Motoring octane value, gasoline

Acidic isomerization of the C5-C6 naphtha and some heavy alcohols from the aqueous product refinery (not shown in Figure 18.5) produced a reasonable-quality olefinic motor gasoline (Table 18.10). The octane value varied depending on the carbon number distribution of the feed, which could result in a product with an octane number up to ten units higher. 

The bulk of the naphtha was hydrotreated and catalytically reformed over a chlorided Pt/Al203-based catalyst to produce an aromatic motor gasoline. However, the hydrotreated Fischer-Tropsch naphtha is a poor feed for standard catalytic reforming on account of its high linear hydrocarbon content (>75%).37 In order to limit liquid yield loss, typical operation resulted in a reformate with quite low octane value (Table 18.10). Higher octane reformate could be produced, but at the expense of significant liquid yield loss. 

Sensitivity The difference between the research octane number (RON) and the motor octane number (MON) of a gasoline. Fuels blended with alkylate material have low sensitivity values. 

Alkylation—A refinery process for chemically combining isoparaffin with olefin hydrocarbons. The product, alkylate, has a high octane value and is blended with motor and aviation gasoline to improve the antiknock value of the fuel. 

Methanol has good octane properties compared to gasoline. With a research octane value of 108.6 and a modified motor octane value1 of 88.6 ([R+M]/2 of 98.6),... 

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. 

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