Automotive knock

The Ethyl Corp. and DuPont held the TEL patent, and controlled the TEL monopoly. The company held the sole right to the only known material that could eliminate automotive knocking. And it used its influence in the gasoline market to manipulate prices. Over the next few years, the company wielded its monopoly power to maintain a 3—5 cent differential between its ethyl gasoline and the regular, unleaded gasoline sold by the rest of the industiy. 

It is interesting to consider the effect of the multiplication as it may apply in a practical problem such as that associated with automotive knock. However exten-... 

Even though k2 is a hypothetical rate constant for many reaction chain systems within the overall network of reactions in the reacting media and hence cannot be evaluated to obtain a result from Eq. (10), it is still possible to extract some qualitative trends, perhaps even with respect to automotive knock. Most importantly, Eq. (9) establishes that a chemical explosion is possible only when there is chain branching. Earlier developments show that with small amounts of chain branching, reaction times are extremely small. What determines whether the system will explode or not is whether chain termination is faster or slower than chain branching. 

Tetra ethyl lead (TEL) was used as an anti-knock agent in automotive gasoline. Small amounts were normally added. During the compression stroke TEL reacts with the air to form very small lead oxide particles. Give an explanation why you believe TEL would be an effective anti-knock agent. 

Ignition by compression is similar to the conditions that generate knock in a spark-ignited automotive engine. Thus it would indeed appear that compression ignition and knock are chain-initiated explosions. Many have established... 

Of these chemicals, the EPA has traditionally focused its monitoring efforts on only one, lead. The reason is that lead (in the form of tetraethyl lead (C2H5) Pb) was once used extensively as a fuel additive to reduce the problems of engine "knocking in automotive vehicles. Because of the health problems posed by lead, however, tetraethyl lead was banned from use in automotive fuels in 1976. 

In practice, short-chain alkanes and alkenes are normally used as feedstock for shape-selective catalytic formation of isooctanes at relatively low temperatures. Until the 1980s, lead alkyls (Section 18.1) were added to most automotive fuels to help suppress engine knock, but they have been phased out in North America because of the chronic toxicity of lead and lead compounds. The most commonly used nonlead antiknock additive is now methyl tert-butyl ether [MTBE CH30C(CH3)3], which is made by the reaction of methanol with 2-methylpropene, (CHs C—CH2 (see Section 7.4). The latter is obtained by catalytic cracking of petroleum fractions to give 1-butene, which is then shape-selectively isomerized on zeolitic catalysts. 

The automotive engineers were also busy. In 1931 Lovell, Campbell, and Boyd (23) published data on an extended series of pure paraffin and olefin hydrocarbons in fairly dilute solution in gasoline. These data showed a number of definite relations between the molecular structure of the pure hydrocarbon and the tendency of the fuel to knock. The... 

Other tests have been used in the past, particularly for aviation gasoline, where it was more important to discriminate accurately between fuels with ON > 100. These had the advantage of being more related to real physical phenomena. For example, the performance number [11] was based on a single standard fuel, iso-octane, and the relative indicated mean effective power (imep) (defined in terms of the cylinder pressure [3]), and so is directly related to combustion. The performance number was 100 times the ratio of the knock limited imeps of the fuel and iso-octane. Much of the API 45 project on octane number of mixtures of pure hydrocarbons (see Section 7.2.5) was reported in terms of performance number. This project of the American Petroleum Institute ran from 1938 to 1957, and has provided an invaluable source of basic data. The articles by Lovell [10] and Scott [12] review and interpret these data. Whilst this criterion and these values of CCRs [10,13] are no longer in widespread use for automotive fuels, the data available in the older literature could still be useful in testing chemical models. Because the octane number scale is based on two reference fuels, modelling the octane number of any hydro-... 

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