Gasoline-alcohol mixtures

The application of alcohol and gasoline-alcohol mixtures in the gasoline (Otto) engines began in the first half of the twentieth century. It is possible to find information about various studies on the change in octane numbers of gasoline-alcohol... 

In gasoline-methanol mixtures containing 0.1% water i-propanol is added to the environment (medium) in order to decrease the phase separation temperature. Fuels containing different ratios of gasoline-methanol-i-propanol and water are also composed, which are proved to be stable in the climatic conditions. An increase in the aromatic character of the gasoline, a decrease in the water content of the mixtme, an increase in the amount of the additive used results in a decrease in the phase separation temperature of the mixture. In gasoline-ethanol mixtures the additive used is also i-propanol. In gasoline-alcohol mixtures various additives like i-propanol, n-butanol, i-butanol, and i-amylalcohol are used. 

One possible solution is to increase the use of ethanol as an oxygen additive to gasoline. Some experts had long recommended a gasoline-alcohol mixture known as gasohol as an inexpensive, efficient fuel for use in motor vehicles that would reduce the emission of carbon... 

Reformulated gasoline blends have several advantages over gasohol (gasoline-alcohol mixtures) and MTBE blends. REG blends evaporate less readily because they have a lower vapor pressure, and they have lower benzene and sulfur contents. Gasoline blends, as well as other petroleum distillates, are an inhalation hazard to humans. Hydrocarbon distillates have been shown to cause cancer in laboratory animals. The products from the combustion of gasoline, specifically carbon monoxide and nitrogen oxides, have been linked to the dissipation of the protective ozone layer... 

Add the soap powder to the gasoline-alcohol mixture, aiui stir occasionally until the mixture thickens (about 15 minutes). 

The tendency to separate is expressed most often by the cloud point, the temperature at which the fuei-alcohol mixture loses its clarity, the first symptom of insolubility. Figure 5.17 gives an example of how the cloud-point temperature changes with the water content for different mixtures of gasoline and methanol. It appears that for a total water content of 500 ppm, that which can be easily observed considering the hydroscopic character of methanol, instability arrives when the temperature approaches 0°C. This situation is unacceptable and is the reason that incorporating methanol in a fuel implies that it be accompanied by a cosolvent. One of the most effective in this domain is tertiary butyl alcohol, TBA. Thus a mixture of 3% methanol and 2% TBA has been used for several years in Germany without noticeable incident. 

Some of the observed physical properties of hydrocarbons result from the nonpolar character of the compounds. In general, hydrocarbons do not mix with polar solvents such as water or ethyl alcohol. On the other hand, hydrocarbons mix with relatively nonpolar solvents such as ligroin (a mixture of alkanes), carbon tetrachloride, or dichloromethane. Since the density of most hydrocarbons is less than that of water, they will float. Crude oil and crude oil products (home heating oil and gasoline) are mixtures of hydrocarbons these substances, when spilled on water, spread quickly along the surface because they are insoluble in water. 

Tau LM, Fort AW, Bao S, et al. 1990. Methanol to gasoline 14C tracer studies of the conversion of methanol/higher alcohol mixtures over ZSM-5. Fuel Processing Technology 26 209- 219. 

Figure 2. Exposure of 40% glass-reinforced PPS )o gasoline 1 % alcohol mixtures at 12l°C. Key lo alcohol , methanol and , ethanol.

A homogeneous mixture is a combination of two (or more) pure substances that is uniform in composition and appearance throughout. Examples of homogeneous mixtures include rubbing alcohol (70% isopropyl alcohol and 30% water) and gasoline (a mixture of hydrocarbons). 

In a conventional gasoline containing hydrocarbons or even ethers, the presence of water is not a problem in fact, water is totally soluble up to about 50 ppm at ambient temperature. Beyond this value water separates without affecting the hydrocarbon phase and the water leg can be withdrawn if necessary. On the other hand, in the presence of alcohols (ethanol and especially methanol), trace amounts of water can cause a separation of two phases one is a mixture of water and alcohol, the other of hydrocarbons (Cox, 1979). 

The Fischer-Tropsch reaction is essentially that of Eq. XVIII-54 and is of great importance partly by itself and also as part of a coupled set of processes whereby steam or oxygen plus coal or coke is transformed into methane, olefins, alcohols, and gasolines. The first step is to produce a mixture of CO and H2 (called water-gas or synthesis gas ) by the high-temperature treatment of coal or coke with steam. The water-gas shift reaction CO + H2O = CO2 + H2 is then used to adjust the CO/H2 ratio for the feed to the Fischer-Tropsch or synthesis reactor. This last process was disclosed in 1913 and was extensively developed around 1925 by Fischer and Tropsch [268]. 

J. V. D. Weide and R. J. Wineland, "Vehicle Operation with Variable Methanol/Gasoline Mixtures," 6th Int. Symp. on Alcohol Euels Technology (Ottawa, Canada, May 21—25, 1984), Vol. 3. 

The most extensive worldwide program on methanol blend gasoline was in Italy where from 1982 to 1987 a 1.9 x lO" m /yr (5 x 10 gal/yr) plant produced a mixture containing 69% methanol. The balance contained higher alcohols. This mixture was blended into gasoline at the 4.3% level and marketed successfully as a premium gasoline known as Super E (82). 

Sasol Fischer-Tropsch Process. 1-Propanol is one of the products from Sasol s Fischer-Tropsch process (7). Coal (qv) is gasified ia Lurgi reactors to produce synthesis gas (H2/CO). After separation from gas Hquids and purification, the synthesis gas is fed iato the Sasol Synthol plant where it is entrained with a powdered iron-based catalyst within the fluid-bed reactors. The exothermic Fischer-Tropsch reaction produces a mixture of hydrocarbons (qv) and oxygenates. The condensation products from the process consist of hydrocarbon Hquids and an aqueous stream that contains a mixture of ketones (qv) and alcohols. The ketones and alcohols are recovered and most of the alcohols are used for the blending of high octane gasoline. Some of the alcohol streams are further purified by distillation to yield pure 1-propanol and ethanol ia a multiunit plant, which has a total capacity of 25,000-30,000 t/yr (see Coal conversion processes, gasification). 

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. 

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