I. ENERGY AND TRANSPORTATION I.4. Petrolchemical fuels 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 byproducts, a vacuum distillation process that operated at lower temperatures was in use by 1928. The use of an inert catalyst (catalytic cracking) rather then high temperatures to achieve cracking was developed by Eugene Houdry in 1936, introduced commercially in 1937, and quickly revolutionized the gasoline refining process. Oil refinery Fuel additives 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 fuel line freezing. Catalytic converters 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. 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