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<u>'''This needs a lot of editing and rewording.'''</u><BR><BR>
<u>'''This needs a lot of work yet'''</u><BR><BR>


'''Gasoline''' or '''petrol''' is derived from [[petroleum crude oil]]. Conventional gasoline is mostly a blended mixture of more than 200 different [[hydrocarbon]] [[liquid]]s ranging from those containing 4 [[carbon]] [[atom]]s to those containing 11 or 12  carbon atoms. It has an initial [[boiling point]] at [[atmospheric pressure]] of about 35 °[[Celsius|C]] (95 °[[Fahrenheit|F]]) and a final boiling point of about 200 °C (395 °F).<ref name=FAQ>[http://www.faqs.org/faqs/autos/gasoline-faq/part4/ Gasoline FAQ - Part2 of 4], Bruce Hamilton, Industrial Research Ltd. (IRL), a [[Crown Research Institute]] of [[New Zealand]].</ref><ref>{{cite book|author=Gary, J.H. and Handwerk, G.E.|title=Petroleum Refining Technology and Economics|edition=2nd Edition|publisher=Marcel Dekker, Inc.|pages=page 8|year=1984|id=ISBN 0-8247-7150-8}}</ref><ref name=Assi>[http://hqweb.unep.org/pcfv/PDF/JordanWrkshp-Unleaded-Rafat.pdf The Relation Between Gasoline Quality, Octane Number and the Environment], Rafat Assi, National Project Manager of Jordan’s Second National Communications on Climate Change, Presented at Jordan National Workshop on Lead Phase-out, [[United Nations]] Environment Programme, July 2008, [[Amman]], [[Jordan]].</ref><ref>{{cite book|author=James Speight|title=Synthetic Fuels Handbook|edition=1st Edition|publisher=McGraw-Hill|pages=pages 92-93|year=2008|id=ISBN 0-07-149023-X}}</ref> Gasoline is used primarily as fuel for the [[internal combustion engine]]s in automotive vehicles as well in some small airplanes.  
'''Gasoline''' or '''petrol''' is derived from [[petroleum crude oil]]. Conventional gasoline is mostly a blended mixture of more than 200 different [[hydrocarbon]] [[liquid]]s ranging from those containing 4 [[carbon]] [[atom]]s to those containing 11 or 12  carbon atoms. It has an initial [[boiling point]] at [[atmospheric pressure]] of about 35 °[[Celsius|C]] (95 °[[Fahrenheit|F]]) and a final boiling point of about 200 °C (395 °F).<ref name=FAQ>[http://www.faqs.org/faqs/autos/gasoline-faq/part4/ Gasoline FAQ - Part2 of 4], Bruce Hamilton, Industrial Research Ltd. (IRL), a [[Crown Research Institute]] of [[New Zealand]].</ref><ref>{{cite book|author=Gary, J.H. and Handwerk, G.E.|title=Petroleum Refining Technology and Economics|edition=2nd Edition|publisher=Marcel Dekker, Inc.|pages=page 8|year=1984|id=ISBN 0-8247-7150-8}}</ref><ref name=Assi>[http://hqweb.unep.org/pcfv/PDF/JordanWrkshp-Unleaded-Rafat.pdf The Relation Between Gasoline Quality, Octane Number and the Environment], Rafat Assi, National Project Manager of Jordan’s Second National Communications on Climate Change, Presented at Jordan National Workshop on Lead Phase-out, [[United Nations]] Environment Programme, July 2008, [[Amman]], [[Jordan]].</ref><ref>{{cite book|author=James Speight|title=Synthetic Fuels Handbook|edition=1st Edition|publisher=McGraw-Hill|pages=pages 92-93|year=2008|id=ISBN 0-07-149023-X}}</ref> Gasoline is used primarily as fuel for the [[internal combustion engine]]s in automotive vehicles as well in some small airplanes.  
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*''Isomerate'' (produced in a [[Catalytic isomerization|catalytic isomerization unit]]): has a high content of the branched isomers of pentane and hexane.
*''Isomerate'' (produced in a [[Catalytic isomerization|catalytic isomerization unit]]): has a high content of the branched isomers of pentane and hexane.


== Gasoline specifications and properties==
== Gasoline formulations and air quality regulations ==


As mentioned above, conventional gasoline may contain more than 200 different liquid hydrocarbons and has a boiling point range at atmospheric pressure of about 35 °C (95 °F) to about 200 °C (395 °F).
=== In the United States ===
 
Some gasolines marketed in parts of the United States and elswhere also contain a significant amount of one of the so-called "oxygenates", namely [[ethanol]] and [[MTBE]] (methyl tertiary butyl ether), either of which are a a source of  [[oxygen]] to reduce the engine exhaust emissions of [[carbon monoxide]] and unburnt gasoline. Both ethanol and MTBE are also octane rating enhancers. However, the use of MTBE in the United States is being phased out by legislation banning its use because of its contamination of underground water aquifers.
 
End-product gasoline also contains relatively small amounts of various additives such as antioxidants to improve the gasoline stability during storage by inhibiting the formation of gums, deposit modifiers to reduce engine deposits and fouling, corrosion inhibitors to protect gasoline storage tanks, freezing point depressants to prevent icing, and color dyes for safety or governmental regulatory requirements.<ref name=FAQ/><ref name=Assi/><ref name=Jones>{{cite book|author=David S.J. Jones and Peter P.Pujado (Editors)|title=Handbook of Petroleum Processing|edition=First Edition|publisher=Springer|year=2006|id=ISBN 1-4020-2819-9}}</ref>
 
=== Specifications determined by governmental air quality regulations ==
 
==== In the United States ====


There is no "standard" composition or set of specifications for gasoline. In the United States, because of the complex national and individual state and local programs to improve air quality, as well as local refining and marketing decisions, petroleum refiners must supply fuels that meet many different standards. State and local air quality regulations involving gasoline overlap with national requlations and that leads to adjacent or nearby areas having significantly different gasoline specifications. According to a detailed study in 2006, <ref name=CRS>[http://www.scribd.com/doc/1537932/US-Air-Force-rl31361 CRS Report For Congress] ''"Boutique Fuels" and Reformulated Gasoline: Harmonization of Fuel Standards'' (May 10, 2006) , Brent D. Yacobucci, Congressional Research Service, [[Library of Congress]]</ref> there were at least 18 different gasoline formulations required across the United States in 2002. Since many petroleum refiners in the United States produce three grades of fuel and the specifications for fuel marketed in the summer season vary significantly from the specifications in the winter season, that number may have been greatly understated. In any event, the number of fuel formulations has probably increased quite a bit since 2002. In the United States, the various fuel formulations are often referred to as "boutique fuels".<ref name=CRS/><ref>[http://www.epa.gov/oms/boutique.htm Boutique Fuels: State and Local Clean Fuels Programs] From the website of the [[U.S. Environmental Protection Agency]]</ref><ref>[http://www.epa.gov/oms/boutique/420r06901.pdf EPAct Section 1541 Boutique Fuels Report to Congress] Report No. EPA420-R-06-901, December 2006, co-authored by the U.S. Environmental Protection Agency and the [[U.S. Department of Energy]].</ref>
There is no "standard" composition or set of specifications for gasoline. In the United States, because of the complex national and individual state and local programs to improve air quality, as well as local refining and marketing decisions, petroleum refiners must supply fuels that meet many different standards. State and local air quality regulations involving gasoline overlap with national requlations and that leads to adjacent or nearby areas having significantly different gasoline specifications. According to a detailed study in 2006, <ref name=CRS>[http://www.scribd.com/doc/1537932/US-Air-Force-rl31361 CRS Report For Congress] ''"Boutique Fuels" and Reformulated Gasoline: Harmonization of Fuel Standards'' (May 10, 2006) , Brent D. Yacobucci, Congressional Research Service, [[Library of Congress]]</ref> there were at least 18 different gasoline formulations required across the United States in 2002. Since many petroleum refiners in the United States produce three grades of fuel and the specifications for fuel marketed in the summer season vary significantly from the specifications in the winter season, that number may have been greatly understated. In any event, the number of fuel formulations has probably increased quite a bit since 2002. In the United States, the various fuel formulations are often referred to as "boutique fuels".<ref name=CRS/><ref>[http://www.epa.gov/oms/boutique.htm Boutique Fuels: State and Local Clean Fuels Programs] From the website of the [[U.S. Environmental Protection Agency]]</ref><ref>[http://www.epa.gov/oms/boutique/420r06901.pdf EPAct Section 1541 Boutique Fuels Report to Congress] Report No. EPA420-R-06-901, December 2006, co-authored by the U.S. Environmental Protection Agency and the [[U.S. Department of Energy]].</ref>
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==== In other nations ====
=== In other nations ===
 
=== Properties that determine the performance of gasolines ==  


Characteristics and properties that affect the performance of gasolines:
== Properties that determine the performance of gasolines ==


Some of the characteristics or properties of gasoline that affect its performance as an automotive fuel are:<ref name=Assi/><ref name=Jones/>
=== Volatility


*Volatility:
=== Octane rating ===
*Octane rating:
{{main|Octane rating)
*Sulfur content:
*Stability:


== Octane rating ==
{{main|Octane rating}}
{{Image|Iso-octane and n-Heptane.png|right|250px|Simplified structure of 2,2,4-trimethylpentane and n-heptane.}}  
{{Image|Iso-octane and n-Heptane.png|right|250px|Simplified structure of 2,2,4-trimethylpentane and n-heptane.}}  


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The octane rating became important in the search for higher output powers from [[aero engine]]s in the late 1930s and the 1940s as it allowed higher [[compression ratio]]s to be used.
The octane rating became important in the search for higher output powers from [[aero engine]]s in the late 1930s and the 1940s as it allowed higher [[compression ratio]]s to be used.


== Additives ==
=== Sulfur content ===


=== Tetra-ethyl lead (TEL) ===
The mixture known as gasoline, when used in high [[Physical compression|compression]] internal combustion engines, has a tendency to autoignite (''detonation'') causing a damaging "[[engine knocking]]" (also called "pinging") noise. Early research into this effect was led by A.H. Gibson and [[Harry Ricardo]] in England and [[Thomas Midgley]] and Thomas Boyd in the United States. The discovery that [[lead]] additives modified this behavior led to the widespread adoption of the practice in the 1920s and therefore more powerful higher compression engines. The most popular additive was [[tetra-ethyl lead]]. However, with the discovery of the environmental and health damage caused by the lead, and the incompatibility of lead with [[catalytic converter]]s found on virtually all newly sold US automobiles since 1975, this practice began to wane (encouraged by many governments introducing differential tax rates) in the 1980s. Most countries are phasing out leaded fuel; different additives have replaced the lead compounds. The most popular additives include [[aromatic hydrocarbon]]s, [[ether]]s and [[alcohol as a fuel|alcohol]] (usually [[ethanol]] or [[methanol]]).
In the US, where lead had been blended with gasoline (primarily to boost octane levels) since the early 1920s, standards to phase out leaded gasoline were first implemented in 1973 - due in great part to studies conducted by [[Philip J. Landrigan]]. In 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2,000 [[short ton]]s of lead per year. From [[January 1]], [[1996]], the [[Clean Air Act]] banned the sale of leaded fuel for use in on-road vehicles. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum $10,000 fine in the US. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines.<ref>{{cite press release | title =  EPA Takes Final Step in Phaseout of Leaded Gasoline | date = 1996-01-29 | url = http://www.epa.gov/history/topics/lead/02.htm | publisher = [[U.S. Environmental Protection Agency]]}}</ref>  The ban on leaded gasoline led to thousands of tons of lead not being released in the air by automobiles. Similar bans in other countries have resulted in lowering levels of lead in people's [[blood]]streams.<ref>{{cite journal | title = Blood Lead Secular Trend in a Cohort of Children in Mexico City (1987–2002) | author = Lourdes Schnaas, Stephen J. Rothenberg, María-Fernanda Flores, Sandra Martínez, Carmen Hernández, Erica Osorio,1 and Estela Perroni | journal = [[Environ. Health. Perspect.]] | year = 2004 | volume = 112 | issue = 10 | pages = 1110–1115 | doi = 10.1289/ehp.6636 | url = http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1247386 | format = [[Open-access]] full-text reprint | pmid = 15238286}}</ref><ref>{{cite journal | journal = [[Archives of Environmental Health: An International Journal]] | volume = 59 | issue = 4 | year = 2004 | pages = 182–187 | doi = 10.3200/AEOH.59.4.182-187 | title = Rapid Drop in Infant Blood Lead Levels during the Transition to Unleaded Gasoline Use in Santiago, Chile | author = Paulina Pino, Tomás Walter; Manuel J. Oyarzún A3, Matthew J. Burden; Betsy Lozoff}}</ref>


A side effect of the lead additives was protection of the [[poppet valve|valve]] seats from erosion.  Many [[classic car]]s' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "Lead substitute" products are also produced and can sometimes be found at auto parts stores. These were scientifically tested and some were approved by the Federation of British Historic Vehicle Clubs at the UK's Motor Industry Research Association (MIRA) in 1999. [http://www.fbhvc.co.uk/fuel/index.htm http://www.fbhvc.co.uk/fuel/index.htm]
=== Stability ===


Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve [[combustion]], and to allow easier starting in cold climates.
End-product gasoline also contains relatively small amounts of various additives such as antioxidants to improve the gasoline stability during storage by inhibiting the formation of gums, deposit modifiers to reduce engine deposits and fouling, corrosion inhibitors to protect gasoline storage tanks, freezing point depressants to prevent icing, and color dyes for safety or governmental regulatory requirements.<ref name=FAQ/><ref name=Assi/><ref name=Jones>{{cite book|author=David S.J. Jones and Peter P.Pujado (Editors)|title=Handbook of Petroleum Processing|edition=First Edition|publisher=Springer|year=2006|id=ISBN 1-4020-2819-9}}</ref>


In some parts of [[South America]], [[Asia]], Eastern [[Europe]] and the [[Middle East]], leaded gasoline is still in use. Leaded gasoline was phased out in [[sub-Saharan Africa]] effective [[1 January]], [[2006]]. A growing number of countries have drawn up plans to ban leaded gasoline in the near future.
{{Image|E10 Water Tolerance.png|right|281px|Temperatures and associated water contents at which a blend of gasoline and 10 volume % ethanol separates.<ref>[http://www.scribd.com/doc/1970087/Environmental-Protection-Agency-Ethanol-Workshop E10 & E85 and Other Alternate Fuels] Bruce Bauman, [[American Petroleum Institute]](API)</ref>}}
When gasoline is left for a period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel." This will cause gums to build up in the fuel tank, lines, and carburetor or fuel injection components making it harder to start the engine. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1–2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting.  Users have been advised to keep gasoline containers and tanks more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures,<ref>{{cite web|url=http://www.alpharubicon.com/altenergy/gasstoretg.htm|title=Fuel storage practices}}</ref> to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the [[carburetor]].<ref>{{cite web|url=http://www.perr.com/tip1.html|title=PER Notebook}}</ref>


=== MMT ===
Gummy, sticky resin deposits result from [[oxidation|oxidative]] degradation of gasoline.  This degradation can be prevented through the use of [[antioxidant]]s such as [[phenylenediamine]]s, [[alkylenediamine]]s ([[diethylenetriamine]], [[triethylenetetramine]], etc), and [[alkylamine]]s ([[diethylamine]], [[tributylamine]], [[ethylamine]]). Other useful additives include gum inhibitors such as N-substituted [[alkylaminophenol]]s and colour stabilizers such as N-(2-aminoethyl)piperazine, N,N-diethylhydroxylamine, and triethylenetetramine.<ref name=EP0534668>{{patent|EP|0534668|Stabilization of gasoline mixtures}}</ref>
[[Methylcyclopentadienyl manganese tricarbonyl]] (MMT) has been used for many years in [[Canada]] and recently in [[Australia]] to boost octane. It also helps old cars designed for leaded fuel run on unleaded fuel without need for additives to prevent valve problems.


US Federal sources state that MMT is suspected to be a powerful neurotoxin and respiratory toxin,<ref>{{cite web | title = Comments of the Gasoline Additive MMT |url = http://www.epa.gov/otaq/regs/fuels/additive/mmt_cmts.htm | accessdate = 2008-08-10 }}</ref> and a large Canadian study concluded that MMT impairs the effectiveness of automobile emission controls and increases pollution from motor vehicles.<ref>{{cite web | title = Final Report: Effects of MMT in Gasoline on Emissions from On-Road Motor Vehicles in Canada | date = 2002-11-11 | publisher = Canadian Vehicle Manufacturers’ Association, and Association of International Automobile Manufacturers of Canada | url = http://cvma.ca/eng/publications/FinalMMTReport.pdf|format=PDF}}</ref>
Improvements in refinery techniques have generally reduced the reliance on the catalytically or thermally cracked stocks most susceptible to oxidation.<ref>{{patent|US|3994698| Gasoline additive concentrate composition}}</ref> Gasoline containing acidic contaminants such as [[naphthenic acid]]s can be addressed with additives including strongly basic organo-amines such as [[N,N-diethylhydroxylamine]], preventing metal corrosion and breakdown of other antioxidant additives due to acidity.  Hydrocarbons with a [[bromine number]] of 10 or above can be protected with the combination of unhindered or partially hindered phenols and oil soluble strong amine bases such as [[monoethanolamine]], N-(2-aminoethyl)piperazine, [[cyclohexylamine]], 1,3-cyclohexane-bis(methylamine), 2,5-[[dimethylaniline]], 2,6-dimethylaniline, [[diethylenetriamine]] and [[triethylenetetramine]].<ref name=EP0534668 />


In 1977 use of MMT was banned in the US by the Clean Air Act until the Ethyl Corporation could prove that the additive would not lead to failure of new car emissions-control systems. As a result of this ruling, the Ethyl Corporation began a legal battle with the EPA, presenting evidence that MMT was harmless to automobile emissions-control systems. In 1995 the US Court of Appeals ruled that the EPA had exceeded its authority, and MMT became a legal fuel additive in the US. MMT is nowadays manufactured by the Afton Chemical Corporation division of Newmarket Corporation.<ref>{{cite web | publisher = Afton Chemical | title = History of mmt | url = http://www.aftonchemical.com/Products/MMT/History+of+MMT%AE.htm | accessdate = 2008-02-22}}</ref>


=== Oxygenates ===


[[Oxygenate]] blending adds oxygen to the fuel in [[oxygen]]-bearing compounds such as [[MTBE]], [[ETBE]] and [[ethanol]], and so reduces the amount of [[carbon monoxide]] and unburned fuel in the exhaust gas, thus reducing smog. In many areas throughout the US oxygenate blending is mandated by EPA regulations to reduce smog and other airborne polutants. For example, in Southern California, fuel must contain 2% oxygen by weight, resulting in a mixture of 5.6% ethanol in gasoline.  The resulting fuel is often known as ''reformulated gasoline'' (RFG) or ''oxygenated gasoline''. The federal requirement that RFG contain oxygen was dropped [[May 6]], [[2006]] because the industry had developed VOC-controlled RFG that did not need additional oxygen.<ref>{{cite web | url = http://www.epa.gov/otaq/rfg_regs.htm#usage | title = Removal of Reformulated Gasoline Oxygen Content Requirement (national) and Revision of Commingling Prohibition to Address Non-0xygenated Reformulated Gasoline (national) | date = 2006-02-22 | publisher = [[U.S. Environmental Protection Agency]]}}</ref>


MTBE use is being phased out in some states due to issues with contamination of ground water. In some places, such as California, it is already banned. Ethanol and to a lesser extent the ethanol derived ETBE are a common replacements. Especially since ethanol derived from biomatter such as corn, sugar cane or grain is frequent, this will often be referred to as ''bio''-ethanol. A common ethanol-gasoline mix of 10% ethanol mixed with gasoline is called [[Ethanol fuel|gasohol]] or E10, and an ethanol-gasoline mix of 85% ethanol mixed with gasoline is called [[E85]]. The most extensive use of ethanol takes place in [[Brazil]], where the ethanol is derived from [[sugarcane]]. In 2004, over 3.4 billion US gallons (2.8&nbsp;billion imp&nbsp;gal/13 million m³) of ethanol was produced in the United States for fuel use, mostly from [[maize|corn]], and E85 is slowly becoming available in much of the United States. Unfortunately many of the relatively few stations vending E85 are not open to the general public.<ref>{{cite web | url = http://www.eere.energy.gov/afdc/fuels/stations_locator.html | title = Alternative Fueling Station Locator | publisher = [[U.S. Department of Energy]]}}</ref>  The use of [[bioethanol]], either directly or indirectly by conversion of such ethanol to ''bio''-ETBE, is encouraged by the European Union [[Directive on the Promotion of the use of biofuels and other renewable fuels for transport]]. However since producing bio-ethanol from fermented sugars and starches involves [[distillation]], ordinary people in much of Europe cannot legally ferment and distill their own bio-ethanol at present (unlike in the US where getting a [[BATF]] distillation permit has been easy since the 1973 oil crisis.)




=== Ethanol ===
In the United States, [[ethanol]] is sometimes added to gasoline but sold without an indication that it is a component. Chevron, 76, Shell, and several other brands market ethanol-gasoline blends.{{Fact|date=May 2007}}


In several states, ethanol is added by law to a minimum level which is currently 5.9%.  Most fuel pumps display a sticker stating that the fuel may contain up to 10% ethanol, an intentional disparity which allows the minimum level to be raised over time without requiring modification of the literature/labeling.  The bill which was being debated at the time the disclosure of the presence of ethanol in the fuel was mandated has recently passed.  This law ([[Energy Policy Act of 2005]]) will require all auto fuel to contain at least 10% ethanol. Many call this fuel mix [[gasohol]].


In the EU, 5% ethanol can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10% blending of ethanol. Most countries (fuel distributors) today do not add so much ethanol.{{Fact|date=April 2008}} Most gasoline (petrol) sold in Sweden has 5% ethanol added.
In Brazil, the [[Brazilian National Agency of Petroleum, Natural Gas and Biofuels]] (ANP) requires that gasoline for automobile use has 23% of ethanol added to its composition.


== Stability ==
== Stability ==


{{Image|E10 Water Tolerance.png|right|281px|Temperatures and associated water contents at which a blend of  gasoline and 10 volume % ethanol separates.<ref>[http://www.scribd.com/doc/1970087/Environmental-Protection-Agency-Ethanol-Workshop E10 & E85 and Other Alternate Fuels] Bruce Bauman, [[American Petroleum Institute]](API)</ref>}}
When gasoline is left for a period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel." This will cause gums to build up in the fuel tank, lines, and carburetor or fuel injection components making it harder to start the engine. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1–2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting.  Users have been advised to keep gasoline containers and tanks more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures,<ref>{{cite web|url=http://www.alpharubicon.com/altenergy/gasstoretg.htm|title=Fuel storage practices}}</ref> to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the [[carburetor]].<ref>{{cite web|url=http://www.perr.com/tip1.html|title=PER Notebook}}</ref>
Gummy, sticky resin deposits result from [[oxidation|oxidative]] degradation of gasoline.  This degradation can be prevented through the use of [[antioxidant]]s such as [[phenylenediamine]]s, [[alkylenediamine]]s ([[diethylenetriamine]], [[triethylenetetramine]], etc), and [[alkylamine]]s ([[diethylamine]], [[tributylamine]], [[ethylamine]]).  Other useful additives include gum inhibitors such as N-substituted [[alkylaminophenol]]s and colour stabilizers such as N-(2-aminoethyl)piperazine, N,N-diethylhydroxylamine, and triethylenetetramine.<ref name=EP0534668>{{patent|EP|0534668|Stabilization of gasoline mixtures}}</ref>
Improvements in refinery techniques have generally reduced the reliance on the catalytically or thermally cracked stocks most susceptible to oxidation.<ref>{{patent|US|3994698| Gasoline additive concentrate composition}}</ref>  Gasoline containing acidic contaminants such as [[naphthenic acid]]s can be addressed with additives including strongly basic organo-amines such as [[N,N-diethylhydroxylamine]], preventing metal corrosion and breakdown of other antioxidant additives due to acidity.  Hydrocarbons with a [[bromine number]] of 10 or above can be protected with the combination of unhindered or partially hindered phenols and oil soluble strong amine bases such as [[monoethanolamine]], N-(2-aminoethyl)piperazine, [[cyclohexylamine]], 1,3-cyclohexane-bis(methylamine), 2,5-[[dimethylaniline]], 2,6-dimethylaniline, [[diethylenetriamine]] and [[triethylenetetramine]].<ref name=EP0534668 />


== References ==
== References ==

Revision as of 22:54, 2 April 2009

This needs a lot of work yet

Gasoline or petrol is derived from petroleum crude oil. Conventional gasoline is mostly a blended mixture of more than 200 different hydrocarbon liquids ranging from those containing 4 carbon atoms to those containing 11 or 12 carbon atoms. It has an initial boiling point at atmospheric pressure of about 35 °C (95 °F) and a final boiling point of about 200 °C (395 °F).[1][2][3][4] Gasoline is used primarily as fuel for the internal combustion engines in automotive vehicles as well in some small airplanes.

In Canada and the United States, the word "gasoline" is commonly used and it is often shortened to simply "gas" although it is a liquid rather than a gas. In fact, gasoline dispensing facilities are referred to as "gas stations".

Most current or former Commonwealth countries use the term "petrol" and dispensing facilities are referred to as "petrol stations". The term "petrogasoline" is also used sometimes. In some European countries and elsewhere, the term "benzin" (or a variant of that word) is used to denote gasoline.

In aviation, "mogas" (short for "motor gasoline") is used to distinguish automotive vehicle fuel from aviation fuel known as "avgas".

Gasoline production from crude oil

(PD) Image: Milton Beychok
Average U.S. refinery product yields.

Gasoline and other end-products are produced from petroleum crude oil in petroleum refineries. It is very difficult to quantify the amount of gasoline produced by refining a given amount of crude oil for a number of reasons:

  • There are quite literally hundreds of different crude oil sources worldwide and each crude oil has its own unique mixture of thousands of hydrocarbons and other materials.
  • There are also hundreds of crude oil refineries worldwide and each of them is designed to process a specific crude oil or a specific set of crude oils. Furthermore, each refinery has its own unique configuration of petroleum refining processes that produces its own unique set of gasoline blend components.
  • There are a great many different gasoline specifications that have been mandated by various local, state or national govermental agencies.
  • In many geographical areas, the amount of gasoline produced during the summer season (i.e., the season of the greatest demand for automotive gasoline) varies significantly from the amount produced during the winter season.

However, from the data presented in the adjacent image as an average of all the refineries operating in the United States in 2007,[5] refining a barrel of crude oil (i.e., 42 gallons or 159 litres) yielded 19.2 gallons (72.7 litres) of end-product gasoline. That is a volumetric yield of 45.7 percent. The average refinery yield of gasoline in other countries may be different.

From a marketing viewpoint, the most important characteristic of a gasoline is its octane rating (discussed later in this article). Paraffinic hydrocarbons wherein all of the carbon atoms are in a straight chain have the poorest octane ratings. Hydrocarbons with more complicated configurations such as aromatics, olefins and highly branched paraffins have much higher octane ratings. To that end, many of the refining processes used in petroleum refineries are designed to produce hydrocarbons with those more complicated configurations.

Some of the most important refinery process streams that are blended together to obtain the end-product gasolines[6] are:

Gasoline formulations and air quality regulations

In the United States

There is no "standard" composition or set of specifications for gasoline. In the United States, because of the complex national and individual state and local programs to improve air quality, as well as local refining and marketing decisions, petroleum refiners must supply fuels that meet many different standards. State and local air quality regulations involving gasoline overlap with national requlations and that leads to adjacent or nearby areas having significantly different gasoline specifications. According to a detailed study in 2006, [7] there were at least 18 different gasoline formulations required across the United States in 2002. Since many petroleum refiners in the United States produce three grades of fuel and the specifications for fuel marketed in the summer season vary significantly from the specifications in the winter season, that number may have been greatly understated. In any event, the number of fuel formulations has probably increased quite a bit since 2002. In the United States, the various fuel formulations are often referred to as "boutique fuels".[7][8][9]

Some of the major properties and components regulated by the various national and state or local programs are:

  • Vapor pressure: The vapor pressure of a gasoline is a measure of its propensity to evaporate. Evaporative emissions of the hydrocarbons in the gasoline lead to the formation of ozone in the atmosphere which reacts with vehicular and industrial emissions of [nitrogen oxides]] (NOx) to form what is called photochemical smog. Smog ias a combination og the words smoke and fog and traditionally referred to the mixture of smoke and sulfur dioxide that resulted from the burning of coal for heating buildings in places such as London, England. Modern photochemical smog does not come from coal burning but from vehicular and industrial emissions of hydrocarbons and nitrogen oxides. It appears as a brownish haze over large urban areas and is irritating to the eyes and lungs.
  • Heavy metals:


In other nations

Properties that determine the performance of gasolines

=== Volatility

Octane rating

{{main|Octane rating)

(PD) Image: Milton Beychok
Simplified structure of 2,2,4-trimethylpentane and n-heptane.

An important characteristic of gasoline is its octane rating, which is a measure of how resistant gasoline is to the abnormal combustion phenomenon known as pre-detonation (also known as knocking, pinging, spark knock, and other names). Deflagration is the normal type of combustion. Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane) and n-heptane. There are a number of different conventions for expressing the octane rating; therefore, the same fuel may be labeled with a different number, depending upon the system used.

The octane rating became important in the search for higher output powers from aero engines in the late 1930s and the 1940s as it allowed higher compression ratios to be used.

Sulfur content

Stability

End-product gasoline also contains relatively small amounts of various additives such as antioxidants to improve the gasoline stability during storage by inhibiting the formation of gums, deposit modifiers to reduce engine deposits and fouling, corrosion inhibitors to protect gasoline storage tanks, freezing point depressants to prevent icing, and color dyes for safety or governmental regulatory requirements.[1][3][10]

(PD) Image: Milton Beychok
Temperatures and associated water contents at which a blend of gasoline and 10 volume % ethanol separates.[11]

When gasoline is left for a period of time, gums and varnishes may build up and precipitate in the gasoline, causing "stale fuel." This will cause gums to build up in the fuel tank, lines, and carburetor or fuel injection components making it harder to start the engine. Motor gasoline may be stored up to 60 days in an approved container. If it is to be stored for a longer period of time, a fuel stabilizer may be used. This will extend the life of the fuel to about 1–2 years, and keep it fresh for the next uses. Fuel stabilizer is commonly used for small engines such as lawnmower and tractor engines to promote quicker and more reliable starting. Users have been advised to keep gasoline containers and tanks more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures,[12] to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor.[13]

Gummy, sticky resin deposits result from oxidative degradation of gasoline. This degradation can be prevented through the use of antioxidants such as phenylenediamines, alkylenediamines (diethylenetriamine, triethylenetetramine, etc), and alkylamines (diethylamine, tributylamine, ethylamine). Other useful additives include gum inhibitors such as N-substituted alkylaminophenols and colour stabilizers such as N-(2-aminoethyl)piperazine, N,N-diethylhydroxylamine, and triethylenetetramine.[14]

Improvements in refinery techniques have generally reduced the reliance on the catalytically or thermally cracked stocks most susceptible to oxidation.[15] Gasoline containing acidic contaminants such as naphthenic acids can be addressed with additives including strongly basic organo-amines such as N,N-diethylhydroxylamine, preventing metal corrosion and breakdown of other antioxidant additives due to acidity. Hydrocarbons with a bromine number of 10 or above can be protected with the combination of unhindered or partially hindered phenols and oil soluble strong amine bases such as monoethanolamine, N-(2-aminoethyl)piperazine, cyclohexylamine, 1,3-cyclohexane-bis(methylamine), 2,5-dimethylaniline, 2,6-dimethylaniline, diethylenetriamine and triethylenetetramine.[14]





Stability

References

  1. ↑ 1.0 1.1 Gasoline FAQ - Part2 of 4, Bruce Hamilton, Industrial Research Ltd. (IRL), a Crown Research Institute of New Zealand.
  2. ↑ Gary, J.H. and Handwerk, G.E. (1984). Petroleum Refining Technology and Economics, 2nd Edition. Marcel Dekker, Inc., page 8. ISBN 0-8247-7150-8. 
  3. ↑ 3.0 3.1 The Relation Between Gasoline Quality, Octane Number and the Environment, Rafat Assi, National Project Manager of Jordan’s Second National Communications on Climate Change, Presented at Jordan National Workshop on Lead Phase-out, United Nations Environment Programme, July 2008, Amman, Jordan.
  4. ↑ James Speight (2008). Synthetic Fuels Handbook, 1st Edition. McGraw-Hill, pages 92-93. ISBN 0-07-149023-X. 
  5. ↑ Where Does My Gasoline Come from?, U.S. Department of Energy, Energy Information Administration, April 2008.
  6. ↑ See the schematic flow diagram in the Petroleum refining processes article.
  7. ↑ 7.0 7.1 CRS Report For Congress "Boutique Fuels" and Reformulated Gasoline: Harmonization of Fuel Standards (May 10, 2006) , Brent D. Yacobucci, Congressional Research Service, Library of Congress
  8. ↑ Boutique Fuels: State and Local Clean Fuels Programs From the website of the U.S. Environmental Protection Agency
  9. ↑ EPAct Section 1541 Boutique Fuels Report to Congress Report No. EPA420-R-06-901, December 2006, co-authored by the U.S. Environmental Protection Agency and the U.S. Department of Energy.
  10. ↑ David S.J. Jones and Peter P.Pujado (Editors) (2006). Handbook of Petroleum Processing, First Edition. Springer. ISBN 1-4020-2819-9. 
  11. ↑ E10 & E85 and Other Alternate Fuels Bruce Bauman, American Petroleum Institute(API)
  12. ↑ Fuel storage practices.
  13. ↑ PER Notebook.
  14. ↑ 14.0 14.1 Template:Patent
  15. ↑ Template:Patent


External links


References

  • David S.J. Jones and Peter P.Pujado (Editors) (2006). Handbook of Petroleum Processing, First Edition. Springer. ISBN 1-4020-2819-9. 
  • John McKetta (Editor) (1992). Petroleum Processing Handbook. CRC Press. ISBN 0-8247-8681-5. 


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