Antiknock properties

In addition to their antiknock properties, organic lead compounds possess bactericidal properties and motor fuels with lead are known to inhibit bacterial growth during storage in contact with water. With the disappearance of lead-based compounds, it is necessary to incorporate biocides from the cyclic imine family, (piperidine, pyrrolidine, hexamethyleneimine), alkylpropylene diamines or imidazolines (Figure 9.2). 

Concerning non-metallic compounds, the antiknocking properties of nitrogen compounds such that derivatives of aniline, indole and quinoline, and certain phenol derivatives have been mentioned. 

Alkylate. Alkylation means the chemical combination of isobutane with any one or a combination of propylene, butylenes, and amylenes to produce a mixture of highly branched paraffins that have high antiknock properties with good stabiUty. These reactions are cataly2ed by strong acids such as sulfuric or hydrofluoric acid and have been studied extensively (98—103). In the United States mostly butylenes and propylene are used as the olefins. 

Antikatalysator, m. anticatalyst, antikatalytisch, a. anticatalytic. Antiklopf-eigenschaft, /. antiknock property. 

Catalysts that decrease reaction rates are usually referred to as inhibitors. They usually act by interfering with the free radical processes involved in chain reactions, and the mechanism differs from that involved in accelerating a reaction. The most familiar example of the use of inhibitors is the addition of tetraethyl lead to gasoline to improve its antiknock properties. 

Tetraethyllead was the first known organolead compound, synthesized in 1853. Its antiknock properties were discovered in 1922, and since then its consumption has rapidly increased. 

Tetraethyl Lead - used to improve the octane number (antiknock) properties of gasoline. Use is mandatory in aviation gasoline. Tetraethyl lead is not permitted in civil and military jet fuel. 

Octane A hydrocarbon with the formula C8H18 having 18 different isomers. These isomers have typical boiling points between 210.2°F and 257°F (99°C and 125°C). The most important of these isomers is 2,2,4-trimethyl pentane or isooctane. It is a colorless liquid with a boiling point of 210.2°F (99°C) and is used as a standard for rating the antiknock properties of gasoline. 

Organic boron compounds reportedly have some antiknock effectiveness in addition to altering combustion-chamber deposit effects (35, 46). Other compounds showing antiknock properties have recently been reviewed (50). 

Tetraethyl Lead (TEL)—A volatile lead compound which is added to motor and aviation gasoline to increase the antiknock properties of the fuel. Pb(C2H5)4. The use of this compound has diminished in recent years because of pollution regulations. 

Copolymers of adipic acid, glycerol, and 1,3-diaceloxy-methyltetra-mcthyldisiloxanc, or similar compound, arc sometimes used. The silicon adaptation of the alkyd le in possesses, in general, increased hardness and flexibility, In addition, there is greater stability at higher temperatures. Copolymers can also be prepared using amyldibutoxyboron. Antiknock properties are claimed for this type of product as well as increased heat resistance,... 

Addn of small quantity, such as 0.1%, of Centr 2 to motor fuels improves their antiknock properties) 15)Perez Ara(1945), 423 (Some props) l6)J.Taylor et al, JPhysCollChem 51, 590(1947)(Some thermochemical props)... 

Tetrakis(2,2,6,6-tetramethyl-3,5-heptanedionato)cerium(IV) has been found to have antiknock properties for petrol.153 Other lanthanide complexes of the same ligand are also effective and mixtures may be used, especially those rich in cerium.154... 

The greatest use for methanol is in the manufacture of formaldehyde (see Section 14.5). Additional uses include the synthesis of other chemicals, including acetic acid, applications as an organic solvent, and addition to unleaded gasoline for fuel, antifreeze, and antiknock properties. 

ON Octane number. A numerical measure of the antiknock properties of motor fuel, based on percentage by volume of isooctane in a standard reference fuel. 

Organolead compounds have been recently widely used. They are used in agriculture (as pesticides), in medicine, as well as in various chemical processes as catalysts for the polymerisation of vinyl monomers, chlorination of hydrocarbons, etc. Lead tetraalkyl derivatives are used as additives for engine fuels due to their antiknock properties. 

Alkylate is a gasoline blending component with exceptional antiknock properties, which seems to avoid the legislative pressure. Alkylate consists exclusively of isoalkanes and is obtained from the C3-C4 cut of the FCC units. In many instances, isobutene from the C3-C4 fraction is transformed selectively with methanol into methyl tert-butyl ether (MTBE). Therefore, a mixture of 1-butene and 2-butene is used for alkylation purposes. The other reactant is isobutane. The major constituents of the alkylate are 2,2,3-, 2,2,4-, 2,3,3- and 2,3,4-trimethyl pentane (TMP). Besides, the alkylate contains other C8 isoalkanes, such as dimethyl hexane (DMH), 3-ethyl 2-methyl pentane, methyl heptane and ethyl hexane, and even isoalkanes with carbon numbers that are not multiples of 4. 

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