Petroleum - Composition; The proportion of hydrocarbons in the mixture is highly variable and ranges from as much as 97% by weight in the lighter oils to as little as 50% in the heavier oils and bitumens.The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium.
Crude oil varies greatly in appearance depending on its composition. It is usually black or dark brown (although it may be yellowish or even greenish). In the reservoir it is usually found in association with natural gas, which being lighter forms a gas cap over the petroleum, and saline water, which being heavier generally floats underneath it. Crude oil may also be found in semi-solid form mixed with sand, as in the Athabasca oil sands in Canada, where it may be referred to as crude bitumen.
Petroleum is a mixture of a very large number of different hydrocarbons ; the most commonly found molecules are alkanes (linear or branched), cycloalkanes, aromatic hydrocarbons, or more complicated chemicals like asphaltenes. Each petroleum variety has a unique mix of molecules, which define its physical and chemical properties, like color and viscosity.The alkanes, also known as paraffins, are saturated hydrocarbons with straight or branched chains which contain only carbon and hydrogen and have the general formula CnH2n+2 They generally have from 5 to 40 carbon atoms per molecule, although trace amounts of shorter or longer molecules may be present in the mixture.
The alkanes from pentane (C5H12) to octane (C8H18) are refined into gasoline (petrol), the ones from nonane (C9H20) to hexadecane (C16H34) into diesel fuel and kerosene (primary component of many types of jet fuel), and the ones from hexadecane upwards into fuel oil and lubricating oil. At the heavier end of the range, paraffin wax is an alkane with approximately 25 carbon atoms, while asphalt has 35 and up, although these are usually cracked by modern refineries into more valuable products. Any shorter hydrocarbons are considered natural gas or natural gas liquids.
The cycloalkanes, also known as napthenes, are saturated hydrocarbons which have one or more carbon rings to which hydrogen atoms are attached according to the formula CnH2n. Cycloalkanes have similar properties to alkanes but have higher boiling points.
Petroleum is used mostly, by volume, for producing fuel oil and gasoline (petrol), both important "primary energy" sources.A fully loaded Ford F-250 pickup truck is a whole lot of vehicle. It can tow a horse trailer with multiple horses. It comes with a DVD-based navigation system for the driver as well as a DVD player for passengers who are sitting in the extended cab. And how much does an F-250 set you back these days? Try $100,000. The F-250 is part of the first generation of mass-market vehicles — along with the Lincoln Navigator, Lexus LX 570 and a few others — to approach the six-figure mark. Now, if you walked into a showroom today and asked to see one of these trucks, the price tag wouldn’t be anywhere near $100,000. It would be much closer to $50,000.