Gasoline blending additives

Capacity Limitations and Biofuels Markets. Large biofuels markets exist (130—133), eg, production of fermentation ethanol for use as a gasoline extender (see Alcohol fuels). Even with existing (1987) and planned additions to ethanol plant capacities, less than 10% of gasoline sales could be satisfied with ethanol—gasoline blends of 10 vol % ethanol the maximum volumetric displacement of gasoline possible is about 1%. The same condition apphes to methanol and alcohol derivatives, ie, methyl-/-butyl ether [1634-04-4] and ethyl-/-butyl ether. 

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. 

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 Ultimately, the waiver was rescinded and no isobutyl or -butyl alcohol has been marketed for gasoline additive end use since 1984. 

In addition to MTBE, two other ethers commonly used as fuel additives ate /n/f-amyl methyl ether (TAME) and ethyl in/f-butyl ether [637-92-3] (ELBE). There ate a number of properties that ate important in gasoline blending (see Gasoline and OPHER MOTOR fuels) (Table 3). 

The principal use of the alkylation process is the production of high octane aviation and motor gasoline blending stocks by the chemical addition of C2, C3, C4, or C5 olefins or mixtures of these olefins to an iso-paraffin, usually isobutane. Alkylation of benzene with olefins to produce styrene, cumene, and detergent alkylate are petrochemical processes. The alkylation reaction can be promoted by concentrated sulfuric acid, hydrofluoric acid, aluminum chloride, or boron fluoride at low temperatures. Thermal alkylation is possible at high temperatures and very high pressures. 

In addition to the Fischer-Tropsch-derived material, coal-derived liquids were also recovered from low-temperature coal gasification (not shown in Figures 18.3 and 18.4). These products were processed separately to produce chemicals, such as phenols, cresols, and ammonia, as well as an aromatic motor gasoline blending stock.34 The latter was mixed with the Fischer-Tropsch-derived motor gasoline. 

Cost Is about 10-12/GJ for both methanol and synthetic gasoline for transportation usage. The additional conversion costs of methanol to gasoline by the Mobil process roughly balance the distribution and usage costs of methanol/gasoline blends. 

An additional problem with alcohol-gasoline blends is the increase in vapor pressure of gasoline in the mixture (e.g., see National Research Council, 1991 Calvert et al., 1993 and Timpe and Wu, 1995). This can contribute to much higher Reid vapor pressures, increasing the relative importance of evaporative emissions. 

Production of Alcohols by Hydration ofAlkenes. Several alcohols (ethyl alcohol, isopropyl alcohol, sec-butyl alcohol, ferf-butyl alcohol) are manufactured commercially by the hydration of the corresponding olefins.2 45 46 Ethanol, an industrial solvent and a component of alcohol-gasoline blends, and isopropyl alcohol—a solvent and antiknock additive—are the most important compounds. Isopropyl alcohol is often considered the first modem synthetic petrochemical since it was produced on a large scale in the United States in the 1920s. 

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