CRUDE OIL COMPONENTS On average, crude oils are made of the following elements or compounds: Carbon - 84% Hydrogen - 14% Sulfur - 1 to 3% (hydrogen sulfide, sulfides, disulfides, elemental sulfur) Nitrogen - less than 1% (basic compounds with amine groups) Oxygen - less than 1% (found in organic compounds such as carbon dioxide, phenols, ketones, carboxylic acids) Metals - less than 1% (nickel, iron, vanadium, copper, arsenic) Salts - less than 1% (sodium chloride, magnesium chloride, calcium chloride)
Crude Oil PREV PREV NEXT NEXT Crude oil is the term for "unprocessed" oil, the stuff that comes out of the ground. It is also known as petroleum. Crude oil is a fossil fuel, meaning that it was made naturally from decaying plants and animals living in ancient seas millions of years ago -- most places you can find crude oil were once sea beds. Crude oils vary in color, from clear to tar-black, and in viscosity, from water to almost solid. Crude oils are such a useful starting point for so many different substances because they contain hydrocarbons. Hydrocarbons are molecules that contain hydrogen and carbon and come in various lengths and structures, from straight chains to branching chains to rings. There are two things that make hydrocarbons exciting to chemists: Hydrocarbons contain a lot of energy. Many of the things derived from crude oil like gasoline, diesel fuel, paraffin wax and so on take advantage of this energy. Hydrocarbons can take on many different forms. The smallest hydrocarbon is methane (CH 4 ), which is a gas that is a lighter than air. Longer chains with 5 or more carbons are liquids. Very long chains are solids like wax or tar. By chemically cross-linking hydrocarbon chains you can get everything from synthetic rubber to nylon to the plastic in tupperware. Hydrocarbon chains are very versatile!
The major classes of hydrocarbons in crude oils include: Paraffins general formula: C n H 2n+2 (n is a whole number, usually from 1 to 20) straight- or branched-chain molecules can be gasses or liquids at room temperature depending upon the molecule examples: methane, ethane, propane, butane, isobutane, pentane, hexane Aromatics general formula: C 6 H 5 - Y (Y is a longer, straight molecule that connects to the benzene ring) ringed structures with one or more rings rings contain six carbon atoms, with alternating double and single bonds between the carbons typically liquids examples: benzene, napthalene Napthenes or Cycloalkanes general formula: C n H 2n (n is a whole number usually from 1 to 20) ringed structures with one or more rings rings contain only single bonds between the carbon atoms typically liquids at room temperature examples: cyclohexane, methyl cyclopentane Other hydrocarbons Alkenes general formula: C n H 2n (n is a whole number, usually from 1 to 20) linear or branched chain molecules containing one carbon-carbon double-bond can be liquid or gas examples: ethylene, butene, isobuteneDienes and Alkynes general formula: C n H 2n-2 (n is a whole number, usually from 1 to 20) linear or branched chain molecules containing two carbon-carbon double-bonds can be liquid or gas examples: acetylene, butadienes
To understand the diversity contained in crude oil, and to understand why refining crude oil is so important in our society, look through the following list of products that come from crude oil: Petroleum gas - used for heating, cooking, making plastics small alkanes (1 to 4 carbon atoms) commonly known by the names methane, ethane, propane, butane boiling range = less than 104 degrees Fahrenheit / 40 degrees Celsius often liquified under pressure to create LPG (liquified petroleum gas) Naphtha or Ligroin - intermediate that will be further processed to make gasoline mix of 5 to 9 carbon atom alkanes boiling range = 140 to 212 degrees Fahrenheit / 60 to 100 degrees Celsius Gasoline - motor fuel liquid mix of alkanes and cycloalkanes (5 to 12 carbon atoms) boiling range = 104 to 401 degrees Fahrenheit / 40 to 205 degrees Celsius Kerosene - fuel for jet engines and tractors; starting material for making other products liquid mix of alkanes (10 to 18 carbons) and aromatics boiling range = 350 to 617 degrees Fahrenheit / 175 to 325 degrees Celsius Gas oil or Diesel distillate - used for diesel fuel and heating oil; starting material for making other products liquid alkanes containing 12 or more carbon atoms boiling range = 482 to 662 degrees Fahrenheit / 250 to 350 degrees Celsius Lubricating oil - used for motor oil, grease, other lubricants liquid long chain (20 to 50 carbon atoms) alkanes, cycloalkanes, aromatics boiling range = 572 to 700 degrees Fahrenheit / 300 to 370 degrees Celsius Heavy gas or Fuel oil - used for industrial fuel; starting material for making other products liquid long chain (20 to 70 carbon atoms) alkanes, cycloalkanes, aromatics boiling range = 700 to 1112 degrees Fahrenheit / 370 to 600 degrees Celsius Residuals - coke, asphalt, tar, waxes; starting material for making other products solid multiple-ringed compounds with 70 or more carbon atoms boiling range = greater than 1112 degrees Fahrenheit / 600 degrees Celsius You may have noticed that all of these products have different sizes and boiling ranges. Chemists take advantage of these properties when refining oil. Look at the next section to find out the details of this fascinating process.
The different chain lengths have progressively higher boiling points, so they can be separated out by distillation. This is what happens in an oil refinery -- crude oil is heated and the different chains are pulled out by their vaporization temperatures. (See How Oil Refining Works for details.)How Oil Refining Works The chains in the C 5, C 6 and C 7 range are all very light, easily vaporized, clear liquids called naphthas. They are used as solvents -- dry cleaning fluids can be made from these liquids, as well as paint solvents and other quick-drying products.dry cleaning fluids The chains from C 7 H 16 through C 11 H 24 are blended together and used for gasoline. All of them vaporize at temperatures below the boiling point of water. That's why if you spill gasoline on the ground it evaporates very quickly.gasoline Next is kerosene, in the C 12 to C 15 range, followed by diesel fuel and heavier fuel oils (like heating oil for houses). Next come the lubricating oils. These oils no longer vaporize in any way at normal temperatures. For example, engine oil can run all day at 250 degrees F (121 degrees C) without vaporizing at all. Oils go from very light (like 3-in-1 oil) through various thicknesses of motor oil through very thick gear oils and then semi-solid greases. Vasoline falls in there as well.gear Chains above the C 20 range form solids, starting with paraffin wax, then tar and finally asphaltic bitumen, which is used to make asphalt roads. All of these different substances come from crude oil. The only difference is the length of the carbon chains! Still curious about petroleum uses and processing? Check out the links below for related articles and quizzes to test your knowledge.
What's the difference between gasoline, kerosene, diesel, etc? The "crude oil" pumped out of the ground is a black liquid called petroleum. This liquid contains aliphatic hydrocarbons, or hydrocarbons composed of nothing but hydrogen and carbon. The carbon atoms link together in chains of different lengths.aliphatic hydrocarbons It turns out that hydrocarbon molecules of different lengths have different properties and behaviors. For example, a chain with just one carbon atom in it (CH 4 ) is the lightest chain, known as methane. Methane is a gas so light that it floats like helium. As the chains get longer, they get heavier.helium The first four chains -- CH 4 (methane), C 2 H 6 (ethane), C 3 H 8 (propane) and C 4 H 10 (butane) -- are all gases, and they boil at -161, -88, -46 and -1 degrees F, respectively (-107, -67, -43 and -18 degrees C). The chains up through C 18 H 32 or so are all liquids at room temperature, and the chains above C 19 are all solids at room temperature. So what's the real chemical difference between gasoline, kerosene and diesel? It has to do with their boiling points. We'll get into that on the next page.
What does octane mean? Octane History The name "octane" comes from the following fact: When you take crude oil and "crack" it in a refinery, you end up getting hydrocarbon chains of different lengths. These different chain lengths can then be separated from each other and blended to form different fuels. For example, you may have heard of methane, propane and butane. All three of them are hydrocarbons. Methane has just a single carbon atom. Propane has three carbon atoms chained together. Butane has four carbon atoms chained together. Pentane has five, hexane has six, heptane has seven and octane has eight carbons chained together. It turns out that heptane handles compression very poorly. Compress it just a little and it ignites spontaneously. Octane handles compression very well -- you can compress it a lot and nothing happens. Eighty-seven-octane gasoline is gasoline that contains 87-percent octane and 13-percent heptane (or some other combination of fuels that has the same performance of the 87/13 combination of octane/heptane). It spontaneously ignites at a given compression level, and can only be used in engines that do not exceed that compression ratio.
During WWI, it was discovered that you can add a chemical called tetraethyl lead (TEL) to gasoline and significantly improve its octane rating above the octane/heptane combination. Cheaper grades of gasoline could be made usable by adding TEL. This led to the widespread use of "ethyl" or "leaded" gasoline. Unfortunately, the side effects of adding lead to gasoline are: Lead clogs a catalytic converter and renders it inoperable within minutes.catalytic converter The Earth became covered in a thin layer of lead, and lead is toxic to many living things (including humans). When lead was banned, gasoline got more expensive because refineries could not boost the octane ratings of cheaper grades any more. Airplanes are still allowed to use leaded gasoline (known as AvGas), and octane ratings of 100 or more are commonly used in super-high-performance piston airplane engines. In the case of AvGas, 100 is the gasoline's performance rating, not the percentage of actual octane in the gas. The addition of TEL boosts the compression level of the gasoline -- it doesn't add more octane.Airplanes Currently engineers are trying to develop airplane engines that can use unleaded gasoline. Jet engines burn kerosene, by the way.Jet engineskerosene
TORQUE Imagine that you have a big socket wrench with a 2-foot- long handle on it, and you apply 50 pounds of force to that 2-foot handle. What you are doing is applying a torque, or turning force, of 100 pound-feet (50 pounds to a 2-foot- long handle) to the bolt. You could get the same 100 pound-feet of torque by applying 1 pound of force to the end of a 100-foot handle or 100 pounds of force to a 1- foot handle.