Octane, gasoline additives

These are effective high-octane gasoline additive oxygenates. The conversion of isobutane into isopropyl, methyl ketone, or isopentane into isobutyl, methyl ketone is illustrative. In this reaction, no branched carboxylic acids (Koch products) are formed. 

Bert, J.A., J.A. Gething, T.J. Hansel, H.K. Newhall, R.J. Peyla and D.A. Voss (1983), A gasoline additive concentrate removes combustion chamber deposits and reduces vehicle octane requirement . SAE paper No. 83-1709, Fuels and Lubricants meeting, San Francisco, CA. 

For these reasons, ethanol is most likely to find use as a motor fuel in the form of a gasoline additive, either as ethanol or ethanol-based ethers. In these blend uses, ethanol can capture the high market value of gasoline components that provide high octane and reduced vapor pressure. 

Isomeri2ation of straight-chain hydrocarbons is of particular importance for lead-free gasoline. Addition of high octane aromatic hydrocarbons or olefins is questionable based on environmental considerations (77). An efficient octane enhancing additive is methyl tert-huty ether (MTBE). 

The cumene product is 99.9 wt % pure, and the heavy aromatics, which have a research octane number (RON) of 109, can either be used as high octane gasoline-blending components or combiaed with additional benzene and sent to a transalkylation section of the plant where DIPB is converted to cumene. The overall yields of cumene for this process are typically 97—98 wt % with transalkylation and 94—96 wt % without transalkylation. 

Sodium amalgam is employed ia the manufacture of sodium hydroxide sodium—potassium alloy, NaK, is used ia heat-transfer appHcations and sodium—lead alloy is used ia the manufacture of tetraethyllead and tetramethyUead, and methylcyclopentadienylmanganesetricarbonyl, a gasoline additive growing ia importance for improving refining efficiency and octane contribution. 

Some efforts were made in the early 1980s to employ isobutyl and -butyl alcohols as octane extenders in gasoline. American Methyl Corporation in 1983, under a special waiver of the 1977 Clean Air Act (24), marketed a gasoline blend called Petrocoal containing methanol and a C-4 alcohol which was principally isobutyl alcohol. About 10,000 t of isobutyl and 5000 t of -butyl alcohol were consumed in this appHcation (10). In 1984, the EPA attempted to rescind this waiver and demand for isobutyl alcohol as a gasoline additive dropped to 136.3 t (10). Ultimately, the waiver was rescinded and no isobutyl or -butyl alcohol has been marketed for gasoline additive end use since 1984. 

Oxirane Process. In Arco s Oxirane process, tert-huty alcohol is a by-product in the production of propylene oxide from a propjiene—isobutane mixture. Polymer-grade isobutylene can be obtained by dehydration of the alcohol. / fZ-Butyl alcohol [75-65-0] competes directly with methyl-/ fZ-butyl ether as a gasoline additive, but its potential is limited by its partial miscibility with gasoline. Current surplus dehydration capacity can be utilized to produce isobutylene as more methyl-/ fZ-butyl ether is diverted as high octane blending component. 

Table 1 shows the major gasoline additives that were introduced from the 1920s through the 1980s. The increase in octane number of gasoline with use of these additives is shown. 

Similar to MTBE, TAME is used as gasoline additive for its high octane rating and its ability to reduce carbon monoxide and hydrocarbon exhaust emissions. Properties of oxygenates used as gasoline additives are shown in Table 5-2. °... 

Within two decades of the introduction of tetraethyl lead, engine efficiency doubled, power per cylinder tripled, and the octane of regular gasoline rose from 55 to 75. Midgley s gasoline additive symbolized the technological wonders of industrial research and corporate America. Cheap... 

In addition to its octane enhancement ability described above, ZSM-5 also increases the feed to alkylation, methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) units. Since the products from all these processes contain high Research and Motor Octane components, ZSM-5 provides the refiner additional flexibility in his downstream processing whenever the need exists to increase overall gasoline pool octane. In addition, the overall refinery can be rebalanced to take... 

Thus, the potential octane boost which can be obtained from ZSM-5 addition is not only a function of its activity and the fraction of ZSM-5 in inventory, but it also depends on its base gasoline octane (gasoline octane without ZSM-5 addition). 

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