Antiknock agent

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An antiknock agent is a gasoline additive used to reduce engine knocking and increase the fuel's octane rating by raising the temperature and pressure at which auto-ignition occurs. The mixture known as gasoline or petrol, when used in high compression internal combustion engines, has a tendency to knock (also called "pinging" or "pinking") and/or to ignite early before the correctly timed spark occurs (pre-ignition, refer to engine knocking).

Contents

Notable early antiknock agents, especially Tetraethyllead, added to gasoline included large amounts of toxic lead. [1] [2] The chemical was responsible for global negative impacts on health, and the phase out of leaded gasoline from the 1970s onward was reported by the United Nations Environmental Programme to be responsible for "$2.4 trillion in annual benefits, 1.2 million fewer premature deaths, higher overall intelligence and 58 million fewer crimes." [3] [4] Some other chemicals used as gasoline additives are thought to be less toxic.

Research

Early research was led by A. H. Gibson and Harry Ricardo in England and Thomas Midgley Jr. 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 tetraethyllead. However, with the discovery of the environmental and health damage caused by the lead, attributed to Derek Bryce-Smith and Clair Cameron Patterson, and the incompatibility of lead with catalytic converters found on virtually all US automobiles since 1975, this practice began to wane in the 1980s. Most countries are phasing out leaded fuel although different additives still contain lead compounds. Other additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).

Typical agents

Typical agents that have been used for their antiknock properties are:

Tetraethyllead

In the U.S., where tetraethyllead 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. In 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2,000 tons of lead per year. From January 1, 1996, the Clean Air Act banned the sale of leaded fuel for use in on-road vehicles in the United States. Possession and use of leaded gasoline in a regular on-road vehicle now carries a maximum US$10,000 fine in the United States. However, fuel containing lead may continue to be sold for off-road uses, including aircraft, racing cars, farm equipment, and marine engines. The ban on leaded gasoline led to thousands fewer tons of lead being released into the air by automobiles.

Similar bans in other countries have resulted in sharply decreasing levels of lead in people's bloodstreams. [6] [7]

A side effect of the lead additives was protection of the valve seats from erosion. Many classic cars' engines have needed modification to use lead-free fuels since leaded fuels became unavailable. However, "lead substitute" products are also produced and can sometimes[ when? ] be found[ by whom? ] at auto parts stores[ example needed ].[ citation needed ]

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.

In some parts of South America, Asia, and the Middle East, leaded gasoline is still in use. Leaded gasoline was phased out in sub-Saharan Africa, starting 1 January 2006. A growing number of countries have drawn up plans to ban leaded gasoline in the near future.

Some experts speculate that leaded petrol was behind a global crime wave in the late 1980s and early 1990s. [8]

To avoid deposits of lead inside the engine, lead scavengers are added to the gasoline together with tetraethyllead. The most common ones are:

MTBE

As tetraethyllead use declined, industry had to decide how to make up the octane deficit between the principal marketable light fuels produced by their refineries, and the higher octane fuels needed for high-compression gasoline engines in the automobile fleet. Around 70% of the difference was accommodated by more advanced processes at the refinery stage, cracking other hydrocarbon products from the distillation stack to modify them into fuels that would blend gasoline closer the appropriate octane. Most of the rest of the octane deficit required chemical additives not derived from the refinery process. Tetraethyl lead was largely replaced in the US with methyl tert-butyl ether starting in 1979. MTBE is a toxic water pollutant, and a series of groundwater contamination scandals starting in the 90's prompted the EPA to begin phasing MTBE out in 2000. [9]

Ethanol

MTBE's water pollution issues prompted plans for a phaseout, starting in 2000 with an EPA draft proposal, which was addressed several times at the state level in the years to follow, and eventually cemented in place federally with a 9-year phaseout in 2005's Energy Policy Act, with significant proportions of fuel ethanol designated as the replacement antiknock agent for the US automotive fuel system. Congress' attempts to promote ethanol for its geopolitical use as a backstop on any attempts to limit the US' gasoline supply, and also its incentives to reward Iowan corn farmers, whose state political primaries hold a special place in the electoral system, escalated ethanol from an additive to be used as needed, then to a fixed blending proportion of 5%, and then 10%, which is today the most common US fuel blend. [10] [11]

Ethanol has several issues as an antiknock additive. It is hydrophilic, pulling water vapor out of moist air, and it also increases the level of free oxygen in the fuel significantly. Both of these cause significant degradation to traditionally constructed engines, posing both residue and corrosion issues in increasing proportion with increasing fractions of ethanol. Whereas age-degraded gasoline may simply polymerize, evaporate, and thus lose its flammability, age-degraded gasoline-ethanol blends can cause severe damage if allowed to sit in an engine. Automotive engines addressed this with the mandated shift over to ethanol-tolerant metals and seals, and with the use of smart electronic fuel injection, which has some flexibility to adjust combustion properties and timing. Automotive engines did not see major issues because of these factors, and because automobiles in active use typically cycle through their gas tank in a matter of weeks. In small carburetor engines, like generators and lawnmowers, ethanol damage became the dominant mode of failure.

MMT

Methylcyclopentadienyl manganese tricarbonyl (MMT) has been used for many years in Canada and recently in Australia to boost octane ratings. It also allows old cars, designed to use leaded fuel, to run on unleaded fuel without the need for additives to prevent valve stem erosion.

A large Canadian study from 2002 (funded by automakers, who are against its use) concluded that MMT impairs the effectiveness of automobile emission controls and increases pollution from motor vehicles. However, a later study by the Canadian government found that "no Notice of Defect was found to be potentially caused by MMT." [12]

Many studies have been undertaken over time that confirmed the use of MMT is compatible with vehicles and safe for human health and the environment. In particular, a 2013 risk assessment on MMT was undertaken by ARCADIS Consulting, following a methodology developed by the European Commission. This risk assessment was verified by an independent panel and found by the EU Commission to be compliant with their methodology. It concluded that "when MMT is used as a fuel additive in petrol, no significant human health or environmental concerns related to exposure to either MMT or its transformation [combustion] products (manganese phosphate, manganese sulphate and manganese tetroxide) were identified even in locations where MMT is approved for use at levels up to 18 mg Mn/L." [13]

As stated by Health Canada in their risk assessment on the widespread use of MMT in Canadian gasoline, "all analyses indicate that the combustion products of MMT in gasoline do not represent an added health risk to the Canadian population" [14]

MMT is manufactured by reduction of bis(methylcyclopentadienyl) manganese using triethylaluminium. The reduction is conducted under an atmosphere of carbon monoxide. MMT is a so-called half-sandwich compound, or more specifically a piano-stool complex (since the three CO ligands are like the legs of a piano stool). The manganese atom in MMT is coordinated with three carbonyl groups as well as to the methylcyclopentadienyl ring. These hydrophobic organic ligands make MMT highly lipophilic, which may increase bioaccumulation. While the structure of MMT suggests lipophilicity and potential to bioaccumulate, comparison of bioconcentration factors (BCF) reported for plant and animal species in comparison to regulatory-based cutoffs (i.e., US EPA and EU REACH) indicates a low bioaccumulative potential of MMT. Figures 2 and 3 of the study (pages 182 & 184) shows the BCF plotted against time and illustrates the potential BCF of MMT. From these figures, the upper curve (A) demonstrates the 9-day MMT BCF plateauing at approximately 400 in plants and 200 in fish, with both values well below the Bioaccumulative / Very Bioaccumulative (B/vB) thresholds of US EPA, EU REACH and Environment & Climate Change Canada. [15]

A variety of related complexes are known, including ferrocene, which is also under consideration as an additive to gasoline.

Ferrocene

Ferrocene is the organometallic compound with the formula Fe(C5H5)2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds. [16] The rapid growth of organometallic chemistry is often attributed to the excitement arising from the discovery of ferrocene and its many analogues.

Ferrocene and its numerous derivatives have no large-scale applications, but have many niche uses that exploit their unusual structure (ligand scaffolds, pharmaceutical candidates), robustness (anti-knock formulations, precursors to materials), and redox reactions (reagents and redox standards). Use for global cooling has been proposed. [17]

Ferrocene and its derivatives are antiknock agents added to the petrol used in motor vehicles, and are safer than the now-banned tetraethyllead. [18] Petrol additive solutions containing ferrocene can be added to unleaded petrol to enable its use in vintage cars designed to run on leaded petrol. [19] The iron-containing deposits formed from ferrocene can form a conductive coating on the spark plug surfaces.

Iron pentacarbonyl

Iron pentacarbonyl, also known as iron carbonyl, is the compound with formula Fe(CO)5. Under standard conditions Fe(CO)5 is a free-flowing, straw-colored liquid with a pungent odour.

This compound is a common precursor to diverse iron compounds, including many that are useful in organic synthesis. [20] Fe(CO)5 is prepared by the reaction of fine iron particles with carbon monoxide. Fe(CO)5 is inexpensively purchased.

Iron pentacarbonyl is one of the homoleptic metal carbonyls; i.e. metal complexes bonded only to CO ligands. Other examples include octahedral Cr(CO)6 and tetrahedral Ni(CO)4.

Most metal carbonyls have 18 valence electrons, and Fe(CO)5 fits this pattern with 8 valence electrons on Fe and five pairs of electrons provided by the CO ligands. Reflecting its symmetrical structure and charge neutrality, Fe(CO)5 is volatile; it is one of the most frequently encountered liquid metal complexes.

Fe(CO)5 adopts a trigonal bipyramidal structure with the Fe atom surrounded by five CO ligands: three in equatorial positions and two axially bound. The Fe-C-O linkages are each linear.

Fe(CO)5 is the archetypal fluxional molecule due to the rapid interchange of the axial and equatorial CO groups via the Berry mechanism on the NMR timescale. Consequently, the13C NMR spectrum exhibits only one signal due to the rapid interchange between nonequivalent CO sites.

In Europe, iron pentacarbonyl was once used as an anti-knock agent in petrol in place of tetraethyllead. Two more modern alternative fuel additives are ferrocene and methylcyclopentadienyl manganese tricarbonyl. Fe(CO)5 is used in the production of "carbonyl iron", a finely divided form of iron used in magnetic cores of high-frequency coils for electronics, and for manufacture of the active ingredients of some radar absorbent materials (e.g. iron ball paint). It is famous as a chemical precursor for the synthesis of various iron-based nanoparticles.

Iron pentacarbonyl has been found to be a strong flame speed inhibitor in oxygen based flames.

Toluene

Toluene is a clear, water-insoluble liquid with the typical smell of paint thinners, redolent of the sweet smell of the related compound benzene. It is an aromatic hydrocarbon that is widely used as an industrial feedstock and as a solvent. Like other solvents, toluene is also used as an inhalant drug for its intoxicating properties. [21] [22]

Toluene and benzene were used as octane rating boosters for aviation fuel by the Royal Air Force in the World War Two. Tetraethyl lead was manufactured in the USA and was on short supply, so Rolls-Royce engineers built the Rolls-Royce Merlin to work with fuel affed with benzene and toluene. This was called as "aromatic fuel". [23] The Allison V-1710 engine would not run with the RAF fuels as it required tetraethyl lead for lubrication of its valvetrain, but the Packard-built Merlins would. This is why the Merlin-engine P-51 Mustangs had a text "Suitable for Aromatics" on their USAAF type description. [24] [25]

Toluene can be used as an octane booster in gasoline fuels used in internal combustion engines. Toluene at 86% by volume fueled all the turbo Formula 1 teams in the 1980s, first pioneered by the Honda team. The remaining 14% was a "filler" of n-heptane, to reduce the octane to meet Formula 1 fuel restrictions. Toluene at 100% can be used as a fuel for both two-stroke and four-stroke engines; however, due to the density of the fuel and other factors, the fuel does not vaporize easily unless preheated to 70 degrees Celsius (Honda accomplished this in their Formula 1 cars by routing the fuel lines through the exhaust system to heat the fuel). Toluene also poses similar problems as alcohol fuels, as it eats through standard rubber fuel lines and has no lubricating properties as standard gasoline does, which can break down fuel pumps and cause upper cylinder bore wear.

Toluene has also been used as a coolant for its good heat transfer capabilities in sodium cold traps used in nuclear reactor system loops.

Properties of xylenes and ethylbenzene are nearly identical to toluene, with the latter advertised by a refinery as "component of high performance fuels".

2,2,4-Trimethylpentane (isooctane)

2,2,4-Trimethylpentane, also known as isooctane, is an octane isomer which defines the 100 point on the octane rating scale (the zero point is n-heptane). It is an important component of gasoline.

Isooctane is produced on a massive scale in the petroleum industry, usually as a mixture with related hydrocarbons. The alkylation process alkylates isobutane with isobutylene using a strong acid catalyst. In the NExOCTANE process, [26] isobutylene is dimerized into isooctene and then hydrogenated to isooctane.

Xylidine

In World War II, xylidine was an important antiknock agent in very high performance aviation gasolines. Its purpose was to permit high levels of boost pressure in multiple-stage turbochargers, and thus high power at high altitudes, without causing detonation that would destroy the engine. The high pressures brought high temperatures of inlet air, making engines prone to knock. This use and storage stabilization methods were important military secrets. [27] [28]

See also

Related Research Articles

<span class="mw-page-title-main">Organometallic chemistry</span> Study of organic compounds containing metal(s)

Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide, cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal phosphine complexes are representative members of this class. The field of organometallic chemistry combines aspects of traditional inorganic and organic chemistry.

<span class="mw-page-title-main">Gasoline</span> Liquid fuel derived from petroleum

Gasoline or petrol is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When formulated as a fuel for engines, gasoline is chemically composed of organic compounds derived from the fractional distillation of petroleum and later chemically enhanced with gasoline additives. It is a high-volume profitable product produced in crude oil refineries.

Ferrocene is an organometallic compound with the formula Fe(C5H5)2. The molecule is a complex consisting of two cyclopentadienyl rings sandwiching a central iron atom. It is an orange solid with a camphor-like odor that sublimes above room temperature, and is soluble in most organic solvents. It is remarkable for its stability: it is unaffected by air, water, strong bases, and can be heated to 400 °C without decomposition. In oxidizing conditions it can reversibly react with strong acids to form the ferrocenium cation Fe(C5H5)+2. Ferrocene and the ferrocenium cation are sometimes abbreviated as Fc and Fc+ respectively.

<span class="mw-page-title-main">Tetraethyllead</span> Organolead compound

Tetraethyllead (commonly styled tetraethyl lead), abbreviated TEL, is an organolead compound with the formula Pb(C2H5)4. It was widely used as a fuel additive for much of the 20th century, first being mixed with gasoline beginning in the 1920s. This "leaded gasoline" had an increased octane rating that allowed engine compression to be raised substantially and in turn increased vehicle performance and fuel economy. TEL was first synthesised by German chemist Carl Jacob Löwig in 1853. American chemical engineer Thomas Midgley Jr., who was working for the U.S. corporation General Motors, was the first to discover its effectiveness as an antiknock agent in 1921, after spending several years attempting to find an additive that was both highly effective and inexpensive.

An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand before detonating. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates the resistance to detonating under pressure without a spark.

<span class="mw-page-title-main">Avgas</span> Aviation fuel

Avgas is an aviation fuel used in aircraft with spark-ignited internal combustion engines. Avgas is distinguished from conventional gasoline (petrol) used in motor vehicles, which is termed mogas in an aviation context. Unlike motor gasoline, which has been formulated without lead since the 1970s to allow the use of catalytic converters for pollution reduction, the most commonly used grades of avgas still contain tetraethyl lead, a toxic lead containing additive used to aid in lubrication of the engine, increase octane rating, and prevent engine knocking. There are ongoing efforts to reduce or eliminate the use of lead in aviation gasoline.

Methyl <i>tert</i>-butyl ether Chemical compound

Methyl tert-butyl ether (MTBE), also known as tert-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble in water. Primarily used as a fuel additive, MTBE is blended into gasoline to increase its octane rating and knock resistance, and reduce unwanted emissions.

<span class="mw-page-title-main">Liquid fuel</span> Liquids that can be used to create energy

Liquid fuels are combustible or energy-generating molecules that can be harnessed to create mechanical energy, usually producing kinetic energy; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels; however, there are several types, such as hydrogen fuel, ethanol, and biodiesel, which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy.

Ethanol, an alcohol fuel, is an important fuel for the operation of internal combustion engines that are used in cars, trucks, and other kinds of machinery.

Ethyl <i>tert</i>-butyl ether Oxygenate gasoline additive in the production of gasoline from crude oil

Ethyl tertiary-butyl ether (ETBE), also known as ethyl tert-butyl ether, is commonly used as an oxygenate gasoline additive in the production of gasoline from crude oil. ETBE offers equal or greater air quality benefits than ethanol, while being technically and logistically less challenging. Unlike ethanol, ETBE does not induce evaporation of gasoline, which is one of the causes of smog, and does not absorb moisture from the atmosphere.

<span class="mw-page-title-main">Methylcyclopentadienyl manganese tricarbonyl</span> Chemical compound

Methylcyclopentadienyl manganese tricarbonyl (MMT or MCMT) is an organomanganese compound with the formula (C5H4CH3)Mn(CO)3. Initially marketed as a supplement for use in leaded gasoline, MMT was later used in unleaded gasoline to increase the octane rating. Following the implementation of the Clean Air Act (United States) (CAA) in 1970, MMT continued to be used alongside tetraethyl lead (TEL) in the US as leaded gasoline was phased out (prior to TEL finally being banned from US gasoline in 1995), and was also used in unleaded gasoline until 1977. Ethyl Corporation obtained a waiver from the U.S. EPA (Environmental Protection Agency) in 1995, which allows the use of MMT in US unleaded gasoline (not including reformulated gasoline) at a treat rate equivalent to 8.3 mg Mn/L (manganese per liter).

In the liquid fuel industry, oxygenates are hydrocarbon-derived fuel additives containing at least one oxygen atom to promote complete combustion. Absent oxygenates, fuel combustion is usually incomplete, and the exhaust stream pollutes the air with carbon monoxide, soot particles, aromatic and polyaromatic hydrocarbons, and nitrated polyaromatic hydrocarbons.

<span class="mw-page-title-main">Iron pentacarbonyl</span> Chemical compound

Iron pentacarbonyl, also known as iron carbonyl, is the compound with formula Fe(CO)5. Under standard conditions Fe(CO)5 is a free-flowing, straw-colored liquid with a pungent odour. Older samples appear darker. This compound is a common precursor to diverse iron compounds, including many that are useful in small scale organic synthesis.

<span class="mw-page-title-main">Alcohol fuel</span> Alcohols used as fuel for internal combustion engines

Various alcohols are used as fuel for internal combustion engines. The first four aliphatic alcohols are of interest as fuels because they can be synthesized chemically or biologically, and they have characteristics which allow them to be used in internal combustion engines. The general chemical formula for alcohol fuel is CnH2n+1OH.

MCMT may refer to:

The MTBE controversy concerns methyl tert-butyl ether (MTBE), a gasoline additive that replaced tetraethyllead. MTBE is an oxygenate and raises gasoline's octane number. Its use declined in the United States in response to environmental and health concerns. It has polluted groundwater due to MTBE-containing gasoline being spilled or leaked at gas stations. MTBE spreads more easily underground than other gasoline components due to its higher solubility in water. Cost estimates for removing MTBE from groundwater and contaminated soil range from $1 billion to $30 billion, including removing the compound from aquifers and municipal water supplies, and replacing leaky underground oil tanks. Who will pay for remediation is controversial. In one case, the cost to oil companies to clean up the MTBE in wells belonging to the city of Santa Monica, California is estimated to exceed $200 million.

Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. Organoiron compounds are relevant in organic synthesis as reagents such as iron pentacarbonyl, diiron nonacarbonyl and disodium tetracarbonylferrate. Although iron is generally less active in many catalytic applications, it is less expensive and "greener" than other metals. Organoiron compounds feature a wide range of ligands that support the Fe-C bond; as with other organometals, these supporting ligands prominently include phosphines, carbon monoxide, and cyclopentadienyl, but hard ligands such as amines are employed as well.

N-Methylaniline (NMA) is an aniline derivative. It is an organic compound with the chemical formula C6H5NH(CH3). The substance is a colorless viscous liquid, Samples turn brown when exposed to air. The chemical is insoluble in water. It is used as a latent and coupling solvent and is also used as an intermediate for dyes, agrochemicals and other organic products manufacturing. NMA is toxic and exposure can cause damage to the central nervous system and can also cause liver and kidney failure.

<span class="mw-page-title-main">Half sandwich compound</span> Class of coordination compounds

Half sandwich compounds, also known as piano stool complexes, are organometallic complexes that feature a cyclic polyhapto ligand bound to an MLn center, where L is a unidentate ligand. Thousands of such complexes are known. Well-known examples include cyclobutadieneiron tricarbonyl and (C5H5)TiCl3. Commercially useful examples include (C5H5)Co(CO)2, which is used in the synthesis of substituted pyridines, and methylcyclopentadienyl manganese tricarbonyl, an antiknock agent in petrol.

References

  1. ↑ "Phase-out of leaded petrol brings huge health and cost benefits". UN News. 27 October 2011. Retrieved 2020-11-28.
  2. ↑ Tsai, P.L.; Hatfield, T.H. (December 2011). "Global Benefits From the Phaseout of Leaded Fuel" (PDF). Journal of Environmental Health. 74 (5): 8–14. Archived from the original (PDF) on 2016-12-23. Retrieved 2022-04-26.
  3. ↑ "Phase-out of leaded petrol brings huge health and cost benefits". UN News. 27 October 2011. Archived from the original on 16 October 2016. Retrieved 2020-11-28.
  4. ↑ Tsai, P.L.; Hatfield, T.H. (December 2011). "Global Benefits From the Phaseout of Leaded Fuel" (PDF). Journal of Environmental Health. 74 (5): 8–14. Archived from the original (PDF) on 2016-12-23. Retrieved 2022-04-26.
  5. ↑ "Fact Sheet - A Brief History of Octane in Gasoline: From Lead to Ethanol | White Papers | EESI".
  6. ↑ findarticles.com
  7. ↑ Schnaas L, Rothenberg SJ, Flores MF, et al. (July 2004). "Blood lead secular trend in a cohort of children in Mexico City (1987-2002)". Environ. Health Perspect. 112 (10): 1110–5. doi:10.1289/ehp.6636. PMC   1247386 . PMID   15238286. Archived from the original on 2012-07-08.
  8. ↑ Casciani, Dominic (2014-04-21). "Did removing lead from petrol spark a decline in crime?". BBC News.
  9. ↑ Minjares, Ray J.; Walsh, Michael, Methylcyclopentadienyl Manganese Tricarbonyl (MMT): A Science and Policy Review (PDF), International Council on Clean Transportation
  10. ↑ "The Ethanol Illusion". November 2006.
  11. ↑ "Fuel Ethanol: Hero or Villain?".
  12. ↑ General Review of Emission-Related Notices of Defect and Recalls (Canada and the U.S.), Environment Canada (January 31, 2005)
  13. ↑ Risk Assessment of Methylcyclopentadienyl Manganese Tricarbonyl (mmt) when used as a Fuel Additive, Arcadis (November 2013).
  14. ↑ Risk Assessment for the Combustion Products of Methylcyclopentadienyl Manganese Tricarbonyl (MMT) in Gasoline," Health Canada (December 6, 1994)
  15. ↑ Garrec, J.P.; Kudo, A. (1985). "Distribution and accumulation of methylcyclopentadienyl manganese tricarbonyl (MMT-antidetonating agent) in an experimental freshwater ecosystem". Environmental Pollution. Series B (3): 173–188. doi:10.1016/0143-148x(85)90042-4.
  16. ↑ R. Dagani (3 December 2001). "Fifty Years of Ferrocene Chemistry". Chemical and Engineering News . 79 (49): 37–38. doi:10.1021/cen-v079n049.p037.
  17. ↑ Oeste, Franz Dietrich; de Richter, Renaud; Ming, Tingzhen; Caillol, Sylvain (2017-01-13). "Climate engineering by mimicking natural dust climate control: the iron salt aerosol method". Earth System Dynamics. 8 (1): 1–54. Bibcode:2017ESD.....8....1O. doi: 10.5194/esd-8-1-2017 . ISSN   2190-4979.
  18. ↑ Application of fuel additives Archived 2006-05-05 at the Wayback Machine
  19. ↑ U.S. patent 4,104,036
  20. ↑ Samson, S.; Stephenson, G. R. "Pentacarbonyliron" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi : 10.1002/047084289X.
  21. ↑ Streicher HZ, Gabow PA, Moss AH, Kono D, Kaehny WD (1981). "Syndromes of toluene sniffing in adults". Ann. Intern. Med. 94 (6): 758–62. doi:10.7326/0003-4819-94-6-758. PMID   7235417.
  22. ↑ Devathasan G, Low D, Teoh PC, Wan SH, Wong PK (1984). "Complications of chronic glue (toluene) abuse in adolescents". Australian and New Zealand Journal of Medicine. 14 (1): 39–43. doi:10.1111/j.1445-5994.1984.tb03583.x. PMID   6087782.
  23. ↑ "AROMATIC HYDROCARBONS AS COPONENTS OF AVIATION GASOLINE | CIA FOIA (foia.cia.gov)". www.cia.gov. Retrieved 2024-10-06.
  24. ↑ "Mustang was 'suitable for aromatic fuels'". 30 April 2014.
  25. ↑ "North American P-51 Mustang military aircraft fuel legend Stock Photo - Alamy".
  26. ↑ NExOCTANE - Neste Jacobs Archived December 23, 2007, at the Wayback Machine
  27. ↑ Meyer, Carl L. (August 1943). "Antiknock effectiveness of xylidine in small-scale engines". U.S. NASA NTRS. U.S. Government, NASA. Retrieved 2 February 2022.
  28. ↑ Starr, Charles E Jr.; et al. "Method of stabilizing xylidine, U.S. Patent No 2,509,891" (PDF). Google Patents. U.S. Patent Office. Retrieved 2 February 2022.
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