hydrocarbons
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What are hydrocarbons? They are compounds of carbon and hydrogen only. What are the hydrocarbons in gasoline? What is the history of gasoline? Where does crude oil come from? When will we run out of crude oil? What is the history of gasoline? What are the hydrocarbons in gasoline? Saturated hydrocarbons ( aka paraffins, alkanes ) Unsaturated Hydrocarbons What are oxygenates? Why were alkyl lead compounds added? Why not use other organometallic compounds? What do the refining processes do? What energy is released when gasoline is burned? What are the gasoline specifications? Vapour Pressure and Distillation Classes. Vapour Lock Protection Classes Antiknock Index ( aka (RON+MON)/2, "Pump Octane" ) Lead Content Copper strip corrosion Maximum Sulfur content Maximum Solvent Washed Gum ( aka Existent Gum ) Minimum Oxidation Stability Water Tolerance What are the effects of the specified fuel properties? Are brands different? What is a typical composition? Is gasoline toxic or carcinogenic? Is unleaded gasoline more toxic than leaded? Is reformulated gasoline more toxic than unleaded? Are all oxygenated gasolines also reformulated gasolines? Why pick on cars and gasoline? Why are there seasonal changes? Why were alkyl lead compounds removed? Why are evaporative emissions a problem? Why control tailpipe emissions? Why do exhaust catalysts influence fuel composition? Why are "cold start" emissions so important? When will the emissions be "clean enough"? Why are only some gasoline compounds restricted? What does "renewable" fuel or oxygenate mean? Will oxygenated gasoline damage my vehicle? What does "reactivity" of emissions mean? What are "carbonyl" compounds? What are "gross polluters"? Who invented Octane Ratings? Why do we need Octane Ratings? What fuel property does the Octane Rating measure? Why are two ratings used to obtain the pump rating? What does the Motor Octane rating measure? What does the Research Octane rating measure? Why is the difference called "sensitivity"? What sort of engine is used to rate fuels? How is the Octane rating determined? What is the Octane Distribution of the fuel? What is a "delta Research Octane number"? How do other fuel properties affect octane? Can higher octane fuels give me more power? Does low octane fuel increase engine wear? Can I mix different octane fuel grades? What happens if I use the wrong octane fuel? Can I tune the engine to use another octane fuel? How can I increase the fuel octane? Are aviation gasoline octane numbers comparable? Can mothballs increase octane? What is the Octane Number Requirement of a Vehicle? What is the effect of Compression ratio? What is the effect of changing the air-fuel ratio? What is the effect of changing the ignition timing? What is the effect of engine management systems? What is the effect of temperature and load? What is the effect of engine speed? What is the effect of engine deposits? What is the Road Octane Number of a Fuel? What is the effect of altitude? What is the effect of humidity? What does water injection achieve? What causes an empty fuel tank? Is knock the only abnormal combustion problem? Can I prevent carburetter icing? Should I store fuel to avoid the oxygenate season? Can I improve fuel economy by using quality gasolines? What is "stale" fuel, and should I use it? How can I remove water in the fuel tank? Can I used unleaded on older vehicles? How serious is valve seat recession on older vehicles? Do fuel additives work? Can a quality fuel help a sick engine? What are the advantages of alcohols and ethers? Why are CNG and LPG considered "cleaner" fuels. Why are hydrogen-powered cars not available? What are "fuel cells" ? What is a "hybrid" vehicle? |
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Hydrocarbons derived from petroleum, natural gas, or coal are essential in many ways to modern life and its quality. The bulk of the world’s hydrocarbons is used for fuels, electrical power generation, and heating. The chemical, petrochemical, plastics and rubber industries are also dependent upon hydrocarbons as raw materials for their products. Indeed, most industrially significant synthetic chemicals are derived from petroleum sources. The overall oil use of the world now exceeds ten million metric tons a day. Ever increasing world population (about 6 billion to increase to 10 billion in a few decades) and energy consumption and finite non-renewable fossil fuel resources, which are going to be increasingly depleted, are clearly on a collision course. New solutions will be needed for the 21st century if we are to maintain the standard of living the industrialized world has gotten used to and the developing world is striving to achieve. v Recognizing the need for a long-range program of basic research and graduate education in the field of hydrocarbon chemistry, the University of Southern California established its "Loker Hydrocarbon Research Institute" in 1977. Generous donations from Donald and Katherine Loker, as well as other friends and supporters helped build an outstanding facility and program. Hydrocarbon Chemistry Hydrocarbons, the principal compounds of oil and natural gas, have to be chemically altered to make useful products and materials. This is carried out by chemical and petrochemical industries in processes such as isomerization, alkylation homologation, etc. These processes are frequently catalyzed by acids and involve electron deficient intermediates called carbocations. The Loker Institute has pioneered new methods to study such processes and their mechanisms. Research is also aimed at more efficient utilization of fossil fuel resources including recycling of carbon dioxide (a greenhouse gas) to useful materials. Studies are also directed towards developing new synthetic methodologies for chemical bond making and bond breaking processes. Polymeric materials derived from simple hydrocarbon precursors are the basis for new materials with exceptional electrical, optical, and magnetic properties. These materials find applications in information technology, photochemical energy conversion and biomedical devices. Carbocarbons and their Chemistry In studying hydrocarbons and their conversions, a wide variety of highly acidic systems called superacids have been developed. When higher valent Lewis acid fluorides such as SbF5 and TaF5 are combined with Brönsted acids such as HF or FSO3H, acids many billions of times stronger than sulfuric acid are obtained. In such superacidic media the lifetime of carbocations are sufficiently long to be examined by a variety of chemical and physical methods including nuclear magnetic resonance spectrometry. Acid catalyzed conversion of hydrocarbons such as cracking, isomerization, alkylation, oligo- and poly-condensation, etc. are of substantial importance. The fundamental chemistry of such hydrocarbon conversions involves carbocations and their reactions. Novel environmentally benign acid systems, including solid acids, are developed to overcome difficulties connected with toxic acids such as hydrofluoric or sulfuric acid. Isomerization and alkylation of saturated hydrocarbons to provide high octane gasoline are of particularly great importance in the petroleum industry. The Loker Institute has developed an environmentally friendly and practical alkylation process for the manufacture of high octane gasoline by using a modified hydrogen fluoride catalyst system of greatly reduced volatility and toxicity. In addition, the use of superacidic catalysts allow new ways to hydro-treat coals, shale oil, tar sands and other heavy petroleum sources and residues, and yield liquid hydrocarbons. New and environmentally safe gasoline and diesel fuel additives were also developed, resulting in higher octane gasoline and higher octane diesel fuels. These additives have also resulted in cleaner burning fuels and opened the way to exclude currently used other toxic additives. Conversion of Methane or Carbon Dioxide to Hydrocarbons The direct conversion of methane (i.e. natural gas) to higher hydrocarbons and derived products offers a viable alternative to Fischer-Tropsch chemistry (utilizing synthesis gas, i.e. CO and H2). Until recently, the utilization of methane as a chemical building block was limited to free radical reactions (combustion, nitration, chlorination, etc.). Various stoichiometric organometallic insertion reactions were also discovered, but their use is so far not practical. Superacid catalysts developed at the Institute permit oxidative condensation of methane to higher hydrocarbons, as well as the selective electrophilic conversion of methane to its mono-substituted derivatives such as methyl halides and methyl alcohol. Monosubstituted methanes can be further condensed to ethylene, propylene and derived hydrocarbons over zeolites or bifunctional acidic-basic catalysts, giving access to a whole range of hydrocarbons essential to our everyday life. Mechanistic aspects of the methane conversion chemistry, particularly the role of pentacoordinate CH5+-type carbocationic intermediates, were also studied. Kekule’s conclusion dating back to the 1860’s that carbon cannot bound to more than four atoms of groups, i.e. it cannot exceed tetravalency, was refuted by discoveries obtained at the Institute. Dr. Olah’s substantial body of work in this area resulted in the realization that in electrodeficient (carbocationic) systems carbon can coordinate with five, six or even seven atoms or groups simultaneously and laid the foundation to what is now recognized as hypercarbon chemistry. When hydrocarbons are burned they form carbon dioxide and water. They are thus non-renewable on the human time scale. Excessive burning of fossil fuels leads to increased atmospheric levels of carbon dioxide, which has been linked to global warming and climatic changes. In addition to trying to keep carbon dioxide levels down through reducing burning of fossil fuels (the basis of the 1997 Kyoto agreement), new solutions are needed. An innovative new approach pursued by the Institute is directed at reversing the process by producing hydrocarbons from carbon dioxide and water via methyl alcohol. Some of the underlying chemistry to convert carbon dioxide using hydrogen gas (obtained by electrolytically splitting water) is known. Metal or superacid catalyzed reduction pursued by the Institute has made significant progress to bring about the feasibility of CO2 conversion to methanol. However, electricity needed for generating hydrogen is costly and remains the key to practical applications. As we still cannot store electricity efficiently, power plants in their off-peak periods could produce hydrogen as a means of storing electricity. Hydrogen then could be used to recycle CO2 (from smokestack emissions or other concentrated sources, eventually even the atmosphere) into methyl alcohol and derived fuels. The carbon dioxide recycling technology now under development allows us not only to produce useful fuels and hydrocarbon products, at the same time can contribute to mitigating CO2 related global warming. Methyl alcohol and derived fuels can also be used to produce electricity in the new direct oxidation liquid feed fuel cells developed jointly by the Loker Institute and Caltech-JPL. When operating the fuel cell in its "reversed mode", carbon dioxide and water can be electro-catalytically reduced to methyl alcohol. While the recycling of carbon dioxide into hydrocarbons is a highly energy demanding process some applications, i.e. solar power related applications, may not be overly concerned with this high energy input requirement. Even if technologies to generate energy from alternate sources are further developed (i.e. atomic, solar, wind, etc.), a concentrated research effort is required to find long-range solutions for future hydrocarbon needs. The effort must include the development of alternative hydrocarbon sources, a search for new chemistry directed towards exploitation of renewable fuels, as well as the development of more efficient and environmentally acceptable ways of utilizing and recycling our present resources. The final solution to the shortage of hydrocarbons will come only when mankind can produce cheap energy through safer atomic energy (or even fusion) and other alternate sources. With abundant cheap energy, hydrocarbons will be produced from carbon dioxide of the atmosphere and water. In the meantime, however, it is essential that solutions be found that are feasible within the framework of our existing technological base. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.[1] Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls.[2] Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons. The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.[3][4]
Types of hydrocarbonsThe classifications for hydrocarbons defined by IUPAC nomenclature of organic chemistry are as follows:
Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. hexane and benzene), waxes or low melting solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene). General propertiesBecause of differences in molecular structure, the empirical formula remains different between hydrocarbons; in linear, or "straight-run" alkanes, alkenes and alkynes, the amount of bonded hydrogen lessens in alkenes and alkynes due to the "self-bonding" or catenation of carbon preventing entire saturation of the hydrocarbon by the formation of double or triple bonds. This inherent ability of hydrocarbons to bond to themselves is referred to as catenation, and allows hydrocarbon to form more complex molecules, such as cyclohexane, and in rarer cases, arenes such as benzene. This ability comes from the fact that bond character between carbon atoms is entirely non-polar, in that the distribution of electrons between the two elements is somewhat even due to the same electronegativity values of the elements (~0.30), and does not result in the formation of an electrophile. Generally, with catenation comes the loss of the total amount of bonded hydrocarbons and an increase in the amount of energy required for bond cleavage due to strain exerted upon the molecule; in molecules such as cyclohexane, this is referred to as ring strain, and occurs due to the "destabilized" spatial electron configuration of the atom. In simple chemistry, as per valence bond theory, the carbon atom must follow the "4-hydrogen rule", which states that the maximum number of atoms available to bond with carbon is equal to the number of electrons that are attracted into the outer shell of carbon. In terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons, and thus has 4 electrons available for covalent or dative bonding. Hydrocarbons are hydrophobic and are lipids. Some hydrocarbons also are abundant in the solar system. Lakes of liquid methane and ethane have been found on Titan, Saturn's largest moon, confirmed by the Cassini-Huygens Mission.[12] Hydrocarbons are also abundant in nebulae forming polycyclic aromatic hydrocarbons - PAH compounds. ] Simple hydrocarbons and their variations
UsageHydrocarbons are one of the Earth's most important energy resources. The predominant use of hydrocarbons is as a combustible fuel source. In their solid form, hydrocarbons take the form of asphalt.[13] Mixtures of volatile hydrocarbons are now used in preference to the chlorofluorocarbons as a propellant for aerosol sprays, due to chlorofluorocarbon's impact on the ozone layer. Methane [1C] and ethane [2C] are gaseous at ambient temperatures and cannot be readily liquified by pressure alone. Propane [3C] is however easily liquified, and exists in 'propane bottles' mostly as a liquid. Butane [4C] is so easily liquified that it provides a safe, volatile fuel for small pocket lighters. Pentane [5C] is a clear liquid at room temperature, commonly used in chemistry and industry as a powerful nearly odorless solvent of waxes and high molecular weight organic compounds, including greases. Hexane [6C] is also a widely used non-polar, non-aromatic solvent, as well as a significant fraction of common gasoline. The [6C] through [10C] alkanes, alkenes and isomeric cycloalkanes are the top components of gasoline, naptha, jet fuel and specialized industrial solvent mixtures. With the progressive addition of carbon units, the simple non-ring structured hydrocarbons have higher viscosities, lubricating indices, boiling points, solidification temperatures, and deeper color. At the opposite extreme from [1C] methane lie the heavy tars that remain as the lowest fraction in a crude oil refining retort. They are collected and widely utilized as roofing compounds, pavement composition, wood preservatives (the creosote series) and as extremely high viscosity sheer-resisting liquids. Burning hydrocarbonsMain article: Combustion
Hydrocarbons are currently the main source of the world’s electric energy and heat sources (such as home heating) because of the energy produced when burnt. Often this energy is used directly as heat such as in home heaters, which use either oil or natural gas. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated. A similar principle is used to create electric energy in power plants. Common properties of hydrocarbons are the facts that they produce steam, carbon dioxide and heat during combustion and that oxygen is required for combustion to take place. The simplest hydrocarbon, methane, burns as follows:
Another example of this property is propane:
Burning of hydrocarbons is an example of exothermic chemical reaction. [edit] PetroleumMain article: Petroleum
Extracted hydrocarbons in a liquid form are referred to as petroleum (literally "rock oil") or mineral oil, whereas hydrocarbons in a gaseous form are referred to as natural gas. Petroleum and natural gas are found in the Earth's subsurface with the tools of petroleum geology and are a significant source of fuel and raw materials for the production of organic chemicals. The extraction of liquid hydrocarbon fuel from sedimentary basins is integral to modern energy development. Hydrocarbons are mined from tar sands and oil shale, and potentially extracted from sedimentary methane hydrates. These reserves require distillation and upgrading to produce synthetic crude and petroleum. Oil reserves in sedimentary rocks are the source of hydrocarbons for the energy, transport and petrochemical industry. Hydrocarbons are economically important because major fossil fuels such as coal, petroleum and natural gas, and its derivatives such as plastics, paraffin, waxes, solvents and oils are hydrocarbons. Hydrocarbons — along with NOx and sunlight – contribute to the formation of tropospheric ozone and greenhouse gases. Hydrocarbons are abundant[citation needed] in the universe and the hydrocarbons were trapped inside the Earth's mantle during accretion.[citation needed] They are primordial materials that emerge from great depths to shallower levels in the crust. After migration of the mantle to the crust, microorganisms invade the hydrocarbon accumulations, feed them and also die leaving their parts in this context as contaminants, such as biomarkers.[citation needed] [edit] See also
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Gasoline Ultra low sulfur diesel Off-road ultra low sulfur diesel Ultra low sulfur kerosene Low sulfur residual fuels Jet fuel Propane Butane Phenol Acetone Nonene Tetramer Alpha-methylstyrene Toluene Xylene Benzene Cyclohexane Bisphenol-A |
| Jet Fuel |
| http://www.worldofmolecules.com/ |
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Carbon is unique among the elements of the periodic table because of the ability of its atoms to form strong bonds with one another while still having one or more valences left over to link to other atoms. The strength of the carbon-carbon bond permits long chains to form: This behavior is referred to as catenation. Such a chain contains numerous sites to which other atoms (or more carbon atoms) can bond, leading to a great variety of carbon compounds, or organic compounds. The hydrocarbons contain only hydrogen and carbon. They provide the simplest examples of how catenation, combined with carbon’s valence of 4, gives rise to a tremendous variety of molecular structures, even with only two elements involved. Single bonded hydrocarbons are called alkanes. A example of an alkane is butane: Butane These hydrocarbons can be in straight chains of varying length, or they can branch out, with one carbon bonded to three or four other carbons. This allows for isomers, such as iso-butane, a branched hydrocarbon: Isobutane Hydrocarbons can also form ring structures, which are referred to as cycloalkanes. An example is cyclohexane: Cyclohexane Carbons are capable of forming double and triple bonds with other carbons. This leads to molecules called alkenes, which contain a double bond, and alkynes, which contain a triple bond. An example of an alkene is ethene (ethylene), and an example of a alkyne is ethyne (acetylene): Ethene Together, they are referred to as unsaturated hydrocarbons, since there are fewer hydrogen atoms in the molecule due to multiple bonds as compared to alkanes. A special class of multiple bond hydrocarbons are the aromatic hydrocarbons, which all take the form of hydrocarbon ring structures with double bonds between the carbons. Benzene is an example: Benzene The hydrocarbons are also extremely important from an economic and geopolitical point of view. The fossil fuels, coal, petroleum (or crude oil), and natural gas consist primarily of hydrocarbons and are extremely important in everyday life. Petroleum turns out to be a mixture of many different hydrocarbons. Molecules of different sizes are useful for different tasks. The following schematic of petroleum fractional distillation shows the different types of hydrocarbons fractions taken from petroleum. Figure 1 A schematic of the fractional distillation of crude oil used in petroleum refining. The mixture is separated into Gases, Gasoline, Kerosene, Fuel oil, Lubricating oil, and Residue(asphalt). Following is a short overview of the the different fractions from petroleum[1] . (Natural) Gases The gas fraction contains hydrocarbons containing 1 to 4 carbon atoms in each molecule. These can be used for fuels. Another use is to derive materials such as plastics and synthetic fibers from such hydrocarbons, accomplished by polymerization techniques. An example is given below, propane: Propane Gasoline Probably the most familiar of the hydrocarbon distillates is gasoline. Gasoline consists of hydrocarbons with 5 to 12 carbon atoms in each molecule. It is difficult to overstate the importance of gasoline to modern society, given the central role of automobile travel in our society. Gasoline also serves as an industrial solvent. An example of a hydrocarbon found in gasoline is toluene: Toluene Kerosene Kerosene consists of hydrocarbons containing between 12 and 16 carbon atoms per molecule. The foremost uses of kerosene are as lamp oil, diesel fuel, and for catalytic cracking, a processes discussed in the section on unsaturated hydrocarbons. This allows these larger hydrocarbons to be broken down to a size that can be used for gasoline. An example of a hydrocarbon that would be in the kerosene fraction is tetradecane: Tetradecane Fuel Oil Fuel Oils consist of hydrocarbons ranging between 15 and 18 carbon atoms per molecule. Like kerosene, this distillate is used for heating oil, for diesel fuel, and for catalytic cracking. An example is hexadecane: hexadecane Lubricating Oil Lubricating oils consist of 16 to 20 carbon atoms per hydrocarbon molecule. Referred to sometimes as mineral oil, lubricating oils are used to decrease friction between moving parts. Perhaps the most familiar application is motor oil. An example of a hydrocarbon in the size range for lubricating oil is eicosane: Eicosane Residue(asphalt) Hydrocarbons which are not boiled away remain after the distillation as hydrocarbons with more than 20 carbon atoms per molecule. These hydrocarbons can be used as asphalt. An example is tetracosane: Tetracosane |