I.4. Petrochemical Fuels. Production of gasoline from crude oil.
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Production of gasoline from crude oil
To improve gasoline recovery from crude oil, refiners initially used heat to break down the larger molecules of the heavy oil fraction into the smaller ones found in gasoline, using a process called thermal cracking (1913). Since high temperatures also formed unwanted products, a vacuum distillation that operated at lower temperatures was used by 1928. The use of an inert catalyst (catalytic cracking) rather then high temperature to achieve cracking was developed by Eugene Houdry in 1936, introduced commercially in 1937 and quickly revolutionized the gasoline refining process.
Eugene Houdry with the model of the catalytic converter
Thomas Midgley Jr. use tetraethyl lead as antiknock additive in gasoline (1921)
Early automotive engines ‘knocked’ whenever poor quality gasoline was used. In 1921, tetraethyl lead was added to gasoline to make engines run more smoothly and quietly. By 1926, an octane rating was introduced to measure the quality of gasoline (compression tolerance). The use of lead additives was discontinued in the 1970s because of environmental concerns. Today, small amount of chemicals (alcohols, ethers) are added to gasoline to improve octane rating, enhance gasoline performance (metal deactivators), and reduce engine friction and wear to extend engine life (detergents). Seasonal chemical additives are used in some areas for geographical concerns, such as the addition of methanol to prevent freezing of fuel line.
Two-stage catalytic converters were introduced in 1975 to control carbon monoxide and hydrocarbon emissions. Soon, a third stage was added to clean nitrogen oxides from the exhaust gas. Catalytic converters function by causing a series of chemical reactions to occur around the metal, usually platinum catalyst. Nitrogen oxides are converted into nitrogen and oxygen gases, carbon monoxide is converted into carbon dioxide, and the unburned hydrocarbons are converted to water and carbon dioxide.
Three-stage catalytic converter
Advanced materials for design, comfort and safety
The automobile of 21st century bears little resemblance to its early predecessors in design, comfort, and safety for passengers. High-intensity discharge headlamps allow maximum nighttime illumination. Corrosion has been drastically reduced by special coatings and materials. Chemical refrigerants circulate in a closed-environment system. Automotive safety glass was introduced in 1914. Today, special polymers coat glass to reduce weight and outside noise and to protect from glare and ultraviolet radiation. Safety innovations include polymer fibers in seat belt (required in the 1960s) and in air bags (required in 1996).
Reducing weight in automobiles by transitioning from metal to plastics and identifying new high-performance materials is made possible by chemical achievements. After World War II., automobile manufacturers began using synthetic petroleum-based polymers for rigid structural components because of their toughness, hardness and weather resistance that are require. After the 1970s energy crisis, lightweight alternatives were sought for metals in order to improve fuel efficiency. Design applications include: complex body shapes fabricated by injection molding, thermoplastic bumpers, polypropylene fibers that are colorfast and UV-stable, and special paints coatings, and adhesives.
Natural rubber products appeared in the early 1800s, but were impractical due to softening or brittleness in hot or cold weather. An American inventor Charles Goodyear developed the vulcanization process for natural rubber in 1839, linking unsaturated bonds with sulfur. This basic process is still used with additional chemical accelerants and stabilizers. By 1945, synthetic rubber was being produced commercially. As tire demand increased, other improvements were introduced including an inner tube to replace solid rubber tires, reinforcement with natural or synthetic fabric cord for strength, and added materials for reduced wear, and the eventual debut of tubeless tires .
From 1783 when the first human flew in a balloon propelled by hot air rising an open fire, innovations in hot-air balloons have been revolutionary. Hot air was quickly replaced by hydrogen, which was easier to control. Hot-air ballooning has become a popular sport with more than 5000 hot-air balloon pilots in the United States. Chemistry has contributed the durable, inexpensive and heat-resistant nylon fabric and the liquid propane technology used for propulsion.
Although hydrogen-filled balloons, such as the exploded Hindenburg (1937), had rigid structures, the flammability of hydrogen always posed a safety hazard. In 1905, two chemists discovered helium in a Kansas gas well, and this rare element was suddenly plentiful. During World War I., chemical technology extracted, stored, and shipped large quantities of helium, and the helium-filled blimps in World War II. safely escorted troop and supply ships around submarines. In the 1950s, helium was useful as welding atmosphere during rocket construction and as the propellant which pushed the rocket’s fuel to the engines.
The Hindenburg disaster (1937)
From early test rockets first launched in the 1920s to communication satellites of the 1950s, to the reusable Space Shuttle of the 1980s, the human expansion into space is an amazing engineering feat. Successful space travel depends on rockets possessing high thrust- velocity to overcome the gravitational force of the Earth. The first rocket was launched in 1926 using a liquid fuel of gasoline and liquid oxygen oxidizer. Subsequently, different fuels and oxidizers have been used in either solid or liquid form. The Space Shuttle uses liquid hydrogen as the fuel, but the launch engines use solid fuel of aluminum and ammonium perchlorate as the oxidizer/binder.
Construction materials for aircraft and rockets
As aircraft design evolved from wood and fabric to sophisticated engineered materials, chemical technology has provided materials that met design requirements. Metal alloys using aluminum and titanium were developed to provide strength, light weight, high-temperature stability, and corrosion resistance for aircraft. Rockets have special material requirements because of the extreme conditions under which they operate. One example is the special tile in strategic locations that protects the space shuttle (1980s) from high temperatures on reentry. After an exotic zirconium composite material was tried, the final tile design used silica fibers derived from common sand.