Antiknock compounds

Much of the bromine output in the U.S. was used in the production of ethylene dibromide, a lead scavenger used in making gasoline antiknock compounds. Lead in gasoline, however, has been drastically reduced, due to environmental considerations. This will greatly affect future production of bromine. 

In 1957, Ethyl Corp. announced anew antiknock compound, methylcyclopentadienyknanganese tricarbonyl [12108-13-3] (MMT). MMT is almost as effective as lead on a per gram of metal basis, but because manganese was more expensive than lead, MMT was not widely used until limits were placed on the lead content of gasoline. MMT was used in unleaded fuel between 1975 and 1978. After a large fleet test suggested that MMT could increase exhaust emissions because it interfered with catalysts and oxygen sensors, EPA banned its use in unleaded fuel in 1978. MMT is used in Canada in unleaded fuel. 

The largest consumption of sodium worldwide, as of the mid-1990s, is the production of tetraethyUead and tetramethyUead antiknock compounds for gasoline. This production is outside of North America. Sodium is also used for the production of other organometaHic compounds such as methylcyclopentadienyknanganese tricarbonyl (MMT), another gasoline additive. 

Metal carbonyls have been used as antiknock compounds in unleaded gasoline (see Gasoline and other motor fuels). The Ethyl Corp. marketed methylcyclopentadienyknanganese tticarbonyl (MMT) however, as in the case of tetraethyllead (180), its use is prohibited because of environmental concerns. 

The most common toxic metals in industrial use are cadmium, chromium, lead, silver, and mercury less commonly used are arsenic, selenium (both metalloids), and barium. Cadmium, a metal commonly used in alloys and myriads of other industrial uses, is fairly mobile in the environment and is responsible for many maladies including renal failure and a degenerative bone disease called "ITA ITA" disease. Chromium, most often found in plating wastes, is also environmentally mobile and is most toxic in the Cr valence state. Lead has been historically used as a component of an antiknock compound in gasoline and, along with chromium (as lead chromate), in paint and pigments. 

A recently marketed fuel additive is MMT (methyl cyclopentadienylmanganese tricarbonyl). MMT was first developed by the Ethyl Corporation in 1957 as an octane enhancing agent and has experienced a growth in demand in the 1990s. MMT was Ethyl Corporation s first major new antiknock compound since TEL. 

Muskie s public hearing, held in Washington, D.C., in June 1966, revealed that 480,000 of petroleum industry money was helping to finance a Bureau of Mines study of antiknock compounds. With no funds to conduct its own research, the government agency had agreed to publish the petroleum-funded study only if the American Petroleum Institute approved its contents. 

In 1921, the DELCO lab, which was now part of GM, found that tetraethyl lead was an excellent antiknock compound. By 1923, leaded gas was being pumped at Dayton, Ohio. In the following year, GM, DuPont... 

Uses. In the synthesis of antiknock compounds for gasoline in the production of fumigants, fire retardants, sanitation preparations, and chemical warfare gas... 

Arkipova OG et al Tjxicity within a factory of the vapor of new antiknock compound, manganese cyclopentadienyl-tricarbonyl. Gigiena Sanitoriya 20 40-44, 1965... 

Sulfur is limited to 0.05 wt%. Sulfur degrades the efficiency of antiknock compounds and can lead to metal corrosion. 

Diminishes the Effectiveness of Alkyl Lead Antiknock Compounds... 

The compds to prevent knock which is undesirable in internal combustion engines were described as "Antidetonating or Antiknock Compounds in Vol 1 of Encycl, pp A462-A463... 

By incorporating in the proplnt small quantities of Antiknock Compounds, described as "Antidetonating or Antiknock Compounds" in Vol 1, pp A462-R A463-L. One of such substances, tetraethyl lead, was proposed by the French. They were supposed to eliminate flash, at least partially (Ref 2, p 139)... 

In general, it would appear that some degree of trouble must always be expected from deposits—trouble which in some part, though by no means wholly, is due to the antiknock compound. However, progress has been made to the point where the present problems cannot be regarded as critical. Moreover, present research indicates that there is hope for substantial further improvement. In any case, the extent to which tetraethyllead contributes to these problems is a small price to pay for its value as a fuel constituent. 

Methyl chloride is used in the production of tetramethyllead antiknock compounds for gasoline and methyl silicone resins and polymers, and as a catalyst carrier in low-temperature polymerization (e g., butyl rubber), a refrigerant, a fluid for thermometric and thermostatic equipment, a methylating agent in organic synthesis, an extractant and low-temperature solvent, a herbicide, a topical antiseptic, and a slowing agent (lARC, 1986 Lewis, 1993). 

Prepared from methylcyclopentadienylmanganesetricarbonyl (a commerical antiknock compound with the acronym MMT) according to a published procedure.5 Also available from Strem Chemical, Newburyport, MA 01950. 

Dyes to indicate kind of antiknock compounds used and to identify brand and grade of gasoline. 

The desire to improve the octane rating of fuels after the refining process without the use of lead has intensified a search for other "antiknock compounds. For example, compounds of Mn (5) and Ce (9) have been explored for this purpose. Methylcyclopentadienyl manganese tricarbonyl, in particular, is already being marketed for octane improvement. At a recommended level of 0.125 g Mn/gal, 200-500 g of Mn can be expected to pass the exhaust system within 50,000 miles. The main criteria in accepting such fuel additives are their compatibility with catalytic systems, and, of course, health-safety considerations. 

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