Gasoline

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Gasoline

The United States is the world's leading consumer of petroleum. In 2001, Americans consumed over nineteen million barrels of oil per day.

Gasoline is a volatile (evaporates quickly), flammable (readily burns) liquid obtained from the refining (purifying) of petroleum, or crude oil. Almost all gasoline produced is used to fuel automobiles. A small percentage is used to power farm equipment and airplanes.

Underground treasure

Scientists are not sure how petroleum is formed, but most believe that it is formed from the remains of tiny plants and animals called plankton. According to this theory, millions of years ago these plankton lived on the surfaces of the oceans that covered a large part of the earth. When they died, they sank to the bottom of the ocean where they were covered by mud and sediments, or materials that had settled to the ocean bottom. Over the years, this process was repeated until the extreme pressure and heat from the sediments turned the plankton remains into petroleum and natural gas. It is believed that the crude oil and gas seeped upward into porous rocks (rocks with pores, or small holes). Solid rocks eventually formed around the porous rocks, trapping the oil and gas within them.

Some scientists do not believe that crude oil deposits come from formerly living things subjected to great heat and pressure for millions of years. They believe that crude oil deposits were created when the planet Earth was being formed and that many of these reservoirs are as yet untapped.

Since the beginning of civilization, people have recovered the oil that seeped through the earth's surface and put it to use. They used it for water-proofing their clothing and for caulking (patching up cracks) ships and artificial waterways. They also used it as a lubricant and medicine.

The first oil well

On August 27, 1859, Edwin L. Drake (1819–1880) struck oil near Titusville, Pennsylvania, at a depth of 69.5 feet (21.2 meters). This accomplishment could not have come at a better time. Whale oil that was used for lighting was getting more expensive due to scarcity, and people were looking for a cheaper lamp fuel. Prior to Drake's oil discovery, several scientists had already found ways of producing kerosene from the crude oil that seeped out of certain rock formations.

Soon, oil wells were being drilled in the Titus region, as well as in other states, including Ohio, California, Texas, and Oklahoma. One of the biggest oil wells drilled occurred in Spindletop, Texas, on January 10, 1901. Observers claimed that the well spewed oil about 100 feet (30 meters) higher than the 64-foot (19.5-meter) derrick (the support structure surrounding the drilling equipment). The oil continued to flow out of the well for nine days. That tremendous oil find was the start of the American oil industry.

Gasoline and automobiles

When crude oil was originally refined to make kerosene, gasoline was also produced. At first, people tried to use gasoline for lamp fuel, but the explosion that followed such use quickly discouraged the practice. Gasoline was considered of no value and was therefore thrown away. However, the invention of gasoline-powered engines to run the newly invented automobile made gasoline a very valuable product.

In 1883, German engineer Gottlieb Daimler (1834–1900) invented an engine that ran on gasoline. Four years later, he used this gasoline engine in a four-wheeled vehicle. His automobile traveled at a speed of eleven miles per hour. In 1899, Daimler produced the first Mercedes automobile, named after his daughter. Daimler's engine has been the model for almost all automobiles manufactured since the late nineteenth century. The first American car powered by gasoline was built in Chicopee, Massachusetts, by Charles Duryea (1861–1938) and his brother, J. Frank (1869–1967), in 1893.

How much petroleum do we use?

Petroleum supplies more energy to the world today than any other source. The United States is the world's leading consumer of petroleum. In 2001, Americans consumed over nineteen million barrels of oil per day. That same year, the United States had an estimated oil supply of just nine million barrels per day. That means that the nation had to import additional oil to meet the public demand.

Raw Materials

Gasoline is one of the products derived from the distillation and refining of crude oil. Gasoline first has to be separated from the other components through a process called fractional distillation (see below) and then refined and treated with additives to improve its quality. Other chemicals are also added to gasoline to further stabilize it and improve its color and smell in a process called "sweetening."

GASOLINE FOR DIFFERENT SEASONS

Oil refineries manufacture different blends of gasoline for different seasons and climates. In the winter, the gasoline blend has to be such that it vaporizes (changes to gas) faster so that cars will start easily when it is cold outside. In the summer, the gasoline blend must not vaporize quickly, or else the vapor bubbles would block the gasoline supply to the engine.

The Manufacturing Process

The manufacture of gasoline is a complex process. Separating the gasoline fraction (part) from crude oil is just the first step in the process. To produce gasoline of good quality, manufacturers experiment with different combinations of ingredients and additives.

Exploration

1 The first step in the manufacture of gasoline is to find its parent ingredient, crude oil. Sometimes, the presence of oil leakages or of certain sedimentary rocks indicates the possible presence of oil. If obvious signs of oil reservoirs are absent, oil exploration is undertaken.

Oil prospectors, people who explore an area for the presence of oil, may examine the surface characteristics of an area and take pictures of these features. They may set off explosives underground and then analyze the resulting shock waves to determine the rock type and depth. Some explorers use devices to measure the gravity and magnetic field of rock formations, which tend to differ depending on the presence of oil deposits. Others study sound waves that bounce off rocks below the earth's surface, providing information about the types of rocks underground.

2 After a possible oil reservoir is found, core samples are taken from test wells using a drill. These samples of the underground layers of the earth are analyzed to confirm the presence of oil. Chemical tests are also performed to determine if further drilling should be done.

Drilling

3 Crude oil is obtained through wells that can be as deep as 1,000 feet (305 meters). Rotary drilling is the method most commonly used to make holes in the ground. A tower-like steel framework called a derrick is constructed over the site where the well will be dug. This framework holds the drilling equipment. The drill bit, a large circular metal cutting tool fitted with teeth, is attached to a hollow pipe. As the pipe turns, the drill bit spins, cutting through the subsoil (soil below the earth's surface) and hard rock layers. More pipes are added to the equipment top as the bit digs deeper.

A heavy liquid mixture called "mud" is poured down the pipe to keep the drill bit from overheating. The mud also carries crushed rock pieces to the surface, keeps the well wall from collapsing, and prevents oil from "gushing" should the bit reach an oil reservoir. When the oil reservoir is reached, the mud's weight keeps the oil from escaping uncontrollably. The drill is removed and the well is sealed with a contraption called a "Christmas tree," a pyramid-like structure consisting of valves, nozzles, and pressure gauges that control the flow of oil.

Recovery

4 To remove the oil from the well, a complicated system of pipes and valves is installed directly into the drilling well. The natural pressure in the reservoir rock forces the oil out of the well and into the pipes. The pipes are connected to a recovery system, which consists of a series of larger pipes that transport the oil to the refinery by first passing through an oil (liquid) and gas (nonliquid) separator. The refinery is the industrial factory where crude oil is separated into its various parts and converted to usable products.

OFFSHORE DRILLING

In addition to drilling on land, oil companies have also drilled for oil at sea. The offshore drilling techniques are the same as those used for land drilling, using derricks and rotary motors. In addition, a sturdy, raised platform is built to accommodate the equipment and provide living spaces for the crew.

5 Eventually, the natural pressure in the rock reservoir decreases. However, great quantities of oil may still remain in the rock formation. To recover the rest of the oil, pressure is restored using water. Holes are drilled around the perimeter of the well, and water is then added, flooding the well. This causes the crude oil to float on the water. Another recovery method involves injecting carbon dioxide gas into the pocket above the oil deposit, thereby pushing out the oil. Some drillers use chemicals or steam to force more oil from the reservoir rock.

Fractional distillation

6 Crude oil that comes out of the ground cannot be used in its natural form. It has to be separated into its different parts, or fractions, by a process called distillation, which is performed in a fractional distillation column. During distillation, the crude oil components are separated according to molecular weight.

The crude oil is first pumped into a furnace and heated to over 600 degrees Fahrenheit (316 degrees Centigrade), causing it to evaporate (change from liquid to vapor). The vapors enter the bottom of a fractional distillation column (a huge tower fitted with a series of horizontal trays) and rise through the column. The lightest vapors, which rise to the top of the column, condense (change back to liquid) and settle on the different levels of trays throughout the length of the tower. Gasoline, having a low molecular weight, condenses at the top of the column and is one of the first fractions drawn off.

Fractional distillation itself does not produce gasoline from crude oil. It is just the first step in separating the crude oil fractions. Further refining processes are later used to improve the quality of the raw gasoline.

Refining crude oil fractions

7 In order to increase the amount of gasoline produced from crude oil, thermal cracking is used. Thermal cracking cracks, or breaks down, the heavier parts of crude oil by subjecting them to intense heat and high pressure. In the past, only 10 percent of crude oil produced gasoline. With thermal cracking, this proportion has been increased more than four times.

Other refining processes include catalytic cracking and polymerization. In catalytic cracking, the combination of heat and a catalyst (a substance that causes or speeds up a chemical reaction without itself being changed), such as aluminum, platinum, processed clay, and acids, breaks down the larger molecules of crude oil into gasoline. Polymerization is the opposite of cracking. In this process, the smaller molecules of crude oil are combined to form gasoline.

Additives

8 After gasoline is refined, antiknock additives are added to react with the chemicals in gasoline to prevent "engine knock." Knocking is the sound and the damage caused by the premature burning of gasoline in the combustion chamber of the internal-combustion engine. Antiknock compounds added include tertiary-butyl alcohol and methyl tertiary-butyl ether.

Other additives include antioxidants, which prevent the formation of gum in the engine. Gum is a substance formed in gasoline that can coat the internal engine parts, causing damage.

Rating gasoline

9 Gasoline is primarily a mixture of two volatile liquids, heptane and isooctane. Pure heptane, a lighter fuel, burns so quickly that it produces a great amount of knocking in the engine. Pure isooctane burns slowly and produces almost no knocking. The higher the percentage of octane in gasoline, the less knocking occurs. Octane ratings measure the ability of a certain gasoline to prevent knocking. For example, an octane rating of 87 means that the gasoline mixture contains 87 percent isooctane and 13 percent heptane. The higher the octane rating or number, the less likely it is for the gasoline to cause knocking.

Quality Control

Drilling for crude oil is a complex process. Quality control involves using the latest technology that not only preserves the environment but also reduces the drilling time, considered the most expensive part of oil exploration.

Refineries have to meet U.S. Environmental Protection Agency (EPA) regulations in managing the various processes involved in gasoline manufacture. These include the storage of crude oil, intermediate products, and finished products. They also include the discharge of chemical pollutants into the air and the disposal of waste products, such as wastewater, incinerator ash, and used filters and catalysts.

The Future

Petroleum, or crude oil, the source of gasoline, is a nonrenewable resource. Once it is used, it cannot be replaced. Today, crude oil provides about 97 percent of transportation fuels in the United States. Because gasoline is derived from a limited supply of petroleum, scientists are researching other sources of energy that could power cars.

One area of research involves different types of fuel cells that would replace the car engine. A fuel cell is basically a device that converts hydrogen fuel into electricity. Essentially, a fuel cell is a battery with an external fuel source—hydrogen—that continually recharges it. Scientists point out that fuel cells produce no pollution since their byproduct is water. Vehicles powered by fuel cells are currently being tested in different countries.

Scientists have also been looking for other sources of energy, including steam power used in steamboats of the past. Electric cars have been developed, and wind energy is also powering cars.

TRANSPORTING PETROLEUM

Crude oil may be transported from the drilling well to the refinery through a long system of steel pipes called a pipeline. Pipelines can run on the ground, underground, and even underwater. Other methods of transport include tankers (large ships), trucks, and railroad tank cars.

In the meantime, the petroleum industry continues to develop advanced technology in drilling for oil. In the Gulf of Mexico, computers are being used to direct drilling operations almost two miles beneath the surface of the water. Drills are fitted with computers that transmit information about wells. Advanced diagnostic and imaging technology allows one to "see" oil and gas reservoir features to a certain point from the earth's surface. Scientists are also looking into using high-intensity lasers for drilling.

bit:: A metal tool attached to a rotary drill and used for breaking up rock formations under the earth's surface.
Christmas tree:: A pyramid-like structure consisting of control valves, nozzles, and pressure gauges and installed at the top of a well to control the flow of oil at the completion of the drilling.
core sample:: A sample of underground mud that is drilled and analyzed for the presence of oil.
gusher:: An oil well that flows freely and abundantly as a result of natural gas pressure.
kerosene:: A fuel produced during the breaking down of crude oil into its parts. It is used for cooking, heating, and lighting.
knocking:: The sound and the damage caused by the premature burning of gasoline in the engine cylinder.
natural gas:: A gas that occurs in nature, usually with petroleum, and believed to have been formed by the actions of extreme pressure and heat on buried plankton millions of years ago.
octane number/rating:: A measure of the ability of a gasoline to prevent engine knocking. Gasolines with a higher octane rating are less likely to cause knocking.
plankton:: Tiny plants and animals found in bodies of water.
refining:: The process by which petroleum is purified and converted into a useful product, such as gasoline.
reservoir rock:: A porous rock formation containing a significant amount of oil and/or natural gas and typically enclosed by nonporous rocks that have prevented the oil from escaping.