Gasoline is a mixture of the lighter liquid hydrocarbons that distills within the range of 38 to 204 OC (100 to 400 OF). Commercial gasolines are a mixture of straight -run, cracked, reformed, and natural gasolines.
It is produced by the fractional distillation of petroleum; by condensation or adsorption from natural gas; by thermal or catalytic decomposition of petroleum or its fractions; by the hydrogenation of producer gas or by the polymerization of hydrocarbons of lower molecular weight Gasoline produced by the direct distillation of crude petroleum is known as straight-run gasoline.
It is usually distilled continuously in a bubble tower, which separates the gasoline from the other fractions of the oil having higher boiling points, such as kerosene, &el oil, lubricating oil, and grease. The range of temperatures in which gasoline boils and is distilled off is roughly between 38 and 205 OC (100 and 400 OF).
The yield of gasoline from this process varies from about 1 percent to about 50 percent, depending on the petroleum. Straight-run gasoline now makes up only a small part of gasoline production because of the superior merits of the various cracking processes. The flash point of gasoline is well below -17.8 OC (0 OF) at atmospheric pressure. In atmospheric burning smoke production normally occurs.
In some instances natural gas contains a percentage of natural gasoline that may be recovered by condensation or adsorption. The most common process for the extraction of natural gasoline includes passing the gas as it comes from the well through a series of towers containing a light oil called straw oil.
The oil absorbs the gasoline, which is then distilled off. Other processes involve adsorption of the gasoline on activated alumina, activated carbon, or silica gel. High-grade gasoline can be produced by a process known as hydrofining, that is, the hydrogenation of refined petroleum oils under high pressure in the presence of a catalyst such as molybdenum oxide.
Hydrofining not only converts oils of low value into gasoline of higher value but also at the same time purifies the gasoline chemically by removing undesirable elements such as sulfur. Producer gas, coal, and coal-tar distillates can also be hydrogenated to form gasoline.
Kerosene or sometimes referred to as Fuel Oil # 1 is a refined petroleum distillate. Kerosenes usually have flash points within the range of 37.8 OC to 54.4 OC (100 OF to 130 OF).
Therefore unless heated, kerosene will usually not produce ignitable mixtures over its surface. In atmospheric burning smoke production normally occurs. In some applications it is treated with sulfuric acid to reduce the content of aromatics, which burn with a smoky flame. It is commonly used as a fire and a solvent.
Diesel or sometimes referred to Fuel Oil #2 is the fraction of petroleum that distills after kerosene; which is in the family of gas oils. In atmospheric burning smoke production normally occurs. Several grades of diesel are produced depending on the intended service.
The combustion characteristics of diesel fbels are expressed in terms of a centane number, which is a measure of ignition delay. A short ignition delay, i.e., the time between injection and ignition is desirable for a smooth running engine.
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