirement since the light compounds can evaporate into the atmosphere and contribute to ozone and smog.

Gasoline prices are affected by the different seasons. The logistics required getting the gasoline to the proper markets. Commodity markets affect prices because they are guessing about the future needs and supply and demand. The independent owners of gasoline stations set retail prices based on the wholesale price they received as well as prevailing market conditions and competition. Inventories of ready gasoline vary based on when peak conditions occur. Sometimes shortages occur and lead to higher gasoline prices.

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