automotive and aviation gasolines used in carburetor-type internal-combustion engines with supercharging and a high compression ratio. High-octane fuels are knock-resistant and ensure smooth engine operation without disruption of the combustion process. The antiknock rating (a very important fuel characteristic) of high-octane fuels is determined by their high content of isoparaffin hydrocarbons, benzene and its homologues, olefins, and lower cycloparaffins. For aviation gasolines the antiknock rating is specified by the octane number and the gasoline grade, and for automotive gasolines it is specified by the octane number. The better grades of aviation gasoline have an octane rating of 98-100 and a rich-mixture grade of 130-160; better automotive gasolines have an octane rating of 98 (Ekstra brand). The gasolines widely used in automobile engines have octane ratings of 76 and 93. High-octane fuels usually contain the antiknock compound tetraethyl lead (0.82 g/kg in automotive gasoline and as much as 3.3 g/kg in aviation gasoline).
High-octane fuels are obtained by the mixing of catalytically cracked gasoline with catalytically reformed aromatized gasoline, polymerization gasoline (a product of the polymerization of the butane-butylene fraction), or alkylate (a product of the catalytic alkylation of butylenes by isobutane). The proportion of the constituents depends on the required octane rating of the gasoline and on its volatility, heat of combustion, and density.
REFERENCENefteprodukty: Svoistva, kachestvo, primenenie: Spravochnik. Edited by B. V. Losikov. Moscow, 1966.
V. V. SHCHEKIN