U.S. gasoline pool

FCC gasoline has always been the most valuable product of a cat cracker unit. FCC gasoline accounts for about 35 vol% of the total U.S. gasoline pool. Historically, the FCC has been run for maximum gasoline yield with the highest octane. 

In 1990, U.S. gasoline contained about 10 vol% olefins, the majority of which emanate from FCC gasoUne. FCC gasoline has 25 vol% to 35 vol% olefins. Of these olefins, Cg-C olefins account for about 85% of the total pool. For non-RFG gasoline, as with sulfur, the regulation allows the maximum olefin content to be 125% of the 1990 baseline values. 

The upper unleaded-fuel curve shows the octane numbers obtained by adding various amounts of toluene to an 87.5-RON (estimated U.S. clear pool) base gasoline containing 23% aromatics. 

U.S. petroleum benzene prices since 1974 are Hsted in Table 6 (64). Until 1978, benzene prices were relatively stable and through 1985 they increased considerably, peaking in 1981 because of the increased demand for aromatics in the gasoline pool. At that time, there was also a large surplus of low priced imported benzene and a softening of the ethylbenzene—styrene market. The decline of cmde oil prices in 1986 caused a dramatic drop in domestic benzene prices. In 1987, U.S. benzene production increased 13.9% over 1986, and this rise was largely ascribed to a favorable export market for benzene derivatives... 

In the past, there was little incentive to process C5 olefins in the alkylation unit because they were normally included in the gasoline pool due to their acceptable octane rating and they cause higher acid consumption in the alkylation process. However, the recent Clean Air Act Amendment specification on RVP and potential evaporative emissions could force U.S. refineries to back out C5 olefins from the gasoline pool and upgrade them via alkylation or etherification. Although acid consumption will increase, both HF and sulfiiric acid processes can alkylate the C5 olefins, producing similar octanes as shown in Table 19. Table 20 compares the properties of the C5 olefins before and after alkylation (Lew et al, 1991). 

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